Dear All,
based on your experience, what is the optimum criteria for setting the discharge design pressure and hence the PSV set point at compressor outlet, I recommend the following:
take the suction upstream system PSHH trip with the consideration that under a blocked outlet scenario, the upstream system will pack with no credit for any flaring at the upstream via any pressure control valve to flare.
Then, consider compressor speed up to the maximum continuous speed of 105% of the rated speed since under the blocked outlet scenario, the anti-surge valve will be triggered by its high discharge pressure limit loop dictating as well the performance controller to speed up along with it by something called loop decoupling. Approximating the increase in the speed into a compression head will be fan laws where 1.05^2 correspond to 1.1 increase from the rated head or i..e compression ratio.
then finally considering PSHH suction * 1.1 would give the discharge design pressure downstream the compressor.
Or do you propose to consider suction PAHH (alarm) with a multiplier of 1.1 of the normal compression ratio . Overall margin of 5% can be applied to the above term.
In case a PSV is to be eliminated, then a higher margin needs to be considered to mimic the maximum surge differential pressure i.e. maximum suction PSHH + 1.3* normal differential head.
Appreciate your views.