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UL 51-2018 pdf free download

UL 51-2018 pdf free download.Power-Operated Pumps and Bypass Valves for Anhydrous Ammonia , LP-Gas , and Propylene.
20 HydrostatIc Strength Test
20.1 Except as provided in 20.2. liquid-handling parts of a pump or bypass valve shall be capable of withstanding, without rupture or permanent distortion, a hydrostatic pressure of five times the minimum service pressure in accordance with 1.3 for at least 10 minutes.
20.2 When the construction of a pump or bypass valve is such that it is not capable of developing a differential pressure of 125 psig (860 kPa), or 100 psi (689 kPa) for propylene service, the test pressure specified in 20.1 is to be reduced by an amount equal to five times the difference between 125 psig (860 kPa) and the maximum differential pressure developed.
20.3 The pump or bypass valve sample, as appropriate, previously subjected to the Deformation, Leakage, Endurance, and Differential Pressure Determination Tests, Sections 16, 17, 18, and 19, respectively, is to be connected to a source of hydrostatic pressure. A positive shutoff valve and a pressure-measurement device that complies with 15.4, are to be installed in the hydrostatic pressure supply piping. The pressure-measurement device is to be installed in the piping between the shutott valve and the sample under test.
20.4 External leakage observed during this test does not constitute a noncompliance when, following the hydrostatic test, the pump or bypass valve, as appropriate, is in compliance with the requirements in the Leakage Test, Section 17.
21 Moist Ammonia Air Stress Cracking Test
21.1 After being subjected to the conditions described in 21.2 — 21.4, a pressure confining brass part containing more than 15 percent zinc shall:
a) Show no evidence of cracking, delamination, or degradation or
b) Perform as Intended when tested as described in 21.5.
21.2 One test sample of each size is to be subjected to the physical stresses normally imposed on or within a part as the result of assembly with other components. Samples with female tapered pipe threads, intended to be used for installing the product in the field are to have the threads engaged and tightened to the required torque. Samples with female threads other than tapered pipe threads shall be torqued as specified by the manufacturer. Teflon tape or pipe compound are not to be used on any threads. Samples with male threads are evaluated as received.
21.3 The samples are then to be tested in accordance with Apparatus, Reagents and Materials, Test
Media, Test Sample Preparation, and Test Procedure of the Standard Test Method for Ammonia Vapor
Test for Determining Susceptibility to Stress Corrosion Cracking in Copper Alloys, ASTM B858-06, except
the pH level of the test solution shall be High 10.5 ±0.1 and the exposure temperature shall be 25 ±1°C.UL 51-2018 pdf free download.

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