Ammonia Relief vent lines location

[clotiate]

Hie Guys
I am working on an Ammonnia plant and the client's resident Technician has recommended that we connect the high side relief lines to vent to the low side. Is it a correct practice, he says thats what the experts say. The local inspection authority says it should vent to the outside at a high position. Can anyone please help with a standard for this.

[RANGER1]

I think definitely not.
You can have a internal releif on each compressor from discharge to suction set at lower pressure than releifs to atmosphere as a way to prevent unwanted discharge of refrigerant to atmosphere like Danfoss POV & BSV8 pilot

[NH3LVR]

This was once done as a common practice. No more!
It is also still done as Ranger said for an internal relief.
We went through this years ago on this forum.
The commonly used reliefs open on the difference between inlet and outlet pressure. If your valve is set for 300 PSI and the suction at that time was 100 PSI, you now have a 400 PSI relief valve!

[knighty]

If your valve is set for 300 PSI and the suction at that time was 100 PSI, you now have a 400 PSI relief valve!

if the valve is between 300psi and 100psi it only as 200psi acting over it?

[NH3LVR]

That is correct.

[RANGER1]

You can get “Balanced port” releifs which are not down stream pressure effected, but harder to service if no isolating valves & depends on on local regulations.
If a reliefs ever goes off, then your plant is not set up correctly with safety trip settings tripping below releif settings, or it burn’t down.
Mainly operator error on oil drain pot’s.