Scope:

Time-to-Failure of Plastic Pipe test by ASTM D1598 determines the failure time of reinforced thermosetting/resin pipes and thermoplastic pipes at uniform internal pressure. Failure is defined as any continuous loss of pressure with or without the transmission of the test fluid through the test pipe. The failure is caused by one or a combination of different exposures such as ballooning, free end closure, restrained end closure, rupture, and seepage.

Test Procedure:

In the Time-to-Failure of Plastic Pipe test by ASTM D1598, pipe samples are subjected to a constant internal pressure in a controlled environment. The controlled environment is maintained by immersing the samples in a controlled air bath or water. Then, the failure time is measured. Dimensional changes in the samples are measured when the test is carried out for a longer time. The measurements are usually carried out by strain gauges or extensometers and circumferential tapes.

Sample size:

For ASTM D1598, minimum length of small size pipe samples, such as pipes having diameter of 6 inches (150 mm), is taken as 12 inches (300 mm). Minimum length of large size pipe samples is taken as 30 inches (760 mm).

Data:

Hoop stress for the pipe samples in ASTM D1598 is calculated as follows:

S=P(D-t)/2t

or 

where:

S = hoop stress, psi (MPa)
P = internal pressure, psig (MPa)
D= average outside diameter, inches (mm)
t = minimum wall thickness, inches (mm)

Conclusion:

Time-to-Failure of Plastic Pipe test by ASTM D1598 determines the failure time of both reinforced thermosetting/resin pipes and thermoplastics pipes at uniform internal pressure.