ASTM B787-04(R2020) pdf free download

ASTM B787-04(R2020) pdf free download.Standard Specification for 19 Wire Combination Unilay-Stranded Copper Conductors for Subsequent Insulation
1. Scope
1.1 This specification covers bare combination unilay- stranded conductors made from round copper wires, either uncoated or coated with tin or lead alloy for insulated conduc- tors for electrical purposes. These conductors shall be con- structed with a central core wire surrounded by two layers of helically laid wires, resulting in an outer diameter equal to the compressed-stranded equivalent conductor. (See Explanatory Note 1 and Note 2.) N OTE 1—For the purpose of this specification, combination unilay conductor is defined as follows: a central core wire surrounded by a layer of six helically laid wires of the same diameter as the core wire with a helically laid outer layer containing six smaller wires alternated between six wires of the same diameter as the wires in the layer underneath. Both layers have a common length and direction of lay (see Fig. 1). 1.2 For the purpose of this specification, normal conductor classification (Class AA, A, B, C) is not applicable as these conductors are intended for subsequent insulation. The descrip- tive term combination unilay-stranded shall be used in place of conductor classification. 1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.3.1 For conductor sizes designated by AWG or kcmil, the requirements in SI units have been numerically converted from corresponding values, stated or derived, in inch-pound units. 1.3.2 For conductor sizes designated by SI units only, the requirements are stated or derived in SI units. 1.3.3 For density, resistivity, and temperature, the values stated in SI units are to be regarded as standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
9. Physical and Electrical Tests of Conductors Stranded of Hard-Drawn or Medium-Hard Drawn Wires
9.1 Tests for the physical and electrical properties of wires composing conductors made from hard-drawn or medium- hard-drawn wires, uncoated or coated, shall be made before but not after stranding. 9.2 At the option of the purchaser, tension and elongation tests on hard-drawn and medium-hard-drawn wires, uncoated or coated, before stranding may be waived, and the completed hard-drawn and medium-hard-drawn conductors may be tested as a unit. The breaking strength ofthe bare conductors so tested shall be at least 90 % of the total of the specified minimum breaking strengths of the component wires. The maximum breaking strength of conductors made from medium-hard- drawn wires, uncoated or coated, shall be not greater than the sum of the specified maximum breaking strengths of the component wires. The minimum breaking strengths of wires shall be calculated using specified nominal diameters and specified minimum tensile strengths. The maximum breaking strengths of wires shall be calculated using nominal diameters and specified maximum tensile strengths. The free length between grips of the test specimen shall be not less than 24 in. (610 mm), and care shall be taken to ensure that the wires in the conductor are evenly gripped during the test (Explanatory Note 6).