ASME B31.9 & Relief Valves 1

[flyrfan]

What is the specific criteria for providing pressure relief valves on building services piping according to B31.9?

I have a ground source heat pump system that currently does not have a relief valve on the well system. I was always under the impression that B31.9 required them if energy was transferred to any fluid in a closed loop system.

Thanks in advance.

 

[JohnBreen]

flyrfan

First of all be sure that the pressure/temperature of the system is within the LIMITS of B31.9 (see paragraph 900.1.2).

Both internal pressure and external pressure (partial vacuum) must be considered. Look to Paragraph 901.2.3 Required Containment or Relief.

"901.2.3 Required Containment or Relief. Provision shall be made to safely contain or relieve excess pressure to which the piping may be subjected. Piping not protected by a pressure-relieving device, or that can be isolated from a pressure-relieving device, shall be designed for at least the highest pressure that can be developed."

If the pressure from a ground source cannot be controlled or if the pressure is unknown (see B31.9 on "pressure surges" then COMMON SENSE would demand a relief device. The relief device would be sized (and set) for pressure that exceed the maximum allowable pressure consistent with the pressure/temperature limit of the piping and its wall thicknesses. If an isolated (by closed valves) section of piping can be heated or cooled by ambient influences, the same requirements prevail (see paragraph 901.4).

Carefully read Paragraph 922.1 (Pressure Reducing Systems) and its sub-paragraphs.

Regards, John