thread124-280666 first open the AS

[AnhsirkT]

thread124-280666
first open the ASV of high then ip then low pressure casing. i think that would be better
because if you open first LP casing ASV then NEXT casing GO under surge if ASV will not fast responding

 

[georgeverghese]

Yes, that would seem to be the logical sequence.

 

[AnhsirkT]

yes but
is there any sequencing in logic ASV b/w all?
because i see compressore where nothing is given only ASV will open on there individual curve not by any sequencing?

 

[AnhsirkT]

there should be sequencing that if LP casing ASV open then simultaneously HP casing also should open as per logi(may be HP casing not in surge ondition)

 

[georgeverghese]

When there is a general trip of a multistage compression train when all ASVs' are auto opened by shutdown logic, I have only seen all ASVs' simultaneously open. But it would be ideal to sequence the opening as you suggest for general trip, maybe 1-2seconds lapse between each HP, IP and LP ASV. This approach is okay since for almost all cases of general trip, there is nothing blocking the path from one stage to the next.
It is not a good idea to wait for individual stage to go near surge before the stage ASV is open for general compression train trip.

 

[AnhsirkT]

for ESD all will open fast as much as possible because of solenoid de energized but i am talking about normal running condition when LP stage open same time hp should open bcz when LP stage will open the flow to HP stage will also starve.

 

[georgeverghese]

For normal operation, it is better to wait for the antisurge controller on the HP stage to detect approach to surge first.
If you have some concern with the response of the HP stage antisurge controller due to some disturbance coming from the LP or IP stage ASV, you may pls speak to the compressor controls vendor to see if they can improve control response. One way is to install a pneumatic exhaust relay on the ASV actuator to help to increase the speed of depressurisation of the ASV actuator - presume you already have this.