Thermoplastics Pipes and Fittings - Methods of Test
2004 Edition

Specimen preparation involves discarding any samples that fail to break within the parallel section, and using distilled or demineralized water free from air for conditioning or testing. Conditioning is carried out according to the relevant material specifications; if none are specified, specimens should be conditioned at 27 ± 2°C and 65 ± 5% relative humidity for 24 hours. For low-temperature conditioning, specimens are immersed in either liquid bath or air at 0 ± 1°C for the time durations outlined in the standard’s tables. Temperature measurements must be taken with calibrated thermometers having at least 0.5°C graduation and a maximum error of ±0.5°C.

Ring stiffness is calculated by measuring the force at 3% deflection for three test specimens and applying a formula that incorporates force, specimen length, deflection, and internal pipe diameter. Specifically, the stiffness values for each specimen are computed and then averaged to obtain the final ring stiffness value, expressed in kN/m². This process involves plotting force versus deflection curves and may require extrapolation to establish the zero point. Comprehensive reporting includes specimen identification, conditioning details, individual stiffness values, averaged results, and related load-deflection graphs.

Leak-tightness testing includes applying positive internal hydrostatic pressure within a controlled tolerance while optionally subjecting the joint to angular deflection. Another method involves applying negative pressure (vacuum) combined with angular deflection to assess joint integrity. Throughout testing, leakage is monitored, and any failures are classified by type and location relative to the pipe end. Test reports document pressure levels, deflection angles, ambient conditions, and observed leak-tightness results, ensuring realistic simulation of in-service stresses.

Hydrostatic pressure testing requires calculating the test pressure using the pipe’s hoop stress, minimum wall thickness, and mean outside diameter via a given formula. Specimens are cleaned, dried, filled with water preheated to within 5°C above test temperature, and conditioned in a water bath for specified durations based on wall thickness. The test involves applying pressure gradually over 30 seconds to 5 minutes, maintaining it within ±7% tolerance for the test duration. Specimens should not be tested within 24 hours post-production unless for manufacturing checks. Pressure application can be done individually or collectively with isolation valves to avoid interference.

Ash content determination involves thermally decomposing 2 to 5 grams of sample at 850 ± 50°C until only white ash remains, with at least two replicates whose results agree within ±10%. Vinyl chloride monomer content is measured by dissolving pipe samples in NN-dimethylacetamide, equilibrating at 45°C, and analyzing the headspace vapor using gas chromatography with mass spectrometry confirmation. Detection limits are approximately 0.3 mg/kg with specified accuracy ranges. Reports must include pipe type, size, configuration, and measured values, with VCM content rounded to the nearest 0.5 mg/kg.