Compressor Controls

[thiru4vino]

Dear Friends!

Happy Morning!

We have two Reciprocating Compressor trains which are not working for the past two years, in our Gathering Centres. In this compressor train, i found one control logic that controls the pressure of Final Oil accumulator of the third stage (KOD)with the make up gas line flow control valve to the suction of the first stage.

Have anybody come across such system? If so, please explain the system and how this will work. Since the documents related to these trains are not available, i am not able to understand this.

Thanks for everything,

Yours Truly,

A.Thirumaran

 

[BigInch]

Is the high pressure oil driving the make up valve position, or holding the valve open, so when the compressor trips, oil pressure is lost and the suction valve closes?

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"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[chemicalengineerthai]

1) Its look like your system has one fix parameter is the pressure of discharge system and regulate the variable parameter of incomming flow , which it is souds for degree of freedom for control machine.

2) Normally, this scheme use for Centrifugal type not reciprocating type.

3) Reciprocating is prone for fixed volume of inlet flow( by inlet guide vane,etc),if suction can not fixed incoming flow yor compressor will has short life, which has easy for machine breakdown, except you have variable speed to reflect the variance of flow

4) It was not easy to control 2 parallel reciprocating type, since one compressure should control flow rate another one should control pressure.

 

[thiru4vino]

Dear Chemicalengineerthai and BigInch!

Thanks for your replies. I would like to clarify on some points based on your replies.

1.We do not have "High Pressure Oil" based control in the system. We have a digital signal coming from the pressure transmitter that goes to the controller which gives final input to the control valve located in the make up gas line to the suction of the first stage of the compressor.

2. The two trains are reciprocating machines.

3. In our system, either one of the compressor train used to run and the other is kept as a standby.

My understanding of the compressor controls indicates that

For a given compression ratio of the compressor, if the suction pressure is maintained, is it not enough to ensure constant discharge pressure. Am I right or otherwise?

Advanced thanks for all the help and response.

Cheers to life,

ATM

 

[BigInch]

It should normally be the case, with constant suction pressure ...and temperature. Providing that your discharge pressure is not varying due to downstream conditions too. All systems have a system curve, composed of a series of pressure vs flow coordinates. It is possible that your discharge pressure can also be controlled by downstream pipeline conditions, such as when a valve opens or closes and higher or lower flowrates are taken from that discharge line. Your discharge pressure may tend to reduce with increasing downstream takes, or increase, if takes downstream diminished.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[scoho83]

ISd this nothing more than the suction recycle line? This is a common method to ernsure suction pressure is maintained to the recipocating compressor (i.e. that it has enough volume for the compressor to be filled (you don;t starve the suction). It is quite a common method of controlling the suction pressure of the compressor, especially for low pressure sources. It is "energy" inefficient as compared to other control methods (unloading of heads, etc), but on a captial basis, its pretty inexpensive method. Controlling the inlet pressure (as mentioned) is even better, but if you fear having not enough pressure even with the inlet valve wide open, you usde this recycle. It also comes in real handy for start-up procedures (can start up the compressor relatively unloaded with out venting somewhere).