Sharing information here related to a question I received. The question posed was what is the correct timing for the EMD low oil pressure shutdown feature on Woodward PG governors.

There has been more than one timing setting used over the years of EMD engine production. The 567 series engines generally used 40 seconds while the 645 and 710 engines typically used 50-60 seconds.

The purpose of the timer is to allow oil pressure to stabilize and trapped air in the system to vent following a startup, before the engine observes and shuts down for a low oil pressure condition. The feature is bypassed when the engine speed is increased above notch 3, at that point low oil pressure results in shutdown in 1-2 seconds.

Applicable references are EMD No. 252 Engine Maintenance Manuals for 567 engine series, and the EMD Engine Maintenance Manuals for specific applications in 645 and 710 engines. Normally the information is found in the back of the governor section or the front of the chapter on alarms and protective devices.

PC

Does the timer over ride feature also apply to 567 engines with the pneumatic - hydraulic version of governors? We have had a few instances where the low oil trips instantly upon hot restarts. Only seems to happen to the same person though.
Thanks
E

Woodward PG Air actuation governors (called type PGA by Woodward) used on locomotives, mining trucks, and marine applications, use basically the same low lube oil pressure sensing and timing equipment as the PG Electric actuation governers (called type PGE) used on locomotives with eight notch electric controller throttles. The engine speed fulcrum positions the speed control floating bushing that "chops" the oil to the shutdown mechanism, giving a time delay in idle and lowest speed range. The devices and parts are listed in Woodward manual 36652.

The shutdown that is applied to most PGA marine propulsion governors operates a bit differently from the shutdown of the PGA used on locomotives and mining trucks. It throws an alarm switch rather than shutting down the engine with the mechanism in the governor. The alarm can then either allow the operator to make a decision to shut down manually, or it may shut down the engine by a solenoid tripping the overspeed mechanism.

Older Woodward air actuation switcher locomotive governor control systems used a separate lube oil pressure switch (LOPS in early units, called LOP later) that actuates ESD, an engine shutdown magnet valve. The ESD function was simply bypassed in idle.

The problem EWrice is describing might be a result of too much layshaft advance being used for starting with hot oil. The governor is building up speed setting oil pressure faster than the engine is registering oil pressure, that triggers the mechanism in the low oil pressure sensing while the engine has accelerated above the time delay speed range and initiates an immediate shutdown.

PC