BS ISO 10471:2018 pdf download – Glass-reinforced thermosetting plastics (GRP) pipes — Determination of the long-term ultimate bending strain and the long-term ultimate relative ring deflection under wet conditions 7 Number of test pieces Unless otherwise specified in the referring standard, at least 18 test pieces shall be used to obtain the distribution of failure times specified in the referring standard (see the numbered list in Clause 4). 8 Determination of the dimensions of the test piece 8.1 Length Measure the length of each test piece along each reference line in accordance with ISO 3126. Trim or replace, as applicable, the test piece if it does not conform. Calculate the mean length, L, in metres, of each test piece from the six measured values. 8.2 Wall thickness Measure in accordance with ISO 3126 the wall thickness of each test piece at four equally spaced locations on each reference line. For each reference line, calculate the mean wall thickness, e, in metres, of the four measured values. Calculate the sample mean wall thickness using all thickness values. 8.3 Mean diameter Measure in accordance with ISO 3126 either the internal or external diameter (see 3.2). Using either Formula (1) or Formula (2), calculate the mean diameter, d m (see 3.2), of the test piece using the value obtained for the sample mean wall thickness, e, in 8.2. 9 Conditioning If applicable, condition the test pieces in accordance with the referring standard. 10 Procedure 10.1 For each test piece conduct the following procedure at the temperature specified in the referring standard (see Clause 4). 10.2 To assess the uniformity of the test pieces, determine and record in accordance with the constant load procedures in ISO 7685 the initial specific ring stiffness, S 0 , of each test piece. The measured value of S 0 at the pair of reference lines (see Clause 6) may also be used to estimate the force required to compress the test piece to the necessary deflection to achieve a time to failure that, together with those produced from other test pieces, conforms to the distribution of times to failure specified in the referring standard. 10.3 Deflections in excess of 28 % of the diameter may cause local flattening of the pipe and lead to erratic test results. For deflections approaching 28 %, improved accuracy is obtained by use of strain gauges to establish, for each pipe product, a...
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