PSV for solvent thermal expansion

[SelimElibol]

Hello I have a blocked in pipe section in a manifold for which i want to design a relief system.
The issue I have conceptually is the safe location. So downstream of each HVxx i would like to know typically what vents are used.
Now we have a full blown vessel to collect expansion of all 10 solvents but maybe thats overkill.
It consists of a vessel with low and high level alarms, and venting of that one goes to a scrubber (SCL1).
But if we want to do it like this we also need inerting with nitrogen and it starts to become problematic.

Thanks in advance for your advice and reply.

 

[Snickster]

My experience with piping thermal relief valves are that they are installed on the piping that can be blocked in and discharge into the same piping downstream (or upstream) of the block valve so that the flow is back to the same piping. Every section of piping between valves that can be blocked in is provided with a thermal relief valve that discharges into the next section and so on, until the final section relief valve discharges into a vessel in the system that has volume to absorb the flow without over pressuring.

 

[SelimElibol]

Hi, thanks for the advice.
Upstream we have an automatic fire valve so the advice is to not bypass upstream towards the tank with its' own PSV towards safe location (tank).
Downstream we can vent as in the attached picture, but not sure this is allowed because the manifold hand valves (HV) are closed ?

 

[Snickster]

I don't understand what you are saying in previous post. Please be more detailed.

 

[georgeverghese]

Why is inerting the blowdown drum with N2 a problem ?

 

[SelimElibol]

I don't understand what you are saying in previous post. Please be more detailed.

Please specify what you dont understand.

 

[SelimElibol]

Why is inerting the blowdown drum with N2 a problem ?

Because then we need permanent blanketing protection of this drum and it starts to become really complex.
The context is that the HAZOP actions were not properly followed up and we are in the middle of construction now, trying to avoid such engineering changes.

 

[Snickster]

Are you saying that the two lines with hand valves shown are continuation of the lines your PSV's are discharging into? I don't see the whole picture cause I don't have a view of the whole system. If you are just dumping into short dead-ended lines that go nowhere then that will not work. You need to dump into something that can take the extra volume of flow without over-pressuring too. Like a partially filled vessel with vapor space.