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Ron Stiemsma

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Reply with quote  #1 
It seems like I have missed something.  Has it become common practice to remove the automatic trips from the Main Turbines?  Our Nuc Plant is saying this is common practice and working to have then removed just keeping the alarms.
John from PA

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Reply with quote  #2 
I remember this being instituted several years back (while still working).  Part of it was being driven by insurance companies and the desire to stop doing testing on overspeed trips by actually runnning the machine at an overspeed condition.  The desire was to test, but to do so with a simulated speed signal.

Some resources you may wish to review are 

https://pdfs.semanticscholar.org/bee4/9611336cfdb8887c6b1475b6a3979b95d772.pdf

https://inis.iaea.org/collection/NCLCollectionStore/_Public/26/070/26070050.pdf

https://www.nrc.gov/docs/ML1419/ML14191A459.pdf


Ron Stiemsma

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Reply with quote  #3 
Thanks John. 

But, I am talking vibration trips and not overspeed. 
electricpete

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Reply with quote  #4 

At our plant there is no automatic vibration trip for main turbine/generator nor for turbine driven feedpumps. There are automatic trips on thrust for both types of machines. There are of course manual trip actions for high vibration.

Siemens Bulletin SB3-14-0001-ST-EN-01 sort of leads me to believe this is commonplace  for this vendor. Specifically they talk about "alarm", "warning", and "trip" levels for vibration. For each level there is a discussion.  The discussion for trip is "trip the unit if this level is reached". There is no mention of automatic trip in the entire bulletin.

RGf

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Reply with quote  #5 
I echo electripete's comments on the Siemen's steam units. Most trip logic would need 2 inputs at the trip level to initiate a shutdown/trip. In my world of gas turbines the trip levels are pretty hard set. Some use relative vibes from prox probes (Westinghouse/Siemen's) and GE uses inputs from seismic sensors. OEM preference.  
Ron Stiemsma

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Reply with quote  #6 
Ours need one bearing above the hi-hi limit and an adjacent bearing above the high limit.
OLi

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Reply with quote  #7 

I worked at a Nuke with old GEC turbines (when they were new), they never had any trip:-) and will have operated 30-35 years when they shut down next year.
We work now on similar vintage former ABB now Siemens gas turbines, they always had trip, still have.

I think it is good to have a firm level not to exceed as the discussion will anyway be around "we can just increase a bit so we can run until the weekend" etc.
If you have a sudden event like loss of blade parts it would be good to have a automatic trip IMHO.

My father extrapolated a vibration increase on a nuke turbine many years ago and reported that it will touch and fail "on Friday at 1400" and owner said we don't care we operate so he
went home and it failed at the appointed Friday at 1400 to a cost of 2 million Euro, downtime uncounted. It had trip but not for this case.

So how you turn your self the backside will always be pointing backwards we have a saying here.

Overspeed test IRL reluctance may have a connection with a happening here the other year where a less than optimal test blew up a brand new turbine as the
last and final overspeed trip actually didn't work...... I think that was a pretty hefty insurance sum to shake out.

 


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