Steam Turbine Efficiency

[dh328]

Hi,
Recently we have faced a problem in operation of our ethylene refrigerant compressor. Although the compressor is working below full capacity, turbine governor valve is fully opened but steam flow is 18 ton/hr compared to full load steam consumption of 30 ton/hr. we have washed the blades and they are clean. Turbine after first stage pressure is 2.2 kg/cm2G (pretty less than max. allowable). main steam pressure is 15 kg/cm2G and it is surprising that steam pressure after throttling valve is 7.5 kg/cm2G. I think that throttling valve parts are loosen or damaged. some colleagues say that strainer in throttle valve may be chocked. what do you think?
what is solution?

 

[JJPellin]

I would first ask if you are sure that the governor valve is open? Some of these valves are open with the stem in and others are open with the stem out. If the valve is truly open, I would ask if there was any maintenance done to the turbine recently? Could the linkage be assembled incorrectly? Are you sure that the safety travel was set correctly?

If the valve is truly open and everything is assembled and adjusted correctly, then you could have a restriction in the strainer, governor valve, trip valve, or nozzles. I have never seen this, but we have very good steam quality. Is the steam temperature normal? Steam temperature can affect efficiency more than pressure for superheated steam.

The plug could have broken loose from the stem of the governor valve. This would allow the plug to be closed when the stem shows it is open. Most of these plugs are retained against a step when closing, but may only be retained by a roll pin when opening. If the valve was ever forced open beyond the normal range, it could have sheared the pin.


Johnny Pellin

 

[dcasto]

are the hand valves open that manually load the turbine. Most govnor valve can only pass 20% to 50% of the maximum allowable load.

 

[ScottyUK]

Can I suggest posting this in forum666 ? There are some very good turbine specialists in there. Johnny Pellin's suggestions are right on the mark, but you might get a few more ideas from the mechs.

dcasto - is that typical for small turbines in refinery applications? I'm from a power generation background and have never heard of that kind of practice, but now I'm in O&G and to my mind the O&G guys do some odd things with their machines.


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If we learn from our mistakes I'm getting a great education!

 

[dh328]

thanks to all. I copied this post to "engine& turbine engineering forum". Please reply there.
JJPelin & Dcasto
we are sure that all manual valves are open. the governor valve is open and working correctly. throttle valve is located before governor valve. as i said before, the problem is high delta-P in throttling valve.
please reply in forum 666 "engine& turbine engineering forum".

 

[rmw]

I will post this reply here to Scotty's question.

Scotty, in the type and size of machines that you are used to working with, it is not common. But in smaller industrial (industrial over here means other than electric utility power) machines, it is a common feature because they don't have the sophisticated nozzle block / inlet configurations and controls that a power generating turbine does, nor the high DP or temps.

They typically don't operate over as large a range as power generators either, but that doesn't necessarily have to be true.

rmw

 

[ScottyUK]

Thanks rmw.

I've seen the governor arrangements here and they seem almost primitive - but adequate for purpose too. I'm still slightly aghast that the steam cycle is a once-through system and goes to vent and that there's no condenser!


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If we learn from our mistakes I'm getting a great education!