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Electronic OST test of Diesel Engine with Pump
Need the procedure for Electronic OST test for horizontal split casing type centrifugal pump flexibly coupled to diesel engine on the fire-fighting system


We have two horizontal split casing type centrifugal pumps flexibly coupled to their respective diesel engines on our fire-fighting system. The specifications are:

PUMP MODEL : JOSLYN 150-100-310, Cl-Casing, BR-Impeller, SS-Shaft
DIESEL ENGINE: N45MNT41, 145kW, 2900RPM, 12V Battery Start, Water Cooled


We need to perform the Electronic OST (Overspeed Trip) test for this pump for the first time but do not have any procedures available. The general understanding is that we can bring the set-point down and then try it. But if someone has a proper procedure or can offer guidance in this regard, it'll be really helpful!

You really need to consult the manuals for the diesel engine control system and/or the electronic overspeed protection device to understand what is possible.

Yes, a lot of prime mover overspeed testing is done these days by lowering the overspeed trip setpoint on the electronic control system or overspeed protection device to something less than rated speed and then start the unit and as it accelerates through the lowered trip setpoint the fuel should be shut off and the proper alarm(s) annunciated.

This is usually acceptable practice by insurance companies and owners because the electronic trip function is easily adjustable and if it trips at a low speed then it should trip at the normal, higher rated speed, and it avoids overstressing the prime mover and driven device (the pump in your case) by running them to overspeed which could potentially be harmful or destructive.

Hope this helps!

1 out of 1 members thought this post was helpful...


Since we are conducting the test to fulfill Insurance company's requirement and do not have sufficient documentation on these pumps available at the plant, I believe conducting the test at a lower set-point should suffice. I have however raised the query with the manufacturer as well alongside, awaiting a response on that.

Thanks you!