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BANGLADESH RESEARCH PUBLICATIONS J OURNAL

ISSN: 1998-2003, Volume: 5, Issue: 4, Page: 381-386, July -August, 2011

WOODWARD GOVERNORS TROUBLESHOOTING AND

RECTIFICATION: A CASE ON J AMUNA FERTILIZER COMPANYPERSPECTIVE

*Md Mamunur Rashid1 and Md. Abdul Mannaf2

Md Mamunur Rashid and Md. Abdul Mannaf (2011). Woodward GovernorsTroubleshooting and Rectification: A Case on J amuna Fertilizer Company Perspective.Bangladesh Res. Pub. J . 5(4): 381-386. Retrieve from

http://www.bdresearchpublications.com/admin/journal/upload/09246/09246.pdf

Abstract

Woodward governor is a mechanical sophisticated device. Normally

this governor is not maintenance in Bangladesh. Generally, if governor

falls in trouble then we replaced it by new one simply. Woodward

governor manufacturer does not permit to the users for maintenance

works of governor. This governor generally is used in heavy-duty turbine

and engine. The maintenance of the Woodward governor is successfully

done in J amuna Fertilizer Company. In this perspective, a Woodward

governors trouble shooting and rectification related study is presented

in this article.

Key Words: J amuna Fertilizer Company Limited, Woodward Governor,Rectification, Turbine.

Introduction

Governor is a device, which maintains the constant speed of an engine or

turbine, regardless of load, that is, if the load changes of an engine, the speed of

the engine will also change but the governor will control the fuel flow

instantaneously to maintain the constant speed of the engine. A turbine is also

considered an engine. Thus, in this paper is discussed regarding steam turbine

generator (STG), which is operated by steam turbine, to obtain steady voltage

and frequency. Moreover, J amuna Fertilizer Company (J FCL) related some

papers are published [Rashid, (2011), Manaf. and Rashid, (2002, 2004), Rashid and

Islam, (2004)]. The generator speed must be constant. On running condition, the

generator load may be changed. Suppose, the generator is loaded suddenly,then the speed of the generator instantaneously decreased, at once the

governor will increase the fuel flow or steam flow to obtain the generator speed

constant as before. On the other hand, due to sudden unloading the speed of

the generator will be increased instantaneously, then the governor will decrease

the fuel flow or steam flow until the generator speed becomes previous set

speed. In this way, governor maintains the constant speed during running

condition. Old model governor has no internal oil pump, control oil is supplied to

the governor by external arrangement, but modern governor has internal oil

pump (gear pump), which is used for better and safe operation. WOOD WARD

GOVERNOR CO. LTD, USA is only modern governor manufacturer in the world.

They do not suggest repairing the governor locally like J FCL [Rashid, (2011),

*Corresponding Authors email:[email protected]

1 Bangladesh Institute ofManagement, 4, Sobhanbag, Mirpur Road, Dhaka-1207.2 J amuna Fertilizer Company Limited, Tarakandi, J amalpur-2055, Bangladesh.
mailto:[email protected]:[email protected]

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Ra shida n d Ma n na f

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Manaf. and Rashid, (2002),] of Bangladesh, although already some governors

have rec tified, which are running in the plant. To test and to calibrate the

governor by the governor test bench only in Chittagong Urea Fertilizer Limited

(CUFL) in Bangladesh. Now a day, elec tronics governor, which is most modern

and sophisticated equipment, is used in turbine or engine control system. In J FCL,

only electronics governor is used at GTG. Only WOOD WARD GOVERNOR CO.

LTD. USA, [8] in the world manufactures the governor and they advice the usersnot to do maintenance works. Although the governor trouble and rectification

works have been done at J FCL. This paper is focused on this maintenance works

and divided the following sections:

Description of Woodward governor Remarkable Maintenance works in J FCL Discussion Recommendation Conc lusion

Description of Woodward governor

Governor maintains the constant speed of an engine or turbine irrespective of

load by sequence of action and operation. Governor drive shaft is connecteddirectly to the turbine shaft by reduction gearbox to sense the speed from the

turbine. Simple explanation of input-output signal to the governor as below:Speed Setting Input

Speed Input

Governor Output Shaft C.W/C.C.W

As Output

Figure 1. Input-output signal of Governor

This drive shaft mainly operates two elements: One lube oil pump (gear

pump) another ball head mechanism. Lube oil pump generates control oil and

the ball head mechanism regulates this control oil to actuate the governor output

shaft. The ball head mechanism consists of two flyweights, speeder spring and

pilot valve plunger. Flyweight movements inward or out ward direction dependupon the speeder spring pressure and speed of the turbine. If the governor speed

is more, then the flyweight becomes outward position, which pushes the pilot

valve plunger upward, direction, regulating the control oil to the power piston as

the governor shaft decreases fuel position. In reverse matter, if the governor

speed is suddenly decreased, then the flyweight becomes inward position, which

allows the pilot valve plunger downward, direction, regulating the control oil to

the power piston as the governor output shaft increases fuel position. Speed

setting system is nothing but the pressure of the speeder spring, which is operated

manually or by servomotor remotely. Governor output shaft moves clockwise or

counter clockwise i.e. fuel increase or decrease position, which depends upon

the speed setting and input speed. The conditions of the speed setting and inputspeed are following:

If the input speed is greater than the setting speed, the governoroutput shaft will decrease fuel position.

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If the input speed is less than the setting speed, the governor outputshaft will increase fuel position.

If the input speed is equal than the setting speed, the governoroutput will become stationary that is governor will remain steady

state condition.

Speed control systemA Speed control system of a turbine is shown in the following block diagram

figure. Assume the speed 1500 rpm of the generator have to maintain. Initially, the

governor setting speed 1500 rpm have to set.

Steam in

Turbine Speed Reducer

Speed

Generator

Speed

Governor

Speed Setting Signal

Output

Shaft

move

Pilot

System

Mech.

move

Power

Cylinder Mech.move

Governor

Valve

Steam outHigh pressure Steam (control)

High Pressure Steam Header

Figure 2.Speed control diagram

Now, if the governor is suddenly loaded, the speeds of the generator will

little less than 1500 rpm, instantaneously. Then the governor will actuate that is

governor output shaft moves clockwise direc tion (increase fuel). Consequently

the pilot valve moves downward by linkage arrangement then the pressure oil

enter to the power cylinder which moves the governing valve up, the more steamflows to the turbine to maintain the speed of the generator through 1500 rpm.

Reversibly, if the generator is suddenly unloaded, the speed of the generator will

little higher than 1500 rpm, instantaneously. Then the governor output shaft moves

counter clockwise direction (decrease fuel). Subsequently, that the pilot valve

moves upward by linkage arrangement, pressure oil cut the flow to the power

cylinder, which moves the governing valve down, then steam flow decreases to

the turbine as a result generator speed, will become 1500 rpm again.

Additional items of governor

The following items of governor, which are to adjust to the governor during

operation:Compensation: Compensation system is to give stability to the governor andobtains steady state speed control by adjusting the needle valve orifice, which

control the oil flow between both compensation piston and oil sump.

Droop Mode: Drop is the decrease in speed taking place when the governoroutput shaft moves from minimum to maximum fuel position in response to a load

increase.

Droop= [(No load speed Full load speed)/ Full load speed] X 100=3.5%; Reducing

droop to zero allows the unit to change the load without changing speed, which

is called ISO-mode. Only J FCL, Gas turbine Generator (GTG) runs ISO mode.

Load limit: The purpose of the load limit control is to hydraulically and

mechanically limit, the load that can be placed on the turbine by restricting thetravel of the governor output shaft in the increase fuel direction. The load limit

control may also be used for shutting down the turbine by turning it to zero.

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Governor components for speed setting

A brief description of the governor components will facilitate understanding the

speed setting and operation of the governor.

Oil pump:The oil pump (gear pump) is driven by governor driven shaft, which isdriven by the prime mover (turbine). Oil flow is directed into the accumulator

system.2.3.2 Accumulator: The purpose of the accumulator is to store oil under pressure

for operation of the governor.

Power piston: The power piston is to rotate the governor output shaft to theincrease or decrease fuel position.

Pilot valve system

The pilot valve plunger and bushing is to control the oil flow to or from the bottom

of the power piston.

Ball head systemThe ball head system is to sense speed changes of the prime mover (turbine) as

compared to the speed setting reference given by the speeder spring and to

give position the pilot valve plunger.

Remarkable Maintenance works in JFCL

Only WOOD WARD GOVERNOR CO. LTD. USA, in the world manufactures

the governor and they advice the users not to do maintenance works. Although

the following examples of governor trouble and rectification works have been

done at J FCL:

Case 1

In J FCL, Carbon-di-oxide compressors minimum governor speed was

comparatively high. It was near about rated speed, which was observed during

start up period since erection December 1991. For this reason steam turbinespeed becomes sudden high and turbine was being hunting for long time. This

adjustment especially in high speed and high power turbine was so risky on

running condition. Any mistakes during adjustment may cause severe damage.

This situation was conquered by adjusting pilot valve system.

Case 2

Gear operated manual speed setting Knob of Induced draft fan (IDF)

turbine was broken and the minimum governor speed of IDF turbine was become

undefined. The trial and error method at startup period and defined the minimum

governor speed successfully.

Case 3

NG compressor seal oil turbine governor (SG governor) was hunting for

long time. For this reasons, this problem has been rectified to replace the new ball

bearing in drive end side of the turbine, to fabricate new coupling bush with

governor. Hence, control has been dismantled for inspection, but the hunting of

the turbine was existed. Later adjusted the droop of the governor by opening

governor head, subsequently the hunting was stopped.

Case 4

Due to fire in natural gas (NG) compressor, PG-PL governor was completely

damaged. This governor was stored under open sky for long time. Later on thisgovernor dismantled and checked each and every parts of the governor. Some

parts replaced by another rejected governor. Then it made fully in service

condition. This type of governor from WOOD WARD CO.LTD, USA can be

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385purchased, then need around BDT. 1 (one) million. Consequently, that money was

saving of J FCL.

Case 5

Lean turbine governor speed sensing device was broken completely. It

was made in by own J FCL design and it was set successfully for operation. Now

this is running with good condition.

Discussion

A maintenance platform may introduce unprecedented levels of

transparency and efficiency into the entire industry producing an integration of

business process that significantly contributes to the acceleration of total

processes, to an easier design (lean processes) and to synchronize maintenance

with production, maximizing process throughout and minimizing downtime cost

[Hausladen and Bechheim, 2004]. Data and information flows into the decisionmaking and planning process at all levels can be improved [Ucar and Qiu, 2005].

The maintenance analysis of Woodward governor of J FCL has done based on

different situations has been discussed on the five cases. By minimizing themaintenance cost allocation to various subsystems with any governor, the

optimum repair policy can be determined through details study. Maintenance is

linked with safety and quality maintenance; moreover preventive, remote,

predictive, collaborative maintenance can save plant damage and also save

foreign currency. For this purpose, Inspection, monitoring, modification,

improvement, knowledge capitalization and management can be consideredalso for Woodward governor maintenance, and also for overall plant

maintenance.

Recommendations

The following recommendations are for maintenance work ormanagement purpose:

E-manufacturing, e-business and e-maintenance can beconsidered for plant operation.

Fault/ Failure analysis can be done properly. Maintenance documentation can be kept properly. Predictive, preventive maintenance can be functional in plant

operation.

Business process integration may be consideration.Conclusion

This paper presents an overview of Woodward governor maintenancecapabilities and challenges in Bangladesh perspective. According to finding, any

adjustment, calibration, setting and troubleshooting regarding turbine control

system can be solved in Bangladesh with foreign expert. Any trouble of specific

Wood ward governors rectification, trouble shooting and modification can be

done in Bangladesh. Hence it is saving foreign currency.

References

Hausladen, I. and Bechheim, C., (2004).E-maintenance platform as a basis for

business process integration. In: Proceedings of INDIN04, 2nd IEEE

International Conference on Industrial Informatics, pp.46-51, Berlin,

Germany.Manaf, M. &. Rashid, M.M. (2004). A process upgrading of urea synthesis and

high pressure recovery section by reducing pressure from high pressure

loop, Proc ee d ing s of the na t iona l pa p er m ee t ing on fert ilizer sec tor , IEB,

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Rangadia, Chittagong, Bangladesh, J uly 09, 2004, Paper No 1B, pp. 68-72

Manaf, M. &. Rashid, M.M. (2002). Technical Challenge about Woodward

Governors Trouble Shooting and Rectification in J amuna Fertilizer

Company Limited.Proc ee d ings of the Seventh Annua l Pap er Mee t ing a ndthe Sec ond In te rna t iona l Co nferenc e on Me c ha n ic a l Eng ineering ,

February15, 2002, IEB, Chittagong,Bangladesh, Paper No.26, pp. 206-211

Rashid M.M. (2011). Management Information System of J amuna Fertilizer

Company Limited: A Case Study, International Business and

Managemen t , Vol. 3 (1) pp118-124, 2011

Rashid, M. M. (2003). Innovation of Programming Keyboard in J amuna Fertilizer

Company Limited, Proc ee d ing s of the Eig hth Annua l Pa p er Me et ing and

the Third Internat iona l C onfe renc e o n M ec ha nic a l Eng inee ring ,March 20-

22, 2003, IEB, Ramna, Dhaka-1000, Bangladesh; Abstract No.60

Rashid, M. M., &Islam, A. M (2004). A Technical proposal on analyzing

Management Information Systems of the J amuna Fertilizer Company

Limited: A case Study,Pro c ee d ing s of the na t ion a l p a p er me et o n fer tilizersector at IEB Rangadia, Chittagong, Bangladesh, J uly 09, 2004, Paper No

1A, pp. 73-79

Ucar, M. and Qiu R.G. (2005). E-maintenance in support of E-automated

Manufacturing Systems. J ournal of the Chinese Institute of Industrial

Engineers, 22(1), pp.1-10.

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09246BRPJ-J10