5 replies to this topic

[Lisia]

Good day all

I would like to know if someone could help on this matter.

Due to a revamp we are installing new pressure relief valves (PSVs) and the most obvious idea for the discharge of the valve is a tie-in nearby to a process line (with a much lower pressure in a robust system that is also protected by PSVs).

However, there is a control valve and a flow meter in our path, i.e. between the discharge of the new PSVs and the ones protecting the more robust, bigger system. The maximum discharge flow of the new PSV is estimated at about 1 ton/h of steam, whereas the control valve of the main flow we are discharging is about 1600 ton/h of water (FV is fail open).

My question is whether or not exist any provision in any standard that prohibits this type of arrangement.

Thanks in advance for your attention.

Regards

 

[Bobby Strain]

If it is really steam, the relief valve can discharge to atmosphere. Forget about discharging the PSV into a water line!

 

Bobby

[Mahdi1980]

Lisia,

 

Your description is ambiguous. please explain your case via a simple sketch or PFD to clarify the question.

 

Mahdi

[Lisia]

Thank you for your attention to this matter

 

Forgot to mention that the relieving stream is slightly contaminated with hydrocarbons, including traces of benzene.

The PSV is designed for the case of external fire exposure only.

 

You will find attached a simplified flow diagram!

Attached Files

•  sketch.jpeg   36.51KB   1 downloads

[Bobby Strain]

I would discharge the PSV to atmosphere. You can't connect it to the water line.

 

Bobby

[Mahdi1980]

Lisia,

 

You are not allowed to connect the discharge of the PRV to a line on which a flow control system is located.

If it is important for you to send back the excess material to the upstream vessel , you should think of connecting the line after the control valve directly to the vessel. You can review the API and IPS standards.

 

I have just looked into the matter from design point of view. Please check yourself the aspect of process requirements.