Dear All,
When calculating the relief load for each credible scenario this is a common practice that ignore about any help from instrumented devices to reduce the relief load.
But I want to ask that are there any exceptional cases for this common practice?
Your valuable comments are appreciated.
Mojtaba

We can use the credit of HIPPS (high integrity pressure protection system) at upstream, for relief load calculation. But it depends on the company specifications . eg. we have a relief valve on a trunkline. which is fed by 10 oil wells. This relief valve is sized for the flow rate equivalent to 10% of producing well's HIPPS failure. ie. the RV is sized for a flow rate equal to that of 1 no. well (10% of 10 wells = 1nos.)

reg
umesh.

Umeshr,

A simple but important question... you response implied that you have HIPPS on each dedicated well.

HIPPS is provided to replace ultimate protection devices such as PSV in order to avoid excessive relief load... When you apply HIPPS, do you still consider HIPPS failure ?

Yes based on the process safeguarding philosophy of the company. failure of HIPPS on 10% of total number of wells have to be considered.

Regards
Umesh

What a stringent philosophy!

Yes. It looks stringent. I had a similar experience. For one of our projects we were to specify the PSV load for the ethylene fractionator column . The column had HIPPS protection to cut down steam to rebolier on column overpressure. The idea was to prevent PSV pop-up to reduce ethylene loss. But our Licensor did not agree to give credit to HIPPS and specified full load. So it could be a matter of Safety philosophy based on ulitimate protection to the vessel. Or it could be a matter of reliability of the HIIPS instrumentation.

Regards

PAR