Where to vent pressure relief?

[Superfridge]

Hi all.
I would like to know where the pressure relief lines are vented too on the plants you deal with, what works best and what regulations need to be complied with in your country.

Most plants I have seen have the vent lines piped to the evaporative condenser air outlet so the NH3 would mix with the water saturated air. Not so good if the fans not running.

Cheers

[CanadianIce]

Hi Superfridge

It's pretty much he same here. Reliefs are piped to the roof, generally up past the condensers. One regulation we must follow in my part of the country is, end of relief stack must be 25 ft above roof level and 25 ft away from any opening into the building.

[james10]

prv's should be vented to the outside using steel pipe work not sure on the regs for NH3

[sterl]

US from Expat Canadian:

(2) model Constuction type codes concerned with what happens to neighbourhood should refrigerant be expelled; and national Design codes concerned with that and integrity of system....So they don't agree. And they are all subject to endorsement or rejection by the local jurisdiction having authority. And some jurisdictions adopt and retain old versions.

Constuction type codes indicate: 10 Aborption tank (used to have to hold entire R-717 charge at 1 lb/gal concentration) but practicalities have decreased that to 1-hours discharge from your hgihest capacity SRV; 2) flare which required some good siting and an external fuel source and usually caused sour looks from the local fire prevention folks; 3) to atmosphere: largely per the ASHRAE 15 and the IIAR-2: a lot like Canadian Ice indicates though there are a couple of additional restraingts. It gets more rigoruus once you exceed a certain charge, because with PSM/RMP you have to go through plume modelling and consider location of (multiple) roof accesses and prevailing wind rollover and so on; basically to establish that a0 your own people can get out and b) the neighbouts and the fire fighters will survive....

And none of that covers leak detetion, emergency ventilation, means of identification for the point of release, design of the discharge piping and so on.

[Superfridge]

Thanks for replys.
It would appear "best practice" prevails with regards to the vent line release point.

[RG-NH3]

Do you know the Constuction codes number that indicates 1 hour for discharge from your highest capacity SRV? or it´s only a practical rule. I need documentation about this issue.

[Rcsac]

IMC 2009 code 1105.6.1 specifically states outdoors not less than 15 ft. Above the adjoining grade level and not less than 20 ft. From any window, ventilation opening or exit.

[Rcsac]

I apologize my memory is slipping, it's IMC 2009 1105.7

[Tycho]

Hi Superfridge

It's pretty much he same here. Reliefs are piped to the roof, generally up past the condensers. One regulation we must follow in my part of the country is, end of relief stack must be 25 ft above roof level and 25 ft away from any opening into the building.

Same in Norway for land installations.

On ships the rules say "406 A pipe with outlet opening at a position which is not considered dangerous for the ship or the surroundings of
the ship, shall be led from the safety valve or the safety disc.
If led to the atmosphere the outlet opening shall be protected against rain and snow and shall be fitted with a protection
net made of corrosion resistant material to prevent ingress of foreign objects.
When R717 is used as refrigerant the outlet shall be at a safe location as high as possible on the ship e.g. top of funnel
or top of mast. The outlet shall be directed upwards."