smp final report 10-12-08

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PROJECT MANAGEMENT CELL, NEW DELHI

BASE DOCUMENT

ST ND RD M INTEN NCE PR CTICES

RE-ROLLING MILL PROPER & RE-HEATING FURNACE

Compiled and Prepared

BY

SYCOM PROJECTS CONSULTANTS PVT. LTD., NEW DELHI

NOVEMBER 2008



PROJECT MANAGEMENT CELL (PMC)

UNDP /GEF Project (Steel Rerolling Mills)Ministry of Steel, Government of India

301-306, Aurobindo Place, Hauz Khas,

New Delhi-110016

SYCOM PROJECTS CONSULTANTSPVT LTD

Vatika, 6 Kaushalya Park, Hauz KhasNew Delhi – 110016

Ph: 011-26969452,41674051Email: [email protected] Website: www.s com ro ects.com

&

SEVAT

(Technical Partners) Prateeksha Madona, Thittamel,Chengannur - 689 121

KeralaMob:09387676039

SUBMITTED TO

SUBMITTED BY



TABLE OF CONTENTS

S.NO. PARTICULARS PAGE NO.

CHAPTER 1 INTRODUCTION

1.1 Important Parameters considered forMaintenance

1

1.2 Major types of Maintenance 1

1.2.1 Reactive maintenance 1

1.2.2 Preventive maintenance 2

1.2.3 Predictive maintenance 3

1.2.4 Proactive maintenance 10

1.2.5 The Right Maintenance Mix 11

1.3 Major Maintenance Tools required 13

1.3.1 Major Maintenance Tools required 13

1.3.2 Description of a few Monitoring Instruments 14

1.3.3 Reliability-based maintenance 20

1.4 Critical Equipments installed & theirSpecifications

21

1.4.1 Re-Heating Furnace 21

1.4.2 Rolling Mill 21

1.5 History Card Format 29

1.6 Manpower for Maintenance 30

1.7 Case Study 31

CHAPTER 2 STANDARD PREVENTIVE & PREDICTIVEMAINTENANCE PRACTICES ADOPTED FORRHF

2.1 Mechanical & Rotating Equipments 32

2.1.1 Major Equipments/Parts 32

2.1.2 Major identified Preventive & PredictiveMaintenance Practices

33

2.2 RHF SHELL PLATES & REFRACTORY LINING 38

2.2.1 Major Parts 38

2.2.2 Initial Heating of Furnace Refractories 38

2.2.3 Preventive & Predictive Maintenance Practices 38

2.3 Instrumentation Control System includingPC-PLC; Power Supply & Distribution system

41


2.3.2 Major identified Preventive & PredictiveMaintenance practices

41



CHAPTER 3 STANDARD PREVENTIVE & PREDICTIVEMAINTENANCE PRACTICES ADOPTED FORRM

3.1 Critical Mill Equipments 44

3.1.1 Major Equipments/Parts 443.1.2 The Major Identified Preventive & PredictiveMaintenance Practices

44

3.2 Instrumentation Control System includingPC-PLC; Power Supply & Distribution System

50


3.2.2 Major identified Preventive & PredictiveMaintenance practices

50

3.3 Centralized Lubrication System; WaterCooling System & Air Compressors

50


3.3.2 Major identified Preventive & PredictiveMaintenance Practices

50

3.4 Miscellaneous Machines, Housekeeping,Building Sheds

55


3.4.2 Major identified Preventive & Predictive

Maintenance Practices

55

CHAPTER 4 OVERHAULING/CAPITAL REPAIRS;GENERAL TROUBLE SHOOTING & REPAIR

WORK BASED ON CASE STUDIES4.1 Reheating Furnace 58

4.1.1 Overhauling/Capital Repairs 58

4.1.2 General Trouble Shooting & Repair 67

4.2 Rolling Mill 70

4.2.1 Overhauling/Capital Repairs 70

4.2.2 General Trouble Shooting & Repair Work basedon Case Studies

73

CHAPTER 5 OVERALL MAINTENANCE SCHEDULE FOR

SRRM; SAFETY PRECAUTIONS, STANDARDINSTALLATION PROCEDURES FORCRITICAL EQUIPMENTS

5.1 Detailed Overall Maintenance Schedule forSRRM

75

5.2 Major Spares to be maintained 81



5.3 General Safety precautions for equipments &operators

83

5.3.1 Re-Heating Furnace (RHF) 83

5.3.2 Rolling Mill 87

5.4 Standard Installation procedures for criticalEquipments

88

5.4.1 Re-Heating Furnace (RHF) 885.4.2 Rolling Mill Stand 91



LIST OF TABLES & FIGURES

LIST OF TABLES

TABLE NO. PARTICULARS PAGE NO.

1.1List of Critical Equipments/Parts Installed

in RHF Of 15 TPH Capacity & TheirSpecifications

22

1.2List of Critical Equipments/Parts installedin RHF Of 15 TPH Capacity & TheirSpecifications

25

1.3Format For History Card

29

2.1Standard Preventive & PredictiveMaintenance Practices For RHF-Mechanical & Rotating Equipments

34

2.2Standard Preventive & PredictiveMaintenance Practices For RHF –ShellPlates & Refractory Lining

40

2.3Standard Preventive & PredictiveMaintenance Practices For RHF -Instrumentation Control System includingPC – PLC; Power Supply & DistributionSystem

42

3.1

Standard Preventive & PredictiveMaintenance Practices adopted ForCritical Rolling Mill Equipments

46

3.2Standard Preventive & PredictiveMaintenance Practices adopted ForRolling Mill - Instrumentation ControlSystem Including PC – PLC; Power Supply& Distribution System

51

3.3Standard Preventive & PredictiveMaintenance Practices adopted for Rolling

Mill – Centralised Lubrication System;WaterCooling System & Air Compressors

53

3.4Standard Preventive & PredictiveMaintenance Practices for Misc. MillMachines, Housekeeping, Building sheds.

56



4.1Overhauilng/Capital Repairs of CriticalEquipment - RHF

59

4.2General Troubleshooting & Repair WorkFor RHF based on Case Studies

67

4.3Overhauling/Capital Repairs of CriticalEquipment-RM

71

4.4General Troubleshooting & Repair WorkFor RM based on Case Studies

73

5.1List of Spares to be Maintained For RHF 81

5.2List of Spares to be Maintained For RM

82

LIST OF FIGURES & APPENDIX

FIGURESNO.

PARTICULARS PAGE NO.

1.1Maintenance Practices adopted in TypicalSRRM Units & Best Practices

11

1.2Belt Tensiometer & its Application

15

1.3 Digital Vibrometer

16

1.4Hand Held Thermal Imaging InfraredCamera

18

1.5

Oil Testing Kit

20

5.1Overall Maintenance Schedule for SRRMUnit

75

Appendix 1 TOTAL PRODUCTIVE MAINTENANCETPM

93-111



1

CHAPTER 1

INTRODUCTION

1.1 IMPORTANT PARAMETERS CONSIDERED FOR MAINTENANCE

The important Parameters considered while formulating an Ideal

Maintenance Plan for SRRM include the following:

Zero Unplanned Downtime

Zero Defects

Zero Speed Losses

Zero Accidents

High productivity & Mill yield

Lower cost of production & Higher profitability of unit

A good maintenance strategy reduces repeated equipments failures,

loss of production & expensive capital repairs.

1.2 MAJOR TYPES OF MAINTENANCE

1.2.1 Reactive maintenance

The oldest maintenance approach is reactive, or “run-to-failure.”

Equipment isn’t repaired or replaced until it breaks.

The major disadvantages of Reactive Maintenance are:

• Costly downtime. Equipment fails with little or no warning, so the

process could be down until replacement parts arrive, resulting in

lost revenue.

• Higher maintenance costs. Unexpected failures can increase

overtime labor costs, as well as expedited delivery of replacement

parts.



2

• Safety hazards. Failure with no warning could create a safety issue

with the failing equipment or other units that might be affected.

Reactive maintenance can be appropriate in some circumstances, such

as for non-critical and low cost equipment with little or no risk of

collateral damage or lost production. There is virtually no non- critical

equipment in the SRRM which has no risk of collateral damage or lost

production. Hence there is no equipment that can be left to reactive

Maintenance in SRRM.

1.2.2 Preventive maintenance

The preventive maintenance philosophy is also known as time-based or

planned maintenance done at definite time intervals. The goal of this

approach is to maintain equipment in a healthy condition. Selected

service and part replacements are scheduled based on a time interval

for each device and lead to reduction in failures. However this leads to

over maintenance & human intervention in equipment technology.

The Maintenance is mainly carried out by:

1

Lubrication consisting of Oiling & oil topping of Gear Boxes, andGreasing of Bearings either through Centralized oil and grease

Lubrication Systems or manual individualized lubrication.

Manually oiling can be done using oil cans with a long spout or

through lubrication hand held oil pump dispensers. Oil should not

be topped up in gearboxes over the glass oil level indicator mark

fitted on the gearbox or dipstick indicator. The correct grade of

oil should be used at each location as specified in the supplier’smanual. Normally GP 90 oil is used in helical or spur geared drives

and GP 140 in worm drive gearboxes. Filling of oil in the gearbox

is done through the opening provided for the purpose on the top

cover of the gearbox. Make sure that there is no contamination in

the oil and that the top of the gearboxes are cleaned thoroughly



3

before opening the oil caps on the gearboxes. Spillages from the

gearbox during topping up should be wiped clean and never

reused.

Manually greasing can be done by:

a. Hand held grease gun

b. Pneumatically operated grease gun which is available in India

of Elgi make.

c. Grease EP-3 Lithium based mixed with 1 percent

Molybdenum Di-Sulphide is mostly used.

d. The procedure involves opening the housing, examining the

bearing, hand packing the grease into the housing, closing

the housing and tightening the holding down bolts. It should

be ensured that only two thirds of the housing is filled,

otherwise there would be churning, overheating and

consequent separation of the soap and oil which constitute

the grease.

1.2.3 Predictive maintenance

In predictive maintenance, equipment condition rather than time

intervals determine the need for service. Condition monitoring with the

aids of instruments, helps one to identify when wear-out risk begins to

increase and predict when failure is likely to occur. At present, in the

absence of digital on line monitoring instruments, only manual monitoring

is being done. Since manual monitoring is limited by the subjective

judgment of the individual it cannot be as cost effective as when using

monitoring instruments which have the limits of good performance preset

in the instrument. Moreover the data logging system attached to an online

condition monitoring instrument does away with manual recording of the

results of monitoring. The only monitoring instrument in use in some of



4

the SME-SRRM units is the vibrometer which is very helpful in detecting

bearing problems leading to bearing failure or equipment balancing

problems.

This approach can save time and money because it enables one to correct

the problem before the equipment actually fails, avoid the downtime and

repair costs caused by unexpected failure — as well as the costs and lost

production caused by preventive maintenance.

Advanced predictive maintenance programs frequently modify the

definition of a failure. Traditionally, a failure is defined as the point

where the equipment breaks down and is no longer available for

production. A more appropr ia te def in i t ion of fa i lure is that the

equipment is no longer able t o produce t he r ight qual i t y at t he r ight

product ion rat e and t he r i ght cost . At t h is point , t he plant is losing

pr of i t abi l i t y and maintenance should be considered.

Till date only manual monitoring is possible but since the number of

equipment is large it is advisable for the SRRM Units to install the

required on line monitoring programmes and instruments as part of the

Standard Maintenance Practices, which can be shared between the

Rolling Mills, Reheating Furnaces and other plant & machinery in the

Units.

The condition monitoring of various critical equipments/parts is carried

out by:

1. Visual Inspection

Each machine operator keeps a watch on the equipment he operates

and looks out for abnormality. The Maintenance group in its daily

round of the Plant also inspect all critical equipments, both on the

shopfloor and outside or in cellars etc. During the visual inspection

they also keep a watch on the running of the equipment and look out



5

for any abnormality and take the appropriate action which could be

any of the following:

a. If the abnormality is very serious and could endanger the

equipment itself or the surroundings or the electrical system ifallowed to run, the Maintenance personnel could ask for an

immediate stop in the running of that equipment and sound the

alarm by giving a prolonged siren in bursts of three. The

abnormality which could be excessive Temperature around the

RHF shell; vibrations or smoke coming out of the bearings;

unusual noise from the gear boxes; Leakage of fluids such as oil,

water from pipelines, valves etc. Immediately the core

Maintenance group attends to the Equipment, normally by

replacement with a spare, and afterward gives clearance for

continuation of operations.

b. If the rectification of the abnormality could be postponed till

the night or weekend, then a note is made of the abnormality

and Maintenance taken up later at the operational convenience.

c. If the rectification could be done without stopping the

equipment, then that is done. This could be lubrication of

bearings and topping up of lubricant in gearboxes. In such an

event full safety precautions should be taken not to work near

the moving components, not to use hardware tools near moving

components. Only experienced fitters/electricians should

undertake this type of rectification and under no circumstance

should safety of either man or Machine be compromised.

2 Bolts Tightening/Changing

As per the requirements of the Preventive Maintenance schedule all

such locations which require bolt checking are thoroughly checked

for tightness. Ring spanners of correct size should be used for



6

checking the tightness and for tightening. If ring spanners are not

available then DE (double ended) spanners can be used, and ring

spanners procured immediately. Never use pipe wrenches for this

purpose as the nuts or bolt heads could get damaged. It is advisable

to use sockets with torque wrenches for checking and tightening as

correct torques are applied for the bolt. The torque setting is done

on the wrench as per the bolt size, which is available from the

standards available with the torque wrench manual or from the

supplier’s manual. Socket head spanners are also available and can

be used. The Maintenance fitter wheels a tool box kit on a small

trolley to the various locations. The tool box kit has a box spanner

kit, DE Spanner kit, ring spanner kit, 6”, 8” or 12” Slide wrenches,

short pipe lengths for applying leverage for tightening, screw driver

kit having flat head and star head, allen key sets, ball peen

hammer, oil can and grease gun. The tool kit trolley and its

contents are kept in the stores.

3 Checking Belt Tension & Tightening/Changing

• Fenner Company markets a tensiometer for checking the tension

of the V belts. This is a small hand held instrument with a

telescopic attachment which when pressed on the belt at the

centre of the span, gauges the looseness and the reading is

registered on the meter.

• All the V belts are tested similarly on the same set of pulleys.

• This will give the correct tension to be maintained, but also

gives the indication when the belts need to be changed. The

belt tension is adjusted by loosening the motor base bolts

and the motor moved backward or forward by tightening or

loosening the jack screws on the slide frame. After obtaining

the correct tension as indicated by the tensiometer, the



7

alignment of the pulleys is checked by holding a straight

edge on the faces of the pulleys.

• In case the centre to centre distance of the pulleys is large

then a twine is used and alignment done by ensuring the

twine touches at all four points on the faces of the pulleys.

If alignment is improper, then the belts will wear out on one

side and threads on the belt start coming out.

4 Vibration Monitoring of Rotating Equipments

• In most units vibration is monitored by placing ones fingers

on the base of the gearbox or motor.

• An improvement on this is by placing a long screw driver

steel portion on the base and an ear on the handle. This will

indicate if there is a vibration or not and also if there is an

abnormality in the bearing.

• This principle is utilized in the digital vibrometer which is

permanently connected to the base of critical equipment.

This on-line monitoring accurately indicates the exact time

when maintenance is required on the equipment.

• The cause of vibration is investigated, which could be

bearing damage/ wear out, bend in shaft, or misalignment.

The cause is attended to and eliminated.

• In case online Digital vibrometer is not permanently installed

then portable Vibration Monitoring equipment could be used

which measures overall Amplitude & records vibration

signature, has Data logging & Down loading facility.



8

5 Alignment checking of Motors & Gearbox

• If it is noticed that the coupling halves are wobbling on

rotation then the realignment of the motor and gearbox has

to be done.

• During the first available stoppage the motor is stopped and

a shutdown taken on the drive.

• The coupling bolts are taken out and if it is a gear coupling

then the cover halves are pulled back to expose the gear

halves.

• The grease on the couplings is cleaned using cloth rags and

kerosene.

• The gaps between the gear coupling halves are measured at

the top and bottom as well as laterally of the diameter using

feeler gauges or machined flat pieces of 6 -10mm depending

on the size of the gear couplings. If the gaps are different

then realignment is carried out by adjusting the position of

the motor.

• The base bolts of the motor are loosened and the front or

rear of the motor is lifted by a lever until the gaps are

uniform at top and bottom.

• The requisite shim plates of brass are inserted between the

motor base and the base frame and the bolts are tightened

and the gaps are rechecked and the process repeated if

different.

• Similarly the sideways alignment is also checked and

corrected.



9

• Now a dial gauge mounted on a circular clamp around the

gearbox coupling half is used by rotating the motor coupling

half. If the stylus of the dial gauge shows different readings,

the final alignment is done as per the above procedure.

• In many motors, jacking screws are provided on the motor

base itself to lift or lower the front or rear of the motor. The

process is repeated until the dial reading is steady.

• The gearbox coupling half is now rotated by 900 and the

procedure repeated.

• It must be noted that the life of the bearings and gears

depends on how accurate the alignment is, hence time for

alignment and effort expended should not be a criterion for

leaving even a slight misalignment.

6 Lube Oil Condition Monitoring

The Condition of the Lube Oil used for lubrication can be

monitored with the help of portable Lube oil Test Kits in which

physio-chemical tests such as Viscosity Index, Moisture content,

Mechanical impurities and Wear Debris Tests like Ferrography, PQ

Test, SOAP are carried out to ascertain if the Lube Oil needs

changing or any centrifuging.

7 Infrared Thermography

Infrared Thermography (IRT) is a very versatile NDT (Non-

Destructive Testing) procedure that can be utilized in the SRRM

units for carrying out a host of diagnostic tests on various

equipments/parts of the unit using one portable instrument like:

a) Non Contact type temperature measurement based on IRprinciple.



10

b) Thermal Insulation Condition inspection of RHF, pipes etc.

c) Mechanical inspection of Bearings, Pumps, Gear Boxes,Motors etc.

d) Monitoring of Hot spots in Electrical power distribution

system (all contact terminals, transformer bushing,

conduction stands etc).

Thermography technique takes very less time for inspection

of equipment and involves easy identification &

interpretation from colour thermal image of the scanned

equipment.

For operating IRT instrument, data logging, interpretation of

Data & images, trained personnel from ITI who have

attended NDT Courses offered by them would be needed.

An Inspection Report is prepared on-site summarizing any

needed repairs or other Maintenance Action to be initiated

by the Maintenance group.

Once the problem has been identified and if the solution is

external then immediate resolution is done and if internal,

the problem is tackled at the first shut down opportunity.

1.2.4 Proactive maintenance

While predictive maintenance uses online condition monitoring to help

predict when a failure will occur, it doesn't always identify the root

cause of the failure.

That's where proactive maintenance comes in. Proactive maintenance

relies on information provided by predictive methods to identify

problems and isolate the source of the failure. It is a maintenance done

to eliminate the Root cause of frequent repetitive breakdowns on same

equipment.



11

Take the case of a pump that has periodic bearing failures. A condition-

monitoring program may apply vibration sensors to the bearings, monitor

the bearing temperature, and perform periodic analysis of the lube oil.

These steps will tell when but not why the bearings are failing.

Proactive maintenance might add laser alignment and equipment

balancing during installation to reduce bearing stress, lowering failure

rates and extending bearing life. But it will also take the next step to

find the sources of failures — for example, looking at cleaning

procedures before tear-down to see if contamination during rebuild is a

root cause for early bearing failures.

By determining these root causes and acting to eliminate them, one cannot only prolong the life of the equipment, but also eliminate many

seemingly random failures — and avoid repairing the same equipment for

the same problem again and again.

1.2.5 The Right Maintenance Mix

A typical SRRM generally uses a combination of Preventive, Predictive &

Reactive approaches. The approach used for a particular piece of

equipment is determined by the following factors:

• Criticality of equipment/process

• Safety and environmental issues

• Cost/Profit

Figure 1.1 shows that SRRM units in general over-depend on Reactive

maintenance (46% share), followed by Preventive Maintenance practice

(40% share) and under-utilize predictive maintenance (14% share). The

result is higher reactive maintenance and an increased overall cost.



12

Figure 1.1

Maintenance Practices adopted in typical SRRM units & Best Practices

Predictive maintenance is generally 10-15% of the maintenance activities

in a typical plant. Ideally, this figure should be close to 50% followed by

Preventive Maintenance (25%) & Reactive Maintenance (25%). Predictive

maintenance is under-used because it is perceived as too expensive. This

is because the range of tools available is not understood, or plant

maintenance personnel are "too busy" to implement predictive

techniques.

These perceptions are incorrect. Many field instruments, for example,

have diagnostics built in. Predictive maintenance can be conducted on

them at a minimal cost. In addition, advances in technology are reducing

the cost of monitoring required for predictive maintenance in equipment

such as rotating equipment.

Finally, smarter diagnostic software is reducing the human analysis

needed to diagnose equipment health in equipment such as valves and

process equipment. These factors combine to make predictive

maintenance surprisingly cost effective.



13

1.3 MAJOR MAINTENANCE TOOLS REQUIRED

1.3.1 The major maintenance tools required are:

A) Mechanical Tools

i) EOT Crane/Chain block Pulley for lifting heavy machines

ii) For bolt/belt tightening & changing : different sizes of RingSpanners; socket head spanners, torque wrenches

iii) For greasing, hand held grease gun or pneumatically operatedgrease gun

iv) For oiling, oil cans with a long spout or hand held oil pumpdispensers

v) Misc. tools like Double Ended Spanners, Screw drivers, Allen keysets, ball pen hammer, Bearing Extractors, Punches, Inside &

Outside Circlip Pliers, short pipe lengths, Work table with SteelTop & a Bench vice and Pipe vice fitted firmly etc.

vi) 6mm to 12 mm hand drilling machines

vii) Electric Hand grinders

viii) Rotary burr machines

ix) Safety Belts

B) Measuring/Monitoring Tools

i) Vibrometer for measuring vibrations in Bearings of Gear

box/Motors.

ii) Tachometer for measuring Motor RPM

iii) Ammeter & KWH Meter for measuring current & power consumedby Electric Motors

iv) Multimeter for checking Electrical Instruments mounted onControl Panel

v) Tensiometer for checking tension of V belts

vi) Feeler gauges, dial gauges for alignment checking.

vii) Megger for checking Motor winding Instrument

viii) Infrared Thermography

ix) Oil Test Kit for FO, Lube Oil, DG Set Oil, Transformer oil etc.



14

C) Safety Hardware

i. Safety overall (dungarees)

ii. Safety Boots with steel toe caps

iii. Safety Boots with steel toe caps & rubber soles for electricians

iv. Safety Helmets

v. Safety Hand gloves with leather palms

vi. Blue goggles for welders

vii. Plain glass goggles

viii. Leather elbow length hand gloves for welders

ix. Asbestos elbow length hand gloves for working at or near RHF

x. Asbestos shin protectors for working at or near RHF

xi. Rubber handgloves for electricians

xii. Safety belts for working at heights

xiii. Hand tool belt pouch for fitters for slide wrench, pipe spanner &allen key set

xiv. Hand tool belt pouch for electricians for slide wrench, screw drivercum tester

xv. Gumboots for working in water logged areas

1.3.2 Description of a few Monitoring Instruments

a. Belt Tensiometer

The Belt Tensiometer accurately measures the static tension of flat, V

and ribbed belts of rubber, leather, fabric and composite materials by

measuring the natural frequency (Hz) of a segment of the belt that has

been tapped and then converting it into tension units of Newton (N) or

pounds force (lbf).

The instrument uses a pulsed ruby red light source to measure the

natural frequency of the vibrating belt and is not affected by ambient

noise, providing quick reliable results in all production and field

applications.



15

Features

Includes two (2) separate Sensors – a plug-in type for one-handed operation and a cable-connected type for measuringbelts with limited access space

Compact, easy-to-use design

Readings unaffected by nearby magnetic fields or noise

Displays tension in Newton (N) or pounds force (lbf) or naturalfrequency in Hertz (Hz) – selectable

The Belt Tensiometer & its Application are provided at Figure 1.2.

Figure 1.2: Belt Tensiometer & its Application

b. Vibrometer

The Digital Vibrometer (shown at Figure 1.3) accurately measures the

vibration in the bearings of Gear Box, Motors and gives advance

indication of an impending breakdown

Detailed Technical specifications of Hand-held digital Vibrometer are

provided below:

Technical Data

Vibration Sensor Piezoelectric Accelerometer 100 mV/g

Display 3.5 digit LCD with measurement, Hold andLow Battery indicators

Range Acceleration: 0.01 to 19.99 g (RMS)

The belt tension, or vibrating

frequency, should be measured nearthe mid-point of the longest free belt

span between drive pulleys.



16

Velocity: 0.01 to 19.99 in/sec (RMS)199.9 mm/sec (RMS)0.20 to 500 mm/sec (RMS)

Frequency Range Overall: 10 Hz to 10 kHzEnvelope: 0.5 kHz to 10 kHz

Output Audio (3.5 mm) mini plugSensor Power: 12 vdc @ 2mA

Power (2) Alkaline "AA" batteries

Operating Time 20 hours continuous

Weight 1.30 kg for complete kit

Dimensions 152 x 83 x 32 mm

Operating Conditions -10 to 500C

Figure 1.3: Digital Vibrometer

c. Thermal Imaging Infrared Camera

The Infrared Camera (shown at Figure 1.4) provides detailed thermal

images of hot spots and minor variations in temperature that can



17

signal electrical or moisture problems. The Infrared camera is designed

as a non-intrusive condition monitoring and diagnostic tool. The

thermal imager features storage of 1000 thermal hotspot images to SD

card, 2% high accuracy, 3.5" LCD color display and a laser pointer.

Thermal Imaging Camera Specifications:

Temperature Range -10°C to 350°C

Image Storage 1000 Images (SD Card Memory)

Emissivity 0.1 to 1.0 (Adjustable)

Field of View/ Min FocusDistance

25° x 25° /0.3m

Thermal Sensitivity (NETD) <0.12°C at 25°C

Detector Type Focal Plane Array (FPA) Uncooled

Microbolometer; 120 x 120 PixelsSpectral Range 7.5 to 13µm

Display 3.5" Color LCD

Video Output MPEG-4 via USB

Image Controls Palettes (Iron, Rainbow andBlack/White), Level Span, AutoAdjust (Continuous/Manual)

Set-up Controls Date/Time, Info, LCD intensity,Power Down

Laser Classification Class 2

Laser Type Semiconductor AlGalnP Diode Laser:

1 mW/635nm (red)Measurement Modes Spot, Area, Min/Max

Battery Type Lithium-Ion

Battery Operating Time 7 Hours, Display Shows BatteryStatus

AC Operation AC Adapter 90VAC to 260VAC,50/60Hz 12 VDC out

Voltage 11 to 16 VDC

Operating Range Temperature: -15°C to 50°CHumidity: 20% to 80%, non-condensing

Storage Range Temperature: -20°C to 70°CHumidity: 20% to 80%, non-condensing

Shock 25G, IEC 68-2-29

Vibration 2G, IEC 68-2-6

Weight 235 grams

Dimensions 200mm x 140mm x 95mm



18

Thermal Imaging Camera Applications:

Detection of Hot Spots, avoiding Electrical and Mechanical Failures

Monitor Load Imbalances and Overheating of Wires and Cables

Shaft Imbalances, Worn Bearings, and Impeller Damage in Pumps

Checking the Integrity of Cable Fixings (Loose Connections) on HighVoltage Jumper Cables

Inspection of High Voltage Connectors

Checking for Loose Connections and Intermittent Faults on RelayPanels and Terminal Bars

Monitoring Motor Temperatures around Bearing Casings on Blowers

Figure 1.4: Hand Held Thermal Imaging Infrared Camera

d. Oil Condition Monitoring Kit

The Kit (shown in Figure 1.5) is used to carry out condition tests on

Lubricating oils, FO, Transformer Oil etc including viscosity density,

moisture content, other impurities etc.



19

The Specifications of Standard Oil Testing kit and Test specifications

are provided bellows:

• Dimensions 76.5 x 76.5 x 43 cms

• Operating Temp 0-40°C

•

Power 240 VAC

• Weight 49 Kgs

• Overview of Test Specifications

Test Range CalculationsTypicalAccuracy

Correlation

Viscosity(Heated)

15-810 cStat 40°C and50°C. RMA10 to RML

55 SAE 5 to50

cSt at100°C.CCAI.Density 50

to 15°C invacuo

+/- 3% (15-450 cSt)

ASTMD445/ IP71

Density800 to 1010kg/m3 at15°C

DensityKg/m3 at15°CinvacuocPto cSt,CCAI.

+/- 0.1%ASTMD1298/1P160

CompatibilityAs per ASTMD 4740

1 rating in20 repeat

ASTMD 4740

Water

0-1%, 0-10%, 0-20%,1-10,000ppm.

+/- 0.1%

(on 0-1%range),+/- 1000ppm (0-10,000ppm), +/-1% (0-10/20%ranges)

TBN5 – 50mg/KOH.

+/- 5% IP 400

Insolubles0 - 3.5%w/w.

+/- 0.1%IP 316Mobil SootIndex

Salt N/AGo / NoGo

Pour Point 0 - 50°C +/- 6°CASTMD97/ IP15



20

Figure 1.5: Oil Testing Kit

1.3.3 Reliability-based maintenance

Reliability-based maintenance is a comprehensive strategy to cut costs

by balancing preventive, predictive, and proactive maintenance. It

identifies critical equipment assets, and then uses monitoring and

diagnostic technologies to reduce failures and increase availability.

There are agencies that offer a complete range of reliability-based

maintenance solutions that include online and route-based equipment

monitoring, data management, data analysis, and reporting for

maintenance of electric motors, pumps, fans, compressors, turbines,

gear boxes, and other mechanical equipment.

These solutions include AMS Machinery Manager Software, which

supports predictive maintenance through diagnostic technologies such as

vibration analysis, infrared thermography, oil analysis, ultrasonic

scanning, and motor diagnostics. It also helps provide longer operational

life through support for maintenance tools such as equipment balancing



21

and laser alignment. Together, these technologies provide a complete

picture of mechanical equipment health in a plant.

AMS Performance Monitor complements these capabilities by providing

Internet access to information on the operating performance of Rolling

Mills Motors, gas turbines, steam turbines, compressors, pumps, and

other mechanical and process equipment. It provides early notification

of deteriorating performance, enabling timely preventive and corrective

action. It also helps determine when maintenance should be scheduled

to extend run times and maximize throughput.

1.4 CRITICAL EQUIPMENTS INSTALLED,THEIR SPECIFICATIONS &

SUGGESTED MAINTENANCE TYPE TO BE ADOPTED

1.4.1 Re-Heating Furnace

The List of Critical equipments/Parts of a standard 15 TPH CapacityPusher type furnace, their Specifications and suggested Maintenance typeto be adopted have been provided at Table 1.1. In addition Specificationshave also been provided for different fuel systems i.e. FO, PulverizedCoal firing system & Producer Gas generator and also Walkingbeam/hearth furnace & Hydraulic systems as additional options formechanical systems.

1.4.2 Rolling MillThe List of critical equipments/Parts of a standard 15 TPH capacity crosscountry type rolling mill, their specifications and suggested Maintenancetype to be adopted have been provided at Table 1.2.



TABLE 1.1: LIST OF CRITICAL EQUIPMENTS/PARTS INSTALLED IN RHF OF 15 TPH CAPACITY, THEIR SPECIFMAINTENANCE TYPE TO BE ADOPTED

S.No.

Critical Equipment/Partinstalled

Broad Technical Specifications

1 Pusher Type: Gear Box operated Electro-Mechanical, 40 T Stroke: 1000 mm, Cycle time 170 secs. Motor: 40 HP- AC 3 Phase Induction type, 1480 RPM Row Charging: Single Worm reduction gear box with 200 mm dia Screw & nut and 21:1

reduction ratio.

2 Refractories

A. On side walls High Al2O3 (70%) +HFI + CFI Total Thickness: 460 mm

B. On Hearth For Hearth : Fusion Cast 80% Al2O3 Bricks (250mm Thick) Bottom Two layers are 75 mm thick IS8 firebricks & 230 mm CFI

bricks.

C. On roof High Alumina + HFI + Blanket + ACC Powder Total thickness: 300 mm

3 Soaking Zone Burners Mounted on the End wall at discharge end Number of Burners: 4, 100 mm Dia Type : Hot Air (4500C) Luminous Flame Capacity : 50 lph Air Pressure : 2-3 kg/cm2 Air/Fuel ratio controller-Ratiotrol, turndown ratio: 1:7

4 Pre Heating & Heating ZoneBurners

Mounted either on each side wall or on raised wall with endfiring or both

Number of Burners: 12,100 mm Dia Type : Hot Air (4500C) Luminous Flame Capacity : 50 lph Air Pressure : 2-3 kg/cm2

Air/Fuel ratio controller-Ratiotrol, turndown ratio: 1:75 Ejector Water cooled Mechanical Ejector-Externally cooled

100 mm x 100 mm billet driven by Pinch Rolls



Motor : 15 HP- AC 3 Phase Induction type, 1480 RPM with G/Box. 6 Door Operating Mechanism Mostly Manual opening/closing of Doors

Door operating Hand winch

7 Recuperator Shell & Tube Type, Single/Double Pass, with SS Tubes.

8 Chimney Height : 30 m Diameter: 2.2 m Lining : Unlined mostly

9 Instrumentation & ControlSystem (including PC-PLC)

Control Panel consisting of Ammeter, voltmeter, Power meter,PF meter, Temperature Indicators cum Controllers for 3 Zones ofFurnace, RPM motors for Motors, gauges for oil pr, Temp & flow,Combustion air pr & flow meters. All Instruments Manuallycontrolled (On/Off Type)

PID, PLC only in larger capacity (30/40 TPH) RHF to controlFurnace Temp, pr, fuel consumption.

Thermocouples : 2x R Type Pt - PtRh 13% for 1350 oC & 4 x KType chromel Alumel for 1000 0C temperature measurement in

furnace & recuperator. VFD for oil pumps & Blower Motors

10 Fuel & Air Flow Piping System The Hot Air Piping (100 mm Dia) is lagged with 75 mm thick slagwool blanket covered with galvanized steel cladding.

The FO, piping (100 mm Dia) is lagged with 50 mm thick slagwool blanket covered with galvanized steel cladding.

11 Control Valves & Actuators Gate & Globe valves (100 mm dia) installed on Fuel line &Butterfly valves on Airline (100 mm dia), with mostly manualcontrol

Actuators: Electrical type provided to automatically actuate(open/close) Valves on Air & Fuel lines & Damper in select SRRM.

12 F.O Heating and Pumping Unit Duplex System having Two Oil Gear pumps with VFD of 15 K.Wcapacity each, one oil heater of 45 KW.

Primary & Secondary oil filters

Oil Flow rate: 600 lit/hr Oil pressure: 5 kg/cm2

13 Pulverized Coal Firing System Coal Pulverser: Pulverises Coal lumps (37-50 mm size) into fine



Powder (150-200 Mesh Size) of 1.5 TPH Capacity. Storage Hopper: 27T Capacity Coal Powder Dispenser: 1x 1000 kg/hr & 1 x 500 kg/hr capacity

Air Blower : 40 HP, 2960 RPM with VFD

14 Coal /Biomass based ProducerGas Generator

Moving bed Updraft Gasifier operating at atmospheric pressure,using Air as gasifying medium

Fuel Size: 20-200 mm for Biomass & 25-75 mm for Coal. Capacity: 5 million Kcal/hr output Producer gas pr: 1.5-2.5 kg/cm2, Temp: 9000C

15 Combustion Air Blower Capacity : 2960 Nm3/hr Delivery pressure : 1000 mm Motors: 2 Nos, each 40 HP with VFD (80 HP total)

16 Hydraulic System as an optionfor Pusher & Ejector operation

2 x 200 mm ø, 1700 mm stroke Hydraulic cylinder @ 140 kg/cm2Pressure

17 Hydraulic System as an optionfor W.H/W.B furnace

Hydraulic power pack complete with variable volume pistonhydraulic pump & motor, filters 150microns, solenoid operated

hydraulic 3-position valves, pressure regulating valve, unloadingvalve

18. Furnace Shell – Pusher HearthRHF

Made of steel plates of 10 mm thickness Length: 15 m Outer width: 4.3m Height : 3 m

19 Collecting Bed 8 m x 3m with four slide rails

20 Flue Gas Ducting 45 % Alumina Refractory Lined



TABLE 1.2

THE LIST OF CRITICAL EQUIPMENTS/PARTS OF A STANDARD 15 TPH CAPACITY CROSS COUNTRY TYPE ROLLINGTHE SUGGESTED MAINTENANCE TYPE TO BE ADOPTED

S. No. Critical Equipment/Part installed Broad Technical Specifications

1. Roughing Mill • 22” Mill complete with AC drive motor of 1350 HP, 760RPM, Squirrel Cage Slip Ring Induction Motor, reductiongear box 1:6 reduction ratio, pinion housing with threeoutput shafts, 3x three high Rolling Mills stands with22” Dia rolls mounted in fibre bearings in 1st Stand, andantifriction bearings in other stands, 6 T weight CastSteel Fly wheel installed between Mill Motor &reduction gear box.

• Pred

• Prev

2. Intermediate Mill • 14” Stand as above complete with 850 HP Squirrel CageSlip Ring Induction AC Motor, reduction gearbox, pinionhousing and five stands in two groups, 1st group of 3

stands and then a speed increaser and 2 more standsafter that.

• Pred

• Prev

3. Finishing & Continuous Mill • 12”/ 10” Stand train with 3 stands in Finishing Millwhich are driven by a single AC motor of 450 HP

• 2 more stands in the continuous mill drivenindividually by DC motors of 250 HP capacity each.

• Pred

• Prev

4. Mill Rolls • Alloy Steel, SG Iron, Chilled CI etc. • Pred

• Visu

5. Reduction Gear box • Torsion proof rigid steel fabricated body

• Case hardened & ground En 24 pinion spur gear &En 8 helical gears

• Splash/Forced lubrication

• Pred

6. Pinion Gear Box • 3HI, High Speed

•

Torsion proof rigid steel fabricated body• Double helical gears made of EN-19 Quality Steel

with roller bearings.

• Pred



7. Mill Housing • Mostly Top cap opening type to enable changing ofrolls vertically using EOT crane.

• Pred

8. Mill Stands • CI or Fabricated MS Steel Stands with screw down

mechanism and steel chocks.

• Pred

9. Roll Neck Bearings • Spherical Roller Anti friction bearings or Fibre bearings • Pred

10. Gear Couplings • Gear Coupling (Flexible type) made from forged steelinstalled between Motor & flywheel; Flywheel &Reduction gear box; Reduction gear box & Pinion GearBox.

• Pred

11. Spindles & Couplings • Each Set of Spindle & Coupling will consist of 1 spindle& 2 Coupling heads.

• Spindles made of EN8 Steel & Universal type Couplings.

• Pred

12. Repeaters • Steel fabricated oval and square repeaters & pipe

nozzles.

• Pred

13. Roller Guides • Cassette/mounted roller guide box: Cast Steel Boxwith leaf springs, rocker rollers entry guides,lubricating & water cooling system.

• Friction guides (open/closed)

• Prev

14. Roller Tables • Roller Tables of fabricated MS, with seamless pipes forrollers driven in groups of 8 to 12 rollers at each table,driven by a single motor of 15-20HP for each groupthrough V-Belts or Sprocket and Chains

• Prev

15. Tilting/Y-Roller Table • The tilting tables are roller tables as described above.Each tilting table is hinged at one end and lifted by aPneumatic Cylinder at the other. The tilting table isfitted with a balancing mechanism. In some Units thetable is lifted by an overhead motorized winch. The table

has to be tilted to take the bar up to enter the passbetween the middle and top roll. Y- Roller table takesthe bar through a sloping platform to the upper pass. The

• Prev



roller table rollers are skewed to take the bar to the Y-Table in front of the sloping platform.

16. TMT System • This is for martempering the steel bar through controlledcooling of the bar through water sprayed under pressure.The hot bar at about 850

0C is cooled down to 350

0C.

• Pred

17. Front & End Cropping Shears • Swivel type rotary shear with which is on a movable trayactuated by pneumatic cylinder which brings the housinginto the rolling line and out of it after the cutting is over.(Front & End cutting).

• Pred

18. Flying Shear • This shear is provided in TMT bar mills, has a pinch rolland cuts material on the fly.

• Pred

19. Cut to Length Shear • This is a fixed type rotary shear with 400 mm dia cuttingwheel of H11 grade mounted on the machine.

• Pred

20. Cooling Bed • A long bed of structural steel (about 30 m length) with airgaps in between to cool the finished bars for furtherbundling and dispatch. The cooling bed is mostly W-channel type.

• Pred

21. Hydraulic/Pneumatic Systems • Pneumatic system for end crop shear, flying shear, TiltingTable operation

• Prev

22. Instrumentation & Control System(including PC-PLC)

• Automation of end cropping shears, TMT water system,Flying Shear, Capacitor loading/unloading for powerfactor improvement.

• Thyristor control for regulating speed of AC main milldrive motors.

• VVF Drive for Control of Finishing Mill Motor Speed.

• Pred

23. Electrical Power Supply & DistributionSystemHT & LT Capacitor Bank

• The 3 Phase power supply at 33/ 11/ 6.6KV is receivedfrom the State Electricity Board (SEB) and distributedwithin the factory by the Units. The incoming powersupply is first metered by the SEB (through CT/PTMetering unit) before being taken into the system’s step-down transformers (About 4 Nos.). Each Transformer isnormally of about 1000KVA at 440 V load and all Main ACMotors, utilities and lighting loads are sourced from this.The power cables are taken from the transformers into aMain distribution panel, which in turn has leads to allauxiliary drives and their individual panels. Each panelhas essentially the following instruments:

• Pred



a) Ammeter/ voltmeter, RPM Meter & PF meterb) KWH meter

• HT Capacitor Banks- About 350 KVAR each, installed tocontrol PF of main Motors of Roughing, Intermediate,Finishing Mills.

• OCB’s & ACB’s for every transformer circuit.

24. Centralized Oil lubrication system • Each of the main mill motor to g/box to pinion housingis served by a centralized oil lubrication System. Eachcentralized system has its own reservoir of 1500 litrescapacity, two pumps (1 running and 1 standby) of 15HPeach, Coarse and fine filters for oil(Strainers), Shell &Tube Type heat exchanger to cool the oil, and pipingto transport the oil from the CS to the gearbox nozzlesand back to the tank by gravity flow.

25. Cooling Water system • The roll cooling water gets hot during the process. TheHotwell collects the return water flowing by gravityfrom the roll stands. The water is pumped from the

recirculation tank to the stand cooling water headers.The pumps are normally 3 Nos of 40 HP each.Additionally there is a separate cooling water tank forthe TMT system since the quality of water is farsuperior and also the pumping pressure is higher (7.5 –10Kg/cm2).

26. Major Auxiliary Motors a) Pinch Roll Motor (2 x 60 HP)b) Shear Motor (1 x 60HP)c) Tail Breaker Motor ( 2 x 60 HP)d) Hotwell Motor ( 3 x 25 HP)e) Conveyor (Roller Table )Motor ( 4 x 10 HP)f) Cold Shear Motor ( 1x 30 HP)g) End Cutting M/c Motor (2 x 10 HP)

h) Notching M/c Motor (1 x 15 HP)i) EOT Crane Motor ( 2 x 30HP)



29

1.5 HISTORY CARD FORMAT

The Format for History Card to be maintained with respect to maintenance of

the critical equipment & its sub component is provided at Table 1.3 with RHF-

HPU-Pump Motor; RHF-HPU-Gear Pump and Roughing Mill- Mill Drive-Pinion TopGear as typical examples.

TABLE 1.3

FORMAT FOR HISTORY CARD

Department Rolling MillsEquipment Reheating

FurnaceLocation

Cost Centre 401 Item Code 401 001

Component HeatingPumping Unit

Sub Component Pump Motor

Date ofPurchase

Supplier Name

Specifications: -- HP, InductionMotor, 1440RPM,TEFC

InstallationDate

Renewal /repair Date

Reason forrenewal/ repair

Burnt/ bearingseized/other

Department Rolling MillsEquipment Reheating

FurnaceLocation


Component HeatingPumping Unit

Sub Component Gear Pump

Date ofPurchase

Supplier Name

Specifications: -- HP, 1440RPM, --

litres/sec, 10kg/cm2

InstallationDate



Low pressure/bearingseized/other



30

Department Rolling MillsEquipment Roughing Mill

Pinion HousingLocation Roughing Mill

Drive


Component Roughing MillDrive

Sub Component Pinion Top Gear

Date ofPurchase

Supplier Name

Specifications: -- HP, 120 RPM,double helical

InstallationDate



Gear toothdamaged/ bearingseized/other

1.6 MANPOWER FOR MAINTENANCE

To fulfill the Maintenance Schedule, there has to be separate skilled staff

dedicated for this purpose. A typical Maintenance group will consist of

fitters, pipe fitters, bench fitters, welder-cum-gas cutters, and riggers.

Nowadays the Machine operators have been trained to deal with most of the

preventive Maintenance issues, like visual inspection, daily lubrication, bolt

tightening etc. This is known as Autonomous Maintenance. Where specialized

attention is required, the specialized Maintenance group is given the task.

The Manpower has to be trained in the operation of the equipment and its

functions to obtain a better understanding of the needs of the operating staff

and the product. Maintenance Staff should definitely be ITI trained workers

with intimate knowledge of their field of specialization. Workers already on

the rolls of the Unit should be made literate and be able to fill in the forms,

read drawings and trained to analyze. By following the principles of

Maintenance like Predictive and Total Productive Maintenance the Unit can

be assured of 100% availability of equipment its full efficiency, and the cost

of Maintenance would not exceed 3% operating cost.



31

1.7 CASE STUDY:

Replacement parts of machinery should be from best technologically sound

materials of manufacture. E.g. If a pinion shaft of a reduction gearbox is

broken, the replacement should be made with one from En 24 steel, forged

down from an ingot of size that is six times the area of the final shaft

diameter. The shaft should be annealed and normalized prior to machining to

remove all stresses that would develop during proof machining, then the

proof machined shaft is hardened and tempered to obtain 280 -300BHN

hardness and finally the shaft is ground finished. The total cost of a pinion

shaft manufactured as above would be around Rs 250 /kg as against another

pinion gear shaft made from the same En 24, with a reduction ratio of 1.5

that would cost around Rs 70 /kg. The life of the first shaft would not be less

than 5 years whereas the life of the second would not exceed 6 months under

the same conditions of loading. This means that 10 such shafts would have to

be changed for each properly manufactured shaft. The number of hours of

outages in the mill @ Rs 75000* per hour is to be included in the cost of a

spurious product. The consequential damage to other mating gears in the

reduction gearbox has not been taken into account or the damage to the

products already on the production line. So it is wise economics to spend alittle more on a superior product than a spurious product.

*Considering production rate of 15tph and margin @ Rs 5000 per tonne

Such cost benefit analysis should be carried out for each and every purchase,

including capital purchases.



32

CHAPTER 2

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCEPRACTICES ADOPTED FOR RHF

2.1 MECHANICAL & ROTATING EQUIPMENTS

2.1.1 Major Equipments/Parts

The critical RHF –Mechanical & Rotating Equipments/Parts coveredinclude:

• FO-HPU

• Burners

• Blowers

• Motors

• Bearings

• V belts

• Pusher

• Doors & Door operating Mechanism

• Ejector

• Extractor

• Recuperator

• Chimney

• Flue Ducting

• Fuel & Air piping and valves

• Walking Beam Mechanism

• Hydraulic systems

• Collecting Bed



33

2.1.2 Major identified Preventive & Predictive Maintenance Practices

The Major identified Maintenance practices to be adopted for CriticalRHF- Mechanical & Rotating Equipments include:

A. Preventive

Periodic Oiling & Greasing

Cleaning

The quantity of Bearing Re-Greasing requirement (in gm) isCalculated by: 0.005 x Bearing ID (mm) x Bearing Housing Width(mm)

B. Predictive

Visual Inspection

Inspection of Bolts for looseness/corrosion and tightening /

changing

Condition Monitoring of Various Critical parts & taking necessarymaintenance & repair work to prevent breakdown & enhancereliability like:

• Monitoring Vibrations of Bearings of all rotating equipments likeGear box, Motors, Pumps, Blowers etc using Vibrometer.

• Checking Electric motor performance using Ammeter, PowerMeter, Megger, Tachometer, with respect to current drawn;power consumed; rpm and condition of Insulation.

• Checking of Proper Alignment of all Shafts, Couplings, andBearings etc. of all rotating equipments using gauges. Anadvance Technique of Laser Alignment is also available foraccurate alignment of all rotating parts/equipments.

• Testing Belt Tension of Electrical Drives with the aid ofTensiometer & Belt Tightening/Changing.

• Testing of Furnace oil condition using Oil Testing kit.

• Infrared Thermography-Scanning of all critical parts foroverheating due to malfunctioning including motors, bearingsetc.

• The acceptable level of Bearing Temperature rise aboveambient temperature is calculated by :

ΔT (0F) = {Bearing ID (in mm) x rpm)}/2000

The Standard recommended Preventive & Predictive MaintenancePractices to be adopted for Critical RHF-Mechanical & RotatingEquipments are detailed at Table 2.1.



TABLE 2.1

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES FOR RHF- MECHANICAL & ROTATI

Type of MaintenancePreventive(Periodic

Maintenance)

Predictive(Condition Monitoring &

Maintenance) SL No Critical Equipment/part O- Oiling

G- GreasingCl- Cleaning

V -Visual InspectionC – condition monitoring using

instrumentsBT- Bolts Tightening/changingBeT- Belts tightening/changing

Maintenance Process

1. FO - HPU

a Oil Pump & Heater

V

• Monitor oil pump for pressure development,temperature from gauges.

• Change if pressure is below 5 kg/cm2 or temheater is on does not rise to 100 degC.

b Oil filters

Cl

• Close the flow of oil to the filter by operatin

on the filter housing.• Unscrew the flask from the housing and take

Soak it in a can of diesel or kerosene. Blow coutside and bottom of element.

• Fill the flask with clean fuel oil, refit the elehousing and screw up the flask into the hous

• Repeat the cleaning of the other filter elemfine filters.

• Open the oil flow valves to and from the filt

c. FO Condition √ C

• The condition of FO is monitored using oil Timproper it is centrifuged/changed .

2. Burners Cl • Dismantling & Cleaning - remove central maburner, soak it in a tray of diesel oil or kerothree hours.

• Scrub with a soft brass/ copper brush and cl

burnt carbon. Clean the oil groove with thin• Blow dry with compressed air. Re-assemble

tighten the mandrel nut.



3. Blowers

a ImpellerV

• Monitor for proper functioning, corrosion, enecessary

4. Motors(Pusher, Ejector, OilPumps, Air Blowers etc.)

√ C

• Monitor the current drawn by the motor by AConsumed by Power Meter & RPM by Tachomhigh, the motor is checked for bearing lubricwinding insulation failure or weakening.

• The winding insulation is checked with a mevarnish is applied to the windings if found w

• If damaged then the motor is changed and tfor rewinding. Use the same gauge of copperewinding. After rewinding a coat of varnishin an oven before re-assembly.

• Mechanical Inspection of Motors by IRT

• Alignment Checking using gauges and realign

5. Bearings of Motors, Shafts G

√ C

• Monitor the vibrations with vibrometer.

• Monitor bearings for undue temp. rise by IRavailable otherwise by hand feel.

• The bearings are greased.

6. V-Belts VBeT

• V belt tension checked by Tensiometer and adjusting the motor position on the slide fra

7. Pusher

a Screw & Nut Mechanism G

V

• Monitor the movement of the screw, nut & gchange if necessary.

• Apply grease to the working lengths of screwguide bushes.

b Gear Box O

V

• Monitor the g/box for excessive play in gearshafts move more than 4mm). Adjust the plaChange the gear pair if play redevelops with

• Monitor the oil level in g/box, change the oi

detected.• Check Alignment with Motor.



8. Doors & door operatingmechanism V

• Monitor the doors for refractory and patch aMonitor the door operating mechanism and found necessary.

9. Ejectora Ejector mechanism (Pinch

Roll, Gear Box, CoolingWater)

V √ C

• Monitor the Pinch roll wear, spring tension, ejector bar straightness and repair/replace

• Check Alignment of Motor & Gear Box & rea

b Ejector Gear BoxLubrication

OV • Check and top up oil in g/box

10. Extractor

GV

• Check and top up oil in g/box

• Monitor the rotating table mechanism and lubushes

11.

Recuperator

Cl √ C

• Close the damper on the exit from the furnacethe damper for the chimney.

• Open the bolts of the inlet & outlet piping of tremove the piping. Lift out the recuperator wderrick.

• Blow the tube interstices with compressed airwash around the tubes. Clean each and every outside with compressed air through nozzles.

• Check for leakages and repair by welding if acthose tubes.

• If leaking tubes exceed 10% of total tubes, therecuperator and open out the top and bottomcutting at the root of the pipes, repair and keafter giving a coat of lime wash &the headersplywood covers.

• Mechanical Inspection using IRT.

12. ChimneyV

• Monitor for choking with soot at base, wear on tnecessary. Renew the surface coat of paint withaluminum paint.

13. Flue ducting Cl

V

• Monitor the furnace temps at inlet & outlet of t

• If abnormal then the inspection covers over the

removed and inspected for excessive deposits ofand cleaned as required. Cleaning can be done ahas been shutdown.



14. Fuel & Air Piping & Valves

V √ C

• Monitor the pipes & valves for leakages, rec• Leakage in pipe joints can be rectified by op

and retighten the same after wrapping a Tethreads.

• Leakages in valves can be rectified by tightestem gland packing/ or changing the valve iout seats.

• Insulation Conditioning Monitoring & Repair 15. Walking Beam Mechanism

V

• Monitor the movement of the walking beamscould be due to hydraulic failure or tightnesLinkages can be lubricated to free the same

• The beams could also lift or lower unevenly,because of uneven wear in the roller treads the rollers. The rollers can be changed as a can be opened out and bearings changed/ lu

• The worn out treads can be built up by weldto size after flame hardening.

16.

Hydraulic Systemsa Pump

V √ C

• Monitor the pressure developed by the pumpless than 80% normal, then it requires attendue to leaking valve, or worn out pump comrequired and recondition the changed compspare.

• Alignment checking & realignment. b Filters Cl • The filters are cleaned by taking out the ele

housing and reverse blow compressed air. Ifpaper filter then the element is changed.

17. Collecting BedV

• Monitor rail condition, if wear is excessive wrequired and grind to smoothen the surface

18. Nuts & Bolts VBT

• Check all the Machine Nuts & Bolts for Loosethem.



38

2.2 RHF SHELL PLATES & REFRACTORY LINING

2.2.1 Major Parts

The Parts considered are:

• RHF Shell Plates• Furnace Hearth• Burner Blocks• Refractories on roof, Side Walls.

2.2.2 Initial Heating of Furnace Refractories

When starting RHF from cold i.e. after major overhaul or new installationthe Refractories should be gradually heated with wood fire in all theThree Furnace Zones to dry moisture inside the Furnace & Refractories attemperature of 2000C which needs to be maintained for 48hrs beforeactual firing

After drying the refractories, 50% of Heating Zone Burners and a singleSoaking Zone Burner are lit up. For lighting up of furnace, the Oil pump &Air Blowers are operated through Electric Panel. Oil pressure at 2.5kg/cm2 and air pressure at 900mm WC is maintained. A Flame (Mashaal) isheld in front of the burner oil/Air mixture at Burner nozzle by holdingsome old cotton waste dipped in old oil and lit up. First the soaking zoneburner is lit up, the temperature inside furnace gradually rises to 650 0C,after which other burners are automatically fired using Air/Fuel controlsystem. The Burners are kept at lowest turndown ratio and ratiotrolgradually increases this and temperature in furnace gradually rises@500Cper minute to ultimately reach a level of 11000C.

2.2.3 Preventive & Predictive Maintenance Practices

i) The major Preventive Maintenance practices for Refractory lininginclude their periodic cleaning.

ii) The major Predictive Maintenance practices for RHF shell plates &Refractory lining include:

Visual Inspection.

Mapping of Refractory lining by using IRT camera for Hot Zones(where surface Temp is more than acceptable level). The Hot

Zones may be due to damaged Refractories. The skin Temperature of the RHF Shell should be monitored with

the help of IRT and it should not be more than Ambienttemperature plus 300C. If skin temperature is more check onfurnace refractory lining is necessary.



39

iii) The Standard Preventive & Predictive maintenance practices to be

adopted by SRRM with regard to RHF-Shell lining & Refractory lining

are elaborated at Table 2.2.



TABLE 2.2

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES FOR RHF –SHELL PLATES &

SL No Critical Equipment/part Type of Maintenance Maintenance Process

Preventive(Periodic

Maintenance)


Maintenance) Cl- Cleaning V-Visual Inspection

C – condition monitoring usinginstruments

1. Reheating Furnace shellplates

V √ C

• Check for furnace shell distortions & High tempCamera.

• If local bulging is there due to falling down of rarea is not accessible then cut open the shell parea and reinstall the refractories as required.

• Straighten out the plates and reweld in positiotake about eight hours, depending on the exten

2. Hearth

a. Condition

V √ C

• Monitor the hearth condition visually or using I

ingot/ billet can no longer be pushed, the furntwo days- one and a half days for cooling and fthe hearth with fusion cast high alumina castabscale/ slag off from the hearth, make the surfa

• Give four hours for drying and light up the heathe soaking zone

b. Cleaning

Cl• The Hearth should be cleaned using a scraper,

connected to the ejector bar & Hearth can conclean of accumulated Scale & Slag.

3. Burner blocks

Cl

• Clean the burner blocks daily during the time tburner & nozzle by removing the drippage and poking with a scraper rod and taking care not titself.

4. Refractories on roof, SideWalls

V

√ C

• While most of the refractories are inaccesible,Camera or by opening the opposite side doors condition can be visually inspected and repair a

• A watch is made for detecting hot spots on the

could be due to refractory failure.• Changing replacement of refractories can be do

shutdown of 3- 7 days depending on the locatiodamage.



41

2.3 INSTRUMENTATION CONTROL SYSTEM INCLUDING PC-PLC; POWER

SUPPLY & DISTRIBUTION SYSTEM


The major equipments/parts related to Instrumentation Control

System, Power Supply & Distribution covered include:

PLC

PLC Actuated Valves

Thermocouples, Temperature Indicator cum Controller

Power Supply & Distribution System

RHF Electrics including Control Panels (In Coming Main Panel; VFD

motor panels etc).

2.3.2 Major identified Preventive & Predictive Maintenance practices

The standard recommended preventive maintenance includes periodic

cleaning and predictive maintenance practices include Visual

Inspection, Condition monitoring using IRT Camera & necessary repairs

as elaborated at Table 2.3.



TABLE 2.3STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES FOR RHF - INSTRUMENTATION CONTROL SYSTEM INC

DISTRIBUTION SYSTEM


Preventive(Periodic

Maintenance)


Maintenance)

Cl- CleaningO- Oiling

V-Visual InspectionC – condition monitoring using

instruments

1. PLC

V

• The sequence of the Logic and the settings are c

if OK then move on to the next check. If not OK

settings is required then it is introduced. The PL

the control circuit and operation as per settings cadvisable not to do further Maintenance on the Pthe supplier for further action.

2. PLC Actuated Valves

O V

• Check the actuator valve operation by manually pr buttons. If it is sluggish or not operating, firstly thchecked. If OK then the freeness of the spools are spools manually and watching if the actuator move

• If Ok then the link bushes are oiled at the hinges a

3. Thermocouples &Temperature indicatorcum controller

V √ C

• Monitor the readings on the Temperature contro

(TIC). If absent then change the TIC or the Ther

checking the electric connections.

• The output signal current intensity is checked fo

indicator cum controller using Ammeter. This sh

Ok then the Thermocouple cable & connectionsand tightness at the points. If still it is not ok the

the TIC are changed.

• The TC will have to be recalibrated against stanfurnace. Change if found defective.



4. REHEATING FURNACEELECTRIC PANELS

a. MAIN INCOMING PANEL

Cl V

• The panel is monitored during furnace ofactor readings, power consumption per Temperature readings for SZ, HZ, PHZ, Freadings, Combustion air temp, chimneyblower and oil pump motors. In case of mnormal readings corrective action is takepower factor the capacitors are increaseprocess is automated.

• In case VFD is installed there can be no cpower factor improvement. Current readpusher motor, ejector motor, hydraulic pulverizer unit motor, blower motors.

b. VFD Air Blowers & OilPumps Panels

Cl V

• Check only if problem is indicated. KeepCheck the RPM meter and operate the p

and check if speed variation takes placedirection and reverse then nothing to bechange the pot and recheck, (b) call themaintenance support and get the necessdone.

5. Power Supply &Distribution

ClV

√ C

• The condition of Distribution TransformConductors, Bus Bars, relays/contacts isCamera for overheating, Looseness, BrokConductor etc and repaired accordingly

• Take shutdown, isolate, clean bushes ofBuccholz relay, check oil filter, clean kcontacts with sand paper and CTC, checmeter to SEB for recalibration. The condoil is checked using Oil Testing Kit, if no



44

CHAPTER 3

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCEPRACTICES ADOPTED FOR RM

3.1 CRITICAL MILL EQUIPMENTS


The critical RM-Equipments/Parts covered include:

• All roller tables, like Ingoing, outgoing, mill feed tables, cooling bedtables etc

• Reduction G/Box & Pinion Drive on all Group of Stands

• Mill Roll Bearings

• Screwdown Mechanism of all Stands and the housing side sliding liners

• Cooling Water Piping, Hoses, Nozzles, of all stand rolls

• Guides & guards

• Repeaters structures

• Stand holding down Bolts

• Motor & Commutator brushes

• End cut shear s

• Flying shear

• TMT box water system

• Pinch rolls

• Cooling bed flap system

3.1.2 The Major Identified Preventive & Predictive Maintenance Practices

The major Maintenance Practices to be adopted for Critical Rolling MillEquipments include:

A.

Preventive Oiling & Greasing

Cleaning

The quantity of Bearing Re-Greasing requirement (in gm) iscalculated by: 0.005 x Bearing ID (mm) x Bearing Housing Width(mm)



45

B. Predictive

Visual Inspection

Inspection of Bolts for looseness/corrosion and tightening /

changing

Condition Monitoring of Various Critical parts & taking necessarymaintenance & repair work to prevent breakdown & enhancereliability like:

• Monitoring Vibrations of Bearings of all rotating equipments

like Gear box, Motors, Pinion Box, etc using Vibrometer.

• Checking Electric motor performance using Ammeter, Power

Meter, Meggar, Tachometer, w.r.t current drawn; power

consumed; rpm and condition of Insulation.

• Checking of Proper Alignment of all Shafts, Couplings,

Bearings etc. of all rotating equipments using gauges. An

advance Technique of Laser Alignment is also available for

accurate alignment of all rotating parts/equipments.

• Testing Belt Tension of Electrical Drives with the aid of

Tensiometer & Belt Tightening/Changing.

• Testing of Lubricating oil condition using Oil Testing kit.

• Infrared Thermography-Scanning of all critical parts foroverheating due to malfunctioning including motors, bearingsetc.

• The acceptable level of Bearing Temperature rise aboveambient temperature is calculated by :

ΔT (0F) = {Bearing ID (in mm) x rpm)}/2000

The Standard recommended Preventive & Predictive MaintenancePractices to be adopted for Critical RM Equipments are detailed atTable3.1.



TABLE 3.1

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES ADOPTED FOR CRITICAL ROLLING M


Preventive(Periodic

Maintenance)


Maintenance)

O- OilingG- GreasingCl- Cleaning


instrumentsBT- Bolts Tightening/changingBeT- Belts tightening/changing

1. All roller tables, like Ingoing,outgoing, mill feed tables,cooling bed tables etc

G √ C

BeT

• Monitor the bearings temp using touch pyrometethe bearing housing. If excessive then housing cabearing checked for lubrication, broken cages, dand if necessary change as required.

• If normal, then grease the bearings by grease gu

• Measure tension of the belt/ chain using Tensiomneeded.

2 Reduction G/Box & PinionDrive on all Group of Stands

O V√ C

• Monitor Vibrations using vibrometer on bearing hthen the gearbox cover is opened out and the bechecked for lubrication, broken cages, damaged necessary changed as required.

• If normal, then check and clean the oil lubricatioStart the centralized lubrication system and flowbearings, gears etc are checked during shutdown

• Visually check gears for wear, and lub oil flow threassemble after repair/ replacement/ leaving a

3 Mill Roll Bearings

√ C

• Continuously monitored when rolls are changed. pitting signs on bearing races, check for broken rmetal powder particles etc. clean with keroseneNOT USE COTTON WASTE) and blow clean dry cowith fresh EP3 grease and assemble.

• IRT Camera could also be used for monitoring thebearings which will indicate immediately as soonbehaving abnormally. It detects hot spots (dry opowder entrapment on the raceways and rollers,



chain drive is checked for tension and sprocket wand the chain are changed if damaged or excessi

casing is checked for damages and patched with The individual nozzles are checked inside the TMblowing compressed air.

• The control system is checked by pressing the temimic panel. The quantity of flow of water is chflowmeter and the pump impeller changed if flowbearings are checked by using a vibrometer and damaged.

• The bearings are lubricated by packing grease inas per supplier's specifications. The gland packinare tightened or changed if no more tightening isactuators on the valves are checked for operatioare cleaned of collected dirt and made water tigmonitored on the mimic panel and faults noted anight shutdown.

13 PINCH ROLLS

OG

V √ C

• The roll barrel is checked for wear and built up belectrodes if worn out by more than 6mm depth.

spring tension is checked and the springs are chaare tightened solid before the bar is gripped fully

• The bearings are greased and the gearbox oil is quantity of oil being topped is more than what hpast six months then the cause has to invesleakages through oil seals stopped by repair/ repgear support shafts generating excessive heat levaporation of the oil and the fault rectified acc

14 COOLING BED FLAP SYSTEM

OV

√ C

• The air pressure is checked as per requirement ssupplier, normally it is > 4 kg/cm2. The pipelineattended as and when noticed by sound of escap68 oil is dispensed using an oil can on each link bsupplier's specs when lubicating. Check the kick-any abnormality in alignment is noticed. Check tfloor plate and flaps and rectify as required.



50

3.2 INSTRUMENTATION CONTROL SYSTEM INCLUDING PC-PLC; POWER SUPPLY &DISTRIBUTION SYSTEM


The major equipments/parts related to Instrumentation Control System, PowerSupply & Distribution covered include: PLC

PLC Actuated Valves

Power Supply & Distribution System

RM Electrics including Control Panels (In Coming Main Panel; VFD motorpanels etc).

DG Sets

3.2.2 Major identified Preventive & Predictive Maintenance practices

The standard recommended preventive maintenance includes periodic cleaning& Oiling and predictive maintenance practices include Visual Inspection,Condition monitoring using IRT Camera and testing Transformer Oil, DG Set Oilcondition using Oil Testing Kit etc & necessary repairs as elaborated at Table3.2.

3.3 CENTRALISED LUBRICATION SYSTEM, WATER COOLING SYSTEM & AIR

COMPRESSORS


The major equipments/Parts related to the Rolling Mill Centralised Lubricationsystem; Water Cooling System & Air compressors include:

Centralized Oil Lubrication System Filters

Centralized Oil Lubrication System Tank

Cooling Water Pumps

Air Compressors

3.3.2 Major identified Preventive & Predictive Maintenance PracticesThe standard recommended preventive maintenance includes periodiccleaning, Oiling & Greasing and predictive maintenance practices includeVisual Inspection, Condition monitoring using Vibrometer & necessary repairsas elaborated at Table 3.3.



TABLE 3.2

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES ADOPTED FOR ROLLING MILL - INSTRUMENTATION

PLC; POWER SUPPLY & DISTRIBUTION SYSTEM


Preventive(Periodic

Maintenance)


Maintenance)

O- OilingCl- Cleaning


instrumentsBeT- Belts tightening/changing

1. Power Supply & Distribution

system

Cl V, √ C

• Electrical Power Distribution system consisolators, circuit breakers, current transTransformers, bus bars, capacitor Banks,

encountered in the form of Hot- Spots at comay be due to loose contact, Corrosive conductor strands etc. These Hot Spots aSurface temperature. Higher the current flofault. On-line Thermal Scanning using IRT Caterminals will identify Hot Spots and seattending to these faults will reduce breakdimprove its reliability. If the Differentiaambient is about 40 DegC, the condition is immediately attended.

• The condition of Distribution Transformer, OBus Bars, relays/contacts is monitored uoverheating, Looseness, Broken Strands orepaired accordingly

• Take shutdown, isolate, clean bushes ofBuccholz relay, check oil filter, clean kcontacts with sand paper and CTC, check OC

SEB for recalibration. The condition of Tranusing Oil Testing Kit, if not Ok, oil replaced.



2. Electric Control Panels

Cl V

• The panels are regularly monitored during roPower factor readings, power consumption peof major deviations from normal readings cortaken. For improving power factor the capacidecreased. This process is automated.

• All the relays in the panel are cleaned every shutdown or at night when rolling has been stshould be taken on the panel and danger tag handle. The breaker is switched OFF. The conone by one and the contacts cleaned with CTsteel blade, sand paper or emery paper etc tcontacts are silver brazed and can get damag

• The meters are calibrated once a year by thethe requisite fee.

• All cable joints and lugs are examined for tig

3. PLC

V

• The sequence of the Logic and the settings are

correctness, if OK then move on to the next chany change in the settings is required then it is

is then checked on the control circuit and operconfirmed. It is advisable not to do further Ma

system but refer to the supplier for further acti

4. PLC Actuated Valves

O V

• Check the actuator valve operation by manually pr

buttons. If it is sluggish or not operating, firstly the

checked. If OK then the freeness of the spools are

spools manually and watching if the actuator move

• If Ok then the link bushes are oiled at the hinges an

5. DG SETS

O√C

BeT

• The diesel oil is checked using oil Testing Kit. The

checked and changed as required once every six m

crankcase is checked and topped. If the oil is black

drained out, the crankcase cleaned with kerosene, t

changed. This is done after every 500 hours of runn

brushes are checked and adjusted. The belts are tes

tightened if necessary .



TABLE 3.3

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES ADOPTED FOR ROLLING MILL – CENTRALISED LUBR

SYSTEM & AIR COMPRESSORS


Preventive(Periodic

Maintenance)


Maintenance)

O- OilingG- GreasingCl- Cleaning


instruments

1. Centralized Oil LubricationSystem Filters

Cl V

• The centralized lubrication coarse and fine firemoved from the housing flasks and cleanedcompressed air is blown gently through the fifilled in the filter housing flasks and the asse

• Secondly the temperature of the oil is monito

temperature is higher than normal then the hcovers are opened and the tubes are cleanedbrush cleaner and the brush is pushed into ththe sediments. After cleaning, compressed aitubes to blow away the particles. The water blown with compressed air and the covers arechanging the gaskets and the assembly testedfree flow.

2. Centralized Oil LubricationSystem Tank Cl V

• The tank is checked once a month for sludge is present, then during a shutdown > 3 hours,cover is opened to clean out the sludge, and

3. COOLING WATER PUMPS

OCl

V√ C

• The water system is checked on following poia) Water pressure to be 7 -10 kg/cm2 in ordepressure at the end user points.b) The suction strainer is to be cleaned and tthe water does not remain in the delivery pipdeaeration cock.

c) The water leakages though the gland will htightening the glands or if leakage persists thchanged.



• The delivery valve and the valves at the userfor leakakages and the seats cleaned or valvenecessary.

• All the water piping joints are checked for leare tightened or gaskets changed if leakage p

• The bearings are monitored using a vibrometerequired.

4. AIR COMPRESSORS

GCl

√ C

• The air compressors are monitored during runloading/ unloading valve operation, bearing vspots on bearing housings, intercooler air pretemperatures, aftercooler pressure and temp

• In case of abnormality the running air comprethe standby compressor is activated. Necessaoperations of the heat exchangers, unloadingspring tensions are adjusted. The control systair compressor when required air pressure haafter 5 minutes of continuous unloading the coff. When the pressure drops to the preset porestarts.

• The Bearings are greased.



55

3.4 MISCELLANEOUS MACHINES, HOUSEKEEPING, BUILDING SHEDS


The major equipments/parts considered include: Housekeeping

Building Sheds

Roll Turning Lathes

All Machine Tools, Like Shaper, Milling, Hacksaw & Drilling

EOT Cranes

EOT Crane Rails

3.4.2 Major identified Preventive & Predictive Maintenance Practices

The standard recommended preventive maintenance includes periodic cleaning,

Oiling & Greasing of Equipments. In addition this also includes cleaning & annual

painting of Building sheds.

The Standard predictive maintenance practices include Visual Inspection, Belt

Tightening/Changing, Bolt Tightening/Changing and Condition monitoring using

Tensiometer etc. & necessary repairs as elaborated at Table 3.4.



TABLE 3.4

STANDARD PREVENTIVE & PREDICTIVE MAINTENANCE PRACTICES FOR MISC. MILL MACHINES, HOUSEKEEP


Preventive(Periodic

Maintenance)


Maintenance)

O- OilingG- GreasingCl- CleaningP-Painting


instrumentsBT- Bolts Tightening/ChangingBeT- Belts tightening/changing

1. Housekeeping

Cl V

• Keeping the shopfloor clean is everyone's SRRM parts have to be stacked in their respec

• There should be demarcation in paint on walkways. All SRRM equipment should be pwalkways of Steel chequered grills. Steel cagon the walkways handrailings to prevent

causing hurt to the pedestrians/ visitors.• All cotton waste, clothrags and other unwa

be thrown into the respective garbage cansthe SRRM floor.

2. Building Sheds ClP

V • All the building sheds are cleaned and paint

sheets are replaced. All the girder bolts areare load tested at 150% crane carrying capac

3. Roll Turning Lathes

OCl

√ C

BeT

• The lathe is cleaned using rag cloth soaked the guideways, chucks, toolpost, leadscrews

• Apply a light coating of hydraulic oil on theslide.

• Check & top oil level in the main g/box.

• Check belt tensioning of drive motor.

• Clean out the swarf.

• If the accuracy is affected then the supplier no improvement is noticed after the atightened as required.



4. ALL MACHINE TOOLS, LIKESHAPER, MILLING, HACKSAW

& DRILLING

ClOG V

• Clean the machines, lubricate as per supplservice engineer when major problems occur

5. EOT CRANES

OG

V

√ C

BT

• The EOT Crane in the steel plant is a heavy dmaterial handling equipment, it lifts the wdesigned and travels with it at a height to tto lower it and deposit. This is a source of phas to be ensured that there is no failure.

• The hoist has to be checked for proper braload, the wire rope should not have more thindividual wires per foot length of rope, noshould be broken on each strand. The rlubricated with cardium compound. The manot be exposed or broken.

• Other point of check are the LT & CT whelubrication. Gearboxes of hoist, LT & CT topped. The wheels are checked for excessivIf wear is more on one collar then there iswheel treads and the wheel pairs have to be out wheels built up by welding and machined

6. EOT CRANE RAILS

Cl√ C

BT

• If there are bumps while the crane is in motioexcessive wear of the rails especially at the joportions are built up by welding and ground wAll the cleat bolts are checked for tightness. Tchecked in the panels. The contacts of the coas before.



58

CHAPTER 4

OVERHAULING/ CAPITAL REPAIRS; GENERALTROUBLESHOOTING & REPAIR WORK BASED ON CASE STUDIES

4.1 RE-HEATING FURNACE (RHF)

4.1.1 Overhauling/Capital Repairs

• Overhauling/Capital Repairs of equipment is carried out during thetime the Reheating Furnace is put down for repairs to refractorywork.

• The overhauling of the RHF consists of complete replacement of all

damaged portions of the refractories inside the furnace and therepair of the damaged portions of the furnace shell. The refractorywork could be for the hearth, sidewalls, end walls, burner blocks androofing.

• Before an overhaul is undertaken, complete planning of the jobs isdone and chiefly the required spares and replacement refractoriesare arranged. If extra workforce is required, then the necessarycontractor’s labour force is arranged. Special machines or equipmentrequired for carrying out the repairs is also arranged.

• The customers to whom deliveries have been promised are informed

about the outage and revised delivery schedule agreed upon. Theupstream production is adjusted so that a heavy inventory is notcarried of work in progress.

• Together with the furnace overhaul all other equipment in theReheating Furnace and Rolling Mill are also overhauled. All safetymeasures and gear are arranged and necessary shutdowns taken fromstatutory agencies.

• Generally the furnace is put down as a result of an irreparablebreakdown on the hearth or sidewalls or roof collapse. All the

blowers are kept running to cool the furnace faster. The burnermandrels are removed and soaked in kerosene oil.

• The major jobs/activities to be carried for overhauling/CapitalRepairs of RHF are elaborated at Table 4.1.



TABLE 4.1

OVERHAUILNG/CAPITAL REPAIRS OF CRITICAL EQUIPMENT - RHF

Sl.No

Job description Requirement of special

tools/equipment

Availabilityof spares/

replacement/addition

Worclas

Cost Centre: Power Distribution

1 Transformer Maintenance: Oil heating & Filteringequipment

1E,2H

2 Meters & Relays Send Meters to SEB forcalibration

3 Vacuum ckt breaker:: Testing vacuum & SF6 gas Vacuum tester, 1cylinder SF6 Gas

Stores 1E,2H

4 Isolator Switches: Open out knife edges and cleanthe contacts, oil the linkages with Servosystem 68

Sand paper, Oil Can,CTC solution

Stores 1E,2H

5 Clear the Sub station of grass and other garbage,clean the outside of all the breakers, transformers,spray paint the equipment except at the bushings

Kerosene oil, cottonrags, emery paper/sander discsaluminiumpaint, thinners, steelgrey paint, portable aircompressor

Stores 1E,2H

6 Distribution Panel

Clean all the contactors points with sand paper andCTC, check tightness of all cable lugs. Take carewhile opening the lugs, to reconnect the correctphases

CTC and cotton rags,sand paper

Stores 1E 1H



Cost Centre: REHEATING FURNACE

7 Pusher gear:

a Gearbox: Wipe clean the outside of the g/box withcottonwaste soaked in kerosene. Lean allfoundation bolt heads. Open the coupling and check

for play of the worm shaft by pushing and pulling. Ifthe play is more than 1.5mm the gear box has to beopened and wear of worm wheel examined. If theteeth are wearing out to one side the worm shafthas to be centered by adding/deleting shims at theend covers. If the wear is excessive the worm amdworm shaft pair has to be changed. Drain out the oilin the gearbox and clean the sludge out by a cottonrag mop. Flush the g/box with kerosene and dry theg/box. Fill new oil. Close the gearbox and tightenall bolts. Check the alignment of the couplings usingfeeler gauge for uniformity of gap and a 6" straight

edge for checking level. If there is a misalignmentthen the motor base bolts are loosened and motorraised, lowered/ moved sideways etc until thecouplings are perfectly aligned. The motor basebolts are tightened and the coupling bolts aretightened. Final alignment using dial gauge.

Spanner set, EP160 gearOil, cotton rags,kerosene/diesel.

Straight edge, dialgauge

1F

b G/box to screw Coupling: Check alignment ofcoupling as above. If gear coupling is used then thegear wear is checked. If the teeth are worn thinthen the coupling pair has to be changed, byextracting the couplings from the gearbox and themotor and new couplings fitted by first heating

them immersed in hot oil.Whenthe couplings areextracted the keys and keyways are examined andchecked for wear. There should be a tight fit of keyon the sides of the keyways of both the shaft andcoupling half of both motor and gearbox. If the fit isloose then a new key is prepared at the machineshop and fitted. The key is fixed first on the shaft

Spanner set, EP160 gearoil,cotton rags,kerosene/diesel.Straight edge, dialgauge

1F



and then the heated coupling is slid over it. Thecoupling should not be hammered in otherwise thebearings of the gear shaft or motor shaft could getdamaged.

c Motor: Check the insulation of the motor by using 0-500V megger. If low then the motor is taken out andthe rotor and stator given a coat of varnish from Dr

Beck, dried in anoven and put back. When the rotoris taken out the windings on both the stator androtor are checked for breakages or falling off of thevarnish. New varnish coat is applied and dried in anoven at 220DegC for 4hrs

Spanner set, MP 3grease,cotton rags,kerosene/diesel/megger

0-500V, varnish

1E

d. Motor to g/box Coupling. Same as Item 7 above Spanner set, EP160 gearoil,cotton rags,kerosene/diesel/

1

e Screw: Check the wear on the threads of the screw.If worn out the screw is taken out, the wornportions are built up by welding, then machined.Couplings are realigned during assy using dial gauge

Spanner set, EP160 gearoil,cotton rags,kerosene/diesel/

1

f Nut: Same as Item e above. The nut is changed withspare if worn out


Nut1

g Guide rods: Check for wear by measuring thediameter using vernier calipers.If worn out the rodscan be built up by welding and machined to size


1

h Guide bushes: To be changed if worn out more than1.5 mm


1 set of bushes1

i Pusher head: Normally there is no wear on thePusher Head as there is no relative friction surfaces.

1

j Slide rails: Check for wear and if more than 3mmthe rails are built up on the worn out spots andground to shape.

Hard facing electrodes,Hand Grinder1



8 Ejector

a Gearbox: Wipe clean the outside of the g/box withcottonwaste soaked in kerosene. Lean allfoundation bolt heads. Open the coupling and checkfor play of the worm shaft by pushing and pulling. Ifthe play is more than 1.5mm the gear box has to be

opened and wear of worm wheel examined. If theteeth are wearing out to one side the worm shafthas to be centred by adding/deleting shims at theend covers. If the wear is excessive the worm amdworm shaft pair has to be changed. Drain out the oilin the gearbox and clean the sludge out by a cottonrag mop. Flush the g/box with kerosene and dry theg/box. Fill new oil. Fill the old oil into a drum andkeep for sending to the lab for testing the viscosityand viscosity index (change of viscosity with rise intemperature). Close the gearbox and tighten allbolts. Check the alignment of the couplings using

feeler gauge for uniformity of gap and a 6" straightedge for checking level. If there is a misalignmentthen the motor base bolts are loosened and motorraised, lowered/ moved sideways etc until thecouplings are perfectly aligned. the motor basebolts are tightened and the coupling bolts aretightened.

Spanner set, EP160 gearoil, cotton rags,kerosene/diesel.Straight edge, dialgauge

1F

b G/box to pinch roll Coupling: Check alignment of

coupling as above. If gear coupling is used then the gearwear is checked. If the teeth are worn thin then thecoupling pair has to be changed, by extracting thecouplings from the gearbox and the motor and new

couplings fitted by first heating them immersed in hotoil.Whenthe couplings are extracted the keys andkeyways are examined and checked for wear. Thereshould be a tight fit of key on the sides of the keyways ofboth the shaft and coupling half of both motor and

Spanner set, EP160 gearoil,cotton rags,kerosene/diesel.Straight edge, dialgauge



gearbox. If the fit is loose then a new key is prepared atthe machine shop and fitted.The key is fixed first on theshaft and then the heated coupling is slid over it. Thecoupling should not be hammered in otherwise thebearings of the gear shaft or motor shaft could getdamaged.

c Motor: Check the insulation of the motor by using 0-500V megger. If low then the motor is taken out and

the rotor and stator given a coat of varnish from DrBeck, dried in anoven and put back. When the rotoris taken out the windings on both the stator androtor are checked for breakages or falling off of thevarnish. If the winding wires are broken orseparated then the rewinding is done using thesame gauge wires and no. of wires as before. Newvarnish coat is applied and dried in an oven at220DegC for 4hrs

Spanner set, MP 3grease,cotton rags,

kerosene/diesel/megger0-500V, varnish

d Motor to g/box Coupling. Same as Item 7 above

e Pinch Rolls: The pinch rolls are examined for wearon the tread/ flanges. If more than 6mm then thetread/ flange is built up by welding and machined.Both the rolls should have same diameter. Springsare checked for tension and replaced if necessary

1 set of springs

f Ejector bar: The bar is examined for straightnessand wear. The bar is changed if bend is more than10 mm per meter

g Cooling water: Check for flow and pressure.Pressure should be around 1kg/cm2

9 Furnace Proper 1

Normally the roof and sidewalls and hearth onsoaking and heating zones alone are damaged andrequire repairs/ replacements. Roof: All the ingots/billets inside the furnace are removed through theseveral windows on the sides of the furnace. Check/ repair the rails wear on the hearth in preheating

2FRemMhePi



and part of the heating zones. Remove the roofbricks in the Heating and soaking zones by removingthe key bricks at the centre of the arch. If the roofis flat with hanging bricks the brick holders areremoved. Remove the first row of sidewall and endwall bricks including the burner blocks, burners, airand fuel piping. Dig out the hearth bricks/ castable

upto a depth of 300mm. Loosen the tie rods holdingthe shell plates together. Cut out the bulgedportions of the shell plates and replace/ repairthem and reweld in position making sure that theplates are fully flush against the Hysil blocks. Thenew roof bricks are placed in position, making surethat the key bricks of the arches are fully tight. Ifflat roofing is there replace the hanger bricks.Check and replace the nose wall partition walldamaged portions between the heating and soakingzones. Build up the sidewalls and end wall with 70%Alumina bricks. Place new as-cast high alumina

burner blocks in position. Build up the hearth withfusion cast 70% alumina blocks. The furnace is nowready for slow firing of soaking zone burners at 200DegC for one day to dry out the moisture, then heatup at 150 DegC/hr to 850 DegC. Charge the ingots/billets by the pusher upto the end of the heatingzone. Soak for 3hrs at this temperature. Contnuecharging. Make the rolling mills ready for rolling bythis time. Increase the soaking zone temperature to1150degC. Take out sample ingot/ billet for rolling.If OK then light up the heating zone burners andswitch over to the PLC/ PID Controller system.

fi6H



10 Heating Pumping Unit

a Oil Pump & Heater: Monitor oil pump forpressure development, oil heater fortemperature from gauges. Change if pressure isbelow 5 kg/cm2 or temp.of oil after heater ison does not rise to 100 degC.

b Oil filters: Close the flow of oil to the filter byoperating the by-pass valve on the filterhousing. Unscrew the flask from the housingand take out the element. Soak it in a can ofdiesel or kerosene. Blow compressed air fromoutside and bottom of element. Fill the flaskwith clean fuel oil, refit the element into thefilter housing and screw up the flask into thehousing. Repeat the cleaning of the other filter

elements on coarse and fine filters. Open theoil flow valves to and from the filter. c FO Condition: The condition of FO is monitored

using oil Testing Kit, if improper it iscentrifuged/changed

Spannerset, kerosene,oil Testing Kit

Stores 1F

11 Blowers: Take out impeller shaft assembly and sendfor dynamic balancing and reassemble with newbearings if required after checking the play andbased on the results of the balancing. Also checkthe impeller for any damage and repair.

Bearing extractor/puller, EP3 Grease

Out sourcebalancing

1F

12 Overhaul all the actuator valves by completestripping, cleaning and reassembly

DE Spanner set,Kerosene & Rags

Stores 1F

13 Clean the Heater Tank of old oil and sludge and fillfresh oil

Rags, kerosene. Fillfresh oil

1F

14 Check all the electrical systems in the furnace panelincluding cleaning of all contactors/ changing thecontacts and springs

1E



15 Check the transformer cooling system and clean outthe heat exchanger

1F

16 Check the VFD System. Check & change the Pots ifthey are ineffective

1E

17 Recalibrate the temperature controller cumindicator and the thermocouple

1E

18 Check for proper combustion of the burners by

seeing the flame throw and flame corona. Use theautomation system PLC programme for furnacestartup

1E

1F

19 Hydraulic Systems: Change the hydraulic oiland the filters and strainers. If the pump wasnot delivering full pressure the pump ischanged. All the hydraulic valves are openedand the spools are cleaned with light hydraulicoil and made free in the valve cylinders. All thecylinders hydraulic packings are changed one byone taking precautions to maintain absolute

cleanliness.

Spannerset, LightHydraulic Oil

Stores 1F

20 Restart the furnace by following proceduredescribed in the SOP document.

1F

F -Fitter, E - Electrical/ Electronics Technician, H-helper, FOP- Furnace operator, P-Painter



67

4.1.2 General Trouble Shooting & Repair Work based on Case Studies

The General Trouble shooting & Repair work for RHF based on actual case studiesis provided at Table 4.2 and includes Problem encountered, possible identifiedcauses and remedies adopted/recommended.

TABLE 4.2GENERAL TROUBLESHOOTING & REPAIR WORK FOR RHF BASED ON CASE STUDIES

SlNo

Problemencountered

Possible causes Remedies

1 Ingots piling inthe furnace

a) Hearth unevendue to build up ofscale and slag.

b) Ingots notcharged square.i.e. with opposingtapers.

c) The pusher is notpushing the ingotsstraight and the

ingots are touchingthe sidewalls andturning causing pileup.

a) Try to clear the scale and slag throughthe side windows. Try to pull out someingots through the window and clean thebuilt up scale. If the slag does not comeout, the furnace is put down for cooling,people are sent into the furnace for

breaking the slag/scale if required apneumatic pavement breaker is used.

b) Care is taken to ensure proper charging.

c) The guide bushes could be worn out.They are changed.

2 The shell platesget hot at somespots

a) Refractoriesbehind the hotspots could havefallen or broken.

a) If the hot spot is not too hot then try tocontinue till a long shutdown can bearranged to replace the damagedrefractories. Until then an industrial fan isarranged to cool the hot spot, though itwon’t be very effective.

3 Blower drawingmore currentthan rated andtripping

a) The speed of theimpeller might bemore than deigned.

b) The impellercould be damagedcausing more air tobe discharged

a) Check the RPM of the impeller shaft andchange the pulley diameter to reduce thespeed.

b) Change the impeller.



68

c) The bearingscould be runninghot and requireimmediatelubrication

c) Lubricate the bearings after cleaning andchecking the same for damaged rollers/balls or cage.

4 Furnace oilpressure low a) Gears could beworn out.

b) Clearancesbetween gears andend covers could beexcessive

c) Suction filtercould be choked.

d) Oil viscositycould be low.

a) Change the gear pair.

b) Open the end covers and remove theshims provided and close.

c) Clean the filters.

d) Check the heater temperature. It shouldbe between 90 and 1100C.

5 Walking hearthnot operating/sluggish

a) Hydraulic systemnot developingpressure

b) Linkages tight

c)Hydrauliccylinder leaking

a) Check the pump delivery pressure.Change the pump if required. Clean thesuction filters and strainer and restart.

b) Lubricate the bushes/ bearings of thelinkages.

c) Check if oil is very hot. This indicatesleakage of oil in the system. Take thecylinder piston to one end and loosen theoutlet hose connection by two threads.Pressurize the other side by manuallypressing the pilot valve spool. If oil comesout with high pressure from the loosenedhose connection then the piston packing isleaking. The cylinder holding trunnion pinsare removed and cylinder taken out. Thespare cylinder is put in place and the

linkages refitted and trial taken.



69

d) Cylinderoperating valveleaking

e) Unloading valve

stuck

d) The valve is changed with a spare valveand trial taken.

The unloading valve spool is operated byhand and pump run to see if pressure

develops. Better to change the valve andproduction restarted

6. Pusher notpushing thebillets

a) Billets couldhave piled up inthe furnace

b) Coupling may be

disconnected

c) Screw may bebroken

d) Check if thethreads on the nutare washed out

a) Open the maintenance windows and tryto remove the piled up billets from thefurnace through the window. Try torearrange the billets that are piled up oneon top of the other billets in two-highfashion. Slowly push the billets until thepiled billets are cleared out of the furnace.

b) Replace the coupling bolts. Check for

jamming inside the furnace and clear asabove.

c) Change the nut if so.

d) Change the nut if so

7 Ejector notpushing

a) Pinch roll notgripping the bar

b) Motor not takingsufficient load, buttaking full loadcurrent

a) Gripping surface is too slippery. The ejectorbar is ragged by welding beads on top and

bottom sides.b) Loosen the spring bolts of the top pinch roll.Clean the trough in which ejector bar movesand check for obstructions. Take trial.

8 Ejector-Billet nottaking load

Roll could be wornout. The top springbolts may not besufficientlytensioned.

Tighten the spring bolts of the top pinch roll.Next try to rag the pinch roll with weld beads toincrease the friction.

9 Combustion airtemperature notbuilding up

Recuperator requirescleaning on outsideof tubes.

The recuperator by pass pipe is connected upand the recuperator is lifted out of the flueduct. A false lid is put on the flue duct toprevent the gases escape into the shopfloor.The outside of the tubes are cleaned using awire brush and compressed air. The inside ofthe tubes are cleaned with compressed air. Theoutside of the tubes is given a lime –wash. Therecuperator is replaced into the duct and pipesreconnected.



70

4.2 ROLLING MILL (RM)

4.2.1 Overhauling/Capital Repairs

• Capital repairs in Rolling Mills are generally carried out during the capital

repairs on Reheating Furnaces. During this period some major equipment

could be changed or relocated. Almost all the equipment is overhauled

during this period. Some equipment could be added & some could be

removed. All this would be the result of the experiences of the past few

months/years. There could be simplification of procedures, or

automation of systems etc which could be taken up only during breaks of

4 days or more.

• The major Jobs/Activities to be carried for overhauling/Capital Repairs

of RM are elaborated at Table 4.3.



TABLE 4.3

OVERHAULING/CAPITAL REPAIRS OF CRITICAL EQUIPMENT-R

SlNo

Job description Requirement of special

tools/equipment

Availabilityof spares/

replacement/addition

Workeclassif

Cost Centre: Power Distribution

1 Transformer, Meters & Relays; VCB, OCB, Isolatorswitches, Substation, All panels, gearboxes, PinionBoxes and motors as described in Table 4.1.

1E, 1H

2 RM Stands (Roughing, Intermediate, Finishing) :Open out the top covers by removing the cotters,spring bolts, springs and lift out the top rollassembly by crane and slings. Take out the othertwo roll assemblies and shift them to the roll shop.Use canvas belts for slinging around the roll barrel.

Thoroughly clean out the components like screws,nuts, side liners, base bolts, window clamps andbolts. Change the liners if worn out excessively(more than 3.5mm). Change rolls if due. All theantifirction bearing housings are opened out, andthe bearings removed from the rolls and bothbearing and housing are cleaned and packed withfresh grease. Oil seals are changed if the rubber iscut or damaged. The rolls are reassembled and keptfor reinstallation into the stand. Same procedure isrepeated for all the rolls.

Bearing extractors. ,Oilsump for heating toremove and assemblebearings

Spindlecouplingslippers/universalcouplingbearings,

Main roll neckanti frictionbearings -1set of 2 Nosper type,FibreBearings forStand #1 - 6sets

1F, 2H

3 Wall tilters: Check for worn out plates and change

as required. Check all roller tables, if group drivenby chain then check sprocket teeth for wear,tension the chains by adjusting the idler sprockets.Check all roller shaftsupport bearings and renew thegrease. Check the tilting table operating mechanismand lubricate all the link bushes of the levers.

Bearing

bushes oflinkages

1F, 1H



4 Spindles & Couplings: Opening, Inspection,alignment, grease packing, closing/changing

Spanners, Dial guage,straight edge spirit level

CouplingHeads

2F, 4H

5 End Crop Shears: Check the photocell foroperation. Check if the pneumatic cylinder packingsare OK, change if leaking. Leakage is checked bynoting whether the air flows through the cylinder tothe outlet continuously. Lubricate all the link

bushes with grease through the grease nipplesprovided. Check the condition of the blade teethand change if sufficient teeth (1/3rd the periphery)are blunted.

Pneumaticcylinderpacking kit.

1F, 1H

6 TMT Box: Check all valve actuators and remove alldirt that may be stuck on the valve seatings. Cleaneach and every nozzle using proper size sharpenedcopper pins. Drain out the entire water in the waterrecirculation tank. Check the fill pack in the coolingtowers, replace damaged fills. Check the fan driveassembly and tighten the chains. Lubricate the shaftbearings. Fill the water with fresh water. Check the

centrifugal pumps and change the gland packings.Clean out the suction strainer and change the seatof the suction float valve. Take trial of pump andnote the pressure developed, should be 10kg/cm2.

Nozzle cleaning brushesand copper pins

Nozzles -10Nos, Valveactuators - 2Nos, PVC FillPack forCooling tower- 15 - Nos,Gland

Packing - 1set

1 PF, 2

7 EOT Cranes: Check and change the brake thrustorassembly. Check & change wire ropes. Check &Clean all contact points. Conduct load test.

Silver Brazing Kit, 125%load to be arranged,scale , twistless cordequal to height of railfrom ground

Spare lengthof Rope,Brake drum

2F, 1E,



73

4.2.2 General Trouble Shooting & Repair Work based on Case Studies

The General trouble shooting & Repair work for RM based on actual case studies is

provided at Table 4.4 and includes Problem encountered, possible identified causes

and remedies adopted/recommended.

TABLE 4.4GENERAL TROUBLESHOOTING & REPAIR WORK FOR RM BASED ON CASE STUDIES

SlNo

Problemencountered

Possible causes Remedies

1 Bar skidding at entryof the roll pass

a) The roll setting not proper a)Reset the rolls and pass sample billetpiece through the pass.

b) The bite angle is too largebecause the roll dia is smallwith respect to the size of thebillet/ Bar

b) Increase the gap between the rolls todecrease the bite angle

c) The roll pass is too cold tocreate sufficient friction

c) Burn the roll pass by passing three orfour hot samples with the cooling watershut off

d) The bar is not uniformlyheated & soaked, so front endis not deforming sufficiently toenter the pass

d) Make sure that the bar is properlyheated and soaked before ejecting fromthe furnace

2 Bar becomes bow

shaped on exiting theroll pass, causingdifficulty in enteringthe next pass

The bar is not uniformly

heated & soaked, so there isdifferential elongation betweentop and bottom halves

Make sure that the bar is properly heated

and soaked before ejecting from thefurnace

3 Bar flattens at themiddle of the length ofthe bar

Piping causes this problem Inspect the billet carefully before charginginto the furnace. If Induction Furnace isalso in the Unit the melting & teemingprocess should be better controlled toprevent the excessive piping

4 Bar splits excessively The bar is not uniformlyheated & soaked, so the endsare cold and tends to split

easily

Make sure that the bar is properly heatedand soaked especially at the ends byadjusting the end burners, before ejecting

from the furnace5 Bar gets stuck at entry

to roller guidea) Roller guide gap not setproperly with samples duringmill setting

a) Carry out mill setting as per standardprocedure.

b) Sufficient end cut not doneso bar split has increasedcausing jamming

b) Increase the end cut length to ensureno split remains



74

6 Bar does not enter theroll pass after therepeater

The angle of exit of bar fromprevious pass not correct. Theroller guide may be too tight.The nozzle after the repeatermay be tilted and not allowingthe bar to enter properlyvertically

Adjust the exit guide plate of previous rollpass to ensure correct entry to therepeater which will ensure correct entry tothe roller guide. Also adjust the height ofthe repeater through the jacking screws.The gap in the roller guide should havebeen set properly during mill setting bypassing samples

7 Fe 500 strength notbeing achieved

a) Chemical analysis notcorrect

a) Check the chemical analysis of thesteel and ensure it conforms to therequired analysis

b) Temperature of bar lessthan 850

0C before entry into

the TMT Box

b) Ensure correct exit temperature of thebillet from the RHF in proper heated &soaked condition. Ensure smooth rollingthrough proper mill setting

c) Water spray not asrequired

c) Ensure that the cooling watertemperature at inlet of TMT Box is lessthan 36

0C. Ensure the water pressure is

greater than 5 Kg/cm2. Ensure that all thevalves actuators are working properly



75

CHAPTER 5

OVERALL MAINTENANCE SCHEDULE FOR SRRM; SAFETYPRECAUTIONS & STANDARD INSTALLATION PROCEDURES FOR

CRITICAL EQUIPMENTS

5.1 DETAILED OVERALL MAINTENANCE SCHEDULE FOR SRRM

The Detailed Overall Maintenance Schedule recommended to be

adopted by the SRRM unit for RHF & RM, general housekeeping,

Building Shed, auxiliary machines etc is provided in the form of

a Bar Chart at Figure 5.1 and includes major maintenance

activities which need to be carried out (Equipment wise) their

frequency i.e. Daily Weekly, Monthly etc.

In Figure 5.1, the schedule for one Month is provided which

needs to be replicated over 1 yr period. In addition Maintenance

Activities to be carried out on Semi-Annually & Annually basis

have also been indicated.

It could be observed that ample emphasis has been laid on

Predictive Maintenance (about 60% share of total maintenance)

followed by Preventive Maintenance in order to increase

equipment reliability and reduce break down and Cost of

Capital repairs/overhauling.



Figure 5.1: Overall Maintenance Schedule for SRRM Unit

EQUIPMENT MONITORING & MAINTENANCESCHEDULE

V-Visual InspectionC – Condition monitoring using instrumentsBT- Bolts Tightening/ChangingBeT- Belts tightening/changingO- OilingG- GreasingCl- Cleaning

D – DAILY

W - WEEKLY

F – FORTNIGHTLY

M - MONTHLY,

SA - SEMI ANNUALLY

A - ANNUALLYAction to betaken

Frequency

Days of Months

SlNo

Equipment/PartV,O,G,BT,BeT,C,Cl

D,W,FM,SA,A

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

A REHEATING FURNACE

1 FO - HPU

aOil Pump &

Heat er V

b Oi l f i l t e rs Cl

c FO Condit ion √ C

2 Burners Cl

3 Blowers

a Impeller V

4 Motors √ C

5 Bearings G √ C

6V-Belts V

BeT

7 Pusher

aScrew & Nut

Mechanism

GV

b Gear Box O V



8

Doors & dooroperatingmechanism V

9 Ejector

a

Ejector

mechanism

(Pinch Roll ,

Gear Box,

Cooling Wat er)

V √ C

bEj ector Gear

Box Lubr icat ionO V

10 Extractor G V

11 Recuperator Cl √ C

12 Chimney V

13 Flue ducting Cl V

14Fuel & Air

Piping & Valves

V

√ C

15Walking BeamMechanism

V

16HydraulicSystems

17Pump V

√ C

a Fit ters Cl

b Coll ecti ng Bed V

18Nuts & Bolts V

BT

19

ReheatingFurnace shellplates

V √ C

20 Hearth

aCondition V

√ C b Cleaning Cl

21 Burner blocks Cl



22

Refractories onrood, Side Walls

V √ C

23 PLC V

24PLC ActuatedValves

O V

25

Thermocouples& temperatureindicator cumcontroller

V

√ C

24

REHEATINGFURNACEELECTRICPANELS

a

MAIN

INCOMING

PANEL

Cl V

bVFD AirBlowers & Oil

Pumps Panel s

Cl V

25Power Supply& Distribution

ClV

√ C

B. ROLLING MILL

1. All roller tables,like Ingoing,outgoing, millfeed tables,cooling bedtables etc

G √ C

BeT

2 Reduction G/Box& Pinion Driveon all Group of

Stands

O V√ C



3 Mill Roll Bearings √ C

4 ScrewdownMechanism of allStands and thehousing side slidingliners

GV√ C

5 Cooling WaterPiping, Hoses,Nozzles, of allstand rolls

V√ CBT

6 Guides & guardsG

VBT

7 Repeatersstructures

V

8 Stand holdingdown Bolts

VBT

9 Motor &Commutatorbrushes

GCl

√ C

10 END CUT SHEAR S Cl V

11 FLYING SHEAR V

12 TMT BOX WATERSYSTEM Cl

V

√ C

13 PINCH ROLLS OG

V

√ C

14 COOLING BED FLAPSYSTEM

OV

√ C

15Power Supply &

Distribution systemCl V, √ C

16Electric Control

PanelsCl V

17 PLC V 18 PLC Actuated O V



Valves

19

DG SETSO

√C

BeT

20

Centralized OilLubrication SystemFilters

Cl V

21

Centralized OilLubrication SystemTank

Cl V

22COOLING WATERPUMPS

OCl

V

√ C

23AIR COMPRESSORS G

Cl√ C

C MISC. MILL MACHINES, HOUSEKEEPING, BUILDING SHEDS

1 Housekeeping Cl V

2

Building Sheds Cl

P V

3Roll Turning

Lathes

OCl

√ C

BeT

4

ALL MACHINETOOLS, LIKESHAPER, MILLING,HACKSAW &DRILLING

ClOG

V

5

EOT CRANES OG

V

√ C

BT

6EOT CRANE RAILS

Cl√ C

BT



81

5.2 MAJOR SPARES TO BE MAINTAINED

The Complete recommended List of Spares to be maintained for RHF and RM

have been provided at Table 5.1 & Table 5.2 respectively.

TABLE 5.1LIST OF SPARES TO BE MAINTAINED FOR RHF

SlNo

Equipment Spares to be kept Qty

1. Pusher Screw & Nut assembly 1

Assembly of Pinch roll set of topand bottom complete withbearings and bearing housings

12. Ejector

Motor 1

Set of coarse and fine oil filters 5 each

Heater element 1

Oil pump and motor assembly 1 assembly

Pressure regulator 1

Oil Temperature & Pressure gauges 1 each

3. Heating & Pumping Unit

Oil flow meter 1

Temperature controller cumindicator

1

Thermocouple R-Type 2

Hearth refractory blocks of fusedalumina

1replacement

4. Reheating Furnace

Cast iron hearth rails 1 set

Impeller 1 assembly5. Blower

Motor 1

Electrically actuated Valves 1 assy6. Oil piping & Air piping

Electrically actuated Valves 1 assy

Burner assy 1 assy

Mandrel assy 1 assy

Air hose assy 1 assy

7. Burners-Soaking Zone

Oil hose assy 1 assy

Burner assy 1 assy

Mandrel assy 1 assy

Air hose assy 1 assy

8. Burners-Heating Zone

Oil hose assy 1 assy



82

TABLE 5.2LIST OF SPARES TO BE MAINTAINED FOR RM

Sl No Equipment Spares to be kept QtyPivot shaft assy 1 assy1. Rotating table

Infra red temperature measurement&billet counter with timer

1

Rollers 1 assy2. Ingoing rollertable Bearings 2 Nos

Screw & nut 1 assy

Rest bar 1

Jacking wedges for bottom chocks 1 set

Window clamp 1 set inclbolts

3. Stand (For eachStand of 1 size)

Guide fixing square head bolt with

nuts and washers

2

Between Pinion housing & Roll assy 1 assycompletewith couplingheads

Between Rolls & next stand Roll assy 1 assycompletewith couplingheads

4. ConnectingSpindle

Coupling slippers 3 sets

Swivel cylinder 1 assy

Cylinder wear packing kit 2 setsBlade 4 Nos

Blade support bearing 1 assy

5. Crop shear

Hose Assy 2 sets

Electrically actuated water valves 2 assy

Water spray nozzles 8 Nos

6. TMT box

Solenoids for valves 2 Nos

7. Flying shear Blade 2 Sets

Main Hoist wire rope 1 length

Wheels with bearings and bearing hsg 2 assy

Hoist brake thrustors 1 assy

8. EOT Cranes

Main hoist slip ring motor 1

Hot well Pump assembly 1 assy

Gland packing 4 sets

Impeller with shaft assy 1 assy

9. Watercirculationsystem

Cold well Pump Assembly 1 assy



83

Gland Packing 4 sets

Impeller with shaft assy 1 assy

Contactor assy 1 assy of eachsize

Spare contacts 1 set of eachsize

10. Electricalpanels

Silver brazing kit 10 gms

Commutator ring assy 1 assy foreach size

11. Slip ring Motors

Brush copper carbon assy 2 sets foreach size

12. PLC/Automation

Cards 1 of eachtype

Coarse Filter element 10 Nos

Fine filter element 20 Nos

Pump complete with motor, pumpassy mounted on base frame

1 assy

13. Oil LubricationSystem

Suction strainer 2 Nos

Plunger pump assy with motor 1 assy

Indicator cum dispenser manifold 4 Nos

14. GreaselubricationSystem Connecting Hose assy 8 assy

15. Roller guideBoxes

Roller guide assy for each type 1 assy


RG Box leaf plates 1 set per type


Roller assembly complete withrollers, bearings, circlips, covers

6 Assy pertype


Bearings for rollers 12 Nos pertype


Hose assy 4 Assy

20. Stand # 1 Fibre bearing set for 3 rolls 2 sets

21. Stand # 2 - 13 Antifriction bearings for the mill rolls 2 Nos pertype/ size

5.3 GENERAL SAFETY PRECAUTIONS FOR EQUIPMENTS & OPERATORS

5.3.1 Re-Heating Furnace (RHF)

The way of prolonging the life between repairs is to use sufficient care in

charging centrally in the furnace width, not allowing scaling of the billets,



84

not charging ingots that have heavy piping which can open out in the hot

zones and disgorge the slag onto the hearth, not allowing the flame to

touch any refractory especially the sidewalls and roof, preheating the

combustion air to the maximum extent and preventing blowing in of cold air

which will quench the bricks and cause early thermal shock damage.

The limits of operating the Pusher should be set so that the pusher screw

does not over travel in the forward & return directions otherwise the nut

would get out of the screw and it would take a long time for rethreading

the screw into the nut.

The pusher should not be operated without getting a green signal from the

ejector operator.

The ejector operator should not eject the ingot/ billet unless he gets a bell

signal from the Roughing Mill (RM) desk operator.

The ejector operator should stop ejection once the roughing mill desk

operator rings the “misroll” siren. Ejection should continue only when the

RM desk operator gives the bell signal.

No cotton waste or other inflammable matter should be left lying around

the fuel supply system.

CO2 Fire extinguishers should be kept in an easily accessible location in caseof any oil fire. Water should not be used because the oil would float on the

water and could spread the fire.

Care should be taken to see that any oil spillage should be immediately

wiped clean and sand spread over the spill.

There should be electrical interlock that when the ejector is working the

pusher should not operate and vice versa to avoid serious damage to the

equipment.

There should be an Alarm in RHF to indicate Temperatures above 1300 degC

so that overheating of Refractories, Furance shell could be avoided.

All V-Belts should be suitably protected by acrylic belt guards to get a

proper view of the running belts for condition monitoring.



85

All chain drives should be protected by suitable covers to prevent

accidental entangling of clothes or body parts.

The operators should be clad in full safety attire, including safety shoes,

safety helmet, safety blue goggles, ceramic fibre cloth apron and elbow

length hand gloves while handling ingots/ billets in and out of the furnace

and whenever he works near the furnace with the window open.

The operator shall be trained in fire drill to take care of emergencies.

The Operator should not operate any equipment that is under Maintenance

and when a ‘danger cum do not operate’ tag has been put on the operating

push button.

The Maintenance staff should not work on any equipment until they take a

proper shutdown from the operating and electrical staff, and until they put

a ‘danger cum do not operate’ tag on the operating push button.

Maintenance staff should not work near any rotating equipment wearing

loose clothes.

No safety interlock should be bypassed except for Maintenance purposes.

Such interlocks should be restored as soon as the Maintenance work is over.

In order to obtain good life of the refractories the following points may be

kept in mind:1. Sufficient expansion joints should be provided in each row of

refractory bricks. If castable are used on the furnace hearth then

expansion joints should be provided there also. These joints ensure

that there is no bulging out of refractories while being heated the

first time.

2. Newly laid refractories have to go through a drying cycle as per the

manufacturers specifications.

3. Care must be taken to see that water does not fall on the hot

refractories to avoid spalling. Precaution should be taken for the

hearth in line with the ejector, which is water cooled and there is

every possibility of water drops being carried into the hearth area



86

through the excess water spray splashing or slope formed by the

pusher billet bar overhang.

4. The burner blocks should be regularly cleaned of the carbon deposits

formed due to drip of oil from the burners.

5. Burner nozzle should be regularly cleaned, preferably every night

after shutting down the Reheating Furnace.

6. After shutting off the oil supply for shutting down the furnace the

atomization air should be allowed to flow for at least half an hour to

ensure that no oil cakes form inside the nozzle tube.

7. After allowing flow of air through the burner for half an hour after

shutting down the furnace, the blower should be stopped otherwise

the furnace would cool down.

8. All the doors and windows are then shut tight and the damper before

the recuperator in the flue duct should be closed. The end wall

refractories can be inspected from the charging door at the pusher

end.

9. Before shutting down the furnace, as many billets as possible from

the soaking zone area should be emptied out and rolled without

pushing more billets into the furnace. The next side window to thedischarge window can be opened and the billets manually pushed in

front of the ejector to be pushed out for rolling. This will ensure that

the high temperature billets do not remain in the furnace to form

scale during the time the furnace is shutdown.

10. A scraper head can be attached to the ejector bar and the hearth can

be scraped clean of accumulated scale and slag.

11. After shutting down the furnace the side service windows should be

opened one by one and as much of scale and slag approachable

should be cleaned out from the ends of the billets. At this time the

refractories of the sidewalls can be inspected for any abnormality.

12. The blower shaft support bearings should be greased by grease gun.

13. The furnace oil filters in the HPU should be cleaned.



87

14. Complete all jobs scheduled as per preventive & predictive

Maintenance schedule.

5.3.2 Rolling Mill

At the rotating platform, sometimes the ingot gets stuck in front of the

hearth and the workers would be required to go over to the other side. They

go dangerously by climbing over the hot roller table. Proper cross over

platforms should be erected at all locations where a person is required to go

to the other side of the roller table/ rolling line.

All along the length of the Rolling Mills a designated walkway about 2m

wide should be provided. All along this path there should be necessary

protective handrails wherever the walkway comes near the rolling line.

There should be interlocks to prevent the operation of the tilting table

when the roller table on the Ingoing side of the mill is operational.

There should be interlocks when the centralized lubricating system is not

functioning and oil pump pressure is less than 1kg/cm2 the main drive

should not work.

In case of Miss Roll, the Alarm at RHF is sounded to reduce combustion in

furnace.

The belt drive of the main mill motors should have a safety protective

guard, preferably acrylic transparent. If this is not in position the motor

should not be switched on.

There should be alarm buttons at every 20m on the shop floor so that

anyone can press the alarm button in case he notices an abnormal and

unsafe condition. All alarms should be reset only under the direction of the

shift in charge.

No work, Maintenance or otherwise, should be undertaken on rotating

equipment unless a proper shutdown has been taken and a “Danger Tag”

hung from the handle of the panel pertaining to that particular equipment.

The fuses should be taken out or the breaker switched OFF and the



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electrical shift in charge should give the necessary permission to work on

the equipment.

The crane wire ropes should be inspected for breaks in the wires on the

strands. The EOT Crane should be subjected to load test at 125% full load

with the trolley at the centre of the crane girders and the deflection of the

girders at the centre noted, and tested at 150% rated capacity with the

trolley at the end of the girder and the deflection noted. The deflection

should not exceed 1mm per metre of span of the crane. This test should be

carried out once a year and a log record maintained.

The cooling bed operators should be alerted each time the bar is rolled

after a breakdown or long stoppage.

All the limit settings for Equipment should be done in collaboration with the

suppliers and later from experts within the organizations or consultants

from outside the organization and followed. All displayed in large bold

letters near the equipment as well as in the equipment record book.

Al the overload relays of the electrical system should be operative and

checked at regular monthly intervals.

The factory area should be kept clean and there should be no litter lying

around, otherwise some person could trip and have a fall. The meters on the panel should be periodically calibrated once every six

months.

All the workers should undergo periodic fire-drills and be prepared for any

emergency.

5.4 STANDARD INSTALLATION PROCEDURES FOR CRITICAL EQUIPMENTS

5.4.1 Re-Heating Furnace (RHF)

1. Re-Heating Furnace (RHF) Proper

While planning the installation of a reheating furnace the following points

have to be kept in mind:

It should be located near the roughing Mill Stand #1, and near the exit of

the steel melting shop Continuous Casting Machine (CCM.



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The pusher RHF has to be provided with billet storage and feed table, a

pusher mechanism to push the billets into the furnace, an ejector

mechanism to eject the billets into the furnace, an ejector mechanism

to eject the billet onto a roller table for onward transmission into the

Rolling Mills 1st Stand.

The RHF is a closed firebox and any damage to the interior of the

furnace can be repaired by shutting down the furnace, cooling it

sufficiently for people to go into the furnace and work hence

spacing/clearances from all sides is very essential.

The RHF should be installed properly as per the Supplier’s Drawing &

should be aligned.

2. Pusher

The pusher stroke is determined by the RHF designer. Normally it varies

between 700mm-1200mm. The screw length is accordingly designed

keeping in mind a free length of 150 mm at either end of the stroke

limits. The nut assembly is installed first, at the centre of the furnace

width if single pusher and single row/ double row charged. If individual

pushers are to be installed for each row in a double row charged

furnace, then each pusher is centered at ¼th the furnace width. The nut

is installed at centres as above. The screw is threaded into the nut and

positioned at the rear end of the stroke. The support bearings of the

screw are installed. The worm and worm wheel gearbox is installed and

its coupling aligned with the coupling of the screw. The final alignment

is verified with a dial gauge. The motor is then installed and its coupling

aligned with the gearbox worm shaft coupling. Fill the gearbox with

lubricating oil, Servogear or equivalent. Check & lubricate the screw &

nut assembly with EP3 grease. Make the electrical connections to the

motor. Fix the pusher head to the nut and fit the guide bushes and the

guide rods. Take trials firstly on no load and subsequently on full load.



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3. Ejector

The pinch roll assembly is mounted on the movable platform carrying the

channel in which the ejector billet is placed. The billet is gripped

between the pinch rolls. The bottom pinch roll is aligned exactly at right

angles to the billet. The gearbox output shaft coupling is aligned with the

bottom pinch roll coupling. A gap of 5 mm is maintained between the

couplings, uniformly all around the circumference. A dial gauge is used to

fine align the couplings. The gear coupling covers are then bolted. The

motor is then mounted on the base attached to the gearbox. The coupling

of the motor is aligned with the coupling of the gearbox keeping uniform

gap of 5 mm between the couplings. Final alignment is done using a dial

guage. Oil is topped up in the gearbox, connections made for the motor

and trials taken for smooth operation. To ensure proper gripping of the

billet between the pinch rolls the top pinch roll spring loaded bolts are

tightened sufficiently. Take trials on no load and subsequently on full load

by pushing a billet out of the furnace. Try the cooling water spray on the

billet.

4. Blowers

The blowers are installed close to the burner header as well as close to

the flue ducting so that the air could be preheated. There should be

sufficient space all around the blower for ease of Maintenance in

transporting the heavy motor, installing the motor and blower assembly

etc, easy pipe routing avoiding many bends before it enters the

recuperator. The shaft and impeller should be easily accessible. The shaft

bearing housings should be provided with a grease nipple for ease in

greasing.

5. Recuperator

Line the flue duct with IS6 and insulating bricks. Place the recuperator

in the duct. The top header should rest on the flue duct top opening

collar. A layer of ceramic fibre strip should be placed first on the collar



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of the duct on which the recuperator would rest. The bottom header or

tube bends should be freely suspended to allow for expansion. The

blower outlet is connected to the inlet of the recuperator. The inlet of

the recuperator is on the chimney side of the flue ducting so that the air

inlet is preheated and then enters the hotter side of the recuperator,

and then goes to the burner headers of the soaking and heating zones.

The joints of the air inlet and outlets and the recuperator are sealed

with asbestos flat tapes coated with holdtite compound.

5.4.2 Rolling Mill Stand

Foundation: Prepare the foundation as per the drawing of the civil Engineer.

Pockets should be left for the foundation bolts. For getting exact centredistance of the bolts a wooden or steel template is prepared.

Levelling, Aligning & Grouting:

a) The threaded portion of the foundation bolts should be projecting out

of the nut and checknut and washers by about 30mm.

b) Stretch a piano wire along the two axes of the machine along the

centre lines.

c) Place the pedestals of the Rolling Mill Stand over the bolts as per the

centre lines and fit the nuts loosely in the bolts. Centre the pedestal

by placing a plumb bob from the piano wire to align with the centre of

the pedestal.

d) Level the pedestals using a machine spirit level of 0.001” accuracy and

lift or lower the pedestal corners using the jack bolts provided.

e) Grout the foundation bolts using 1:2:4 concrete mixture in the

respective pockets.

f) Allow minimum 4 days setting time and keep replenishing with curing

water.

g) Tighten the foundation bolts. Check the level again and fine-adjust

with the help of jack screws if there is any error. Pack up the gaps left

by jacking the screws with brass shims and tighten the base bolts once



again. Check with spirit level again. Repeat the operations until the

stand is perfectly level, housing liners vertical and the stand housing

exact centre lines axially and longitudinally.

h) Place the stand over the pedestals and check the verticality by spirit

level which has right angled machined surfaces, centre line and

horizontality. Correct as required. Tighten the Stand base bolts on the

pedestal.

i) Prepare the roll assembly in the roll shop. Lubricate the bearings with

EP3 lithium based Grease. Oil the side wear liners on the stand and

bearing housings. Bring the assembly to the Stand and insert into the

housing. Assemble the middle and top roll assemblies. Close the top

cap of the housing and tighten the spring bolts.

j) Attach the rest bars to the middle and bottom.

k) Repeat for all the Stands

l) Before commissioning the Machine, tighten all the loose wires and

cables.

m) The insulation resistance of the motor windings between each terminal

and earth must be checked. This should be more than 1 mega ohm.

This test should be done after every prolonged shutdown of theequipment.

smp final report 10-12-08

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