Ammonia Blending, Storage, Shipping - Rego Valves

[Bill3752]

I am evaluating the storage unit of a large Ammonia plant. This unit has installed a bunch of Rego thermal relief valves. While the relief case is indeed thermal, these valves are not ASME certified.

Per API 520 "Before the ASME Code incorporated requirements for capacity certification, valves were generally sized for liquid service .... This method assumes an effective Kd = .62 and 25% overpressure. An additional factor, Kp, is needed for relieving pressures other than 25% {.6 for 10% ovp case}. This sizing method may be used where capacity certification is not required or was never established."

My question relates to the "or was never established". I am thinking that I can used the non-certified valves, but the capacity must reflect the .6 factor.

Has anyone run into this, and is my thinking correct - i.e. it is ok to used non-certified valves in ASME service, assuming they pass after de-rating their capacity?

 

[EGT01]

Bill,

You need to be clear about what "codes" apply to your system.

You make reference to API 520 which was developed specifically as a supplement to ASME Section VIII. So does ASME Section VIII apply? If so, and there are no other exceptions to your location, then I think you are required to use ASME "certified" valves in accordance with UG-136(c).

If, by chance, these valves are located only to protect piping, then what piping code applies? Is it ASME B31.3? If so, then according to 322.6.3, you can exclude the requirements of UG-136(c).

I am aware of some other codes specifically for ammonia such as the old ANSI K61.1 which I believe was superceded by CGA G2.1 and I believe there is a ANSI/ASME B31.4 related to liquid transportation systems which include anhydrous ammonia. I'm not familiar with their requirements.

Hopefully those that have gone before you knew what they were doing. It would have been nice for them to have documented their rationale. So be clear about what your requirements are now and be sure to document your rationale for the next person to follow.

 

[bchoate]

bchoate
Hydrostatic relief devices (such as Rego parts) are used to relieve pressure from thermal expansion. Anywhere that a line portion can be block in by valves has to be protected by a hydrostatic relief device. A small liquid release is sufficient to relieve pressure resulting in small relief devices which do not usually have or need liquid flow ratings.

ANSI K61.1 has been superseded by 29 CFR 1910.111. The International Institute of Ammonia Refrigeration handbook (6-13) addresses hydrostatic relief devices. Our ammonia facility piping is either class 150 or class 300. Hydrostats used are 1/2" X 3/4" rated for 250 psig, 350 psig, or 450 psig. Hydrostats are 'poppet' style relief devices often called 'burp' valves since they can relief several times in succession if the pressure re-establishes in the protected lne.

 

[BenThayer]

when you say "ammonia plant" do you mean a site that makes ammonia?

per

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9757

if so, the 1910.111 does not apply

1910.111(a)(1)(ii)
This standard does not apply to:
1910.111(a)(1)(ii)(a)
Ammonia manufacturing plants.
1910.111(a)(1)(ii)(b)
Refrigeration plants where ammonia is used solely as a refrigerant.

that being said, it does offer clues as to what can be acceptable. use the regos as they should meet the requirements.

i have used them extensively and used to work at a 1500 TPD Bechtel plant where we stored over 60,000 tons of liquid ammonia