WOODWARD PGEV & PGE LOCOMOTIVE GOVERNORS Troubleshooting Caterpillar

Introduction

It is impossible to anticipate every kind of trouble that is encountered in the field. This covers the most common troubles experienced. Poor governing may be due to faulty governor performance, or it may be due to the governor attempting to correct for faulty operation of the engine or turbine auxiliary equipment. The effect of any auxiliary equipment on the overall control requirements of the governor also must be considered.

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TO PROTECT AGAINST POSSIBLE PERSONAL INJURY, LOSS OF LIFE, and/or PROPERTY DAMAGE WHEN STARTING the engine, turbine, or other type of prime mover, BE PREPARED TO INITIATE AN EMERGENCY SHUTDOWN to protect against runaway or overspeed should the mechanical-hydraulic governor(s), or electric control(s), the actuator(s), fuel control(s), the driving mechanism(s), the linkage(s), or the control device(s) fail.

Oil

Fill the governor with oil to the mark on the oil level gauge with the engine idling. Oil must be visible in the glass on the gauge during all other conditions.

Dirty oil causes approximately 50 per cent of all governor troubles. Use clean new or filtered oil. Containers used to fill governors from bulk containers should be perfectly clean. Oil contaminated with water breaks down rapidly, causes foaming and corrodes internal governor parts.

Compensating Needle Valve

The compensating needle valve must be correctly adjusted with the governor controlling the engine or turbine, even though the compensation may have been previously adjusted at the factory or on governor test equipment. Although the governor may appear to be operating satisfactorily because the unit runs at constant speed without load, the governor still may not be correctly adjusted.

High overspeeds and low underspeeds, or slow return to speed, after a load change or speed-setting change, are some of the results of an incorrect setting of the compensating needle valve.

Definitions

Use the chart on the following pages to determine the probable causes of faulty operation, and to correct these troubles. Terms used in the chart are defined as follows:

HUNT

A rhythmic variation of speed which can be eliminated by blocking governor operation manually, but which will recur when the engine is returned to governor control.

SURGE

A rhythmic variation of speed, always of large magnitude, which can be eliminated by blocking governor action manually and which will not recur when the engine is returned to governor control, unless speed adjustment is changed or the load changes.

JIGGLE

A high-frequency vibration of the governor fuel-rod end (or terminal shaft) and fuel linkage. Do not confuse this with normal controlling action of the governor.

Preliminary Inspection

Governor troubles are usually revealed in speed variations of the prime mover, but it does not necessarily follow that such variations are caused by the governor. When improper speed variations appear, the following procedure should be performed.

1. Check the load to be sure the speed changes are not the result of malfunctions in the vane servo, generator control circuits, switchgear, etc.

2. Check engine operation to be sure all cylinders are firing properly and that the fuel injectors are in good operating condition and properly calibrated.

3. Check linkage between governor and fuel racks to be sure there is no binding or excessive backlash.

4. Check setting of governor compensation needle valve.

5. Check speed-setting circuits for voltage level and sequencing.

6. Check for fuel-pressure changes.

7. Check governor oil pressure. A test port is provided in two sides of the governor power case for this purpose.

8. The source of most troubles in any hydraulic governor stems from dirty oil. Grit and other impurities can be introduced into the governor with the oil, or can form when the oil begins to break down (oxidize) or become sludgy. The internal moving parts are continually lubricated by the oil within the unit. Valves, pistons, and plungers will stick and even "freeze" in their bores, due to excessive wear caused by grit and impurities in the oil. If this is the case, erratic operation and poor response can be corrected by flushing the unit with fuel oil or kerosene. The use of commercial solvents is not recommended as they may damage seals or gaskets.

Change the oil and flush the governor twice a year if possible. Remove the cover, open the drain cock and drain out the oil. Flush the governor by filling it with fuel oil. With the engine running at low speed, cycle the governor by opening the needle valve two or three turns. Let the governor hunt for a minute or two and then stop engine and drain the governor. Flush the governor once again. Fill the governor with oil, pouring it over all the internal parts that are visible. Start the engine and reset the compensation needle valve.

9. Check drive to governor for any evidence of misalignment, roughness, excessive backlash, etc.

Troubleshooting

Fuel limiter troubles such as erratic operation or slow response to changes in manifold air pressure are usually the result of oil contamination. Correct this type of trouble by flushing the governor with fuel oil or kerosene.