When a pipe rehabilitation crew installs a CIPP liner, they typically do the job in just a few hours, and then move on to the next installation.

But that’s not the end of the story. CIPP is designed to last for decades, and the wastewater systems that use it need to be confident in its efficacy. In some cases, installers are required to submit a sample of every liner installed for third-party testing. Only once testing is complete and the results are approved and reported is the job really “done.”

Rick Eastwood has operated in the world of CIPP testing for over 30 years. As vice president of business development for HTS, which provides consulting, materials testing and inspection services for both the public and private sectors, he and his team are largely invisible to many rehab professionals. But the work they do is essential to public safety and wastewater management.

Before joining the firm, Eastwood spent almost 20 years before working for various lining contractors. He’s seen a lot of change in the relining industry, from the development of new materials and curing methods to the introduction of more efficient and affordable techniques. But different materials and methods don’t change the role played by the tester.

“Materials are designed to meet a standard or a specific design criteria depending on the material and/or application,” he explains. “Once it’s installed and samples are sent to HTS, we test the material in accordance with the appropriate ASTM method. The results will indicate if the samples meet the desired design criteria.”

Reliable testing methods

Testing measures vary depending on materials used in the construction of the liner and the design requirements of the material. Many different parameters go into designing the material and thickness of a CIPP liner, but key factors include depth, water levels and loads. A deeper look into liner design may examine operating pressures and temperatures, potential impact on sensitive environments, pipe diameter, etc.

“Then there’s the strength of the liner itself,” Eastwood says. “CIPP liners are designed to last 50 years, known as the design life, and testing can help you confirm this.”

The standard way to determine design life is with an ASTM D2990 Flexural Creep test. “In this test, five specimens are placed under a calculated stress load for 10,000 hours — about 13 and a half months,” Eastwood explains.

“We record the deflection during this time; then we extrapolate from this data to determine the strength retention of the material at 50 years — typically around 50% or more of the initial strength. This is why job specifications and design programs indicate that the long-term flexural modulus is 50% of the initial short-term value.” It’s the value contractors input in liner design when calculating liner thickness.

All liner and resin products generally require the D2990 Flexural Creep test performed before they’re accepted in the industry; manufacturers typically complete this test long before the product is available for purchase. Depending on the demands of an individual contract or local standards, installers are sometimes also required to have testing performed on their liners. In that case, an operator either takes a sample during installation or manufactures a plate sample that is then cured during the installation process. Once the curing is complete, the project manager submits the sample to a testing facility, documenting chain of custody and pertinent job information.

Common CIPP tests

Samples may also be subjected to a variety of other tests and standards:

- ASTM D790: This test produces the flexural properties of the sample tested. The test is performed in accordance with the requirements listed in ASTM F1216 (for felt liners) or ASTM F2019 (for UV-cured fiberglass liners). It directly ties to ASTM D2990 data for a product. For example, if a liner is designed based on the initial flexural modulus from the ASTM D2990 test, the results of the ASTM D790 test must meet or exceed this value. If this value is not met, installers may face pay deductions or worse. “There is a large difference in the testing methods based on the type of material used in the construction of the liner installed,” Eastwood says. “Although the same test is run for felt or UV-cured fiberglass liners, the sample preparation is quite different.”

- ASTM D638: For tensile tests like this one, specimens are cut in the shape of a dogbone, put in a grip and pulled apart. The resulting data can help the operator know the tensile strength of the liner. This is generally required for pressure pipe applications.

- Sample thickness: Liners must meet the thickness indicated in the design. For felt liners, the tester can take simple measurements of the full thickness (ASTM D2122) or measure the full thickness and deduct the coating thickness (ASTM D5813), since coating is a nonstructural component of the liner. We have customers requesting all of these depending on the job specifications. UV-cured fiberglass liners must be measured as per ASTM D3567, in accordance with ASTM F2019, which differs significantly from ASTM F1216. ASTM F2019 requires a total of 30 measurements (six measurements per test specimen) to determine the “full thickness,” and then places each of the specimens under a microscope to measure the nonstructural layers (films, coatings and neat resin), in the same previously measured six locations, and deduct this measurement from the total wall thickness to determine the “composite thickness.”

- Chemical tests: Various chemical tests can be performed according to ASTM standards, depending on an individual project’s requirements.

How do liners fail?

Nearly all the CIPP liners that complete testing pass. But not every sample gets that far. “We don’t get many, but we get some occasionally. If I can bend it in my hand, I know it’s not going to pass,” Eastwood says.

Over the years, he’s found a pattern in flawed samples. “After you review the failure, which I like to call ‘CIPP: SVU,’ you will find some issues that will have a negative effect on the installed liner. These materials and processes are tried and true. Generally, poor samples we receive are not a fault of the material.

“There is a saying that any product, no matter how good it is, is only as good as how the installation goes that day. During an installation, a number of things can go wrong,” he says. “You lose head pressure, lose your heater, lose a thermocouple, etc. It can be painful but can also be a learning experience. You just hope those instances don’t cost too much.”

That’s why testing exists, after all.