UL 1990-2013 pdf download – Nonmetallic Underground Conduit with Conductors.
6.4 When differences arise between measuring techniques, the vernier wrap tape is to act as the referee for determining compliance with the requirements for average outside diameters. 6.5 When using a tapered sleeve gauge, the entrance and exit diameters of the gauge shall correspond to the maximum and minimum outside diameters for the trade size of conduit being measured. 6.6 When using a sleeve window gauge, the window shall extend beyond the two scribed marks which shall represent the minimum and maximum permitted diameters. 6.7 The measurements from which the minimum and maximum outside diameters of finished conduit are to be determined are to be made by means of: a) A machinist’s micrometer caliper that has a flat-ended spindle, a flat anvil, and is calibrated to read directly to at least 0.001 inch or 0.01 mm; b) A vernier caliper calibrated to read directly to at least 0.001 inch or 0.01 mm; or c) An out-of-roundness gauge accurate to 0.001 inch or 0.01 mm. 6.8 When differences arise between measuring techniques, the vernier caliper is to act as the referee for determining compliance with the requirements for minimum and maximum outside diameters. 6.9 The measurements from which the wall thicknesses of a length of finished conduit are to be determined are to be made by means of a machinist’s micrometer caliper that has a ratchet, a flat-ended spindle, and a hemispherical anvil. The caliper shall be calibrated to read directly to at least 0.001 inch or 0.01 mm.
6.1 3 To determine the average outside diameter when using a tapered sleeve gauge or sleeve window gauge, cut the end of the conduit square and remove burrs. Insert the conduit into the sleeve gauge and observe the position of the end with respect to the ends of the tapered sleeve gauge or the position of the end with regard to the minimum and maximum scribed marks of the sleeve window gauge. 6.1 4 When using a tapered sleeve gauge, the end of the conduit shall enter the largest end of the gauge and shall not pass through the smaller end of the gauge. 6.1 5 When using a sleeve window gauge, the end of the conduit shall be visible between the two scribed marks when the conduit is inserted into the gauge. 6.1 6 The average of all of the recorded diameters is to be determined for the size of conduit involved. The average of the recorded diameters shall not differ from the average diameter in Table 6.1 by more than the specified tolerances. 6.1 7 The wall thickness is to be measured at one or both ends of the conduit by means of the caliper with the hemispherical anvil. At least four measurements are necessary at each end measured to make certain that the thickest and thinnest parts of the wall are found. The maximum and minimum of all the recorded thicknesses are to be determined. Neither limit shall be exceeded. 7 Conductors or Cable 7.1 The conductors or cable shall be suitable for use in wet locations. 7.2 All conductors shall have an insulation rating equal to at least the maximum nominal circuit voltage of any conductors or cable within the conduit. 7.3 Conductors or cable rated 600 V or less shall not occupy the same conduit as conductors or cable of circuits rated more than 600 V.