UL Standard for Safety Pipe Unions for Flammable and Combustible Fluids and Fire-Protection Service - Section / Paragraph Reference: 8 Subject: Pipe Ends – Thread Requirements (Edition 7: June 18@ 2001)
General To assure compliance with these requirements in production@ the manufacturer shall provide the necessary production control@ inspection@ and tests. The program shall include at least the following: a) Unless other proven methods are employed to ensure freedom from leakage@ each union for services other than LP-Gas shall be subjected to an air pressure test of not less than 75 psi (0.52 MPa) and proved tight before shipment. Each union for LP-Gas service shall be subjected to an air pressure test of not less than 250 psi (1.72 MPa) and proved tight before shipment. Samples that show leakage shall be rejected. b) To ensure conformance to the Standard for Pipe Threads@ General Purpose (Inch) Revision and Redesignation of ASME/ANSI B2.1-1968@ ANSI/ASME B1.20.1-1983 or alternative national recognized pipe thread standard@ each manufacturer shall obtain and make use of a set of reference gauges for counterchecking the working gauges.