During SAIT steam lab competencies for turbines, students may be asked to either “TEST the overspeed trip” or “HIT the overspeed trip”.

These are two completely different requests, and it would be a shame to lose marks for not knowing the difference.

I. TEST the overspeed trip

1. Increase the RPMs gradually, by opening the turbine governor slowly and deliberately.
2. Watch the RPM indicator, and report to the instructor the final value at which the turbine tripped.
3. Close the steam inlet valve.

II. HIT the overspeed trip

1. Push the locking bar on the overspeed trip (for the Coppus turbine) or pull the overspeed trip (on the Bellis & Morcom turbine) to bring the turbine to a stop.
2. Close the steam inlet valve.