4 replies to this topic

[thanhsvh5]

we have operated a centrifugal compressor. Steam inlet temperator will trip at low low 340 0C, and alarm 360 0C and high alarm 400 0C, but no trip at high high steam inlet temperator. In case, high steam inlet temperator (ex: 420 0C), what thing happen? please help me to explain. Thanks a lot

[Art Montemayor]

thanhsvh5:

Your post is very badly written – and I don’t refer to your language ability. It is your skill at communications that is bad. You fail to tell us any useful basic data or background with the exception of telling us you are operating a centrifugal compressor. Allow me to show you how you fail in communicating by asking some basic questions:

• What has steam temperature have to do with a centrifugal compressor? Unless someone like me, who has operated steam turbines and steam turbine-driven centrifugal compressors reads this, no one knows what you have. I suspect your centrifugal machine is driven by a steam turbine. If I’m correct, then tell us so, and also tell us the steam quality and conditions as well as the turbine size and type.
• What steam temperatures are you referring to? Are these the inlet steam into the turbine?
• What is the make, model of the steam turbine? Is is directly connected to the compressor?
• Why don’t you supply a P&ID diagram of the turbine-compressor, showing the temperature trips and alarm points? This would make life so much easier and the communications so much better.

Why do you use exclamation points in your titles? What are you trying to say with them?
Await your reply.

[iyer]

Art
-If I am not mistaken a low temperature strip for a steam turbine is generally provided so as to ensure the steam is supplied as superheated steam and we do not have any condensate carry over into the turbine which may destroy the internals.
-From what I can think of, a high steam temperature can affect the internals of the machine. I am not sure what internals and would be obliged if you can explain that part. But I would suspect it would affect the bearings and the seals. Would there be any erosion issues on the trip throttle valve due to this high temperature.
Care to add any more light to the issue

Edited by iyer, 21 December 2009 - 11:26 PM.

[kkala]

we have operated a centrifugal compressor. Steam inlet temperator will trip at low low 340 0C, and alarm 360 0C and high alarm 400 0C, but no trip at high high steam inlet temperator. In case, high steam inlet temperator (ex: 420 0C), what thing happen?

Indeed, more data is needed for a specific answer (without assumptions). Supposing that the centrifugal compressor is driven by a steam turbine, I think that no harmful effect is expected on the materials, if temperature goes temporarily from normal (say 380 0C) up to 420 0C. Most probably the turbine is fed from a steam boiler, able to control temperature of steam out to +/- 5 deg C, so 420 0C will be a very exceptional case.
However harmful effect on materials can be anticipated, in case that inlet steam temperature of 420 0C gets permanent or frequent. Considering local conditions, this temperature is an approximate limit for steam (design press ~ 44 Barg) piping class (material etc). Operation at limits of materials results in unusually frequent failure of them.
So a high high steam temperature cut-off may not be necessary, since steam temperature in is expected to be monitored continually by the Operator.
The operating manual of turbine-compressor may clarify above matters more precisely at real conditions, as well as steam temperature limits of satisfactory control. Probably the turbine is speed controlled in this case (aiming at constant RPM to ensure stable operation of centrifugal compressor) and deviation due to 420 0C steam temperature may be "tolerable".

Edited by kkala, 02 January 2010 - 05:40 PM.

[S.AHMAD]

we have operated a centrifugal compressor. Steam inlet temperator will trip at low low 340 0C, and alarm 360 0C and high alarm 400 0C, but no trip at high high steam inlet temperator. In case, high steam inlet temperator (ex: 420 0C), what thing happen? please help me to explain. Thanks a lot

Hi,
Higher inlet steam temperature has no adverse effect on steam turbine operation but may increase turbine efficiency a little bit (lower steam consumption) unless if the system design temperature (flange/piping)is not designed for that temperature. However a short period of exposure to high temperature is normally acceptable and by this time operator should have made the necessary corrective adjustment. So high temperature trip is not necessary. High temperature alarm is sufficient to warn the plant operator.

Regards

Edited by S.AHMAD, 04 January 2010 - 11:45 PM.