Thermal Relief Valve Requirements on LNG Lines
Thermal Relief Valve Requirements on LNG Lines
(OP)
Does anyone know of any codes or standards for multiple TRVs on long LNG lines? API 521 doesn't state anything about multiple TRVs and I couldn't find anything on NFPA 59A regarding the subject. Any help?





RE: Thermal Relief Valve Requirements on LNG Lines
If you are in the US, you may want to review the Code of Federal Regulations, Title 49 CFR Parts 100 - 199. In particular
http://ops.dot.gov/regs/1999/part193.htm
but I didn't really see anything regarding the number of relief valves.
Since you are talking about thermal relief, I would assume the pipeline design pressure must be high enough to preclude the need for liquid vaporization. However, it seems that the required design pressure may likely be above the critical pressure and you might experience either liquid or dense phase thermal expansion. In either case, it would seem that as long as you provided the required relief area, it wouldn't matter how many valves you used unless you are thinking there is some other criteria that may require a certain number of valves.
I really didn't find much on the internet but I thought these links were interesting
http://www.shell-usgp.com/lngsasrae.asp
http://www.lngfacts.org/
htt
RE: Thermal Relief Valve Requirements on LNG Lines
RE: Thermal Relief Valve Requirements on LNG Lines
Tony Miller
Cornerstone Engineering Group, p.c.
http://www.cegpc.com
RE: Thermal Relief Valve Requirements on LNG Lines
However I agree with EGT01 and don't think that it is wrong to have multiple TRVs providing the relief area is sufficient.
I am not sure about how the set pressures should be staggered though...
Rgds
jbmr
RE: Thermal Relief Valve Requirements on LNG Lines
If the long line has several block valves, several thermal relief valves may be necessary. I do not know the code or guideline for the minimum length to install at least one thermal relief valve between block valves. However, the size of the thermal relief valve always in small size as jbmr's comment.
RE: Thermal Relief Valve Requirements on LNG Lines
RE: Thermal Relief Valve Requirements on LNG Lines
(Strange coincidence- both occured on 30 Aug. )