UL-51:2013 pdf free download – STANDARD FOR SAFETY Power-Operated Pumps and Bypass Valves for Anhydrous Ammonia, LP-Gas, and Propylene.
8 Bodies, Covers, and Heads
8.1 A pump body assembly or bypass valve body shall comply with the requirements specified in the Deformation Test, Section 16; the Leakage Test, Section 17; and the Hydrostatic Strength Test, Section 20.
8.2 Flanges of parts intended to be clamped together shall have sufficient strength to withstand the stresses imposed by tightening of the clamping bolts or cap screws.
8.3 Plugs and other parts, other than cap screws and bolts threaded into noncorrosion-resistant ferrous parts of the pump or bypass valve, shall be of corrosion-resistant metal or be provided with a protective coating if their function is such that they are required to be removed for adjustment, repair, or other care of the pump or bypass valve.
8.4 A plug, cap, or other part threaded into or on the pump or bypass valve body shall engage with at least four full threads.
8.5 A bolt or a screw hole shall not extend through the outer walls of a pump or bypass valve body into a liquid-handling section.
9 Strainers
9.1 A strainer integral with or provided as part of a pump assembly shall conform to the requirements in 9.2 — 9.4 and the applicable requirements for the Standard for Strainers for Flammable Fluids and Anhydrous Ammonia, UL 331.
9.2 A strainer shall be constructed so that when the screen or filter element is removed for cleaning, all foreign matter (sediment or dirt) is removed without the probability of any of the foreign matter being deposited in the outlet side of the strainer.
9.3 A screen or filter element shall be capable of being removed, cleaned, and readily replaced.
9.4 A cap or cover of a strainer or filter shall be of the bolted type or determined to be of equivalent construction. Repeated removal and replacement of the cap or cover shall permit the joint to be made tight against leakage.
10 Springs
10.1 A spring shall be guided and arranged to minimize binding, buckling, or other interference with its free movement. If necessary, both ends of a spring shall be closed and squared.
11 Pumps and Bypass Valves Pressure Ratings
11.1 A bypass valve or pump shall have a service pressure rating not less than that shown in Table 1.1, in accordance with the differential pressure produced at specific flow capacity through the pump or valve when tested in accordance with the Differential Pressure Test, Section 19.
11 .2 A bypass valve shall provide for connection of piping for returning the recirculated liquid back to the supply or storage tank.
11 .3 After the bypass valve is adjusted as intended, it shall be locked or sealed to reduce the risk of tampering; or the adjusting means shall be such that the maximum adjustment obtainable will not permit a differential pressure in excess of the differential at specified flow capacity, and service pressure rating for the valve in accordance with Table 1 .1.