UL-2225:2013 pdf free download – STANDARD FOR SAFETY Cables and Cable- Fittings For Use In Hazardous (Classified) Locations.
23.4 During the explosion tests, the cable sealing fitting shall prevent the passage of sparks or flame to the surrounding atmosphere which are capable of igniting the surrounding atmosphere.
23.5 Tests are to be conducted with cables assembled to the fittings.
23.6 Short lengths of cable having end fittings assembled in accordance with the manufacturer’s instructions are to be connected to a sample enclosure representative of explosionproof equipment. The representative test enclosure is to have a free internal volume of 1800 — 2100 cubic inches (29.5 — 34.4 dm) or (1 cubic foot). Representative samples of the cable assemblies under investigation are to be installed in the enclosure. For cable sealing fittings for Class I, Division 1 or Class I, Zone 1 locations, the inlet of the enclosure is to be provided with 5, 10, and 15 feet (1.5, 3.0, and 4.6 m) of 1-1/2 inch trade-size (48.3 mm outside diameter) conduit. For Class I, Division 2 or Class I, Zone 2, the lengths of conduit are to be omitted.
23.7 For the explosion tests, the cable sealing fitting and the representative test enclosure is to be installed in a test chamber that has inlet and outlet connections to the lines carrying the explosive mixture. The representative test enclosure is to be tapped with threaded holes for connection to the inlet or outlet lines carrying the explosive mixture, attachment of explosion-pressure recording device, and insertion of a spark plug for ignition. The length of conduit attached to the representative test enclosure is to be used for inlet or outlet connection to the line carrying the explosive mixture. For cable sealing fittings for Class I, Division 1 or Class I, Zone 1 locations, a spark plug is to be located in the length of conduit approximately 4 inches (102 mm) from the outer end of the conduit. For Class I, Division 2 or Class I, Zone 2 the spark is to be initiated within the representative test enclosure. The explosive mixture is to be prepared by auxiliary equipment capable of maintaining predetermined concentrations of the mixture.
23.8 The explosive mixture is to be allowed to flow into the test assembly and into the surrounding test chamber until all of the original air has been displaced. The mixture within the test assembly is then to be ignited by the spark plug.
23.9 If a cable sealing fitting is intended to be provided with a metallic paint or other noninsulating coating on a threaded joint surface or on threaded supply connections, the explosion tests are also to be conducted on a sample provided with such coating. See 19.3, Exception (a). Grease or other material applied to joints is to be removed before the test.
23.10 A cable sealing fitting for Class I, Groups A and B, or IIC locations, that has flat, cylindrical, or rabbet-type joints is to be tested with test factors applied by having the metal-to-metal joints reduced to 75 percent of the total joint width to be used and with the joints shimmed to give a clearance of 50 percent greater than the clearance to be used. A fitting that has threaded joints not tapered 3/4 inch per foot, is to be tested with a threaded engagement of 75 percent of the total number of engaging threads to be used. The lateral clearance at a threaded joint is to be the maximum obtainable in production fittings, including maximum manufacturing tolerances.