Protection for General Purpose Steam Turbines

[CaracasEC]

For the protection of general purpose turbines which do not have vibration monitoring, we proposed on our ongoing project to provide an interlock between inlet temperature transmitter (TIC) and the turbine. The interlock shall send an alarm signal to the DCS at low temperature of steam supply and consequently shuts down each of the turbines at low temperature of the steam supply. Hoping to hear from you guys and thank you very much for your comments..

 

[BigInch]

If that's all your worried about, that's fine, just hope you don't lose a bearing, etc. etc. The idea is that monitoring vibration and bearing temperature is cheap insurance when compared to replacing a turbine. Can't believe you've got no money for that.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[rmw]

Somehow it seems like you gave a statement about apples and then ask a question about oranges. What are you trying to accomplish with monitoring steam temperature. It is hard to comment. Most general purpose steam turbines in my experience do not have vibration sensors, but then again, I have never seen one with a temperature sensor.

Low steam temperature causes moisture formation in the turbine in stages earlier than the stages designed to handle moist steam and that can cause damage that could ultimately lead to vibration problems, but that would be my last worry regarding low steam temperature.

Your question is hard to figure out.

rmw

 

[CaracasEC]

Thanks guys for the reply. General Purpose turbine on our project has a supply inlet temperature of 375 deg C and a pressure of 43.5 barg with an exhaust pressure of 3.5 barg, etc. looking to the mollier chart the steam supplied to the turbine are superheated as also to the exhaust steam condition. Do you think that the temperature sensor is useless? We have our vibration monitoring but only for those equipment with 1000 KW and up.

 

[JJPellin]

I would only monitor and alarm on steam temperature for a turbine with a known problem with damage or failure from wet steam. We have approximately 250 general purpose steam turbines. Only one of them has an alarm for steam temperature. This was done to address a particular problem in one unit. This particular turbine had a history of spurious trips and was located near a system known to generate saturated steam. In this instance, I think the alarm has helped the board operators to keep the steam temperature out of the saturation range and reduce the problems experienced with this turbine.

For our other turbines without a history of steam temperature related problems, I don’t see a significant value in steam temperature alarms or trips.

For smaller turbines, continuous vibration monitoring is probably not cost justified. Monitoring case vibration has less value since most of these turbines will have hydro-dynamic bearings. And monitoring vibration with proximity probes tends to be very expensive. I would concentrate on a good PM program and operator surveillance. For smaller, single stage, general purpose turbines, oil condition is the key to good reliability. Problems such as water accumulation are best controlled with skilled and trained operators.


Johnny Pellin

 

[CaracasEC]

Hi JJPellin,
Thanks with this enlightenment and will help me a lot and my team to decide with our ongoing project "Ethylene Cracker Project" that will involve this general purpose turbines. Since the steam characteristic both on the inlet and even on the exhaust is far from saturated point, possibility of steam being saturated is impossible and alarm for steam temperature and even the shutdown will not be installed. Thank you all guys....