BS EN ISO 1746:2001 pdf – Rubber or plastics hoses and tubing Ð Bending tests

BS EN ISO 1746:2001 pdf – Rubber or plastics hoses and tubing Ð Bending tests.
1 Scope This International Standard specifies two methods for the determination of the behaviour of rubber or plastics hoses or tubing when bent to a specified radius. Method A is suitable for hoses and tubing of internal diameter up to about 80 mm; the size of the apparatus for testing hoses and tubing of larger bore sizes becomes excessive. The method also provides a means of measuring the force required to reach a specified bend radius, and the test may be carried out at a specified internal pressure. In method B, the bending characteristics, including the force required for bending, may be determined over a range of temperatures from – 60 ∞C to + 200 ∞C. The nature of the apparatus, however, limits its applicability to hoses and tubing of small internal diameter, i.e. up to about 1 2,5 mm. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 471 :1 995, Rubber — Temperatures, humidities and times for conditioning and testing . ISO 4671 :— 1 ) , Rubber and plastics hose and hose assemblies — Methods of measurement of dimensions. 3 Method A 3.1 Apparatus The apparatus consists of two guides A and B, guide A being fixed in a plane and guide B being movable in that plane, parallel to, and in line with, guide A (see figure 1 ).
If it is desired to measure the force required to attain the specified radius of curvature, this may be done, for example, by means of a system of pulleys and weights (see figure 2). Care shall be taken to minimize the effect of frictional resistance. 3.2 Test pieces 3.2.1 Types and dimensions The test pieces shall consist either of complete manufactured lengths of hose or of suitable test lengths. If the manufactured length is shorter than the length required for the test, test pieces of adequate length shall be specially manufactured. 3.2.2 Number Unless otherwise specified, two test pieces shall be tested. 3.3 Conditioning of test pieces No tests shall be carried out within 24 h of manufacture. For evaluations which are intended to be comparable, the test shall, as far as possible, be carried out after the same time interval after manufacture. ISO 471 shall be followed for time between sample manufacture and testing. Before testing, test pieces shall be conditioned for at least 1 6 h at a standard laboratory temperature and humidity (see ISO 471 ); this 1 6 h period may be part of the 24 h interval after manufacture. 3.4 Test procedure 3.4.1 If required, apply the specified test pressure as given in the relevant product specification. 3.4.2 Measure and determine the average outside diameter D of the hose by means of a suitable measuring instrument as specified in ISO 4671 . 3.4.3 Draw two parallel and diametrically opposed lines along the length of the hose. If the hose has natural curvature, one of the lines shall be on the outside of the curve. On each of these lines, mark a distance of 1 ,6C + 2D or 200 mm, whichever is the longer, where C is twice the minimum bend radius specified in the appropriate specification, so that the marked distances are exactly opposed. This will ensure a sufficient length for the bend test and adequate support of the hose.
3.4.4 Separate guides A and B to a distance slightly less than 1 ,6C + 2D. Place the hose between the guides so that the ends of the marked distances are parallel to the ends of the guides and remain in this position while the guides are closed to a distance of C + 2D (see figure 1 ). 3.4.5 Check that the hose on each side is supported to a length of not less than D. 3.4.6 Measure and determine the minimum outside dimension T in the curved portion of the hose (see figure 3). 4 Method B 4.1 Apparatus 4.1.1 Compression testing machine, with a rate of travel of the moving jaw of 1 00 mm/min, preferably provided with a chart recorder. A scale, graduated in millimetre divisions, may be attached to the moving jaw to enable the bend diameter to be measured or, preferably, this may be determined from a graphical record. 4.1.2 Pair of twin channel-shaped holders, fitted with end stops for the hose test pieces (see figure 4).