Rubber and plastics hoses and hose assemblies

BS EN ISO 8031:2020 pdf free.Rubber and plastics hoses and hose assemblies – Determination of electrical resistance and conductivity.
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 x the pitch of the helical wire(s) (for hoses incorporating helical wires) or 0,5 x 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 4.2.2.1) 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 4.2.2.1), be placed round the full outside circumference of the hose, underneath the electrode described in item a) above.
4.3 Preparation and cleaning for the test
The surfaces of the hose or test piece shall be clean. If necessary, they may be cleaned by rubbing with fuller’s earth (magnesium aluminium silicate) and water, washing with distilled water and allowing to dry. Do not use organic materials which attack the rubber or cause it to swell, and do not buff or abrade the test surfaces.
The surface of the hose shall not become deformed either during the application of the contacts or during the test. When using test pieces, the supports shall be outside the test length. When testing a long length of hose, the hose shall be uncoiled and laid straight on polyethylene or another insulating material. Care shall be taken to ensure that the hose is insulated from any leakage path along the length of hose.
Normally, the articles shall be conditioned for at least 16 h under one of the following sets of standard
conditions:
— (23 ± 2) °C and (50 ± 5) % relative humidity;
— (27 ± 2) °C and (65 ± 5) % relative humidity.
However, where very long lengths of hose are being tested, it is permissible, by agreement between supplier and customer, to use the conditions prevailing in the factory, warehouse or laboratory, provided that the relative humidity is not greater than 70 %. For testing in the field and for routine and product acceptance tests in a manufacturer’s factory of short lengths of hose and hose assemblies, this applies as well.
4.5 Procedure for hoses with conducting lining (on full hose length)
Apply suitable electrodes as specified in 422 on the inside surface at each end of the hose. The edge of the electrode band shall be coincident with the end of the hose. When using a conductive liquid, care shall be taken to avoid creating a leakage path between the lining and the reinforcement or cover of the hose.
Apply the metal contacts to the electrodes.
Apply the test voltage and measure the resistance (5 ± 1) s after the application of the voltage.
For field tests and routine and product acceptance tests in the factory, the equipment specified in
4.2.2.1 is too complicated and impractical. Instead, clean copper or brass contacts at least 100 mm2
in area, shaped to fit thc inside surface of the hose lining and held in position manually, can be used.
Alternatively, suitable electrodes as described in 4.222 can be used.
4.6 Procedure for hoses with conducting cover
4.6.1 Method for full hose lengths
Apply electrodes as specified in 4.2.2.1 on the outside surface at each end of the hose.
Apply the test voltage and measure the resistance (5 ± 1) s after the application of the voltage.
For field tests and routine and product acceptance tests in the factory, the equipment specified in
4.2.2.1 is too complicated and impractical. Instead, clean copper or brass contacts at least 100 mm2
in area, shaped to fit the outside surface of the hose cover and held in position manually, can be used.
Alternatively, suitable electrodes as described in 4.2.2.2 can be used.
4.6.2 Method for test pieces as tested in the laboratory
4.6.2.1 Test pieces
Prepare the test pieces by cutting five lengths of hose approximately 300 mm long from samples taken at random from a production run. Condition the test pieces in accordance with 4A.
Position electrodes as specified in 4.2.2.1 symmetrically along the test piece so that the distance between their nearest edges is (100 ± 1) mm (see Figure 2).
Ensure that contact is maintained with the electrodes around the circumference and that the contact pieces are sufficiently long for the two free ends to be held securely by a tensioning clip (see Figure.2) such that the fit of the electrodes is as tight as possible, consistent with the means employed.Place the test piece on blocks of polyethylene, or other insulating material, to provide a resistance of greater than 1011 8 between the test piece and the surface on which the blocks are supported. Ensure that the leads from the instrument do not touch each other, the hose or any part except the terminal to which each is connected. Connect the leads from the test instrument to the appropriate contact piece.
Apply the test voltage and measure the resistance (5 ± 1) s after the application of the voltage.
Avoid breathing on the test surfaces and thus creating condensation that may lead to inaccuracies.
4.7 Procedure for hoses with conducting compounds throughout
4.7.1 Method for hoses up to 6 m in length
4.7.1.1 Apply suitable electrodes as specified in 4.2.2.1 on the inside surface at one end of the hose (end A) and on the outside surface at the other end (end B).
Apply the metal contacts to the electrodes.
Apply the test voltage and measure the resistance (5 ± 1) s after the application of the voltage.
4.7.1.2 Repeat the test, applying the electrodes to the outside surface at end A and to the inside surface at end B.
For field tests and routine and product acceptance tests in the factory, the equipment specified in 4.2.2.1 is too complicated and impractical. Instead, clean copper or brass contacts at least 100 mm2 in area, one shaped to fit the inside surface of the lining, the other shaped to fit the outside surface of the cover, and held in position manually, can be used. Alternatively, suitable electrodes as described in 4.2.2.2 can be used.
4.7.2 Method for hoses over 6 m in length
4.7.2.1 Apply suitable electrodes as specified in 4122A on the inside surface at a minimum distance of
50 mm from one end of the hose and on the outside surface at distances of 3 m and 6 m from the same end.
Apply the metal contacts to the inside electrode and to the outside electrode at 3 m from the inside electrode.
Apply the test voltage and measure the resistance (5 ± 1) s after the application of the voltage.
4.7.2.2 Repeat the test between the inside electrode and the outside electrode at 6 m from the inside electrode. The difference between these resistance values shall be regarded as the resistance for 3 m of the hose.BS EN ISO 8031 pdf free download.Rubber and plastics hoses and hose assemblies