Weather Caps Needed On Psv Discharges?

Does anyone consider it a requirement to install a rain cap or weather cap on top of the discharge piping?

We typically have a weep hole/drain in the low end to let rain, etc. drain out. I know some consider it a requirement to keep bird's nests, insects out etc. and install weather caps.

API 520 has a note that a "Weather cap may be required" but I could not find a reference on when it is "required."

ASME 1998 Section VIII Div. 1, UG-136(a)(9)( mentions the use of a cover but with regards to its use if the valve cannot be equipped with a drain.

The reverse of this question would also be helpful. If you use a weather cap, do you use a weep hole/drain?

Our applications are for primarily flammable vapors but overfilling could cause a liquid liquid solvent release. So much for the differences between vapor only service conditions and liquid conditions.

Several of our installations seems to be belt and suspenders and we have the weep hole and the cover. But now some PSV's are being flagged by the PSM group as not having the rain caps per API 520 even though they have the weep holes.

Any definitive sources on when you MUST have a rain cap?

Please take a look at our brochure located in the library of our web page. THe address is www.weathercap.com.

Federal regulations require any PRV that is not covered by a roof to be covered by some sort of device. The TECQ penality for non compliance with TECQ regualtions is $ 10,000.00 per day per violation. By definition any exhaust nipple that is not protected requires a cover even if the weep hole exists.

we use various types in our plant. i would say that your ambient temperature extremes may be one consideration.

for us in the northern climes, we are afraid of ice formation in the line even though we have a drain valve.

with regards to the www.weathercap.com comment that federal law requires them, could you please note the section for this?

tia, ben