UL 132-2021 pdf free download.Safety Relief Valves for Anhydrous Ammonia and LP-Gas.
6 Unit Assemblies
6.1 A safety valve may be furnished separately, threaded into, or made integral with the assembly of a multiple-head unit or a manifold. When a safety valve is furnished as a separate unit, the assigned flow capacity applies only when it is mounted in a straight coupling or the equivalent in the top of the tank, and no restriction to flow is introduced on either the inlet or outlet side of the valve. Installation, otherwise, normally introduces restriction to the flow that reduces the flow capacity.
6.2 When a safety valve is:
a) Installed in a multiple-head unit or manifold other than one with which the valve was flow-tested and rated:
b) Used with vapor tubes;
c) Mounted in a fitting in such a manner as to introduce restriction to flow ahead of the valve inlet; or
d) Mounted so that the flow is restricted on the discharge side by the use of vent piping and fittings;
the assigned flow capacity does not apply. The flow tests shall be conducted under such conditions of installation to determine the flow capacity.
7 Assembly
7.1 General
7.1 .1 A safety relief valve shall be of the direct spring-loaded resilient-seat disc or seal construction and shall be characterized by pop action upon opening.
7.1.2 A hydrostatic relief valve shall be of the direct spring-loaded resilient-seat disc or seal construction, but is not required to be characterized by pop action.
7.1.3 A safety valve shall include all of the components required for its intended function and installation, and shall be assembled as a single unit.
7.1.4 A seat disc or seal shall be securely attached to its poppet or holder, so that it is not possible for the disc or seal to become dislocated under service conditions.
7.1.5 The outlet of a pilot valve, or a pilot valve incorporating a vent, shall be constructed to reduce the risk of inoperability due to ice formation or clogging.
7.1.6 Shut-off valves incorporated in the construction of a Safety Relief Valve shall conform to the Standard for Safety for Flow Control Valves for Anhydrous Ammonia and LP-Gas, ULJULC 125.UL 132 pdf download.