Engine Systems Inc. (
ESI) began a
10CFR21 evaluation on 9/18/2012 after an
ESI test technician found a set screw in one of the oil bath stations of the temperature test fixture. After evaluating all components that were tested on the fixture, it was determined that this set screw is the same length, thread size and style as the set screw utilized in the EMD/Detroit temperature switches to lock the differential adjustment screw. The other components tested on the fixture did not contain such a set screw. Either an extra set screw was inside a temperature switch and it fell into the test fixture oil bath when the test technician removed the switch cover; or, the test technician dropped the set screw after removing it from a temperature switch to adjust the differential setting of the switch. If the latter occurred, then the potential exists that a temperature switch was shipped without the differential adjustment screw locked and therefore the switch settings could drift over-time from exposure to vibration on the
EDG skid.
ESI has identified the time period in which this could have occurred to be 4/2/2012 to 9/18/2012. The suspect temperature switches are
EMD parts manufactured by Detroit Switch. These are located in the engine cooling water and
lube oil systems for low standby
lube oil temperature alarm, high coolant temperature alarm/shutdown and coolant immersion heater control applications.
The evaluation was concluded on 10/3/2012 and it was determined that this issue is a reportable defect as defined by 10CFR21. If a switch applied in the immersion heater control application experiences significant setpoint drift, it is possible that the standby temperatures of the lube oil and coolant systems may be degraded enough to affect the start time of the diesel generator.
All affected users should inspect the suspect switches for presence of the set screw at their earliest convenience. If the set screw is missing, the temperature switch should be returned to
ESI for rework.