Turbine Blade broken

Question

Turbine Blade broken

baasi (Mechanical)

(OP)

26 Oct 16 03:10

Can any body explain me that what will happen if some blades of turbine get broken? and how can we detect if some blade is broken or not?

byrdj (Mechanical) · Answer 1 · 2016-10-26 13:54:38

a broken turbine bucket (blade) will be IMMEDIATELY seen as a journal bearing vibration increase. for any turbine stage, with a possible exception of the last stage, there will be resulting colaterail damage to other buckets.

FORCING a turbine back into service with a minor broken bucket will result in harmontics and cause breakage of other buckets with few hours of operation thus being major damage

JJPellin (Mechanical) · Answer 2 · 2016-10-26 18:09:43

You should provide more information on the type of turbine you are interested in. We have overhauled a multi-stage steam turbine and found a broken blade in the last stage. We believe that this break had occurred months or even years ago. There was no clear evidence in the vibration. But, it was a very small piece broken off relative to the size of the blade and the weight of the rotor.

Johnny Pellin

http://files.engineering.com/getfile.aspx?folder=13e6ec7e-80fa-429e-beb6-0c

baasi (Mechanical) · Answer 3 · 2016-10-27 10:19:45

@JJpelim i am interested about steam turbine blades. In your case breakage is very little but if 2 or 3 blades get broken then i think vibration is only phenomenon from where we can get information

JJPellin (Mechanical) · Answer 4 · 2016-10-27 11:50:05

You still have not provided information on the turbine involved. For the turbine that I referenced, the loss of two blades on any stage would certainly result in the turbine tripping off on high vibration. If the turbine did not trip off for some reason, I would expect a bearing failure. Are you proposing placing a turbine back into service with missing blades?

Johnny Pellin

byrdj (Mechanical) · Answer 5 · 2016-10-27 15:30:52

John, does your photo show that damaged bucket? I can't find it,
could you give location

stgrme (Mechanical) · Answer 6 · 2016-10-27 16:01:55

Keep in mind that vibration is a vector, consisting of an amplitude and a direction. If a small portion of a blade is lost and if the location of that damaged blade is 180 degrees from the vibration vector before the loss, there is a change in the vibration vector. However, the amplitude portion of the vibration vector may not increase, or could decrease, since the new vector is 180 degrees away from the original vector.

Best of luck!

JJPellin (Mechanical) · Answer 7 · 2016-10-27 16:25:46

I cannot find a picture that shows the broken blade from our turbine.

Johnny Pellin

Sami Khan (Mechanical) · Answer 8 · 2017-01-25 16:58:10

We observed the same phenomenon of cracks in last stage of reaction turbine. Plants is tripped on high vibration if there occurs turbine dynamic imbalance due to breakage of blades. Vibration of journal bearings across turbine rotor is mirror for turbine behaviour.

Nicolas13 (Petroleum) · Answer 9 · 2017-01-25 17:37:02

in reaction turbine when a small blade fails the rotor vibration could stay at low value without noticeable event.

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