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CAMTECH\E\2007\SVCB\1.0

Maintenance Handbook on Single Interrupter Vacuum Circuit Breaker (Type 22CB) February, 2007

1

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MAINTENANCE HANDBOOK

ON

SINGLE INTERRUPTER

VACUUM CIRCUIT BREAKER

TYPE 22CB

TARGET GROUP – TECHNICIANS & SUPERVISORS OF AC

ELECTRIC LOCO SHEDS, WORKSHOPS

Centre for Advanced Maintenance TECHnology

Excellence in Maintenance

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CAMTECH/E/2007/SVCB/1.0

Qjojh,2007

February, 2007

dsoy dk;Zky;hu mi;ksx gsrq (For Official Use Only)



2

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MAINTENANCE HANDBOOK

ON

SINGLE INTERRUPTER

VACUUM CIRCUIT BREAKER

TYPE 22CB

TARGET GROUP – TECHNICIANS & SUPERVISORS OF AC

ELECTRIC LOCO SHEDS, WORKSHOPS



3

FOREWORD

With increasing freight and passenger traffic, reliability and availability of electric locomotives have become very important. Proper maintenance of vacuum circuit breakers is vital to ensure good reliability and availability of electric locomotives in service.

CAMTECH has prepared this handbook to cover all essential aspects of maintenance and overhauling of Single Interrupter Vacuum Circuit Breaker Type 22CB. It describes various maintenance schedules, overhauling procedure and failures, causes & their remedial measures. It also contains different replacement kits for overhauling, special tools, consumables for maintenance etc.

I am sure the book will prove to be very useful for our maintenance staff in electric loco

sheds and workshops.

CAMTECH, Gwalior Date : Executive Director



4

PREFACE

Single interrupter vacuum circuit breaker is used to protect power and auxiliary circuits of A.C. electric locomotives and electric multiple units. It also connects and disconnects the 25kV OHE power supply to the locomotive/ EMU through pantograph. Its proper upkeep and maintenance is necessary to ensure reliability and availability of electric locomotives/EMUs in service. This handbook on maintenance of single interrupter vacuum circuit breaker type 22CB has been prepared by CAMTECH with the objective of making our maintenance personnel aware of correct maintenance and overhaul techniques to be adopted in field.

It is clarified that this handbook does not supersede any existing provisions laid down by RDSO or Railway Board. The handbook is for guidance only and it is not a statutory document.

I am sincerely thankful to Executive Director, Std./ Elect./ RDSO/ LKO for his valuable comments. I am also thankful to all field personnel who helped us in preparing this handbook.

Technological up-gradation and learning is a continuous process. Hence feel free to write to us for any addition/modification in this handbook. We shall highly appreciate your contribution in this direction.

CAMTECH, Gwalior Jaideep Gupta Date : 09.03.2007 Director Electrical



5

Chapter No. Description Page No.

Foreword iii Preface iv Contents v Correction Slip vii

1. GENERAL DESCRIPTION 01

1.1 INTRODUCTION 01

1.2 TECHNICAL DATA 01

1.3 CONSTRUCTIONAL FEATURES 04

1.4 OPERATION 13 2. MAINTENANCE 15

2.1 TRIP INSPECTION 15

2.2 IA/IB SCHEDULE 16

2.3 IC SCHEDULE 16

2.4 WORK SCHEDULE FOR AOH/ IOH/ POH 17 3. OVERHAULING PROCEDURE 20

3.1 INCOMING INSPECTION 20

3.2 DISMANTLING 20

3.3 OVERHAULING OF TOP INSULATOR AND MECHANISM ASSEMBLY 23

3.4 OVERHAULING OF MAGNET VALVE ASSEMBLY 26

3.5 OVERHAULING OF RELAY VALVE ASSEMBLY 28

3.6 OVERHAULING OF CYLINDER PISTON ASSEMBLY 29

3.7 OVERHAULING OFAUXILIARY CONTACTS UNIT 30

3.8 OVERHAULING OF PRESSURE SWITCH 31

3.9 OVERHAULING OF PRESSURE REGULATOR 32

3.10 OVERHAULING OF AIR FILTER 33

3.11 FINAL ASSEMBLY 33

3.12 TESTING 36

3.13 METHOD OF CONTACT TRAVEL MEASUREMENT RECORDING 40

3.14 MAINTENANCE OF AIR DRYER 41

3.15 MAINTENANCE OF R-C NETWORK 41

4. FAILURES, CAUSES AND REMEDIAL MEASURES 42 4.1 FLASHOVER IN LOWER INSULATOR/ ACTUATOR ROD 42

4.2 PRESSURE REGULATOR PROBLEMS 42

4.3 VCB CHATTERING 43

4.4 AUXILIARY SWITCH BREAKAGE/ LOW CRUSHING 43

4.5 VACUUM INTERRUPTER FAILURE 43

CONTENTS



6

Chapter No. Description Page No.

4.6 AIR LEAKAGE FROM RELAY VALVE 43

4.7 INSULATOR BREAKAGE 44

4.8 MAGNET VALVE FAILURES 44

4.9 DRYER PROBLEM 44

4.10 BASEPLATE BREAKAGE 45

4.11 RC NETWORK FAILURE 45

5. DO’S AND DON’TS 46

5.1 DO’S 46 5.2 DON’TS 46

ANNEXURE ‘I’ REPLACEMENT KITS FOR OVERHAULING 47

ANNEXURE ‘II’ A. SPECIAL TOOLS 48

B. CONSUMABLES FOR MAINTENANCE 48

C. RECOMMENDED TIGHTENING TORQUES 48 ANNEXURE ‘III’ POINTS RAISED DURING SEMINAR HELD ON 24.07.2006 AT CAMTECH, GWALIOR 49

REFERENCE 51



7

ISSUE OF CORRECTION SLIP

The correction slips to be issued in future for this handbook will be numbered as follows: CAMTECH/E/2007/SVCB/1.0/ C.S. # XX date--- Where “XX” is the serial number of the concerned correction slip (starting from 01 onwards). CORRECTION SLIPS ISSUED

Sr. No. Date of issue Page no. and Item no. modified Remarks

CAMTECH/E/2007/SVCB/1.0


CHAPTER 1

GENERAL DESCRIPTION 1.1 INTRODUCTION

It is the most important switching and protecting equipment which connects & disconnects the 25 kV OHE power supply to the locomotive/ EMU through pantograph. It is a single interrupter type vacuum circuit breaker.

Vacuum has excellent insulating properties and therefore a small contact gap can withstand high voltages. The most beneficial characteristic of switching in vacuum is that it allows high fault current during interruption with minimal contact wear.

1.2 TECHNICAL DATA

1.2.1 Complete Vacuum Circuit Breaker

Type 22 CB Make ALSTOM (AREVA) Rated voltage 25kV, Single phase Rated continuous current 1000 Amps (rms) Rated frequency 50 Hz Rated short time current 16 kA rms/ 3 seconds Rated short circuit breaking current (sym) 16 kA rms (400 MVA) Rated short circuit making current 40 kA peak Rated lightening impulse voltage withstand 175 kV peak Rated power frequency voltage (Dry & Wet) 75 kV rms Number of phases One Total weight 125 kg (approx.) Life time

Mechanical Electrical

3,00,000 operations (Under no load conditions) 1,00,000 operations

Figure 1.1 Vacuum Circuit Breaker Type 22CB



2

1.2.2 Contact Travel Parameters

Total travel : 9.8 mm to 11.3 mm

Contact gap (new) : 5.8 mm to 6.4 mm

Contact overtravel : 4.0 mm to 4.9 mm

Contact wear : 3 mm (max.)

Closing time : Within 145 milli-sec

Closing speed : 0.1 m/sec to 0.4 m/sec

Opening time : Within 45 milli-sec.

Opening speed : ≥ 0.7 m/sec.

Contact bounce duration : 10 milli-sec (max.) 1.2.3 R-C Network

Resistance 4.7Ω, 380 Watts Capacitance 25µF, 560 Volts Permissible current across each RC at 415V AC, 50Hz

2.75A to 3.75A

1.2.4 Magnet Valve Assembly

Type 33 MV

Rated operating voltage 110 V DC

Minimum operating voltage 70 V DC

Maximum operating voltage 125 V DC

1.2.4.1 Operating Coil

Coil resistance 840Ω ± 5% at 20°C Power consumption 18 Watts Class of insulation F

1.2.3.2 Surge Suppressor Unit

Permissible current at 110 V AC, 50Hz 14 mA to 19.5 mA

1.2.5 Pressure Switch

Type RT 116 Make Indfoss Range 1 to 10 ATMG Pressure settings Cut-off 3.85 – 4.0 kg/cm2 Cut-in 4.60 – 4.75 kg/cm2 Contact configuration 1 N/O + 1 N/C



3

1.2.6 Pressure Regulator

Type R07

Make Shavo-Norgren

Primary pressure range 0 to 18 kg/cm2

Pressure setting 5.0 – 5.2 kg/cm2

1.2.7 Air Filter

Type F07

Make Shavo-Norgren

Primary pressure range 0 to 18 kg/cm2

Bowl material Aluminium

1.2.8 Auxiliary Contacts Unit

Type Double break, fish bone

Continuous current rating 10 Amps D.C.

Breaking capacity 2.5 A at 125 V DC with a time constant > 15m-sec.

Total travel of moving contact carrier 9 mm (approx.)

Number of contacts Eight

Number of contacts interchangeable All

Contact configuration As per requirement

1.2.9 Molecular Sieves

Type 4A

Make IPCL, Thane

Size and form φ 3mm cylindrical pellets.

Equilibrium water absorption capacity

At 15% R.H.

At 60% R.H.

18.0%

22.0%

Nominal pore diameter 4°A



4

1.3 CONSTRUCTIONAL FEATURES

Two porcelain weather proof insulators are mounted vertically, one above the other, on a cast aluminium baseplate. Upper terminal of the VCB is used as incoming connection from the pantograph and lower terminal is used as outgoing connection to the roof-bushing/ cable for transformer connection on the roof of locomotive. The cross sectional view of the single interrupter vacuum circuit breaker is shown in figure 1.2.

The vacuum interrupter which houses the main switching contacts along with its operating mechanism, is housed in the top insulator and is electrically between the busbars. Chromium copper castings, which are cemented to the top insulator, carry the current between the interrupter and the busbars. Bottom insulator assembly is separately bolted to the baseplate using clamping ring.

Cylinder, piston and relay valve assembly are mounted inside the baseplate. An actuator rod, located inside the hollow bottom insulator is connected on one end to main piston and on the other end to operating mechanism. This actuator rod closes the contacts of VCB when magnet valve is energized. The opening mechanism, which is mounted on vacuum interrupter itself, ensures that the VCB remains open when magnet valve is de-energised. Auxiliary switch and all control equipment used to monitor electrical and pneumatic supplies are mounted within the baseplate.

Details of Figure 1.2

Item Description Item Description 1 Upper terminal (incoming) 27 Packing washer 2 Vacuum interrupter 28 Drive rod for 15 4 Shunt collector ring 29 Link for 15 5 Lower terminal (outgoing) 30 Piston 7 ‘O’ ring 31 Piston seal ring 8 Top casting for 36 32 Bottom access cover 9 Compression ring 33 Sealing section 10 Flexible shunt 34 Air reservoir 11 Connector block for 10 35 Rating plate 12 Actuator rod 36 Bottom insulator 13 Lower casting for 36 37 Drive plate assembly 14 Clamping ring 38 Spring 15 Auxiliary contacts unit 39 Spacer 16 Magnet valve assembly 40 Mechanism stop 17 Pressure switch 41 Spring 18 Pressure regulator 42 Top insulator 19 Gasket 43 Lower spring plate 20 Baseplate 53 Rod end spherical bearing 21 Connector mounting plate 57 Air connector (supply) 22 Air filter 60 * Electrical connector (optional) 24 Relay valve assembly 62 Cable tie bar 26 Shim (steel) 71 Upper spring plate 77 Terminal strip

* This is optional feature and is supplied on demand; it replaces the moulded type terminal strips.



5

Figure 1.2 Cross Section Through the VCB

20 21 22 57 60*

77

32

62

3

1

30

29

53

2

8

24

16

15

1

7

19 34 33



6

Following are the main parts/ sub-assemblies of VCB:- 1.3.1 Vacuum Interrupter

The vacuum interrupter comprises two copper alloy contacts, one fixed and the other moving. The fixed contact is mounted on a metal flange which carries the ceramic envelope of the chamber. The ceramic envelope is generally in two parts with a metal shield fixed between them. This shield protects the ceramic parts against deposition of metallic vapour produced by the arc when the contacts open. The moving contact travels in a guide which assures its axial positioning and the correct angle of movement. Sealing of the moving contact is assured by metal bellows which are welded both to it and to the end flange which is integral to the ceramic cover. The internal view of the vacuum interrupter is shown in figure. 1.3

Figure 1.3 Cross Section through the Vacuum Interrupter 1.3.2 Magnet Valve Assembly

The magnet valve assembly consists of a magnet yoke, to which is bolted a valve body, block and an operating coil. An armature is slotted into the magnet yoke. The valve body assembly consists of two fluted rubber valves, two springs and a valve stem which, located in each valve, passes through a central hole in the valve body.

The valve body has four ports 16/A, 16/B, 16/C and 16/D. Through port-A, the

operating peg (16/5) of the armature plate is in contact with one end of the valve (16/8). When the magnet valve is mounted on relay valve, which it controls, each of the ports

16/B, 16C and 16/D coincide with corresponding ports in relay valve body. One of the corresponding ports in relay valve leads to the compressed-air supply, another leads into the VCB itself and a third port leads to the atmosphere.

The exploded and sectional view of the magnet valve assembly is shown in figure. 1.4

Moving-contact stem

Bellows

Sputter shield

Moving contact Fixed

contact Glass ceramic body

Moving contact Grading Sputter-shield Guide shield mounting

Fixed contact stem



7

Figure 1.4 Magnet Valve Assembly

Sectional view of magnet valve

Exploded view of magnet valve

16/4 16/3 16/2

16/5 16/6

Port 16/A

16/7

16/8

16/9

16/10 16/11

Port 16/B

Port 16/C

16/12

Port 16/D

16/13 16/14

16/15

16/18

16/1

16/17

16/16

16/5 16/6

16/7 16/8 16/9

16/10 16/11

16/13

16/14

16/15

16/4 16/3

16/2

16/16 Port A

16/12

Port B

16/12

Port C

16/12

Port D

16/18

16/19

Item Description 16/1 Magnet yoke 16/2 Armature plate 16/3 Locknut for 16/5 16/4 Retaining nuts 16/5 Operating peg 16/6 Top plate 16/7 ‘O’ ring 16/8 Valve 16/1 Spring 16/10 Valve stem 16/11 Valve body 16/12 ‘O’ ring 16/13 Valve 16/14 Spring 16/15 ‘O’ ring 16/16 Valve body bolt 16/17 Operating coil 16/18 Block 16/19 Surge suppressor



8

1.3.3 Relay Valve Assembly

The relay valve assembly consists valve body, piston, poppet valve, valve stem, two valve discs and the spring. The cross sectional view of relay valve assembly is shown below in fig 1.5

Figure 1.5 Relay Valve Assembly

Item Description Item Description 24/1 Valve body 24/10 Stem 24/2 Top plate 24/11 Stud 24/3 Bottom plate 24/12 M6 x 14Lg Hex Hd screw 24/4 Piston 24/13 Spring 24/5 Piston seal 24/14 M6 x 12Lg Hex Skt C’sk Hd Screw 24/6 Valve disc 24/15 M8 x 30Lg Hex Skt C’sk Hd Screw 24/7 O-ring 24/16 O-ring 24/8 Poppet valve 24/17 O-ring 24/9 O-ring * Bond valve discs to poppet valve and

piston with RTV 1080 sealant

24/12 24/3 24/4

24/17

24/1

From main air supply

To magnet valve From magnet valve

24/15



9

1.3.4 Cylinder Piston Assembly

The cylinder piston assembly consists damper assembly, link, piston, drive link and drive stud as shown in figure 1.6.

Figure 1.6 Cylinder – Piston Assembly

1.3.5 Auxiliary Contacts Unit

As shown in figure 1.7 given below, the auxiliary contacts unit consists four normally closed (NC) contacts and four normally open contacts (NO).

Figure 1.7 Auxiliary Contacts Unit Assembly

Item Description Item Description 15/1 Fixed contact carrier moulding 15/11 Moving contact carrier cover 15/2 End plate 15/12 M4 x 8Lg slotted ch. Hd. Screw 15/3 Moving contact carrier 15/13 6BA x ¼” Lg Slotted Ch. Hd.screw 15/4 Compression spring 15/14 M4 Hex nut 15/5 Roller 15/15 M4 stud 15/6 Moving contact with tip 15/16 Silicon sealant type RTV1080 15/7 Fixed contact with tip 15/17 Mounting bracket (Rear) 15/8 Fixed contact carrier 15/18 Guide bracket 15/9 Retaining clip 15/19 Roller bracket 15/10 Mounting bracket (Front) 15/20 M4 Lock nut

Item Description 24 Relay valve assembly 24/16 O-ring 25 Damper assembly 29 Link 30 Piston 31 Piston seal ring 46 Connecting link 49 Cylinder 50 Drive link 51 Drive stud 52 Bearing pin 53 Rod end spherical bearing 55 Stud 59 Piston stop ring 65 Reducer

15/13

15/3

15/16

15/8 15/11

15/7

31

25

65 24/16

49 59 30 24

50 52 29

51 53

46

15/17 15/6

15/20

15/15 15/14

15/10 15/19

15/5 15/4 15/18

15/2 15/1

15/12 15/9 15/2

55



10

1.3.6 Pressure Switch

It is a differential pressure switch, which operates by changes in fluid pressure. It consists operating mechanism and a micro switch with two sets of contacts, one normally closed (NC) and one normally open (NO).

Different parts of pressure switch are shown below in figure 1.8.

Figure 1.8 Pressure Switch 1.3.7 Pressure regulator

Two types of air pressure regulators are being used on this type of VCB. Previously black coloured plastic body regulator was being used which was later on replaced with brass bonnet regulator. The assembled/ exploded view of pressure regulator is shown in figure 1.9a & Fig. 1.9b given below respectively.

Figure 1.9a Assembled View of Pressure Regulator

Item Description

17/1 Setting knob

17/2 Range scale

17/3 Coil clamp

17/4 Cable entry

17/5 Main spring

17/6 Connection terminals

17/7 Main spindle

17/8 Microswitch

17/9 Upper guiding bush

17/10 Contact arm

17/11 Differential setting roll

17/12 Bellows element

17/13 Mounting holes

17/14 Connection

17/15 Earth screw

17/16 Setting spindle

17/1

17/13

17/2

17/3

17/4

17/5

17/16

17/6

17/7

17/8

17/9

17/10

17/13

17/11

17/15 17/12

17/14



11

Figure 1.9b Exploded Views of Pressure Regulator 1.3.8 Air Filter

It is installed in the pneumatic circuit of VCB, upstream of pressure regulator and inlet

air is connected to the port marked ‘IN’.

The cross section & exploded views of air filter is shown in figure 1.10.

Figure 1.10 Cross Section and Exploded Views of Air Filter

Item Description

18/1 Bonnet Assembly

18/1(a) Adjusting Screw

18/1(b) Lock nut

18/1(c) Bonnet

18/1(d) Upper Spring Rest

18/2 Regulating Spring

18/3 Slip Ring

18/4 Diaphragm Assembly

18/4(A) Diaphragm assly for brass bonnet model

18/5 Valve seat

18/6 Gasket

18/7 Valve assembly

18/8 Valve spring

18/9 Zinc body

18/10 Brass body

18/11 Pipe plug 1/8” BSPT

Item Description

22/1 Body

22/2 ‘O’ ring

22/3 Louver deflector

22/4 Upper gasket element

22/5 Filter element

22/6 Lower gasket element

22/7 Stud

22/8 Valve assembly

22/9 Insert

22/10 ‘O’ ring

22/11 Transparent bowl or metal bowl

22/12 Retainer insert

22/13 Valve

22/14 Insert

22/15 Hexagonal nut

22/16 ‘O’ ring

18/1 (a)

18/1 (b) 18/1 (c)

18/1 (d)

18/4 (A) 18/10

18/11

22/1 22/2

22/3

22/4

22/5

22/6

22/7 22/8 22/16 22/9 22/10 22/11 22/12 22/14 22/10 22/15

IN

Automatic drain

22/13 Manual drain



12

1.3.9 Air Dryer It is installed in pneumatic circuit of locomotive/ EMU just before the VCB to ensure

that compressed air supply being fed to the VCB is dry. This air dryer is filled with molecular sieves that serve as the drying agent. This air dryer should be used for VCB only.

Filter sieve

Filter sieve

Drying agent

Body

Mounting lug

2 mounting holes φ 13.5

150

Figure 1.11 Air Dryer Assembly



13

1.4 OPERATION

As shown in figure 1.12, compressed air reaches the air reservoir (34), via air filter (22) and pressure regulator (18). A spur is connected to the control governor (pressure switch, 17). Air supply is then fed to relay-valve assembly (24). Pressure of compressed air inside VCB is regulated at 5.0 – 5.2 kg/cm2, by the pressure regulator (18).

Pressure switch (17) is connected electrically in series with the magnet valve (16);

therefore the VCB opens automatically if air pressure falls below 3.85 – 4.0 kg/cm2. To close the VCB, pressure of compressed air supply must exceed 4.60 – 4.75 kg/cm2.

Auxiliary Contacts

(15)

To vehicle system

Vacuum Bottle

Pantograph

This equipment is regarded as single assembly

Cylinder (49)

Relay Valve (24)

Magnet Valve (16)

Solenoid

Mechanical interlock

Pressure Switch (17)

Air Supply Air Filter

(22) Pressure regulator

(18)

Air Reservoir (34)

D C

E

B D

Figure 1.12 Simplified Air - System Diagram



14

To close the main contacts of VCB, magnet valve (16) is energised; this operates the relay valve (24). A parallel air-supply is then fed directly through the relay valve into the cylinder (49). As the main VCB piston (30) moves, so does the auxiliary-contacts drive mechanism, this operates the auxiliary contacts.

Refer fig. 1.2, actuator rod pushes against the mechanism below the vacuum interrupter

(2). As the actuator rod moves upwards, so does the drive plate (37) and spacer (39). This in turn moves the spring plate (43) and compresses the springs (41). The moving contact closes under the influence of atmospheric pressure acting on the bellows. As soon as the contacts touch, springs (38) are compressed, giving an immediate increase in contact force through the connector block (11), thereby minimising contact bounce. Mechanism movement continues until drive plate (37) bears against the connector block (11) with the piston force acting against the contacts.

The mechanism is now charged and flexible shunts (10) carry the current out from the moving stem of vacuum interrupter to chromium copper lower terminal casting (5). When the magnet valve is de-energised, the air is discharged from cylinder through exhaust of relay valve assembly to atmosphere and the springs (41) force the spring plate (43) to hit the connector block (11). This ‘Snatch Effect’ breaks any contact weld and opens VCB main contacts.

******



15

CHAPTER 2

MAINTENANCE

Periodical maintenance is essential to ensure safety, reliability and continuous operation of vacuum circuit breakers over long time periods.

Following maintenance schedules are to be followed for vacuum circuit breakers (type

22CB) provided on locomotives.

Schedule Freight locomotives Pass./ Mail/ Exp. train locomotives

TI 20 days Every 3000 Km. or one trip which ever is later

IA 45 days 40 days

IB 90 days 80 days

IC 135 days 120 days

AOH 18 months 12 months

IOH 54 months or 6 lakhs kms. which ever is earlier

36 months or 4 lakhs kms. which ever is earlier.

POH 9 years or 12 lakhs kms. which ever is earlier

6 years or 8 lakhs kms. which ever is earlier.

Note:

1. All maintenance work of VCB on roof of the locomotive must be carried out only after the locomotive is brought under isolated section of OHE and also ensure that OHE isolator is locked in earthed position.

2. Earth OHE properly by earth connected earthing rod and also observe local safety

regulations positively.

Work to be carried under each maintenance schedule is given below. 2.1 TRIP INSPECTION

Carry out the following inspection:

SR. NO.

PART TO BE

INSPECTED INSPECTION DETAILS STANDARD

VALUE

1. Insulators i. Check visually for cracks, chips, flash marks.

ii. Clean with soft, clean and dry cloth.

No abnormality.

2. Air inlet pipe Check air inlet pipe connections for tightness and proper support.

OK.



16

2.2 IA/IB SCHEDULE Carry out the following inspection:

SR. NO.

PART TO BE


VALUE

1. Insulators i. Check visually for cracks, chips, flash marks.

If minor damage (chips, small cracks & scratches) found, it can be repaired with epoxy resin. If the damage is more severe, replace the VCB.


If necessary, first use a cloth moistened with white spirit, then finish off with dry lint-free cloth.

No abnormality.

2. Incoming and out going connections of VCB on the roof of the locomotive.

Check visually for any overheating, flash marks and also check the intactness of connections by hand.

OK.

Intact

3. Air inlet pipe Check air inlet pipe connections for tightness and proper support.

OK.

2.3 IC SCHEDULE

In addition to inspections given in IA/IB schedule, following work also to be carried out.

SR. NO.

PART TO BE


VALUE

i. Remove both air connections from the air dryer. Remove the mounting bolts and release air dryer assembly from locomotive.

ii. Check the weight of air dryer; if it is more than 0.8 kg from the new weight, change/ regenerate molecular sieves. Method of regenerating molecular sieves is given in section 3.14 of chapter 3.

1. Air dryer

iii. Remount air-dryer assembly inside locomotive and reconnect the pneumatic supply connections.

Weight within new weight + 0.8 kg.



17

2.4 WORK SCHEDULE FOR AOH/IOH/POH Indicates item to be checked. Indicates item to be replaced.

SR.

NO

PART TO BE

INSPECTED INSPECTION DETAILS AOH IOH POH

i. Check the contact travel,

New interrupter contacts = 5.8 – 6.4 mm

With eroded contacts = 8.8 – 9.4 mm

ii. Check the mechanism over travel. This should be between 4.0 mm to 4.9 mm, after contacts close.

iii. Check the soundness of interrupter by applying 60 kV, 50Hz for one minute across incoming & outgoing terminals, in breaker open condition.

1. Vacuum interrupter

iv. Check the distance of datum line on the moving contact stem from the edge of interrupter body. For new contacts, this gap = 3 mm and for fully worn contact = 0-1mm, when VCB is closed. Change top insulator & vacuum interrupter assembly with fully worn out contacts.

---

i. Check for cracks, chips, flash marks. 2. Insulators


i. Check the setting of regulator using a calibrated pressure gauge. This should be set at 5.0-5.2 kg/cm2.

ii. Dismantle, wipe clean the parts using lint-free cloth moistened with white spirit and blow out the body with clean compressed air. Re-assemble the parts.

3. Pressure regulator

iii. Change all components provided in replacement kit.

--

4. Pressure switch

i. Check the setting of pressure switch using a calibrated pressure gauge fitted to pressure regulator. Ensure that the switch:

Closes between 4.6-4.75 kg/cm2 & opens between 3.85 – 4.0 kg/cm2.



18

SR. NO

PART TO BE


i. Clean the contacts.

ii. Check the tightness of all fixing bolts, nuts and connections.

iii. Check proper operation of contacts.

iv. Check the contact pressure (crushing).

5. Auxiliary switch

v. Replace complete switch with new one. -- --

i. Check tightness of all connections and fixing screws.

ii. Check air leakage by operating manually

6. Magnet valve

iii. Replace all O-rings & 2 nos. valves (fluted)

i. Drain off condensate from filter.

ii. Wash porous filter element with denatured alcohol or kerosene.

iii. Blow-out body with clean compressed air.

iv. Wash the bowl with household soap.

7. Air filter

v. Change all components provided in replacement kit.

i. Check its healthiness by applying 110V AC, 50Hz across it. Current shall be between 14.0 to 19.4mA. Replace if not in range.

8. Surge

suppressor (Magnet Valve)

ii. Replace old unit with new one. --

i. Replace all O-rings & PTFE valve discs.

ii. Overhaul and lubricate the relay valve.

iii. Replace old piston seal ring with new one. --

9. Relay valve

iv. Replace old poppet valve with new one. -- --

i. Overhaul and lubricate the piston and cylinder bore.

ii. Replace one no. damper assembly. --

10. Cylinder piston assembly

iii. Replace old piston seal ring with new one. --

11. Air piping i. Check for air leakage at all joints.

12. Electrical connections

i. Check for proper tightness of all electrical connections at terminal strips, magnet valve, pressure switch & auxiliary switch.



19

SR. NO

PART TO BE


13. Lubrication i. Lubricate the relay valve assembly, cylinder- piston assembly and all piston seal rings/ O-rings including those of magnet valve assembly, with silicon grease (Molykote 55M).

14. Rubber/ PVC items

i. Change all rubber/PVC/SRBC items supplied in the replacement kits.

15. Springs i. Change all compressions spring supplied in replacement kit.

-- --

i. Check the closing speed/ timings with the help of contact travel recorder.

16. Complete

VCB assembly ii. Measure contact resistance of main circuit.

i. Weigh the air dryer. If increase in weight is more than 0.8 kg from the new weight, regenerate by heating in oven.

17. Air dryer

ii. Replace old molecular sieves. --

18. R-C network

i. Measure current value across individual R-C network at 415 V AC (50Hz). Value should be between 2.75A to 3.75A. replace if not in range.

Detailed overhauling procedure of different sub assemblies of VCB is given in chapter 3.

******



20

CHAPTER 3

OVERHAULING PROCEDURE

3.1 INCOMING INSPECTION

After removing the VCB from the locomotive, bring it to the VCB repairing section and mount it on VCB handling trolley.

• Check both the insulators visually for any cracks and chips.

• Turn VCB over so that base plate is upper most and remove the bottom access cover.

• Visually check the components fitted inside base plate for any sign of damage/ abnormality.

• Connect 110V d.c. supply to coil terminals through a N/O contact of a push button and also connect air supply pipe to VCB air inlet (air connector) and ensure pressure gauge pressure is 5.0 – 5.2 Kg/cm2.

• Operate VCB manually by depressing the armature plate of magnet valve and check that the breaker operates freely and that the auxiliary contacts drive mechanism functions correctly. If any abnormality or air leakage is noticed, record the same.

• Operate VCB electrically and check that the auxiliary contacts drive mechanism functions correctly. If any abnormality or air leakage is noticed, record the same.

• Disconnect 110V dc supply and air supply.

• Refer VCB previous history. 3.2 DISMANTLING (Refer Figure 1.2 & 3.1a/b)

Keeping the base plate upper most, remove the following components:

1. Remove link (29) and connecting link (46) from the drive rod (28). Fold drive rod backwards (towards auxiliary switch).

2. Remove plug (66) from the base of cylinder (49); then unscrew and remove the M12 securing screw from piston (30).

3. Disconnect all cable terminated at the terminal strips. Remove the terminal strips mounting bracket (76) by opening two M6 hexagonal nuts and one M8 screw.

4. Remove the control wires from magnet valve (16). Release coupling screws at relay valve (24), air reservoir (34) and remove air pipe (64).

5. Remove four numbers M8 screws securing the cylinder (49) to baseplate (20). Now remove cylinder assembly complete with the piston (30), relay valve (24) and magnet valve (16). Note that a jerking action may be required in order to release the piston (30) from actuator rod (12).

6. Disconnect and remove air-pipe (3) between air reservoir (34) and pressure regulator (18), by unscrewing the banjo bolts on each component.

7. Disconnect and remove air-pipe (64) between air reservoir (34) and relay valve (24) by unscrewing the banjo bolts on each components.



21

21 57 22 60 17

6

47 63 16 62 82 54

24 65 64

66

88 48

61

18

15 85

81

84

28

53

52

51

50

49

89

3

23

20

48 34 80 76 77 19

Figure 3.1a Under Side View of VCB



22

20 76 78 77

21 56 60

Figure 3.1b Under Side View of VCB

90

Item Description 3 Air pipe (reservoir to regulator) 6 Pressure switch mounting bracket 15 Auxiliary-contacts unit 16 Magnet-valve assembly 17 Pressure switch 18 Pressure regulator 19 Gasket 20 Baseplate 21 Connector mounting plate 22 Air filter 23 Gasket 24 Relay-valve assembly 28 Drive rod for 15 29 Link for 15 34 Air reservoir 46 Connecting link 47 Air pipe (regulator to filter) 48 Reservoir mounting bracket 49 Cylinder 50 Drive link 51 Drive stud 52 Bearing pin 53 Rod-end spherical bearing 54 Cable tie-bar 56 Air pipe (filter to air connector) 57 Air connector (supply) 59 Piston stop ring 60 Electrical connector (optional) 61 Regulator mounting bracket 62 Cable tie-bar 63 Air pipe (pr. Regulator to pr. Sw.) 64 Air pipe (reservoir to relay-valve) 65 Throttling valve 66 Plug 76 Terminal strips mounting bracket 77 Terminal strip 78 Conduit entry plate 80 Grommet 81 Cam 82 Bearing pin for cam 83 Cam shaft 84 Special screw 85 Auxiliary switch mounting bracket 88 Cable tie-bar 89 Cable tie-bar 90 Pressure gauge

89



23

8. Disconnect all control cables from auxiliary contacts unit (15) and pressure switch (17) making a note of the positions of all wires to facilitate reassembly. Since the wires have already been disconnected from magnet valve and terminal strips, the cabling can now be released from cable tie-bars and removed along with the electrical connector (60), if fitted. Unless they have sustained damage, the tie-bars can be left in position.

9. To remove auxiliary contacts unit (15), release the drive rod (28) from cam by opening M 5 hexagonal nut and lock nut. Care should be taken not to damage or disturb the length of drive rod (28). Now unscrew three hexagonal head M6 screws that secure mounting bracket (85) to baseplate and release the complete unit.

10. Free air-pipe (47) between pressure regulator (18) and air-filter (22) by unscrewing the banjo bolts at regulator end. Remove the pressure regulator and its mounting bracket (61) by unscrewing two numbers M6 screw from the side of baseplate.

11. To remove air filter (22), release the remaining banjo bolt at air connector (57). Air filter (22), along with the air pipes (47 & 56) are now free to move. Unless air connector (57) has sustained damage, it may be left in place.

12. To remove pressure switch (17), first remove air pipe (63) between pressure switch and pressure regulator. Open the cover of pressure switch by unscrewing the four screws. With the cover removed, access can now be gained to two screws securing the switch to its mounting bracket (6). Open these screws and remove the switch from its mounting bracket. Release the mounting bracket from baseplate by opening two securing screws.

3.3 OVERHAULING OF TOP INSULATOR & MECHANISM ASSEMB LY

(ONLY DURING IOH & POH) 3.3.1 Dismantling (Refer fig. 1.2, 3.1a/b & 3.2)

• Rotate the VCB so that top insulator assembly is uppermost. Remove sealant that

encapsulates screw heads and break the sealant bond between top and bottom insulator assemblies. Remove the eight numbers M8 socket-head screws (86) that secure top insulator assembly to lower insulator assembly.

• Secure lifting frame to upper terminal of top insulator assembly. Taking great care, since the actuator rod (12) is still connected, lift and remove the top insulator assembly. Place the assembly in inverted condition on a soft rubber mat.

• Take a M12 bolt and screw a nut onto it. Now fit this screw into metallic insert of

actuator rod and tighten the nut against flange of insert. Unscrew the bolt, thereby releasing actuator rod from drive plate (37). Ensure that shim/ packing washers placed on stud of drive plate are not misplaced.

• Unscrew and remove three numbers M10 countersunk-head socket screws (68) from drive plate (37). Note that the six springs (38) will tend to push the plate upwards. Remove drive plate, spacers (39) and six-springs. Do not misplace shim washer (if present below drive plate).

• Unscrew the six numbers nyloc nuts (69), then remove special washer (70), shunt and

collector ring assembly (4 and 10) and connector block (11). Unscrew compression ring (72) and remove it. Keep connector block (11) in a safe place to avoid any damage.



24

40 73 72 41

Section ‘A - A’

5.8 Min 6.4 Max.

This shim fitted if necessary to obtain over travel dimension

68

67

70 11 69 10

71

74

Section ‘B-B’

Figure 3.2 Top Insulator and Mechanism Assembly

75

1.0 Min 2.75 Max. 4.0 Min

4.9 Max.



25

Details of Figure 3.2

Item Description Item Description 1 Upper terminal (Incoming) 42 Top insulator 2 Vacuum interrupter 43 Lower spring plate 4 Shunt collector ring 44 Tin washer 5 Lower terminal (Outgoing) 67 Special nut 10 Flexible shunt 68 Hex skt CSK Hd Screw 11 Connector block 69 Nyloc nut 37 Drive plate assembly 70 Special washer 38 Spring 71 Upper spring plate 39 Spacer 72 Compression ring 40 Mechanism stop 73 Stud 41 Spring 74 Shim washer (0.5mm thk) 75 φ 6 Copper rivet

• Using peg spanner, carefully unscrew three stops (40) against the force of six main springs (41) and remove them. Now remove lower spring plate (43), main springs (41), upper spring plate (71) and finally the shims (74) placed under the upper spring plate. Ensure that these shims are not misplaced.

3.3.2 Cleaning/ Examination/ Reconditioning

• Wash all components in non-corrosive degreasing fluid like white spirit and dry them out by blowing compressed air and wiping with dry lint free cloth. If necessary, first use a cloth moistened with white spirit, then finish-off with dry lint free cloth.

• Examine all metal for cracks/ deterioration, replace if found defective.

• Examine all moving parts for the extent of wear; replace excessively worn parts.

3.3.3 Reassembling/ Setting

• Determine the length of M24 moving stem of vacuum interrupter from the three stud-mounting faces, using the 28 mm gauge. By using 0.5mm shims (74) make it 28mm.

Example Length = 29.75mm 29.75 – 28 = 1.75mm Use three shims = 1.50mm

Do not reduce the dimension below 28mm and also do not use more than eight shims.

• Fit the upper spring plate (71) and six main springs (41), replace the old springs by new ones during POH.

• Spray the outer surface of three stops (40) with anti-friction coating (Molykote D321R). Fit lower spring plate (43) and secure it with three stops, applying liquid threadlock (Loctite-242). Use peg spanner for tightening these stops.

• Depress the lower spring plate (43) until a gap of 6.0mm (6.4mm Maxm) between stops and spring plate is achieved. Fit the three setting spacers into this gap.

• Screw the compression ring (72) onto the interrupter moving stem, until it just touches lower spring plate (43). Adjust the ring so that two studs of compression ring (72) are set equidistant between the spacers (39) at all positions. Remove the setting spacers. Depress lower spring plate (43) until main contacts of the interrupter make contact (use a continuity tester to sense this condition) and check the gap between spring plate and stops using 6 mm gap gauge.



26

• Smear the contact face of connector block (11) and that of shunts (10) with electrical jointing paste (Unial) and fit it and the shunts to the studs of compression ring (72), securing them with new special washers (70), new M6 belleville washers and new M6 Nyloc nuts (69).

• Using the 1mm/ 2.75mm gap gauge, check that the gap between compression ring (72) and connector block (11) is greater than 1mm, but less than 2.75mm.

• Place the three spacers (or pillars) (39) on lower spring plate (43) and the drive plate (37) on top of these spacers. Check that contact over travel is between 4.0mm and 4.9mm, using 4.0mm/4.9mm gap gauge if it is less than 4.0mm, insert a 0.5mm shim (74) between drive plate and the three spacers.

• Remove drive plate and place six springs (38) on the special washers. Replace the old springs by new ones during POH. Apply anti-friction spray Molykote D321R under countersunk head of M10 screws (68) and liquid thread lock Loctite-242 on the threads and then secure the assembly with three such screw tightened to a torque of 60 Nm. Ensure that springs seat properly in counter bore holes provided on drive plate.

• Check that the shunts (10) are clear of all other components. 3.4 OVERHAULING OF MAGNET VALVE ASSEMBLY (Refer Fig ure 1.4 & 3.3) 3.4.1 Dismantling

• Remove magnet valve assembly along-with the surge suppressor unit from relay valve by unscrewing two M6 hexagonal nuts and by sliding the complete assembly over two studs fitted to the relay valve body. Ensure that three O-rings (16/12) fitted on ports 16/B, 16/C and 16/D are not misplaced.

• Remove surge suppressor by removing its securing screw.

• Remove the retaining nuts (16/4), armature plate (16/2) and the body bolts (16/16). Top plate (16/6), valve body assembly and block (16/18) are now disconnected from the magnet yoke (16/1).

• Remove O-rings (16/7 and 16/15), springs (16/9 and 16/14), fluted valves (16/8 and 16/13) and valve stem (16/10) from the valve body (16/11).

• Remove operating coil (16/17) from the magnet yoke (16/1) by removing one M6 hexagonal head screw.

3.4.2 Cleaning/ Examination/ Reconditioning/ testing

• Wash all metal components in non-corrosive degreasing fluid like white spirit and dry them out by blowing compressed air. Wipe clean all rubber parts/ insulation material with dry lint-free cloth. If necessary, first use a cloth moistened with white spirit, then finish-off with dry lint-free cloth.

• Examine all metal parts/ insulations for cracks; replace if found defective.

• Examine all moving/ rubber parts for the extent of wear; replace excessively worn parts. Ensure replacement of all items prescribed in AOH/ IOH/ POH kits accordingly.

• Examine the operating coil and surge suppressor unit carefully; if any cracks are observed in the encapsulation material, or if there is any evidence of overheating, fit a new one. Check sturdiness of lead wires coming out of surge suppressor unit. Replace if found loose.



27

• Measure the resistance of the coil and if it is not as stipulated in DATA section 1.2, replace with a new one.

• Check healthiness of surge suppressor unit by applying 110VAC, 50Hz across its lead wires. Current should be within range stipulated in DATA section 1.2, replace with new one if found out of range. Provide new surge suppressor unit during POH.

3.4.3 Reassembling/ Setting/ Testing

1. Reassemble magnet valve in the reverse order from that described under dismantling. Slightly smear all O-rings, fluted rubber valves and inside bore of valve body with Molykote – 55M silicone grease.

2. When magnet valve has been reassembled, ensure correct working clearances by

following the procedure as given below:

• Verify that – with the moving parts of magnet valve in de-energised position, clearance exists between outer surface of armature plate and the heads of two numbers retaining nuts. If necessary, slightly bend or twist the magnet yoke in the appropriate direction. When clearance is obtained, remove the nuts, clean the bolts and then apply Loctite-222 to the threads and refit the nuts.

• Look through ports 16/B and 16/D while depressing the armature slowly. Verify

that, as the armature is depressed, a very slight movement of rubber valve (16/8) occurs before rubber valve (16/13) starts to move.

16/2 16/8

Part ‘B’ 16/10

Part ‘D’

16/13

With rubber valve (16/8) just touching seat at ‘Q’ there must be a clearance of 0.51mm to 0.61mm here. Slight clearance must exist here in order that rubber valve (16/13) is not held off-seat at ‘R’ by valve stem (16/10) Seat ‘Q’ Armature plate (16/2) must not bind on surface of retaining nuts (16/4). Seat ‘R’

When operating coil is de-energised, there must be clearance here.

Figure 3.3 Working Clearances of Magnet Valve Assembly



28

• Continue to depress the armature slowly until rubber valve (16/8) just touches its seal at Q, as denoted by the feeling that movement of armature plate is opposed by solid resistance.

• Verify that- with the rubber valve just touching its seat thus, the clearance

between armature plate and core of operating coil, at the point where clearance is greatest, is as stipulated in figure 3.3. Before adjusting this clearance, remove locknut (16/3) and operating peg (16/5), clean them, apply Locite-222 to the threads and refit them. Now set the clearance and immediately lock the peg in position.

• Press and release the armature several times and ensure that it moves freely over

the full length of its travel without any tendency to “Bind” on the surface of retaining nuts.

• An unsatisfactory result from any of the above operations indicates that either the

magnet valve has been assembled incorrectly or that one or more parts have deteriorated and is otherwise unserviceable.

3.5 OVERHAULING OF RELAY VALVE ASSEMBLY (Refer Figu re 1.5) 3.5.1 Dismantling

• Remove the relay valve assembly (24) from cylinder (49) by unscrewing four M6 hexagonal nuts and sliding the complete assembly over four studs (55) fitted to the cylinder flange. Ensure that the O-ring (24/16) fitted on port-D is not misplaced.

• Remove the top plate (24/2) by unscrewing two M6 (24/14) and one number M8 hexagonal socket countersunk head screws (24/15) and gain access to poppet valve (24/8) and valve disc (24/6). Do not misplace the O-ring (24/7) fitted on counter-bore hole of top plate (24/2).

• Remove the bottom plate (24/3) by unscrewing four M6 hexagonal head screws (24/12) to gain access to piston (24/4) and valve disc (24/6).

• Remove piston and poppet valve by pulling outwards.

• Separate out piston seal (24/5) from piston (24/4), valve discs from piston and poppet valve (24/8) and all O-rings (24/7, 24/9, 24/16 & 24/17).


• Wipe clean all components including bore of valve body with dry lint-free cloth. If necessary, first use a cloth moistened with while spirit, then finish-off with dry lint-free cloth.

• Examine all metal components for cracks; replace if found defective.

• Examine all moving/ rubber parts for the extent of wear including O-rings; replace excessively worn parts. Ensure replacement of all items prescribed in AOH/ IOH/ POH kits accordingly.

• Remove and discard old valve discs (24/6) and replace with new ones.

• Scrape-off RTV sealant from counter-bores of poppet valve and piston, using a blunt tool.



29

3.5.3 Reassembling

• To reassemble the relay valve, first smear RTV sealant in counter-bore of poppet valve (provide new poppet valve during POH) and piston. Place new valve discs in these counter-bores; apply pressure on surface of valve discs against respective components and leave in position for one hour for sealant to set.

• Grease O-rings, piston seal, bore of valve body with Molykote-55M silicone grease. Fit the greased piston seal onto piston such that open end of seal points away from the valve disc end of piston.

• Push bonded assembly of piston and valve disc into the correct end of valve body; then with the O-ring (24/17) in place, screw down the bottom plate (24/3).

• Through the valve body, fit stem (24/10) so that it enters hole in piston. Push bonded assembly of poppet valve and valve disc into valve body so that stem fits into the hole of poppet valve.

• Place spring (24/13) on dome of poppet valve (provide new spring during POH). Place the O-rings (24/7 & 24/9) in respective counter-bores on top plate (24/2) and valve body (24/1). Secure top plate to valve using two M6 and one M8 countersunk head screws (24/14 & 24/15).

3.6 OVERHAULING OF CYLINDER PISTON ASSEMBLY (Refer Figure1.6) 3.6.1 Dismantling

• Separate the reducer (65) along with its O-ring (24/16).

• Open one M6 hexagonal nut and release the drive link (29) and connecting link (46). Unscrew the six M4 hexagonal socket countersunk screws securing the piston stop ring (59). Remove piston (30) along with the drive link (50) and piston seal ring (31). Separate the piston seal ring from piston.

• Unscrew bearing pin (52) and two drive studs (51) fitted to drive link (50) and link (29) respectively only if they show signs of deterioration and require replacement.


• Wash all components in non-corrosive degreasing fluid like white spirit and dry them out by blowing compressed air and wiping with dry lint free cloth. If necessary, first use a cloth moistened with white spirit, then finish off with dry lint free cloth.

• Examine all metal parts for cracks; replace if found defective.

• Examine all moving/ rubber parts for the extent of wear; replace excessively worn parts. Ensure replacement of all items prescribed in AOH/ IOH/ POH kits accordingly.

3.6.3 Reassembling

• Smear Molykote 55M silicon grease on piston seal ring (31) and fit it onto piston (30) such that the open face of seal points towards the damper assembly (25).

• Ensure the drive link (50) fitted to piston is not loose; otherwise open the M6 hexagonal socket countersunk head screw and check that φ 2 spiral pin is not damaged. If it is broken, replace with new one and secure drive link to piston with above M6 screw, using liquid thread lock Locite-242.



30

• Examine permanent set of damper assembly (25); replace with new one if permanent set is appreciable or during IOH & POH; using two M4 slotted countersunk head brass screws treated with Loctite-222.

• Smear Molykote 55M grease on bore of cylinder (49) and between two bosses on cylinder. Now offer piston assembly to cylinder such that drive link (50) is guided between the above mentioned bosses.

• Secure piston stop ring (59), in place, using six –M4 hexagonal socket countersunk head screws, treated with Loctite-242. The slot in ring coincides with the slot in cylinder wall and allows freedom of movement of drive link (50) for auxiliary drive mechanism.

• If the bearing pin (52) and drive studs (51) were removed earlier, fit them now. Secure bearing pin (52) to cylinder; one drive stud (51) to link (29) and other to drive link (50) using liquid threadlock Loctite-242.

• Smear drive studs (51) and bearing pin (52) with Molykote 55M grease and secure connecting link (46) and link (29) to the bearing pin (52) with one M6 hexagonal nut.

• Ensure that piston (30), drive link (50), connecting link (46) and link (29) operate smoothly.

• Smear O-ring (24/16) with Molykote 55M, fit to reducer (65) and offer it to counter-bore in cylinder (49).

3.7 OVERHAULING OF AUXILIARY-CONTACTS UNIT (Refer F igure 1.7 & 3.1a/b) 3.7.1 Dismantling

• Unscrew special screw (84) fitted to cam shaft (83). Remove the cam (81). Ensure that

brass shim washers between cam and cam shaft are not misplaced. • Release the auxiliary switch from its mounting bracket by unscrewing two M8 screw in

the front and two M5 screws in the rear. • In case certain components of switch are required to be changed, open the two M4

hexagonal nuts (15/14) and lock nuts (15/20) fitted to the studs (15/15). Dismantle the complete switch by removing end plates (15/2), moving contact carrier (15/3) and fixed contact carriers (15/1), one-by-one.


• Replace old auxiliary contacts unit by new one during POH. • Clean the moving and fixed contacts. In case any contact carrier or moving contact is

broken; replace with new one. • Check condition of contact; if worn-out, replace with new one. • Check the contact pressure; if less replace the moving contact with new one. • Wipe-off grease applied on the cam surface, roller, guide bracket etc.



31

3.7.3 Reassembling • Slide the fixed contact carriers (15/1) onto the two M4 studs (15/15) one-by-one

keeping in mind the contact configuration required. Place the moving contact carrier (15/3), end plates (15/2) and rear mounting bracket (15/17) and secure the complete assembly by tightening two M4 hexagonal nuts (15/14). Apply Loctite-242 to threads of studs and finally secure M4 lock nuts (15/20).

• Apply Molykote 55M grease on surface of camshaft (83) and place cam (81) onto it.

Cover-up extended portion of cam shaft above cam by provided 0.5mm brass shim washers. Apply Loctite-242 on thread of special screw (84) and secure it to the cam shaft (83).

• Fit the auxiliary switch (15) onto its mounting bracket (85) using two M8 screw in

roller end side and two M5 screws on the rear end. Do not tighten these screws fully. • Fit this partially completed assembly to baseplate (20) with three M6 hexagonal head

screws. • Apply Molykote 55M grease on bearing pin (82) fitted on cam (81) and refit drive rod

(28) with M5 hexagonal nut and lock nut. 3.8 OVERHAULING OF PRESSURE SWITCH (Refer Figure 1. 8 & 3.1 a/b) 3.8.1 Cleaning & Inspection

• This pressure switch requires very little routine maintenance. Essential requirement is that the switch interior must be kept clean.

• Clean all internal parts with a small brush.

• Check all parts of the pressure switch visually for any defect/ abnormality.

• Check the terminals of microswitch visually for any defect/ crack etc. 3.8.2 Setting

• Pressure switch is set by rotating knob (17/1) and at the same time by reading the main scale (17/2). This sets the cut-off value of pressure. The difference in cut-in and cut-off value of pressure is set by rotating the differential setting roll (17/11) which is calibrated into 10 equal divisions. Cut-in pressure is the sum of cut-off pressure and the differential.

• Test the pressure switch at test bench, connect compressed air supply to the pressure switch and a continuity tester across the terminals 2-3 of pressure switch (N/O contact).

• Raise air pressure gradually and check that microswitch contact closes between 4.6-4.75 kg/cm2. then decrease air pressure gradually and check that contact opens between 3.85-4.0 kg/cm2.

• In case the adjustment is required, rotate setting knob of pressure switch to achieve the above mentioned cut in and cut off values.

• Repeat the above operations 4.5 times and ensure that the settings have not changed.



32

3.9 OVERHAULING OF PRESSURE REGULATOR (Refer Figure 1.9b & 3.1a/b) 3.9.1 Dismantling

• Unscrew the metallic nut that secures pressure regulator to its mounting bracket.

• Unscrew the bonnet 18/1(c) by hand to remove the regulating spring 18/2, slip ring (18/3), upper spring rest 18/1(d) and diaphragm assembly 18/4(A).

• To release valve assembly (18/7) and valve spring (18/8), unscrew valve seat (18/5) and take out the gasket (18/6).

3.9.2 Cleaning/ Examination

• Thoroughly wipe clean all components with dry lint-free cloth, if necessary first use a cloth moistened with denatured alcohol, then finish off with dry lint free cloth.

• Clean the regulator body by blowing with clean compressed air.

• Inspect slip ring (18/3), valve seat (18/5), gasket (18/6), valve assembly (18/7) for cracks or accumulation of dirt. Replace any worn off or damaged parts.

• Replace all items prescribed in AOH/ IOH/ POH kits accordingly. 3.9.3 Reassembling/ Testing/ Resetting

• Refit valve spring (18/8), valve assembly (18/7), gasket (18/6) and valve seat (18/5) into Brass body (18/10).

• Lightly grease the tube of new diaphragm assembly 18/4(A) with silicon grease

Molykote 55M, then place it into valve seat, ensuring good sliding fit. • Loosen lock nut 18/1(b) and unscrew adjusting screw 18/1(a) to the extreme

outward condition. • Place upper spring rest 18/1(d), regulating spring (18/2) and slip ring (18/3) into

bonnet and tighten bonnet onto body. • Now test the regulator assembly as given below:

Block the test port and outlet port with grub screws. With the adjusting screw fully

retracted, connect compressed air supply to inlet port. No air should be present at the outlet port. If there is an air leak, this is probably caused by a faulty valve seat.

Turn the adjusting screw clockwise and adjust the regulator to the mains pressure. Check that there is no escape of air through the small exhaust hole. If there is an air leak, it is probably caused by diaphragm seat damage.

Loosen the adjusting screw to ensure that the valve exhausts. Failure to exhaust is caused by a blocked venturi hole or a blocked diaphragm seating.

• Remove the grub screws fitted earlier for testing regulator. Secure regulator assembly

(18) to its mounting bracket (61) with the metallic nut.



33

3.10 OVERHAULING OF AIR FILTER (Refer Figures 1.10 & 3.1a/b) 3.10.1 Dismantling

• Unscrew the threaded bowl (22/11) by rotating it in anti-clockwise direction. The O-ring (22/2) will normally remain in the body.

• Remove stud (22/7) by unscrewing it and remove filter element (22./5), louver (22/3)

and gaskets (22/4 and 22/6). • To clean manual-drain arrangement, unscrew nut (22/16) and remove insert (22/14), O-

ring (22/10) and valve (22/13). 3.10.2 Cleaning/ Examination

• Wash the filter element with denatured alcohol or kerosene and dry it by blowing with clean compressed air in direction opposite to that of normal air flow to dislodge contaminants sticking to surface.

• Clean the body by blowing it with clean compressed air. • Wash the bowl using a household soap and water solution and dry it by blowing with

clean compressed air. • Thoroughly wipe clean all components with dry lint free cloth. If necessary, first use a

cloth moistened with white spirit, then finish-off with dry lint-free cloth. • Examine all components carefully for signs of deterioration. Replace all worn out

components and those provided in AOH/ IOH/ POH kits accordingly. 3.10.3 Reassembling/ Testing

• Reassemble the air filter by carrying out operations in reverse order as given in

dismantling. Hand tighten bowl into body. Excessive tightening might damage body. 3.11 FINAL ASSEMBLY (Refer Figure 1.2 & 3.1a/b)

• Mount the baseplate assembly to handling trolley in the horizontal position and secure it with six M12 screws. Turn it over so that baseplate is uppermost.

• Fit pressure regulator (18) securing its mounting bracket (61) to the baseplate using two M6

hexagonal head screws. Ensure that inlet port is facing towards air filter.

• Fit air filter (22) by securing the banjo bolts at inlet port of regulator (18) and air connector (57). Ensure that inlet air is connected to filter at the port marked “IN” and that bowl of filter is vertical in the final operating position.

• Fit pressure switch (17) onto its mounting bracket (6).

• Rotate the VCB so that bottom insulator assembly is uppermost.



34

• Apply PUR.Flex polyurethane or RTV 1080 sealant to O-ring groove on top flange of bottom insulator assembly (8). Locate new O-ring (7) in this groove. Place top-insulator assembly on bottom insulator assembly and secure them with eight M8 hexagonal socket head cap screws, using liquid thread lock Loctite-242.

• Now secure actuator rod (12) onto drive plate (37) and check the setting dimension, 21mm

(refer figure 3.4 given below for 21mm dimension), using 21mm gauge. Bolt the tool across two opposite holes of baseplate and check for any clearance between actuator rod end (12) and 50mm slot in the tool. Obtain the correct dimension by removing actuator rod and fitting shim washers (26) and packing washers (27) between it and drive plate (37). On final assembly of the packing washers/ shims and actuator rod, secure the rod to drive plate using liquid threadlock (Loctite-242) on the thread.



35

Figure 3.4 Cross Section Through the VCB

20

2

1

57

3

2

87

2

5

68

6

6

3

0

31

24

16

1

5

1

7

33

21

mm

d

imen

sio

n



36

• Take cylinder piston, assembled in accordance to Section 3.6; liberally smear both sides of new special paper/ cork washer and countersunk hole (for the M12 screw) on piston (30), with jointing compound. Fit the new special washer into counter-bore on top surface of piston (30). Now offer up the cylinder (49) with piston inside, to the baseplate. At the same time, as the cylinder is being located with its four M8 screws, so must the actuator rod (12) be located in the counter bore of piston. Feed the M12 hexagonal socket countersunk head screw, smeared with liquid thread seal (Loctite-542) through G0.75 (3/4” BSP) hole in the base of cylinder and through the piston, into actuator rod; then fully tighten the M12 and four M8 screws.

• Assemble magnet valve (16) and relay valve (24) in accordance with Sections 3.4 & 3.5. Then fit the relay valve, reducer (65) with its O-ring (24/16) and magnet valve to cylinder (49). Fit the plug (66) and sealing washer to cylinder base. Ensure that the O-rings between throttle valve – cylinder (24/16); relay valve – throttle valve (24/16) and relay valve – magnet valve (16/12) are properly seated in the counter bores and lubricated with silicon grease Molykote 55M.

• Fit air pipe (3) between air reservoir (34) to pressure regulator (18); air-pipe (63) between pressure regulator (18) to pressure switch (17) and air pipe (64) between air reservoir (34) to relay valve (24).

• Fit auxiliary switch assembly (15) to the baseplate using three M6 hexagonal head screws. Route and clip the cable harness. Connect the cable harness to terminals of auxiliary contacts unit (15) as per the wiring diagram.

• Fit terminal strips (77) to the baseplate using two M6 hexagonal nuts and one M8 screw. Connect cable harness to terminal strips as per the wiring diagram.

• Connect drive rod (28) to link (29) on one end and to bearing pin of cam (82) on the other end.

• Connect cable harness to magnet valve (16) and pressure switch (17).

• Seal the joint face between upper and lower insulator castings (5&8) with polyurethane sealant (PUR.Flex.) or RTV 1080 sealant, so as to ensure waterproof joint. Also cover the heads of eight M8 screws that secure top and bottom insulator assemblies with PUR.Flex. or RTV 1080 sealant.

3.12 TESTING

3.12.1 Safety Precaution

• Never apply high voltage to a naked vacuum interrupter. During H.V. withstand test on vacuum interrupter, low intensity X-rays can get generated. Take necessary precautions against emission of these X-rays.

• With vacuum interrupter mounted inside insulator assembly, the minimum safe distance for personnel to stand from equipment, with high voltage applied, is five meters, unless adequate screening is in place.

• Some operations require the use of compressed air-supply. Appropriate precautions must be observed.

• It is imperative that local safety regulations be observed.



37

3.12.2 Test Equipment

1. Variable pressure compressed air supply upto 7.0 kg/cm2.

2. Varriable DC voltage supply upto 125 volts.

3. 1000 volts Megger set for Insulation resistance test.

4. High voltage test set upto 75 kV rms AC supply.

5. Low voltage 500A DC supply source for contact resistance measurement.

6. Contact travel recording equipments. 3.12.3 Tests to be Conducted

A commercial grade (with low accuracy) pressure gauge is fitted to pressure regulator for indication only. Before testing the circuit breaker it is highly recommended to fit a calibrated pressure gauge with a range of 0 to 7 kgcm2 and accuracy of ± 0.5% to the pressure regulator. Non-return valve should be fitted to air connector (57) since compressed air-supply line is required to be removed for some of tests given below.

3.12.3.1 Visual Inspection

• Ensure that all porcelain insulators are in undamaged and good condition.

• Check that all faces which are used for electrical connections are clean and bright.

• Check that all nuts and bolts are tight and are properly locked.

• Check that all wire terminals are properly tightened and that wiring is in accordance with the wiring diagram.

3.12.3.2 Operations test

• Connect 110V DC supply to coil terminals through a N/O contact of push button.

• Connect air supply pipe to VCB air inlet (air connector) & set pressure regulator at 5.0-5.2 kg/cm2.

• Perform fifty “Close & Open” operations.

• Increase DC voltage to 125 Volts and perform twenty “Close-Open” operations.

• Decrease DC voltage to 70 Volts and perform twenty “Close-Open” operations.

• Check that the breaker operates freely and that the auxiliary contacts drive mechanism functions correctly.

3.12.3.3 Air-Leakage Test

i. VCB in “OFF” position

• Set the pressure regulator at 6.5kg/cm2 air pressure.

• Isolate air supply after air reservoir is filled up with air and note the air pressure on dial gauge.

• Wait for 10 minutes after isolation of air supply and again note the pressure. • Difference of the two readings which is the fall in pressure should not be more than

10% of set value (0.65kg/cm2) i.e. second pressure reading should be between 5.85 to 6.5 kg/cm2.



38

ii. VCB in “ON” position • Open incoming air supply to VCB. • Energise magnet coil by applying 110V DC supply across coil terminals & close the

breaker. • Isolate air supply after air reservoir is filled up with air and note the air pressure on

dial gauge. • Wait for 10 minutes after isolation of air supply and again note the pressure value.

• Fall in pressure should not be more than 10% of set value (0.65kg/cm2) i.e. second pressure reading should be between 5.85 to 6.5 kg/cm2.

NOTE : In case pressure-drop exceeds the permissible value in any of the above two conditions, detect the point of leakage by applying soap water solution to all joints in pneumatic circuit and tighten faulty joint.

3.12.3.4 Insulation Resistance Test (Megger Test)

A. Carry out insulation resistance test on main circuit, in following conditions, using 1kV megger.

a. VCB close , between power terminals & frame Res. > 200 MΩ b. VCB open

i. between incoming terminal to earth Res. > 200 MΩ ii. between outgoing terminal to earth Res. > 200 MΩ

B. Carry out insulation resistance test on control circuit, in following condition, using 1kV megger.

Between auxiliary wiring & frame Res. > 10 MΩ 3.12.3.5 High voltage test

A. On main circuit Apply a test voltage of 60 kVrms (80% of rated power frequency withstand voltage – 75 kVrms), 50Hz for one minute in the following conditions: a. Breaker closed, between power terminals to earth. b. Breaker Open

i. between incoming terminal to earth. ii. between outgoing terminal to earth.

The breaker should withstand the test voltage in all the above three conditions. B. On auxiliary & control circuit

Short all the wiring terminals and apply a test voltage of 2 kVrms for one minute between shorted terminals and earth. Breaker should withstand the voltage without any break down.

3.12.3.6 Milli-volt drop test (Contact resistance of main circuit)

Caution: While carrying out this test, do not switch-off the DC current of 500 Amps by the VCB.

• Connect air supply pipe to VCB, 110V DC supply to coil terminals and close VCB.

• Connect current leads of DC high current set to VCB power terminals rigidly.

• Fix the potential lead of test set near to the current lead connected.

• Pass 500Amps DC through VCB and record the milli-volt drop value.

• The voltage drop across the main circuit should not exceed 46.8 milli-volts (93.6µΩ).



39

3.12.3.7 Checking of Pressure Switch Setting

• Connect 110 V DC supply to magnet coil through a N/C contact of push button.

• Now supply raise air pressure inside VCB.

• Read air pressure value at the instant when VCB closes. This is the cut-in value.

• Now slowly decrease the pressure, through air filter, and read the instant when VCB opens. This is the cut-off value.

The cut-in and cut-off values obtained should be in accordance with specifications stipulated in DATA section-1.2. if the values obtained in both the above cases (rising & falling) is less or more, then pressure switch adjustment has to be done accordingly.

3.12.3.8 Sequence tests

• Set the regulator to 3.2kg/cm2 and bypassing the pressure switch contacts, check that the VCB operates cleanly at 50% of the rated voltage.

• Repeat the above test, but this time with the regulator set to 6.2 kg/cm2.

• On a falling pressure, check that the contacts of the pressure switch open before the mechanism of the VCB moves.

3.12.3.9 Pressure regulator setting

Set the regulator at 5.0-5.2 kg/cm2 by following the instructions given below.

• Loosen the lock nut on setting screw at the top of pressure regulator.

• With a screw driver adjust setting screw at the top of regulator so as to read 5.0-5.2 kg/cm2 in the calibrated pressure gauge.

• Operate VCB five times to ensure that the reading given on pressure gauge is consistent.

• When the setting is correct lock setting screw in position by tightening lock nut.

• Remove the calibrated pressure gauge.

• Apply liquid threadseal (Loctite 542/ Fevicol ANR-171 or PTFE tape) to the thread of commercial grade pressure gauge and fit it to regulator. Allow the sealant to set for 10 to 15 minutes. Do not apply any other sealant as it might cause leakage at a later stage.

• Ensure pressure gauge reading is 5.0-5.2 kg/cm2. 3.12.3.10 Checking of Auxiliary switch configuration

Check all sets of N/O & N/C contacts of auxiliary switch on wiring terminals as per

relevant wiring diagram.



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3.12.3.11 Contact travel measurement It is necessary to carryout timing/ contact travel measurement test on a complete

vacuum circuit breaker after overhauling or whenever any component, which is fundamental to the breaker operation, is changed. Detailed procedure for conducting this test is given in section 3.13. Ensure that all the travel parameters are within the permissible limits as stipulated in DATA, section-1.2.

3.12.3.12 Finishing

• Replace bottom cover retaining ring and stick sealing section (33) with adhesive and fit the bottom cover assembly. Fit fixing screws to bottom cover (32), seal the joint in sealing section with RTV sealant.

• Replace grommet of base plate during IOH/POH.

• Stick new gasket on base plate with adhesive during IOH/POH.

• Touch- up the paintwork as required.

• Prior to installation or transferring for storage, check that all insulator sheds have been polished with silicon grease.

3.13 METHOD OF CONTACT TRAVEL MEASUREMENT/ RECORDIN G 3.13.1 Test Equipment

1. Potentiometer (Range: 0 to 50mm)

2. Mounting bracket for potentiometer

3. Travel recording equipment (HISAC Lab or CRO)

4. 110V DC supply source.

3.13.2 Test Procedure

1. Fit potentiometer onto its mounting bracket using appropriate hardware.

2. Mount the VCB on handling trolley and rotate it so that bottom cover is uppermost.

3. Open bottom access cover and remove the M5 socket head cap screw.

4. Fit potentiometer (with its bracket) on to the baseplate using one number each M6 & M5 hexagonal head screws.

5. Connect compressed air supply to air connector (57) and 110V DC supply to the VCB for breaker operations.

6. Connect potentiometer terminals to the travel-recording instrument.

7. Calibrate potentiometer with travel recording equipment by following the procedure described in recorder operation manual.

8. Operate VCB a few times through the recording device.

9. Record the time-displacement curve both for closing and opening operations of VCB, by the printing device attached to recorded.

10. Analyse the recording and evaluate all the contact travel parameters.

11. Compare these results with the permissible values as stipulated in DATA Section-1.2.



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3.14 MAINTENANCE OF AIR DRYER (Refer Figure no. 1.1 1) 3.14.1 Maintenance Instruction

1. Remove both air connections from the air dryer. Remove the two M12 mounting bolts and release air dryer assembly from vehicle.

2. Check the weight of air dryer; if it is more than 0.8 kg from the new weight change/ regenerate molecular sieves. Method of regenerating molecular sieves is given below.

3. Unscrew one filter element from the body, empty sieve material and replenish with new/regenerated material, leaving sufficient room for filter only. Refit and tighten the filter assembly.

4. Dryer to be ‘blown-down’ by feeding compressed air from one end while keeping the other end open to remove any molecular sieve dust.

5. Check for air leaks around the filter assembly using a soap-water solution. For this purpose, blank-off one air connection and connect the other with compressed air supply.

6. Again weigh the air dryer assembly with new/ regenerated molecular sieves and maintain record of this value for future reference.

7. Remount air dryer assembly inside vehicle and reconnect the pneumatic supply connections.

3.14.2 Method for Regenerating Saturated Molecular Sieves:

1. Measure the weight of molecular sieves to be regenerated.

2. Regenerate saturated molecular sieves by heating in an oven at 200°C for 8 hours.

3. Check the weight again and compare with earlier weight. It should be less by 15-20%.

4. There should be no visual indication of moisture content.

CAUTION : Refilling of sieves should be carried out as quickly as possible by scooping pellets into the air dryer body from the 145 kg drum, in case of replacement. After filling, ensure the drum is properly sealed with its lid and stored in a dry, covered area.

3.15 MAINTENANCE OF R-C NETWORK

1. Disconnect the electrical connections from R-C network assemblies.

2. Remove R-C networks from their mounting boards by releasing the four M10 hexagonal head screws.

3. Connect R-C network to a variable AC supply; apply 415V AC, 50Hz, and measure the current through this R-C network. Value of current should be as stipulated in DATA section-1.2

4. If this value is incorrect, measure the resistance & capacitance values separately and match them with the specifications given DATA section – 1.2. Replace the defective resistance or capacitance, as the case may be.

5. Remount R-C network assemblies on the vehicle and reconnect electrical connections.

******



42

CHAPTER 4

FAILURES, CAUSES AND REMEDIAL MEASURES

Different kinds of failures observed/ reported by various Electric Loco Sheds/ Workshops are given below. The same has been discussed during seminar held at CAMTECH.

• Flashover in lower insulator/ actuator rod • Pressure regulator problems • VCB chattering • Auxiliary switch breakage/ low crushing • Vacuum interrupter failure • Air leakage from relay valve • Insulator breakage • Magnet valve failures • Dryer problem • Baseplate breakage • RC network failure

4.1 FLASHOVER IN LOWER INSULATOR/ACTUATOR ROD

POSSIBLE CAUSES REMEDIES

• Ensure during overhauling that inner surface of insulator and actuator rod are clean and dry.

• Ingress of moisture due to seepage of water and tracking on the inner surface of insulator/Actuator rod. • Ensure replacement of ‘O’ ring between flanges of

top & bottom insulator during IOH/POH. Also ensure proper sealing of flange joints and heads of eight M8 screws.

4.2 PRESSURE REGULATOR PROBLEMS


• Incorrect assembly. • Ensure correct assembly during overhauling as described in section 3.9.3.

• Damage of diaphragm. • Ensure replacement of diaphragm with new one during every overhauling.

• Loosening of lock nut resulting in variation in setting.

• Ensure proper fastening of lock nut during overhauling and also ensure good condition of threads of setting screw and locking nut.

• Air leakage from pressure regulator due to defective rubber parts.

• Ensure proper testing of regulator as described in section 3.9.3 during overhauling. Also ensure replacement of all components given in AOH/IOH/POH kits accordingly.



43

4.3 VCB CHATTERING


• Improper setting of pressure regulator.

• Set the pressure to required settings using a calibrated pressure gauge with a range of 0 to 7 kg/cm2 and accuracy of ± 0.5% during overhauling.

• Low incoming pressure. • Ensure correct incoming pressure to VCB.

• Improper setting of pressure switch.

• Ensure proper setting of pressure switch.

4.4 AUXILIARY SWITCH BREAKAGE/ LOW CRUSHING


• Improper fixing of switch. • Ensure no excessive pressure on contact carrier rod.

• Fixing getting loose. • Ensure proper fixing of switch.

• Bad contact or poor contact between the contacts

• Ensure visually proper crushing on all contacts, both in VCB ‘open’ and in VCB ‘close’ condition during every overhauling.

4.5 VACUUM INTERRUPTER FAILURE


• Lightening/ Switching surges. • Adequate protection from surges may be given by providing gapless surge arrestor in place of ET2.

• Poor vacuum level or loss of vacuum.

• Ensure high voltage testing during every AOH/ IOH/ POH scheduled overhauling is being carried out at 60 kVrms, 50Hz for one minute.

• Main contacts eroded or bad contacts.

• Ensure millivolt drop test is being carried out during every AOH/ IOH/ POH scheduled overhauling passing 500 amps dc and it should not exceed 46.8 millivolt (93.6µΩ)

• Use of VST beyond its recommended life.

• Mechanical life of VST is 3,00,000 operations under no load conditions and recommended replacement at the first suitable time after 2,50,000 operations.

4.6 AIR LEAKAGE FROM RELAY VALVE


• Damaged rubber O-rings. • Ensure timely replacement of rubber items during AOH/IOH/POH schedules.

• Damaged valve discs. • Ensure replacement of valve discs during every overhauling.

• Damaged poppet valve. • Ensure healthiness of poppet valve during every overhauling and also ensure replacement of poppet valve during every POH.



44

4.7 INSULATOR BREAKAGE


• Due to cracks in the insulator body.

• Ensure proper cleaning and examination of cracks and chips during every schedule. Never use pressure or steam cleaning tools on porcelain insulators.

• Improper handling or storage of VCB causing accidental impacts/damages.

• Follow proper procedure for handling, packing or storage of VCB. Do not subject the vertical insulator column to forces or to impacts during transit, storage or lifting.

4.8 MAGNET VALVE FAILURES


• Air leakages due to damage O-rings and fluted valve.

• Ensure timely replacement of rubber items during AOH/IOH/POH schedules.

• Improper engagement of armature plate.

• Ensure proper engagement of armature plate. Also ensure correct working clearances by following the procedure as given in section 3.4.3.

• Terminal connections loose resulting in flashing/heating on terminals and failure of coil.

• Ensure proper tightness of electrical connections.

• Improper resistance of magnet coil.

• Measure the resistance of the coil and if it is not as stipulated in DATA section 1.2, replace it with a new one.

• Damaged or unhealthy surge suppressor.

• Check healthiness of surge suppressor unit by applying 110VAC, 50Hz across its lead wires. Current should be within range stipulated in DATA section 1.2, replace with new one if found out of range. Provide new surge suppressor unit during POH.

4.9 DRYER PROBLEM


• Use of incorrect drying agent. • Use correct and recommended drying agent, molecular sieves.

• Untimely processing of drying agent.

• Ensure processing as recommended in maintenance schedule.



45

4.10 BASEPLATE BREAKAGE


• Excessive pressure on base plate corners

• Do not apply excess pressure in fastening the VCB through fixing holes to prevent alloy casting from breakages.

• Improper alignment on loco rooftop

• Ensure correct fastening bolts and proper alignment while mounting on Loco/EMU roof.

• Improper handling during transit

• Careful Handling during transit keeps the base plate and VCB safe.

4.11 RC NETWORK FAILURE


• Measure the current through R-C network by connecting it to 415V AC, 50Hz supply during overhauling. Ensure the value of current is as per data stipulated in section-1.2.

• Unhealthy RC network.

• If this value is incorrect, measure the resistance & capacitance values separately and match them with the specifications given in section – 1.2. Replace the defective resistance or capacitance, as the case may be.

******



46

CHAPTER 5

DO’S AND DON’TS 5.1 DO’S

• For lifting of VCB chains should be of equal length and while lifting ensure that all sling hooks are properly inserted in 4 nos. – M20 eye-bolts. Chain, in stretched condition (VCB hanged) should not interfere with insulators. To ensure this, use proper lifting frames.

• Always lift VCB vertically upwards by crane. When lowering VCB, downward movement should be slow to avoid any damage due to excessive jerk/ shock.

• During erection of VCB, ensure recommended torques for tightening Main/ Earth busbar to terminals and baseplate to vehicle roof given in Annexure IIC. Excessive tightening may damage terminal castings/ baseplate.

• Ensure that the overhead contact line is dead & is properly earthed, before going to inspect the VCB on the roof of the Locomotive.

• Earth the Circuit breaker’s base by means of temporary flexible strap which is solidly earthed at the other end before doing overhaul/repair.

• New special washers (70) should always be used.

5.2 DON’TS

• Never lift VCB by tying wire rope on porcelain insulator or by using the terminal castings.

Always use the 4 nos. – M20 eye-bolts fitted to baseplate for lifting the complete VCB.

• Do not push, pull or drag the VCB on shop floor.

• Do not tilt the VCB for maintenance without mounting it on the handling trolley.

• Do not place VCB directly on floor. When not in use, it should be either kept in cage packing or on handling trolley.

• Do not place VCB in dirty area or in accumulated rain water. This may cause rusting of bottom cover.

• Do not, in any case, use the old Belleville washers and Nyloc nuts.

• Don’t climb on the roof of Electric loco without taking proper shutdoen by competent authority and before climbing, OHE as well as equipment must be properly earthed.

• Never use Carbon tetra chloride, Tri-chloro athelene, paint thinners, Acetone or other similar solvent in cleaning any parts of VCB.

• Never do the work on pressure switch without shutting of compressed air supply.

• Do not open the bottom cover of VCB during IA, IB & IC schedule, unless there is any problem.



47

ANNEXURE I

REPLACEMENT KITS FOR OVERHAULING

Part No. Code No. Qty/ Kit Description

1 5510740 1 Kit AOH replacement Kit consisting of:

5260700 3 O ring for magnet valve assembly

5260800 2 O ring for magnet valve assembly

5260600 2 Valve (fluted) for magnet assembly

5570080 2 O ring for relay valve & reducer

5570090 1 O ring for relay valve assembly



5150020 2 PTFE valve discs for relay valve

5540060 1 Special washer for main piston

5510163 8 Sealing washer for bottom cover

5510164 8 Retaining ring for bottom cover

3410-55 1 Diaphragm assembly for pressure regulator

5110600 1 Kit Repair kit for Air filter.

2 5510750 1 Kit IOH replacement kit consisting of:

5510740 1 Kit AOH replacement Kit

5380650 1 Grommet for baseplate

5510390 1 O ring (between flanges of insulators)

5510450 1 Selon washer (for plug of cylinder)

5510810 1 Gasket for baseplate

5510162 2.3 Mt Sealing strip for bottom cover

5540030 1 Damper assembly for cylinder

5570050 1 Piston seal ring for relay valve piston

5540023 1 Piston seal ring for main piston

5350100 1 Surge suppressor for magnet valve assly.

5110422 1 Kit Repair kit for pressure regulator

5390090 4 Kg Molecular sieves for Air dryer

3 5510760 1 Kit POH replacement kit consisting of:

5510750 1 Kit IOH replacement KIT

5520200 6 Belleville washer M6

5203400 1 Auxiliary contacts unit (8-way)

5260900 2 Compression springs for magnet valve

5150010 1 Poppet valve for relay assembly

5150090 1 Compression spring for relay valve assembly

5520130 6 Spring for vacuum interrupter mechanism

5520180 6 Spring for vacuum interrupter mechanism



48

ANNEXURE II A. SPECIAL TOOLS

Part No. Code No. Qty/ VCB Description

1 5560050 1 Peg spanner

2 5560070 1 21 mm setting gauge

3 5560060 3 Setting spacers (set of three)

4 -- 1 Forcing tool

5 5560120 1 Alignment gauge

6 5560010 1 1 mm/ 2.75 mm gap gauge

7 5560030 1 6 mm gap gauge

8 5560110 1 28 mm dimension gauge

9 5560020 1 4.0 mm/ 4.9 mm gap gauge

B. CONSUMABLES FOR MAINTENANCE

Consumables required for maintenance of VCB are as given below:

• Silicon grease type Molykote 55M.

• PTFE tape for pneumatic joints.

• Polyurethane sealant type Pur.Flex or RTV 1080 sealant.

• Medium strength Loctite-242.

• Electrical jointing paste type “UNIAL”

• Anti-friction spray type “Molykote D-321R”

• Screwlock Loctite-222

• High strength Loctite-270

• Liquid sealant Loctite –542 or fevicol ANR-171

• Colloidal graphite in oil type “OILDAG” C. RECOMMENDED TIGHTENING TORQUES

For 6 nos. M12 fixing screws of baseplate 30Nm

For M12 main terminals (incoming & outgoing) 48 Nm

For M10 Earth terminals (incoming & outgoing) 30 Nm



49

ANNEXURE III

POINTS RAISED DURING SEMINAR HELD ON 24.07.2006 AT CAMTECH, GWALIOR.

S.No. Points raised by Sheds/ Workshops Remarks by Firm

A. L.C.W. Workshop, Dahod, W. Rly.

1. In POH kit 2 nos. diaphragm assembly (Code No. 3410-55, 5110422) for pressure regulator is being supplied presently whereas only 1 no. is required.

Noted by firm.

2. Consumable items required for maintenance should also be supplied with AOH/ IOH/ POH kits.

Will be reviewed.

B. Electric Loco Shed, Asansol, E. Rly.

1. During high voltage test of VST, the value of leakage current should be specified.

No leakage current is allowed in case of healthy VST during high voltage test.

2. For auxiliary contacts unit the value of contact pressure and contact gap should be specified.

These values are not given due to variation. This might create panic. Only visual crushing should be checked for N/O, N/C contacts.

3. ‘O’ ring 22/10 for air filter assembly is not included in AOH repair kit for air filter (Code no. 5110600). The failure generally occurs on account of this.

Will be reviewed.

C. Electric Loco Shed, Erode, S. Rly.

1. VCB chattering due to low pressure setting of pressure regulator, whether setting may be raised or not to avoid this problem.

Will be reviewed.

2. Washers for Banjo coupling joints should be included in AOH/ IOH/ POH kit.

Will be reviewed.

D. Electric Loco Workshop, Bhusawal, C. Rly.

1. Provision of electrical connector (Gimota Connector) is required in VCB for easy inter changeability of different make Single Bottle VCB.

Already introduced on new VCBs.



50

S.No. Points raised by Sheds/ Workshops Remarks by Firm

2. Provision of counter for counting the operations of interrupter assembly during service is required so that life of VST may be predicted. As firm has given mechanical life of VST is 3,00,000 operations under no load condition and recommended replacement at the first suitable time after 2,50,000 operations.

The matter is already under review.

E. Electric Loco Shed Bandamunda, S.E. Rly.

1. Valve stem (Code no. 5260400) of magnet valve assembly may be included in AOH kit.

Will be reviewed after concerning various sheds.

2. Filter element (part no. 22/5) of air filter assembly may be included in AOH assembly.

Will be reviewed

3. Thickness of slip ring (part no. 18/3) of pressure regulator to be checked because leakage is causing from this ring.

Vendor has taken care and leakage test is being done.



51

REFERENCE

1. Installation, Operation and maintenance Manual for Single Interrupter Vacuum Circuit Breaker type 22 CB for A.C. Traction Application in Indian Railways, issued by M/s AREVA (ALSTOM) T & D India Ltd.

2. CLW specification no. CLW/ES/C/47 August 97, for Vacuum Circuit Breaker

with Single Interrupter for 25 kV AC Electric Locomotives.

3. Field study and Literature collected from various AC Electric Loco Sheds and Workshops.

4. Comments received during discussion in seminar held on dt. 24.07.2006 at CAMTECH,

Gwalior.

*****



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To upgrade maintenance technologies and methodologies and achieve improvement in productivity, performance of all Railway assets and manpower which inter-alia would cover reliability, availability, utilisation and efficiency.

OUR OBJIVECTIVE

If you have any suggestions and any specific Comments please write to us. Contact person : Director (Elect.) Postal Address : Indian railways

Centre for Advanced Maintenance technology, Maharajpur, Gwalior. Pin code – 474 020

Phone : 0751 – 2470740

0751 – 2470803 Fax : 0751 - 2470841

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