BS ISO 10952:2021 pdf download – Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Determination of the resistance to chemical attack for the inside of a section in a deflected condition
10.8 Maintain the depth of the test liquid at not less than 25 mm until leak failure occurs or the test is stopped. For the duration of the exposure of the test piece, periodically check using suitable analytical methods and, if necessary, adjust the test solution to maintain it within ±5 % of the specified concentration.
NOTE Solutions become more concentrated by the evaporation of water. It can be necessary, with some reagents, to clean the deflected test piece periodically and to replace the test solution with a fresh solution.
A plastic film, cut carefully to fit between the dams and floated on top of the test solution, reduces evaporation. 10.9 Unless otherwise specified, inspect the test piece visually, without magnification, for signs of leak failure at the intervals given in Table 2, subject to the permitted deviations given in the rightmost column. When a test solution is being replaced by a fresh solution, a detailed examination of the wet area can be made. Any visual observations such as cracking or delamination should be recorded.
To improve visibility of leak failure, if necessary, prepare the outer surface of the test piece by coating with a lime wash. The use of electronic timers has been found helpful in monitoring time to failure particularly on short-term tests.
10.10 Record the time to failure for each test piece. Test pieces that have not failed after more than 10 000 h can be included as failures to establish the regression line. The non-failed test pieces can be left under test and the regression line recalculated as failures are obtained. 10.11 In the event that failures do not occur at any time, implement alternative procedures (typically called specified levels) as detailed in the referring International Standard or ISO 23856.
11 Test procedure using strain measurement WARNING — Contain any fragmentation or leakage that can occur during the test.
11.1 During the following procedure, maintain the temperature as specified in the referring International Standard. 11.2 Select the range of estimated strains such that the times to failure of at least 18 test pieces are distributed between 0,1 h and over 10 000 h, and the distribution of failure times of at least 10 values conforms to the limits given in Table 1.
11.3 Carefully align and attach three strain gauges (6.2) on the invert of the test piece in the circumferential direction to measure initial circumferential strain. Place the gauges equally spaced along one of the lines of the test piece. The adhesive used to attach the gauges shall, in total, not cover more than 37 % of the test piece length along the invert. Zero the gauges while the test piece is circular in shape. It is recommended that the test piece be placed with its axis vertical to maintain roundness when the bridge is balanced to zero the instrument.
11.4 After installing the strain gauges, place the test piece in the test set-up (see Figure 1) with the strain gauges at the bottom. Take extreme care to ensure that the gauges are located at the point of maximum strain (the “6 o’clock” position), and that the lines on the test piece are parallel to and centred on the axes of the plates or sections.
IMPORTANT — Alignment of the test piece within the loading frame is critical.
11.5 Apply force to the apparatus to deflect the test piece while keeping the top and bottom plates or sections of the apparatus as parallel as possible. When the desired strain level is reached, lock the apparatus to maintain the test piece in the deflected condition. Read the gauges as soon as the apparatus is locked. Record the initial strain measured by each strain gauge within 2 min after locking the apparatus. To validate the test condition, check that at least two gauges give readings within ±2,5 % of the mean value. If any gauge reads more than 7,5 % from the average of the other two gauges, disregard the indication unless a thickness verification implies the strain gauge reading was accurate.BS ISO 10952 pdf download.