UL 1696:2021 free download

UL 1696:2021 free download STANDARD FOR SAFETY Mechanical Protection Tubing (MPT) and Fittings
6.4.7 This test shall be performed on specimens after conditioning, in accordance with 6.2, in a 3-sided metal enclosure in an exhaust hood or cabinet. The metal enclosure shall be 305 mm (12 in) wide, 355 mm (14 in) deep, 610 mm (25 in) high, and the top and front shall be open. A 457 mm (18 in) specimen cut from a length of finished MPT shall be secured at both ends with its longitudinal axis vertical in the center of the enclosure. A fitting or clamp shall be secured with its longitudinal axis vertical in the center of the enclosure. 6.4.8 A burner conforming to ASTM D 5025 or NMX-J-565/3-ANCE that has a bore of 9.5 mm (3/8 in) and a length of 100 mm (4 in) from the top of the air-inlet openings to the top of the mixing tube, or an equivalent burner capable of providing the flame in accordance with ASTM D 5207 or NMX-J-565/3- ANCE, shall supply the flame. While the barrel is vertical and the burner is well away from the specimen, the overall height of the flame shall be adjusted to approximately 100 to 125 mm (4 to 5 in). The blue inner cone shall be 38 mm (1-1/2 in) high, and the temperature at its tip shall be 816°C (1500°F) or higher as measured using a chromel-alumel (nickel-chromium and nickel-manganese aluminum) thermocouple or an equivalent calibrated instrument. Without disturbing the adjustments for the height of the flame, the valve supplying gas to the burner flame and the separate valve supplying gas to any pilot flame shall be closed.
6.4.9 A wedge (dimensions are specified in Figure 3) to which the base of the burner can be secured shall be provided for tilting the barrel 20 degrees from the vertical while the longitudinal axis of the barrel remains in a vertical plane. The burner shall be secured to the wedge and the assembly shall be placed in an adjustable support jig. The jig shall be adjusted toward one side or the other of the enclosure to place the longitudinal axis of the barrel in the vertical plane that contains the longitudinal axis of the specimen. The plane shall be parallel to the sides of the enclosure. The jig shall also be adjusted toward the rear or front of the enclosure to position point A, which is the intersection of the longitudinal axis of the barrel with the plane of the tip of the barrel, 38 mm (1-1/2 in) from point B at which the extended longitudinal axis of the barrel meets the outer surface of the specimen. Point B is the point at which the tip of the blue inner cone touches the center of the front of the specimen. In the absence of a gas pilot light on the burner, the support for the burner and wedge shall be arranged so as to enable the burner to be quickly removed from and precisely returned to the same position where it remains for the duration of each flame application.
6.4.10 When testing a specimen of nonmetallic and composite MPT, a flat, horizontal layer of untreated surgical cotton 6 to 25 mm (1/4 to 1 in) thick shall cover the floor of the chamber. The upper surface of the floor of the chamber shall be 229 to 241 mm (9 to 9-1/2 in) below point B, which is the point at which the tip of the blue inner cone of the test flame touches the specimen (see Figure 1). An additional layer of cotton shall be placed on the wedge and around the base of the burner. These layers of cotton shall be arranged so as not to be disturbed during the performance of this test. No cotton is required when testing fittings or clamps.
6.4.11 For nonmetallic and composite MPT, a strip of unreinforced 94 g/m 2 (60 lb) kraft paper that is 13 mm (1/2 in) wide, approximately 0.1 mm (5 mil) thick, and is gummed on one side shall be used to make an indicator flag. The gumming shall be moistened just to facilitate adhesion. With the gum toward the specimen, the strip shall be wrapped around the specimen once with its lower edge 254 mm (10 in) above point B, the point at which the blue inner cone touches the specimen. The ends of the strip shall be pasted together evenly and trimmed to provide a flag that projects 19 mm (3/4 in) from the tubing toward the rear of the enclosure, with the flag parallel to the sides of the enclosure (see Figure 1). The lower clamp or other support for the tubing shall be adjusted vertically to keep it from being any closer than 76 mm (3 in) to point B.