ISO 9967 plastic pipe testing: creep resistance and procedure

Key points about ISO 9967 for plastic pipe testing

Overview of ISO 9967

ISO 9967 is an internationally recognized standard specifying a test method for determining the creep resistance of thermoplastics pipes under a constant internal pressure at a specified temperature. The test is mainly applicable to thermoplastics pipes intended for buried piping systems such as those used for non-pressure or gravity drainage and sewerage. By following this method, manufacturers and laboratories can assess how pipes retain their mechanical properties and dimensional stability over time under long-term loading conditions, a critical factor for real-world performance in infrastructure.

The standard focuses on the constant internal pressure test over extended durations to evaluate the pipe’s creep behavior.
It is specifically designed for pipes with a circular cross-section and structures solid in wall construction, such as PVC, PE, or PP materials.
ISO 9967 provides clear test conditions including pressure, temperature, and duration to ensure reproducibility and comparability of results across laboratories.

Scope and application

ISO 9967 outlines the conditions required for adequately assessing the structural integrity of thermoplastics pipes when subjected to long-term internal hydrostatic pressure. The results of the testing procedure, including the deformation or failure time, give insights into the pipe material’s quality and its expected durability in practical applications, such as sewer systems or drainage pipelines. The standard applies to newly-manufactured pipes and is used for type testing, quality control, and compliance with regulatory demands by industry stakeholders.

Significance in the industry

Adherence to ISO 9967 ensures that plastic pipes meet established safety, reliability, and quality requirements throughout their intended service life. The ability to replicate the stresses encountered during actual use allows manufacturers to confirm product suitability and provides end-users and regulators confidence in system durability. This assures consistent testing protocols, benefiting both manufacturers seeking compliance and users requiring reliable performance data.

Takeaway

ISO 9967 plays a pivotal role in standardizing the approach to hydrostatic pressure testing of thermoplastics pipes and ensuring product reliability in buried pipe applications.

Widely used for assessing long-term pressure performance
Applicable mainly to drainage and sewerage pipe materials
Supports industry compliance and quality assurance
Test outcomes inform both manufacturers and end-users

How to perform ISO 9967 testing on plastic pipes

General preparation for ISO 9967 testing

The ISO 9967 testing procedure requires careful preparation to achieve reliable and reproducible results. Begin by selecting representative samples of thermoplastics pipes according to the standard’s specifications, ensuring samples are new, undamaged, and have been conditioned at the prescribed temperature for the required minimum time. Make sure that the equipment used—such as pressure test rigs and temperature controls—is calibrated and capable of maintaining the specified test conditions with accuracy throughout the duration of the test.

Mounting the sample

Place the pipe sample horizontally in the test rig, ensuring it is fully supported to prevent any induced stresses that are not related to internal pressure. The test rig must accommodate the sample securely while allowing accurate application and measurement of internal pressure.

Ensure both pipe ends are properly sealed
Fill the pipe with test medium (usually water)
Check for leaks before starting the actual test

Applying internal pressure and monitoring

Once the sample is mounted and filled, apply the internal pressure as specified by ISO 9967 using a suitable pressure source. Maintain the required temperature—typically 20°C or 23°C depending on the material—and adjust for any environmental fluctuations. The pressure must remain constant for the full test duration, which may range from several hours to thousands of hours, depending on the test objective or pipe material. Deformation or time to failure is measured and recorded at regular intervals, as defined by the standard.

Evaluating results and reporting

After completion of the test or upon pipe failure, record all data including pressure, temperature, test duration, and nature of failure or deformation. Compare the results to specification limits as outlined in product or regulatory requirements. Assemble findings into a test report detailing the procedure, observations, and outcomes for industry compliance or product qualification.

Record all equipment settings and calibration details
List sample characteristics and preparation details
Document pressure, time, and temperature data
Describe the observed failure mode or extent of deformation
Include all relevant calculations and standards references

Critical points to consider

Testing by ISO 9967 demands strict adherence to sample preparation, conditioning, and monitoring requirements as outlined by the standard. Consistent and precise control over all parameters is essential to ensure that the results are valid, reproducible, and comparable across different laboratories or production batches. Routine equipment maintenance, proper sample handling, and complete documentation all support test validity and quality assurance for end users and regulators.

Summary

ISO 9967 establishes a clearly defined method for assessing the long-term performance of thermoplastics pipes under internal pressure. Following the procedure step by step ensures reliable data for product evaluation, batch release, or regulatory compliance, providing essential information to both manufacturers and users about the suitability of pipe products for buried piping systems.