Thermal Relief of ASME B31.3 piping
Thermal Relief of ASME B31.3 piping
(OP)
I have a simple question but I don't really see a code reference about it.
I have a flammable liquid full line. 2" Sch40 A106 if it matters.
I want to use a check valve around one of the block valves as my thermal relief.
The "discharge" side of the piping is vented back to the tank so pressure can not build up in that section of the line.
Is there any code restriction against doing that?
My other option would be a relief valve vented to the "discharge" side of the piping.
Thanks
StoneCold
I have a flammable liquid full line. 2" Sch40 A106 if it matters.
I want to use a check valve around one of the block valves as my thermal relief.
The "discharge" side of the piping is vented back to the tank so pressure can not build up in that section of the line.
Is there any code restriction against doing that?
My other option would be a relief valve vented to the "discharge" side of the piping.
Thanks
StoneCold





RE: Thermal Relief of ASME B31.3 piping
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Thermal Relief of ASME B31.3 piping
RE: Thermal Relief of ASME B31.3 piping
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Thermal Relief of ASME B31.3 piping
When the block valve is closed I can get a minute amount of flow in the reverse direction of normal flow with this side check valve.
I could use a thermal relief valve but the effect is the same as the check valve.
Comments?
StoneCold
RE: Thermal Relief of ASME B31.3 piping
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Thermal Relief of ASME B31.3 piping
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Thermal Relief of ASME B31.3 piping
If I used the Thermal Relief Valve, I would definately fall under API RP 521.
But do I fall under that using the Check valve to create a flow path for trapped liquid?
I was originally going to let the relief valves vent on to the concrete containment. We are talking about a couple of mls of liquid.
But I like the idea of it being contained and going back into the system.
I have a another system where they vent into a small containment vessel but the liquid still evaporates and creates another small emmission.
What is everyone else doing for in plant process piping thermal relief?
Regards
Stonecold
RE: Thermal Relief of ASME B31.3 piping
Mine are piped to oily water drain sys to sump.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Thermal Relief of ASME B31.3 piping
RE: Thermal Relief of ASME B31.3 piping
I initiate the use of check valves in the late 80's. The line has purity benzene, where do you relieve purity benzene too? Later, we used then on all our double block and bleed valves. We even worked with Foster Valves to get the flange tapped to take the body check valve back into the pipe without having a tap on the line.
Eventually you will end up with a psv on the system because they will be no route for a check valve. But in the case of the benzene line, that psv was back at the begining near the process flare and vapor recovery systems were available.