ASTM D2992-22 Standard Practice for Obtaining a Hydrostatic or Compression Design Basis for Fiberglass (Glass Fiber-Reinforced Thermoset Resin) Pipe and Fittings

The ASTM D2992-22 Standard Practice for Obtaining a Hydrostatic or Pressure Design Basis for Fiberglass (glass fiber reinforced thermoset resin) Pipe and Fittings, developed by the American Society for Testing and Materials (ASTM) , describes two procedures for obtaining a hydrostatic or pressure design basis for fiberglass pipe products by evaluating strength regression data obtained by testing pipes or fittings of the same material and construction, individually or in assemblies: Procedure A (cyclic) and Procedure B (static). Both glass fiber reinforced thermoset resin pipe and glass fiber reinforced polymer mortar pipe are fiberglass pipes. For the purposes of this standard, polymer does not include natural polymers.

This application can be used to determine hydrostatic design stress for fiberglass pipe where the outside diameter to wall thickness ratio is 10:1 or greater.

This limitation, based on thin-walled pipe design theory, serves to further limit this practice to internal pressures that are approximately 20 percent of the hydrostatic design stress derived from the hoop-stress equation. For example, if the hydrostatic design stress is 34500 kPa, the pipe is limited to an internal pressure of approximately 6900 kPa, regardless of diameter.

When long (continuous) glass fibers are intentionally placed to resist the intended compressive load condition (i.e., free-end pressure testing and 654,7 degree fiberglass wraps), the results obtained from this application may be overly conservative in predicting long-term fiberglass pipe performance when the same pipe is operated at lower (non-damaging) stresses typical of normal pipeline applications.

All data points in the analysis must be in the same failure mode. This practice may not accurately represent the life of the pipe when plastic creep of the resin is prevented from causing pipe failure by undesirable resin matrix cracking or other unforeseen failure modes.

This application provides a compression design basis for complex shaped products or systems where complex stress fields seriously inhibit the use of hoop stress.

The specimen end closures in the underlying test methods may be either constrained or free, which imposes certain limitations. In constrained ends, specimens are stressed by internal pressure only in the hoop direction, and the compression design basis applies only to stresses developed in the hoop direction. In free ends, specimens are stressed by internal pressure in both the hoop and longitudinal directions, so that the hoop stress is twice the magnitude of the longitudinal stress. This practice may not be valid for evaluating stresses developed by loadings where the longitudinal stress exceeds 50 percent of the compression design basis.

For the purposes of this standard, the following terms and definitions apply:

• The closure is a sealing device or mechanism in which the free end is attached to the end of the test specimen so that the internal pressure produces longitudinal tensile stresses in addition to the hoop and radial stresses in the test specimen.
• A closure is a sealing device or mechanism that relies on a bar passing through the restricted end, test specimen, or an external structure to resist the end thrust force generated by internal pressure, thus limiting the stresses in (flat) specimens only in the circumferential and radial directions.
• Failure is any transmission of test fluid through the body of the specimen (whether wall fracture, local leakage, or leakage from a distance greater than one diameter past the tip closure).
• Fiberglass tubing is a tubular product containing glass fiber reinforcement embedded in or surrounded by a cured thermoset resin. The composite structure may include aggregate, granular or platelet fillers, thixotropic agents, pigments, or dyes. Thermoplastic or thermoset primers or coatings may be included.
• Reinforced polymer mortar pipe is a fiberglass pipe containing aggregate.
• Reinforced thermosetting resin pipe is a fiberglass pipe that does not contain aggregates.
• Hoop stress is the tensile stress resulting from internal pressure in the circumferential direction in the wall of the tubular product. Hoop stress is calculated by an ISO equation. Hoop stress should only be determined on flat hollow cylindrical specimens. Product evaluation of more complex shapes may be based on pressure.
• The hydrostatic design basis is a hoop stress developed for fiberglass pipe with this application and multiplied by a service design factor to obtain a hydrostatic design stress.
• Hydrostatic design pressure is the estimated maximum internal hydrostatic pressure that can be applied to a piping component on a cyclical (Procedure A) or continuous (Procedure B) basis with a high degree of confidence that the component will not fail.
• Hydrostatic design stress is the maximum estimated tensile stress in the pipe wall in the hoop direction due to internal hydrostatic pressure that can be applied cyclically (Procedure A) or continuously (Procedure B) with a high degree of confidence that the pipe will not fail.

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