chapter 3 base line data for chp system...

62

CHAPTER 3

BASE LINE DATA FOR CHP SYSTEM

3.1 INTRODUCTION

Any power generated onto the grid must compete economically

with all other sources of generation on that grid. This would mean small

biomass grid connected generation needs to compete with large state-of-the-

art plants, typically with enormous scale of economy advantages. Currently,

in India, “Green Incentives” are legislated which has increased the demand

for renewable power and this supports higher tariffs. However, in many cases,

the only way a small CHP system can compete is due to the enhanced

efficiencies in generating quality and uninterruptable power.

The fuel derived from the plant is conveyed to power the boilers,

where high-pressure steam is generated. A single turbine generator set then

converts the steam energy to electrical power and to low pressure process

steam for use in the refining process. The CHP system is configured to have

flexibility to meet a wide range of processes of steam and electrical power

demands, which may occur independently of each other. Despite the

advantages of CHP system, it remains an untapped potential in most

countries, including India. India is estimated to have a total industrial CHP

System potential of about 18,000 MW, which is yet to be fully exploited.

63

3.2 APPLICATION OF CHP SYSTEMS AND THEIR

PERSPECTIVES

3.2.1 General

CHP system is considered as one of the most important techniques

for achieving a more efficient usage of fuels, savings in natural and financial

resources and environmental protection. CHP system is meaningful for

applications, where, there is a large and continuous (not just seasonal)

demand for heat close to the CHP System facility. If there is no demand for

heat from a CHP System facility, its efficiency for the production of

electricity will be lower than for optimized thermal power stations. In general,

larger CHP System facilities have lower production costs compared to smaller

units.

CHP System means the combined production of electricity and heat

in an energy conversion facility. Technically, it means that part of the heat

(steam, hot air) for the production of electricity in steam or gas turbines, or

residual heat from combustion engines or fuel cells is used for room heating

or as process heat in industry or commerce. Basically, the CHP System

principle could be used in any generation facility. The heat demand should be

large and continuous over a large part of the year.

Two typical application domains for CHP System have emerged:

the combined heat and power (CHP) plant in industry, and the heat and power

sector in the supply of electricity (’municipal heat and power supply’). The

latter produces mainly low-temperature heat for heating and hot water supply

in buildings. The advantages of the combined production of heat and power

results from the more efficient usage of fuel and corresponding reduction in

the greenhouse gas (GHG) emissions.

64

3.2.2 Operation Modes of CHP System Systems

The most important operation modes of a CHP system, i.e. the

modes for setting power and heat capacities at any time, are as follows:

1. Heat generation equal to the heat load (“heat match”).

2. If power is generated in excess of the load, the surplus power

is sold to the national power network.

3. If power generated in short of the load, then the power deficit

is supplemented by the network.

4. Power production equal to the power load (“electricity

match”).

5. An auxiliary furnace supplements the additional heat required,

if necessary, coolers may be installed capable of rejecting the

excess heat

6. Mixed mode - Either monitoring the heat load mode or

monitoring the power load mode.

7. Full coverage of the heat and power load at any time with no

connection to the national network.

This mode of operation requires enough backup capacity and

consequently, a complex CHP System. This is the most expensive solution, at

least the initial cost.

As a rule, subject to any exceptions, the first of the above

mentioned modes provides the highest energy and economical efficiency for

systems in the industrial and commercial-building sector. For CHP System

plants of the public power system of the country, the operation mode to be

65

selected depends upon the extensive needs of the network, the available units

and the obligations towards consumers of heat and power. The operation and

maintenance mode would be more specific to the type of application in

tandem with respect to the continuous process industry. This would help in

selection of suitable type of CHP system.

3.2.3 Applications of CHP System

In general, CHP systems may be implemented in four main sectors

as illustrated below:

a. Public power system

b. Industrial sector

c. Commercial-building sector

d. Agricultural sector.

Power generation plants may be converted into CHP systems in

order to cover heat needs of cities or settlements, industries, water

desalination plants, green-houses, fisheries etc. located in a region. For the

feasibility of the overall installation, proper distance and dispersion of heat

consumers around the plant is essential. With district heating, in particular,

apart from distance and dispersion, the annual number of degree-days and the

required thermal power also play an important role. In the industrial sector,

many processes require heat and power at the same time.

Depending upon the temperature required the following

classification applies:

1. Low temperature processes (below 100°C) e.g. drying of

agricultural products, heating or cooling of areas, utility hot

water.

66

2. Medium temperature processes (100-300°C) e.g. processes in

paper industry, in spinning mills, in sugar industry, in some

chemical industries etc. Typically, these processes require

heat in the form of steam.

3. High temperature processes (300-700°C) e.g. in some

chemical industries.

4. Very high temperature processes (above 700°C) e.g. in

cement plants, metal industries, glass industries etc.

The majority of the industries with a significant combined heat and

power potential include certain production processes, which generate or reject

heat in satisfactory quantity and quality (i.e. temperature level). Recovery of

this heat and its subsequent addition to the heat generated by the CHP system

is considered advisable. Certain chemical processes produce fuel gases which

may be consumed at the furnaces or the CHP system itself. For this analysis,

the CHP system installed in textile and sugar process industry has been

considered as case studies in this thesis.

3.2.4 Advantages of CHP Systems

The following are few of the advantages of CHP systems:

1. A CHP system with steam turbines, fuel consumption is

reduced by 15% (compared to the separate power and heat

generation using a steam turbine unit and a boiler,

respectively).

2. Since CHP systems are of smaller size and their installation

lasts less than a large central plant, they provide a larger

flexibility and adaptability to unexpected power demand

variations in the future.

67

3. The short installation time for the CHP systems contributes to

the reduction of the financial cost, which in turn contributes to

the reduction of the unit cost of power generation.

4. Many small CHP systems operating in parallel to the central

power generation plants increase the reliability of power

supply.

3.3 STEAM TURBINE SYSTEMS

3.3.1 General

These are the most commonly used CHP System systems, suitable

for capacities of 500 kW - 100 MW or higher. They may operate on any kind

of fuel. Even solid wastes may be burned in special furnaces equipped with

systems for retaining or neutralization of pollutants and toxic substances

produced during combustion with efficiencies at 60-85%.

Steam turbine system features the following:

a. High reliability is considered the possibility of satisfactory

operation for a system for a specific time interval and under

predetermined conditions, which may reach up to 95%.

b. High availability is the probability for a satisfactory operation

of the system at a random time. The mean annual availability

is equal to the time percentage (e. g. 8760 hours per year)

during which a system may operate satisfactorily (taking into

account the preventive maintenance and the emergency faults]

(90-95%) and high longevity (25-35 years).

68

The two basic system arrangements in this category are Back

Pressure Steam Turbine and extraction Steam Turbine. A brief description of

these turbines is given below.

3.3.2 CHP Systems with Back Pressure Steam Turbine

High pressure (20-100 bars) and high temperature (480-540°C)

steam is produced in a boiler operating on fossil fuel. This steam is used to

drive the steam turbine which is shaft-coupled with the power generator as

shown in Figure 3.1.

Figure 3.1 CHP System using a back pressure steam turbine

Steam exits the turbine at a temperature and pressure suitable for

thermal processes. The term “back pressure” is used to indicate that this

pressure is higher than the atmospheric pressure (3-20 bars). The extraction of

a portion of the steam from intermediate turbine stages at the desirable

pressures is also possible. The back pressure system has the following

advantages over the extraction system:

1. Simple form

2. Lower cost

Steam

TurbiBoiler

Generator

Condensation Products after use

Steam for Use

WFuel

69

3. Reduced or even elimination of the need for cooling water

4. Higher efficiency (approx. 85%), mainly because heat is not

rejected to the environment through a cooling component.

The main disadvantage is that the produced electric power is

closely related to the required heat.

3.3.3 CHP Systems with Extraction Steam Turbine

A portion of the steam is extracted from one or more intermediate

stage(s) of the turbine at the desirable pressures, while the remaining steam is

depressurized down to the pressure in the condenser as shown in Figure 3.2.

Figure 3.2 CHP System using an extraction steam turbine

The extraction systems are more expensive and exhibit a lower

efficiency (approx. 80%) when compared to back pressure systems. However,

BoilerSteam

Turbine

Cond.

Tank

Steam for Use

Cooling Water

W

Generator

Fuel

Condenser

Pump

Condensation

Products after use

70

they allow for independent (within certain limits) adjustment of electric and

thermal power. This is achieved through the adjustment of the total steam

flow rate and, consequently, of the steam supply rate to the condenser.

3.4 CHP SYSTEM DESCRIPTION AT TEXTILE MILL

3.4.1 Overall Description

The CHP System consists of one number biomass fired boiler of

26.5TPH, 62bar at 480ºC and one number of extraction cum condensing

turbine of nominal capacity to generate power of 4.5MW. The uncontrolled

extraction steam for the turbine is 9bar at 480ºC. The CHP system consists of

fuel handling system, firing system, cooling water system electrical

evacuation system and control system. The general particulars of all systems

and subsystems are detailed below:

Boiler: The biomass fired boiler generates steam at the high purity,

pressure and temperature required for the steam turbine that drives the

electrical generator. To minimize the ash content from the burnt out fuel, a

travelling grade type boiler is opted. The installed boiler can generate steam

of the maximum capacity 26.5TPH, 62bar at 480°C with required piping

system and regulating valves. The steam generated in the furnace side walls

are taken to a steam drum through a series of riser tubes. Generally, the

construction of these boilers is identical to maintain standardization with only

variation on the generation capacity of steam.

Turbine: The turbine is of multistage, nozzle governed, impulse

type extraction cum condensing steam type construction. This turbine is

provided with hydraulically operated stop and emergency valve with integral

steam strainer at the inlet. Similarly, the inlet steam flow control and

71

extraction steam flow control is by hydraulically operated throttle and

governing valves. The type of casing is horizontal split type suitable to

withstand pressure at 65kg/cm2at a temperature of 510ºC. Turbine rated speed

is 8250RPM with speed control and emergency speed trip devices

incorporated. The turbine can handle low pressure steam at 11.5TPH and

high pressure steam at 26.5TPH. The lubrication system for the turbo

generator comprises of main oil pump, auxiliary oil pump and emergency oil

pump.

Condenser: The steam surface condenser is of shell and tube type

to suit exhaust flow and is of divided water box construction. The condenser

is designed for a cleanliness factor of 0.85 with hot well retention time of

3minutes and heat transfer area of 410m3. The condenser is incorporated with

condensate extraction pump, gland steam and ejector condenser.

Alternator: The rated apparent power of alternator is 5625KVA

and rated active power of 4500KW with a rated voltage class of 11KV. The

alternator is brushless excitation type and provided with all controls for

temperature rise, speed and short circuit current.

11KV Sub- Station: The substation system comprises a generator

breaker with a capacity of 11 kV, 800 A, four VCBs (vacuum circuit

breakers) with connected control, relay panel, and a power transformer of

capacity 11 kV, 6 MVA. Other protective devices, such as lighting arrester,

surge capacitor, and metering panel with potential/current transformer have

been incorporated in the circuit.

Controls and Instrumentation: The entire CHP system is

controlled and protected with the Distributed Control System (DCS) which is

considered as the most reliable system. With advanced computerized

72

techniques, the selection of DCS and connected software is made much

simpler for implementation. Both analog and digital signals can be utilized by

incorporating such advanced distributed control system.

3.4.2 Specific Technical Particulars

The specific technical particulars including capacity and type of

construction of all the systems and subsystems are given below:

1. Boiler : 1 * 26.5TPH Biomass Fired Bi-Drum natural

circulation

2. Steam Turbine: 1* 4.5MW Extraction cum Condensing Type

Steam Turbine

3. Electrical Generator : 4.5MVA, 50Hz, 11KV Generator

4. Fuel Handling: Mechanical Conveyors with variable speed

drives

5. Ash Handling System: Mechanical Bag Filters and ID Fans

6. Condenser : Water Cooled Condenser

7. Auxiliary Circulation Water System: Cooling Tower Circuit

8. Switchyard – Generator Transformer : 11KV System

From the Figure 3.3, the schematic diagram of CHP system in

Textile Mill, it can observe that all the parameters indicated above are

incorporated.

73

Figure 3.3 Schematic Diagram of CHP System in Textile Mill

74

3.5 CHP SYSTEM DESCRIPTION AT SUGAR MILL

3.5.1 Overall Description

The CHP System consists of one number stoker fired boiler of

64TPH, 43ata at 415ºC upgraded to 72TPH at 415

ºC and one number of

extraction cum condensing turbine of nominal capacity to generate power of

6MW. The steam pressure at the inlet of the turbine will be 42ata at 400ºC.

Apart from the above, the CHP system consist of fuel handling

system, firing system, cooling water system, electrical evacuation system and

control system.

The general description of all major systems and subsystems are

presented with an illustration below:

Pre-Heater: The pure water from de-aerator is fed to the pre-

heater. The water/steam temperature is to be maintained 150°C above

atmospheric temperature by the pre-heater with a standard tubular type heat

exchanger. It is then fed to the boiler.

Boiler: The steam generating boiler produces steam at the high

purity, pressure and temperature required for the steam turbine that drives the

electrical generator. The installed boiler can generate steam of the maximum

capacity 72TPH above 42ata, 400°C to 420°C with required piping system

and regulating valves. The boiler furnace is of tangent tube construction made

of tubes of OD- 76.1mm with roods between tubes to ensure leak tightness.

The steam generated in the furnace side walls are taken to a steam drum

through a series of riser tubes. The steam drum is equipped with internals

which remove the water particles from the saturated steam before it enters the

75

super heater. The firing system consists of a travel grate, air plenum,

regulating dampers and ash discharge valves. The travel grate is driven by a

hydraulic system. Fuel is fed through fuel handling system comprising of

extractor driven by variable speed drives, screw type conveyor and pneumatic

distributor. The boiler is equipped with wall de-slaggers, long retractable soot

blowers and rotary soot blowers for removal of ash deposited on the heating

surfaces. The last stage of the heat recovery system is the tubular air heater. In

this air heater, the fresh air is heated to a temperature of around 180ºC, by the

outgoing flue gas.

Super Heater: The super heater is of radiant type and heats the

saturated steam from the steam drum by absorbing the convection heat from

the flue gas. These have air vents and drains needed for the initial startup

steam. The steam drum removes moisture from the wet steam entering it and

the dry steam then flows into the super heater coils. The steam vapor picks up

energy and its temperature is now superheated to 400°C to 450ºC. The

superheated steam is then allowed to pass through the main steam lines

through the valves of the high pressure turbine.

Turbine: The turbine installed is reaction type, multistage,

impulse, nozzle governed with extraction cum condensing type of rated

capacity 6 MW and rated speed of 8312 RPM with Alternator Speed:

1500RPM. The casing design is based on an Inlet Steam Pressure: 45kg/cm2

at 420°C. The turbine will be coupled through a reduction gear unit. Steam is

admitted into the turbine through a emergency stop valve actuated by

hydraulic cylinders. There two controlled extractions 8ata and the other at

2.5ata with a exhaust pressure of 0.1ata. The turbine speed is controlled by an

electronic governing system. The lubrication system for the turbo generator

76

comprises of main oil pump, auxiliary oil pump and emergency oil pump. The

turbine is provided with devices to safeguard against over speed, low steam

inlet pressure, axial movement of shaft, low lube oil pressure and excessive

vibration.

Condenser: The condenser system consists of a surface condenser

with divided water boxes, condensate extraction pump, gland steam and

ejector condenser. The condenser is designed to handle a heat load of

30Tons/Hour with steam inlet flow is 21.1TPH with a pressure of 0.1ata and

temperature of 45ºC. The condenser is made of admiralty brass tubes.

Alternator: The alternator is rated 6MW, 11KV, 50HZ with speed

of 1500RPM. Winding is star connected with class “F” insulation. The

alternator has brushless excitation system with air-air heat exchanger. The star

point is earthed through a resistor to limit the fault current to full load current.

11KV Sub- Station: The 11KV Sub – Station comprises of 11KV

Transformer, VCB and connected control panel for metering and protection.

The excess generated power is evacuated through the public utility grid on the

basis of the power purchase agreement. The substation tee off system

comprises of Power Transformer of capacity 11/33KV, 8MVA, circuit

breaker (VCB) 11KV, 350MVA and 33KV, 750MVA with control and relay

panel. Other protective devices like lighting arrester, surge capacitor and a

suitable earthing system is provided.

Controls and Instrumentation: The CHP system is incorporated

with the Distributed Control System (DCS), which is considered as the most

reliable system. The selections of number of I/O units considered are based on

77

the basic design of the CHP system. As per the regular practice, both analog

and digital signals are considered in the system.

The schematic diagram of CHP System in sugar mill depicting all

the systems and subsystems described above is presented in Figure 3.4.

3.5.2 Specific Technical Particulars

The specific technical particulars with capacity and type of

construction of all systems and subsystems are given below:

1. Boiler: 1*72TPH Stoker Fired Bi-Drum natural circulation

Type

2. Steam Turbine: 1*6MW Extraction cum Condensing Type

Steam Turbine

3. Electrical Generator: 8MW, 50Hz, 11KV Generator

4. Fuel Handling: From Mills through Material Handling

Conveyors

5. Ash Separation System: Mechanical Dust Collectors

6. Ash Handling System: Dry Ash Collection

7. DM Plant: 15M3/ hr Capacity DM Plant

8. Condenser: Water Cooled Condenser

9. Auxiliary Circulation Water System: Cooling Tower Circuit

10. Switchyard – Generator Transformer: 33KV System

78Figure 3.4 Schematic Diagram of Cogeneration Power Plant (CHP) in Sugar Mill

79

3.6 SYSTEM CONFIGURATION

The basic steps to determine system reliability in view of how

systems and subsystems are configured are:

1. The systems and subsystems which constitute a given main

system and whose individual reliability factors can be

estimated are identified and computed.

2. The configuration in which the subsystems are connected to

form the system is represented either by a block or circuit

diagrams.

3. The condition for successful operation of the system is then

established, that is, it is decided as to how the systems and

subsystems should function.

4. Based on the above, the combinatorial rules of probability

theory are stated to estimate the system reliability.

3.6.1 Types of Systems

The nature of system models to be used for quantitative evaluation

would often depend on the type of systems considered. The systems can be

distinguished based on whether it is non- repairable or repairable.

Non-repairable system: These systems are known for one shot

instantaneous operation that operate only once and have instantaneous life

requirement like fuses, bulbs etc.

Repairable system: These systems can be broadly classified into

three types namely: a) Continuously Operating System, b) On and Off

Operating System and c) Intermittently Operating System.

80

With the above types of systems, the basic configuration can be

categorized into either series or parallel system. The subsystems of the

systems are assumed to be independent and whose operation are described in

discrete terms as either “Operating” or “Failed” over a specified time interval.

3.7 GENERAL CAUSES FOR FAILURE OF CHP SYSTEM

3.7.1 General

The causes for failure of CHP System are enumerated below:

1. Past experience has shown that the turbine for a CHP System

application should be rugged and preferably with slow speed.

2. Problems in maintaining the steam purity in the boilers affect

the turbine with deposits on the blades. The major

contaminant is silica that gets carried over as vapor, while the

operating pressure of the boiler increases. Such issues are

overcome with the help of the De-Mineralized Plant.

3. Stability of the grid connected to the CHP System is a matter

of concern and requires constant monitoring.

4. The system maintenance team is not adequately staffed and

stock adequate spares. This could pose major problems,

specifically after the warranty periods.

5. The turbine steam path components, generators, AVRs and a

few auxiliary equipments are few of the replacement

components and pose serious problems.

3.7.2 Faults vs. Failures

It is essential to know the difference between faults and failures to

develop the right reliability module. All failures cause faults; not all faults are

81

caused by failures. A system which has been shut down by safety features has

not faulted. Further to the above, the exact difference between a fault and

failure is indicated as follows:

Fault: An abnormal undesirable state of a system or a system

element induced by presence of an improper command or absence of a proper

one, or by a failure.

Failure: Loss, by a system or system element of functional

integrity to perform as intended.

3.7.3 Data Required for Reliability and Availability Analysis

Most industrial plants have been acquiring equipment failure data

for several years, but seldom is the data analyzed in a scientific manner. The

field of reliability offers many technical guidelines for how data should be

acquired, annotated, and used for analysis. As reliability-analysis tools

become more capable, the availability of accurate and timely data for an

analysis becomes the limiting factor in its ability to perform effective

reliability-analyses. To measure the reliability and availability of an item or a

system, the following important data’s are required:

MTBF: Mean Time between Failures. When applied to repairable

products this is the average time that a system will operate until the next

failure.

Failure Rate: The number of failures per unit of stress. The stress

can be expressed in various units and is equal to the reciprocal of MTBF.

MTTF or MTFF: The mean time to failure or mean time to first

failure. This is applied for non-repairable products.

82

MTTR: Mean time to repair. This is the average elapsed time

between a unit failing and its being repaired and returned to service.

Availability: The proportion of time a system is operable. This is

only relevant for systems that can be repaired and is given by:

(MTBF)Availability

(MTBF MTTR) (3.1)

3.7.4 Data Type and Quantification

The need for long-term field data is of great importance for the

evaluation of technical and economical performances. Most industrial plants

have been acquiring equipment failure data for several years, but seldom have

those data been analyzed in a scientific manner. In order to prepare the data

for a reliability analysis, the analyst must convert the information in the

equipment down-time logs into time-between failure and time to repair from

which MTBF (mean time between failures) and MTTR (mean time to repair)

can be determined. The component failure rate and repair-time data can be

obtained from available sources or estimated for the use in the quantitative

analysis of the system’s availability.

The failure data can be classified into three types, complete and

incomplete (censored) and grouped data:

Complete data: The data set available for modeling is the set {t1;

t2;.. tn}: In other words, the actual realized values are known for each

observation in the data set.

Censored data: When the actual realized values are not known for

some or all of the observations, the data is said to be incomplete or censored.

There are many different kinds of censoring.

83

Grouped data: Data may also be grouped or ungrouped. Grouped

data are data that have been categorized into classes (usually non-overlapping

intervals), with only class frequencies known. Note that grouped data is

‘interval’ censored data.

The model selection can be affected by the size of the data set and

are categorized as follows:

Case A: Small data set

Case B: Medium data set

Case C: Large data set

The above three categories is not intended to be prescriptive, but it

does highlight the differences in issues. In our analysis, we have concentrated

on Medium Data Set for ease of understanding the effectiveness of the system

performance. The gathered data are typically complete and are within bounds

on observations.

3.8 DETAILS OF DATA FOR THE PRESENT STUDY

3.8.1 Failure Data of CHP System – Textile Mill

The CHP system after satisfactory trail run was commissioned and

connected to service on the 2nd

January 2002 and on trial run. The failure and

restoration data of the 4.5MW CHP system was sourced from the mill for the

period from Febuary 2002 to December 2008. After due plant inspection and

detailed interaction with the engineer of the plant, the failure data registered in

the plant log book has been further authenticated. The real time data has been

converted into number of hours and indicated in Appendix -3. From the real

time data, mean time between failure ( MTBF) and mean time to restoration

84

(MTTR) have been derived and indicated in Table 3.1 and Table 3.2

respectively.

The initial observations on the failure data of the CHP System

installed at Textile mill is given below:

Sri Renuga Textiles Limited

Observed from Feb.2002 to Dec.2008

Total Number of Failures: 41

Major Failures over 10h: 18 (Considered for one shift)

Table 3.1 System and Subsystem - Mean Time between Failure data –

Textile Mill (As observed from Feb.2002 to Dec.2008)

S.No MTBF in Hours Description of Failure

1. 3319 Turbine Axial Vibration

2. 4217 Boiler Trip

3. 725 MCC Breaker Problem

4. 483 Gasket Leakage

5. 60 Shut Down Work

6. 112.15 HP Brg Temp High

7. 1922.8 Electrical Fault

8. 1269.05 Bed Drain Line Leak

9. 3207.05 Furnace Brick Work

10. 4166.75 Turbine Boiler Trip

11. 732.35 Shut Down Work

12. 1072.35 Plant Shut Down

13. 1771.35 High Voltage Trip

14. 677.65 AVR Panel Maintenance

15. 1255.75 PT Failure

85

Table 3.1 (Continued)


16. 572.65 LASCPT Panel - PT Failure

17. 8427.65 Bus Problem

18. 1326.65 Electrical Problem

19. 4861.9 VAT Oil Leakage

20. 2340.15 Annual Shut Down

21. 692.75 Turbine Trip (M)

22. 712.75 Turbine Trip


24. 6714.45 A&B Mill Trip

25. 2824.86 Nozzle Chest Leak

26. 1243.66 I Compartment Air Nozzle Failure

27. 1223.66 VAT Transformer Changed

28. 688.96 NGR Panel CT Star Point Melt

29. 1245.43 FWP Trip

30. 1553.16 DCS Module CI 830 Card Problem

31. 3685.94 Feed line Gasket Leak

32. 741.69 Turbine Bye pass Valve Problem

33. 3479.82 May shut Down

34. 913.35 Under Voltage Trip

35. 1144.56 Throttle Valve-I bottom Leak

36. 1476.62 Throttle Valve-I bottom-I Leak vibration

probe

37. 1164.49 52LT - Breaker Open

38. 942.66 Under Voltage Relay Act

39. 1363.91 High Frequency Relay Act

40. 867.71 Low Voltage Relay Trip

41. 1630.36 Fuel Jamming Inline

86

Table 3.2 Failed System and Subsystem Restoration Data – Textile Mill

S.NoRestoration Time

in hoursDescription of Failure

1. 13.00 Turbine Axial Vibration

2. 18.00 Boiler Trip

3. 6.00 MCC Breaker Problem

4. 5.00 Gasket Leakage


6. 7.05 HP Brg Temp High

7. 13.00 Electrical Fault

8. 39.00 Bed Drain Line Leak

9. 54.30 Furnace Brick Work

10. 60.00 Turbine Boiler Trip


12. 229.00 Plant Shut Down

13. 5.00 High Voltage Trip

14. 4.30 AVR Panel Maintenance

15. 5.00 PT Failure

16. 43.00 Lightening Arrester PT Panel - PT Failure

17. 3.00 Bus Problem

18. 8.00 Electrical Problem

19. 0.55 VAT Oil Leakage

20. 1.15 Annual Shut Down

21. 2.00 Turbine Trip (M)



24. 0.30 A&B Mill Trip

25. 9.00 Nozzle Chest Leak

26. 15.00 I Compartment Air Nozzle Failure

27. 3.00 VAT Transformer Changed

28. 2.25 NGR Panel CT Star Point Melt

29. 3.53 FWP Trip

87

Table 3.2 (Continued)

S.NoRestoration Time

in hoursDescription of Failure

30. 1.40 DCS Module CI 830 Card Problem

31. 16.25 Feed line Gasket Leak

32. 8.22 Turbine Bye pass Valve Problem

33. 18.40 May shut Down

34. 2.06 Under Voltage Trip

35. 9.00 Throttle Valve-I bottom Leak

36. 25.20 Throttle Valve-I bottom-I Leak vibration

probe

37. 25.43 52LT - Breaker Open

38. 2.41 Under Voltage Relay Act

39. 2.39 High Frequency Relay Act

40. 13.35 Low Voltage Relay Trip

41. 6.19 Fuel Jamming Inline

3.8.2 Failure Data of CHP System – Sugar Mill

The CHP system was commissioned and connected to service on

the 8th

August 2003. As stated above, the failure and restoration data of the

6MW CHP system was sourced from the mill for the period from August

2003 to April 2008. The real time data after authentication has been converted

into number of hours and indicated in Appendix -3. The mean time between

failure ( MTBF) and mean time to restoration (MTTR) is indicated in

Table3.3 and Table 3.4 respectively.

The initial observations on the failure data of the CHP System

installed at Sugar mill is given below:

88

Shree Vani Sugar and Industries Limited

Observed from Aug.2003 to Apr.2008

Total Number of Failure: 17

Major Failure over 10h: 7 (Considered for one shift)

Table 3.3 System and Subsystem Mean Time Between Failure data –

Sugar Mill (As observed from Aug.2003 to Apr.2008)


1. 3610.75 33KV Bus Link Cut

2. 739.75 Exhaust Temp very High

3. 739.75 Shortage of Fuel

4. 1644.6 Reduction Gear Bearing Trouble

5. 2599.35 Alternator Coolant Jamming

6. 5229.55 RCC Pole Cut

7. 1252.1 Level Indicator Sensor Module Failed

8. 5778.85 Vibrating Probe Failed

9. 691.55 Tubes Got Jammed

10. 826.75 33KV PT Failed

11. 7313.5 Tap Changer Link Cut


13. 419 33KV Bus Link Cut

14. 66 Foundation Bolt Cut

15. 328.2 Grid Failure

16. 282.55 Lube Oil Main Valve Leak

17. 74.25 Fuel Feed Elevator Chain Cut

89

Table 3.4 Failed System and Subsystem Restoration Data – Sugar Mill

S.NoRestoration time in

HoursDescription of Failure



3. 99.75 Shortage of Fuel

4. 129.00 Reduction Gear Bearing Trouble

5. 101.50 Alternator Coolant Jamming

6. 7.00 RCC Pole Cut

7. 70.75 Level Indicator Sensor Module Failed

8. 54.50 Vibrating Probe Failed

9. 68.75 Tubes Got Jammed

10. 4.75 33KV PT Failed

11. 2.50 Tap Changer Link Cut



14. 4.00 Foundation Bolt Cut

15. 5.00 Grid Failure

16. 2.25 Lube Oil Main Valve Leak

17. 0.75 Fuel Feed Elevator Chain Cut

3.9 SUMMARY

In this chapter, the selection of type of turbine is extraction cum

condensing type steam turbines of capacity 4.5MW and 6MW with boiler

capacity of 26TPH and 72TPH respectively. Initial analysis of the failure data

shows that number failures and mean time between failures for CHP System

installed at Textile mill is higher than the CHP System installed at Sugar mill.

90

It is noted that in both the installation, distributed control system is

incorporated for effective operation of the CHP System. The fault tree

analysis, weibull distribution, enhanced control logic and taguchi analysis

have been carried out and are outlined in the next chapter.

chapter 3 base line data for chp system...

Documents