Centrifugal compressor control

R

Thread Starter

Raj

Hi Everyone,
Centrifugal compressor discharge pressure is normally controlled by inlet guide vane. The discharge pressure sets the flow through the compressures.

Why the pressure is controlled in suction flow? Why not discharge? For the same flow if i relocate my control valve to discharge what will happen to the power consumption?

Please clarify.
 
O
Hi Raj,
Depending on the used compressor control algorithm, it may vary the application of the control. Inlet guide vanes are typical used for mass flow compressor such as the axial compressor. Volumetric flow compressors are typical the centrifugal compressor. Both systems primary control is based on the surge line control.

Since the axial compressor is more sensitive to surge, the variable inlet guide vanes are used in conjunction with surge line control. Typical for midstream applications, centrifugal compressor is used. The control philosophy is based on pressure ratio control. Normally the discharge pressure is fixed and the suction pressure is variable. In your case it appears that, the fix parameter is the suction pressure and probably the discharge is variable?

As regard the power consumption, there will be not major difference since the head of the compressor will not change. Again, these factors are depending on the compressor configuration (single stage, multi stage, parallel or series operation and the control algorithm).

Docendo Discumus
 
Hi,

Thank you for your reply. I will elabrate my problem a little more detailed. I have a six stage centrifugal compressor taking air from atm and compress it to 19 barg.

Protronic controller is available for anti surge control.

As i understand from ur above statements, the reason for provision of inlet guide vanes in suction is the constant suction pressure and variable discharge pressure. If i take the suction from s different source which can be affected by process conditions),can he flow control be shifted to discharge?
 
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