ASTM D1598 Time-to-Failure of Plastic Pipe Under Constant Internal Pressure

Get Certified ASTM D1598 Testing for Plastic Pipe Pressure Endurance 

Plastic pressure pipes used in potable water supply, natural gas distribution, geothermal loops, and chemical processing applications can withstand internal pressure for decades without failure or environmental stress cracking. Unexpected ductile weeping or brittle slow crack growth (SCG) can cause catastrophic pipeline failures and significant infrastructure repair expenses. Destructive and non-destructive testing helps evaluate pipe quality, structural integrity, and long-term performance. According to ASTM D1598, technicians subject pipe specimens to controlled internal pressure and temperature to determine the time to failure. Certified testing verifies material formulations, confirms production quality, and supports compliance with pipe design specifications, such as ASTM D2837 and PPI TR-3. 

The scope of  ASTM D1598 includes :

• Material type: Thermoplastic and reinforced thermosetting/resin pipe.
• Purpose: A destructive method; technicians dissolve the sample in a solvent and pour the resulting solution into a pressure cell.
• Properties evaluated: Time to failure – determination of stress versus failure time relationships and calculation of hydrostatic design basis.
• Testing method: Internal pressure testing at constant pressure in a controlled environment.Failure time under constant internal pressure; relationships between stress and failure time.
• Result: Stress-versus-time-to-failure data points used to construct log-stress vs. log-time regression curves (per ASTM D2837). 
• Limits of the test: Researchers do not fully understand the factors influencing the creep and long-term strength characteristics of plastic pipe. At short failure times, some materials may show a nonlinear relationship between log stress and log failure time.
• Use conditions: Technicians must use specimens that represent the pipe being evaluated. Nonrecoverable deformation (creep) is as significant as the actual leakage in determining whether or not a pipe has failed.
• Applications: Hydrostatic design basis computation, quality control, and material characterization for plastic pipe.

What are the Uses of ASTM D1598 Testing?

ASTM D1598 provides a method for testing plastic pipe resistance to failure under constant internal pressure in the laboratory. Manufacturers, engineers, and quality control personnel use the results for material characterization, design validation, and quality assurance. This standard—

• Calculates the failure time of thermoplastic and reinforced thermosetting/resin pipe.
• Develops stress-to-failure time relationships for materials used in plastic pipes.
• Covers hydrostatic design-basis calculations for plastic pipe.
• Allows plastic pipe to be characterized under specified conditions.
• Supports quality control and material comparisons for pipe applications.
• Supplies data to aid in the prediction of long-term performance of plastic pipe.
• Helps in materials research and development for plastic pipe.

What Materials Can Be Tested Under ASTM D1598?

The test identifies the time-to-failure characteristics of thermoplastic materials commonly used in manufacturing pipes for residential, industrial, and agricultural applications, including polyethylene, polypropylene, PVC, and CPVC.

 Why is ASTM D1598 Important? 

The specification is very important to assess the long-term performance and safety of plastic pipes in continuous internal pressure applications. It helps in the design of durable systems and prevents costly failures, with improved product reliability and compliance with industry standards.

ASTM D1598 Testing Process and Data Collection

Analysts prepare representative pipe specimens according to the standard procedures. Technicians apply constant pressure to the specimen internally while maintaining controlled environmental conditions. The technician observes the specimen for failure, such as leakage or creep deformation. The analyst automatically records stress and failure time during the test. The lab then compiles and writes a report containing these results. Technicians note the following failure time data, stress-to-failure relationships, specimen identification, and test conditions. 

Common Challenges and Troubleshooting

ASTM D1598 test results are incorrect when the technician fails to use the proper specimen preparation, pressure control, or environmental conditions. At this time, the factors affecting the creep and long-term strength behavior of plastic pipe are not fully understood. At short failure times, the relationship between log-stress and log-failure time may be nonlinear for some materials. Samples showing local ballooning can misinterpret creep results unless a method is developed to identify and rule out ballooning. Measurements taken around the circumference of a specimen at two or three locations may not be sufficient. It is important to take great care to be sure that the specimens are representative of the pipe to be evaluated. Technicians always sample the materials with the standard and proper calibration of the instruments. 

• The laboratory reports the failure times of the artifacts together with the stress vs. failure time relationships.
• Technicians can use the data to establish stress-versus-failure-time relationships in a controlled environment, from which they can calculate the hydrostatic design basis of plastic pipe materials.
• The analysis includes the effect of the number of logarithmic decades of time (hours) over which technicians have determined the stress-failure time relationships.
• The analysis also allows consideration of confidence limits that technicians must set because no single line can fully represent the data.
• The report compares the test results with the applicable product specification or customer requirements.
• Technicians compare time-to-failure test results with relevant product specifications to determine the pipe’s suitability for the application.

Link to ASTM D1598