Steam turbine overspeed trip 1

[sinectica]

Hello guys,
I would like to know if there is any recommendation/guide or norm that indicates which is the frequency to carry out the overspeed trip tests for special steam turbines.
We use to test the trip each 18 months, but it's based in our experience, not in any written guide nor recommendation.

Any information will be greatly appreciated.

Thank you so much,
Marc

 

[JJPellin]

I work in a large US oil refinery. Our policy for trip testing special purpose steam turbines is as follows: They are to be tested at every turnaround or suitable unit shut-down if at this shut-down they have not be tested for more than 1 year. If there are not non-TA shutdowns, then the turbine is tested at every turnaround, not to exceed 6 years. API does not require any particular frequency that I am aware of. OSHA requires that you have a trip test policy and that you abide by it. But, they also do not require any certain frequency. It is up to you. Create a policy and live by it.

Johnny Pellin

 

[metengr]

What does your Boiler/Machinery equipment insurer require?

 

[sinectica]

Hello metengr,
as we will have soon a meeting with the insurers I would like to be sure that the proceeding we are following safely enough and if it supported by a norm it would be better for us.
Even though, if nothing is written about this issue, maybe it's up to the user the frequency to be used...

Thank you so much for your support
Marc

 

[metengr]

Marc;
For our large steam turbines - annually. Also, you should verify this with the turbine OEM, this is where the insurers typically start.

 

[byrdj]

Questions:
Is the emergancy govenor mechanical or electronic?
the utility i'm consulting for is in discussions with insurer now since installer of new controls says once is enough for ever for electronic

If mechanical, do you have provisions to excercise it ie an on line locked out oil injection test. If so following the manufactor (ussually weekly) or insurers (ussually at least yearly) shedule.

the actual overspeed test of the EG is normally recomended yearly by most manufactors

 

[waross]

installer of new controls says once is enough for ever for electronic.

And three mile island never happened,
And, I was never here!
There's a line from a song running through my head;
"When will they ever learn."
And after the event.
"But our controls are working perfectly, it was the (mechanical linkage, sensor, stuck valve, broken wire,)"......pick one or use your own.
There is a reason to do periodic function checks and prove operation, no matter how good one component may be.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[engineearandarm]

Marc,
The standard proceedure for testing a mechanical or electrical overspeed trip is normally after a minor or major inspection. The driving force behind the testing is whatever your insurer requires. Whether it be semi or annual testing, follow the OEM recommendations for overspeeding. Normally it is only 110% of running speed. I work for an OEM and I have only had one mechanical overspeed trip mechanism to fail in 17 years. This was the result of a wrecked unit. If I can be of more service, please respond with other questions.