3 replies to this topic

[henidegushi]

Dear all:

I got a question, is there any standard about how to select the relief valve type for offshore well testing separator, somebody said it is not permitted to use rupture disk type relief valve, so the non-rupture disk will be the only choice; and somebody insisted that it is necessary for offshore well test separator to use rupture disk type relief valve. According to the API RP 14C, pressure vessel such as well test separator must have at least two independent relief valves, but not mentioned they are one RD relief valve + non-RD relief valve or other combination.

Is there anyone could help with above question? or any standards could demonstrate?

Cheers !

[demank]

Dear all:

I got a question, is there any standard about how to select the relief valve type for offshore well testing separator, somebody said it is not permitted to use rupture disk type relief valve, so the non-rupture disk will be the only choice; and somebody insisted that it is necessary for offshore well test separator to use rupture disk type relief valve. According to the API RP 14C, pressure vessel such as well test separator must have at least two independent relief valves, but not mentioned they are one RD relief valve + non-RD relief valve or other combination.

Is there anyone could help with above question? or any standards could demonstrate?

Cheers !

According to the sentence in API 14C below:
"A pressure vessel should always be protected by one or more PSVs with sufficient capacity to discharge maximum vessel input rates."

So the pressure vessel is not must have at least two independent relieves valves.
Maybe that statement is come from spesific COmpany standard, not API 14C.
CMIIW

[henidegushi]

Hi, Demank:

Thanks!

Actually what I mean is that how to choose the backup relief valve type if the first relief valve is non-ruputre disk type on separator for offshore job, as we know, it is very common for onshore job to use rupture disk type relief vale as backup/second relief valve. I think there should have different for onshore job and offshore job due to safety reason.

Cheers

[paulhorth]

Henidegushi,

The principle which is central to API RP14C is that there should be two independent means of protection for each cause of overpressure or other upset condition.

This does not usually mean two separate relief valves or a relief valve plus a bursting disc. What it means in conventional practice is that the first means of protection is provided by a high pressure trip which shuts off the inflow, while the second means of protection is a relief valve.This valve is usually a single valve with a second 100% valve being provided to allow maintenance of the first valve. In the case of fire, the first means of protection is the fire detection and deluge system.

It is not usual practice to fit vessels with bursting discs, either offshore or onshore. I cannot think of a single example of this, in all the onshore plants that I have designed or been involved with. Bursting diiscs have many disadvantages compared to relief valves, their only advantages being lower cost and faster action.

I can see that for the case of a temporary test separator on a wellhead platform, a bursting disc might be preferred to save weight and cost and because the vessel can be easily taken out of service. Otherwise, don't use them.

So, to repeat: to comply with API RP 14C you need to fit (1) a high pressure trip acting on an ESD valve at the vessel inlet (or the well wing valves) (2) a relief valve with 100% spare valve provided. No bursting disc.

Paul