Surge Test on Centrifugal Compressor using CCC ASC Controller

In centrifugal compressor we have safety device to prevent from Surge phenomena.

Surge occur when centrifugal compressor operate at operating point hit its surge line. The physical phenomena at the compressor is severely vibration at radial and axial direction. If this occur for long period of time (let say several second), it will give catastrophic failure to compressor. The actual condition inside compressor is the gas discharge compressor flowing back (reverse) into the compressor again, due to no enough amount of gas to be compressed by the compressor. This condition will occur repeatedly and very quickly.

Operating Zone in Centrifugal Compressor

How Surge Happen

A to B     : 20-50 ms ................. Drop into surge

C to D     : 20 - 120 ms ............. Jump  out surge

ABCDA  : 0.3-3 s ..................... Surge cycle

Surge Description :

As a safety device, there is Anti Surge Valve or Recycle valve installed at discharge of compressor and allow the gas to flowing back to suction scrubber.

Anti Surge valve (ASV) configuration

 During plant commissioning or after process change or operating point change, we need to perform surge test to ensure this safety device system is on place.

Prior to surge test, ensure all antisurge valve in good condition and respond.

Here is step by step performing surge test on 2 stage centrifugal compressor:

Running compressor.

3.      Perform surge test on 1^st stage.

·        Put LSIC on manual 

·        Put ASC 1^st stg and 2^nd stg on Manual

·        Put ASV 2^nd at 98% open

·        Monitor trending at train view for :

o   Flow dP

o   1^st stg Discharge  pressure

o   1^st stg suction pressure

o   ASC deviation

o   Output / command ASV

·        Put Engine speed at LSIC 25%.

·        Minimize margin of :

o   SO : SO line

o   b1 : safety margin SOL

o   b2 : SO margin

o   RT : Margin RT

o   C1 : 1^st respond after hit RT line

o   C2 : time delay to the next RTL opening

o   K   : slope SLL

·        Then manually decrease ASV valve until SO active and flow dP trending was fluctuate suddenly..

·        Do this step for speed 25%, 50% and 85%.

Plot these data Flow dP against Pressure discharge to have new Surge line Map  

4.      Perform surge test on 2^nd  stage.

·        Put LSIC on manual 

·        Put ASC 1^st stg and 2^nd stg on Manual

·        Put ASV 2^nd at 98% open

·        Monitor trending for :

o   Flow dP

o   1^st stg Discharge  pressure

o   1^st stg suction pressure

o   ASC deviation

o   Output / command ASV

·        Put Engine speed at LSIC 25%.

·        Minimize margin of :

o   SO : SO line

o   b1 : safety margin SOL

o   b2 : SO margin

o   RT : Margin RT

o   C1 : 1^st respond after hit RT line

o   C2 : time delay to the next RTL opening

o   K   : slope SLL

·        Then manually decrease ASV valve until SO active and flow dP trending was fluctuate suddenly.

·        Do this step for speed 40%, 60% , 80% and 85%.

Plot these data Flow dP against Pressure discharge to have new Surge line Map

That's all for surge test step, inform field operator to keep away from the pipe arrangement since they will greatly shacking if the support not installed well and noisy.

Thanks

June 21st 2018 @ Jogjiah

My leisure time