6 replies to this topic

[lokesh_09]

Dear all,

Could anybody can explain me the reason why do we always place the Flow transmitter in the compressor suction. We have placed the flow transmitter in the discharge (For my concern Flow transmitter is just going to measure the flow thats why we have used in the discharge)

[Zauberberg]

It's not true that all flowmeters (flow elements) are placed in compressor suction piping - particularly in those applications where additional pressure drop can hardly be justified, e.g. suction of low-stage machines: that is exactly the case in our refrigerant compressor system in LNG plant. All low stage machines (Propane, Ethylene, Methane) have flowmeters on the discharge side.

Of course, the reason for measuring centrifugal compressor flow is to - control and avoid surge conditions that can seriously damage the machine. Usually, just for saving on pressure drop, these flow elements are located on the discharge side for machines having low suction pressure, while for other machines you can use suction side for flow measurement.

[iyer]

Dear all,

Could anybody can explain me the reason why do we always place the Flow transmitter in the compressor suction. We have placed the flow transmitter in the discharge (For my concern Flow transmitter is just going to measure the flow thats why we have used in the discharge)

I think you are talking about a closed loop which the compressor is installed in. If I am not mistaken, the flow is in Nm3/hr, in that case does it make any difference between suction and discharge? Since its normal flow it should be the same.

[JoeWong]

Zauberberg has given a very good reason to locate flow meter at the discharge side especially compressor suction is at very pressure i.e. BOG compressor.

Compressor discharge is at higher temperature and flow meter to cope for higher temperature is required at discharge. Flow meter at suction side experience low temperature may be cheaper.

[fallah]

Could anybody can explain me the reason why do we always place the Flow transmitter in the compressor suction.

It is because the variations in pressures,temperatures and turbulence of the gas are less upstream of the compressor.

[Ameen Shahid]

[quote name='fallah' date='24 December 2009 - 12:14 AM' timestamp='1261596259' post='34957']
[quote name='lokesh_09' date='27 November 2009 - 06:15 AM' timestamp='1259321140' post='34501']
Could anybody can explain me the reason why do we always place the Flow transmitter in the compressor suction.
[/quote]

For measuring Actual Volumetric flow rate, Flow Transmitter is placed at suction. This is because, at Discharge the N-m3/hr is different from Suction (Volume is reduced due to compression). For controlling surging you can use flow meter at discharge, or between stages (for multi-stages)

[djack77494]

Another reason to prefer suction side flowmeters: The compressor curve is based on inlet volumetric flowrate and the suction side meter will conveniently give you that measurement. Of course, you could get to the same answer working backward from discharge side conditions, but why go through all that trouble?