Standard Test Method for Time-to-Failure of Plastic Pipe Under Constant Internal Pressure
The data obtained by this test method are useful for establishing stress versus failure time relationships in a controlled environment from which the hydrostatic design basis for plastic pipe materials can be computed. (Refer to Test Method D 2837 and Practice D 2992.)
In order to determine how plastics will perform as pipe, it is necessary to establish the stress-failure time relationships for pipe over 2 or more logarithmic decades of time (hours) in a controlled environment. Because of the nature of the test and specimens employed, no single line can adequately represent the data, and therefore the confidence limits should be established.
Note 3—Some materials may exhibit a nonlinear relationship between log-stress and log-failure time, usually at short failure times. In such cases, the 105-hour stress value computed on the basis of short-term test data may be significantly different than the value obtained when a distribution of data points in accordance with Test Method D 2837 is evaluated. However, these data may still be useful for quality control or other applications, provided correlation with long-term data has been established.
The factors that affect creep and long-term strength behavior of plastic pipe are not completely known at this time. This procedure takes into account those factors that are known to have important influences and provides a tool for investigating others.
Creep, or nonrecoverable deformation for pipe made of some plastics, is as important as actual leakage in deciding whether or not a pipe has failed. Specimens that exhibit localized ballooning, however, may lead to erroneous interpretation of the creep results unless a method of determining creep is established that precludes such a possibility. Circumferential measurements at two or three selected positions on a specimen may not be adequate.
Great care must be used to ensure that specimens are representative of the pipe under evaluation. Departure from this assumption may introduce discrepancies as great as, if not greater than, those due to departure from details of procedure outlined in this test method.
1.1 This test method covers the determination of the time-to-failure of both thermoplastic and reinforced thermosetting/resin pipe under constant internal pressure.
1.2 This test method provides a method of characterizing plastics in the form of pipe under the conditions prescribed.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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