We were recently overhauling a Woodward EG3P actuator in our governor bay when our engineer Andy came across some damage.
During the first initial inspection, the governor appeared to be in good condition.
After that first inspection, we placed the governor on the test stand and connected it to an oil supply to simulate the oil being supplied by the prime mover.
Andy started the test stand run the governor at 500rpm – as the governor was mounted on a 4:1gear box, it was now running at engine speed.
A milliamp connection was supplied, and a digital protector was placed on the terminal shaft. The signal was varied to ensure the terminal shaft degrees were within specification against a specific milliamp signal.
During the test, it became apparent that the recommended milliamp signal against terminal shaft degrees was not within specification.
With a 20 milliamp signal, the terminal shaft should read 1° and at 160 milliamps the reading should be 38°.
With the pre-test completed, the unit was removed from the test stand, drained of oil and completely dismantled and cleaned.
Upon inspection of the internal components, they were found to have suffered the following damage:
- The main bushing and the oil pump idler gear have gear wear and will require replacing
- The pilot valve also has wear to the top control land which will cause instability if it is reused
- The 2 power pistons show signs of wear on one side, with the wear also evident on the relief valve and its sleeve
- The terminal shaft has needle bearing pin wear marks and is no longer fit for continued service and must be replaced
This is quite common with these governors, as they rely on the prime mover’s oil supply for internal lubrication.
And if the oil is contaminated, the contamination will be supplied to the governor which will then cause excessive wear.
