Biannual. Remove main and auxiliary valve plunger and remove all rust spots and oil varnish with a fine
grade emery cloth (320 to 500) and crocus cloth. Any nicks or scratches should be removed by stoning
with a very fine flat stone. Care must be taken not to round or break the edges of the valve lands. Check
ports in valve bushings for dirt or sludge and clean as required. Check that main valve plunger is free and
can fall of its own weight after reassembly.
Not Scheduled. Completely disassemble main and auxiliary valves. Remove opening, closing, and
pressure plungers and remove all rust spots and oil varnish with a fine grade emery cloth (320 to 500) and
crocus cloth. Check condition of main distributing valve plungers piston rings and replace as required.
9. Miscellaneous Valves
Annual. There may be other hydraulic valves in the governor such as gate limit valves and solenoid valves.
These valves should be disassembled, and all rust spots and oil varnish should be removed with a fine grade
emery cloth (320 to 500) and crocus cloth. Any nicks or scratches should be removed by stoning with a
very fine flat stone. Care must be taken not to round or break the edges of the valve lands. Check ports in
valve bushings for dirt or sludge and clean as required.
Annual. Check dashpot oil level and add oil if necessary. Do not use lubricating oil. Check operation of
solenoid operated bypass. If governor tests from item 1 indicate a sticking dashpot, disassemble, inspect,
and clean dashpot plungers. Before reassembly, check the setting of the small dashpot plunger. On
Woodward governors, the distance from the center of the pivot pin to the top of the bonnet should be 2-7/8
inches. Turn the small plunger spring to adjust this distance. On other governors, check the
manufacturer's instruction book for adjustment procedure. To refill dashpot, reassemble except for the
small dashpot plunger. Tip the dashpot so that the opening for the small plunger is higher than the large
plunger and fill the dashpot through the small plunger opening. Move the large plunger occasionally during
filling to allow air to escape. To check for trapped air once the dashpot is filled, install the small plunger,
close the dashpot needle, and operate the large plunger while holding the small plunger. The small plunger
should react instantaneously to any movement of the large plunger. Any lag in small plunger movement
indicates there is air in the dashpot or a leak past the needle, solenoid bypass, or the plungers. To purge the
air, open the needle, hold the small plunger in place, and operate the large plunger.
To check the condition of the dashpot, close the bypass and the needle completely, push the small plunger down
as far as it will go, and time how long it takes to recenter. It should take more than 50 seconds to travel 0.125
inch. A shorter time indicates excessive leakage past the needle or plungers, and the dashpot should be repaired
After any maintenance on the dashpot, it is important to perform the governor adjustment tests of item 1 to
bring governor back to optimum performance.
11. Linkage and Pins
Monthly. Lubricate links and pivot pins with a light machine oil.