BS EN ISO 8031:2020 pdf – Rubber and plastics hoses and hose assemblies — Determination of electrical resistance and conductivity.
1 Scope This document specifies electrical test methods for rubber and plastics hoses, tubing and hose assemblies to determine the resistance of conductive, antistatic and non-conductive hoses and the electrical continuity or discontinuity between metal end fittings. All the test methods described for rubber hoses in this document can also be applied to plastics hoses. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2878, Rubber, vulcanized or thermoplastic — Antistatic and conductive products — Determination of electrical resistance ISO 8330, Rubber and plastics hoses and hose assemblies — Vocabulary 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 8330 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/ 4 Measurement of resistance of conductive, antistatic and non-conductive hoses 4.1 General Rubber hoses may have a conducting lining only or a conducting cover only, or may be manufactured from conducting rubber compounds throughout. A method of test is specified for each of the three possible types of construction. 4.2 Apparatus The following apparatus is required and shall be basically as described in ISO 2878. 4.2.1 Test instruments 220.127.116.11 To determine the resistance of conductive, antistatic and non-conductive hose 1) , the test should preferably be made with an instrument specifically designed for measuring insulation resistance, having a nominal open-circuit voltage of 500 V d.c., or with any other instrument known to give comparable results.
The resistance values obtained will vary with the applied voltage, and errors may occur when low test voltages are involved. In cases of dispute, the voltage applied to the test piece shall be not less than 40 V, except where this conflicts with the requirement not to dissipate more than 3 W in the test piece. 18.104.22.168 For tests requiring the measurement of the electrical continuity between end fittings or through continuous internal or external bonded wires, the instrument used shall be an ohmmeter sufficiently accurate to determine the resistance to within ±10 %. 22.214.171.124 For tests where, according to the product standard, determination of the electrical continuity between the end fittings of a hose assembly is required, without measurement of the actual electrical resistance, a 4,5 V battery in combination with a 4 V (0,3 A) test lamp can be used. 126.96.36.199 For determination of the electrical resistance through the hose wall (required by some hose product standards for hoses used in explosive atmospheres), the instrument used shall be an ohmmeter with a capacity of 10 12 Ω and the measurement shall be made at 500 V d.c. The instrument shall be sufficiently accurate to determine the resistance between the lining and the cover as measured through the hose wall to within ±5 %. 4.2.2 Electrodes and contacts 188.8.131.52 General For tests conducted in a laboratory, the equipment described below shall be used. For field tests, and for routine tests and product acceptance tests in a manufacturer’s plant, this equipment is not practical, and alternatives may be used as described in 4.6.1, 184.108.40.206 and 220.127.116.11. Electrodes shall be formed on the surface as bands 25 1 2 − + ( ) mm wide around the circumference by means of a conductive silver lacquer, colloidal graphite or a conductive liquid.
18.104.22.168 Special electrodes and contacts The following special electrodes and contacts shall be used for the determination of the electrical resistance through the hose wall, and other test methods: a) Outer electrode: a copper sheet-metal band, of standard width 25 mm, clamped around the outer hose wall (see Figure 1). b) Inner electrode: 1) for hoses of less than 50 mm bore size, it is recommended that a tight-fitting brass plug (solid for small bore sizes and hollow for larger sizes), of minimum length 2 × the pitch of the helical wire(s) (for hoses incorporating helical wires) or 0,5 × ID (for hoses without helical wires), be used; 2) for hoses of more than 50 mm bore size, it is recommended that an adjustable copper sheet- metal band, tightly fitting the bore of the hose (expanded against the lining by spring action), of minimum width 25 mm, be used; c) Contacts for connecting the electrodes to the ohmmeter should preferably be soldered or brazed to the electrodes to minimize resistance between ohmmeter and electrode (see Figure 1). d) Alternative to b): a 25-mm-wide conducting foam plug completely wetted with a suitable conductive liquid (see 22.214.171.124) of outside diameter slightly larger than the inside diameter of the hose to ensure a snug fit with good electric contact with the hose lining and connected to a suitable insulated conductor (see Figure 3, items 1 and 3). This electrode is recommended for use with hoses with corrugated linings or linings which are less flexible than rubber (i.e. PTFE). e) In order to establish good electrical contact with the cover of a corrugated hose, it is recommended that a conducting foam strip 25 mm wide, completely wetted in suitable conductive liquid (see 126.96.36.199), be placed round the full outside circumference of the hose, underneath the electrode described in item a) above.