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 formed 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 placed to constant internal pressure in a controlled environment. The controlled environment is maintained by immersing the samples in a controlled air bath or water. Then, a failure time is measured. Dimensional changes of samples are measured when the tests are carried out for a longer time. The measurements are usually carried out by strain gauges or extensometers and circumferential tapes.

Sample size:

Minimum length of small size pipe samples, such as 6 inches (150 mm) diameter, 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 is calculated using the given equation as follows:

S=P(D-t)/2t

or 

S=P(DR-1)/2

where:

S = hoop stress, psi (MPa)

P = internal pressure, psig (MPa)

D= average outside diameter, inches (mm)

T = minimum wall thickness, inches (mm)