Assessing fiberglass reinforced polymer pipe

Piping made from fiber-reinforced polymer (FRP) composites has a long record of success safely transporting hazardous materials such as corrosive acids where steel and other alloys are unsuitable or cost prohibitive.

However, non-destructive testing (NDT) of FRP piping is relatively new. Conventional inspection approaches, including destructive testing and visual inspections that require confined space entry, are not well-suited to assessing pipeline networks due to the relatively small diameter of the equipment and the vast amount of piping at a typical facility. Regular visual external inspections are important but provide only limited insight. Compare FRP inspection methods.

Pipeline inspection requires ‘unconventional’ UAX approach

UltraAnalytix® NDT by UTComp is an attenuation-based ultrasound (UAX) method that provides plant engineers with a technically valid, non-destructive and non-intrusive process for evaluating in-service FRP piping.

Several components of FRP piping systems require special consideration due to additional stresses and loads that may increase the risk of failures or leaks. The list includes fittings, joints, flanges, spools, spools at joints (SAJ), repads and more. Each component requires slightly different analysis of ultrasound readings taken following UTComp procedures.

Expansion joints

A typical problem area might be the expansion joints, flexible connectors that allow for pipe movement that occurs with changes in temperature or pressure. Expansion joints come in a wide variety of designs and materials, typically made from polymers, elastomers and reinforced polymers.

These materials are affected by the same viscoelastic aging processes as FRP; however, this is invisible and not detectable using any conventional NDT methods. It can be detected by ‘unconventional’ methods such as UltraAnalytix.

Balancing design capacity and in-service stresses

Fitness For Service assessment to prevent failures and optimize the lifespan of FRP piping systems and their various components like flanges and joints is based upon striking a balance between the mechanical and chemical stresses applied on equipment due to service conditions and its design capacity.

Damage mechanisms and failure modes

UltraAnalytix provides plant engineers and reliability experts with the tools to identify the invisible polymer damage that leads to visible failure modes such as cracking, debonding and delamination that can occur to in-service equipment over time. Learn more about FRP damage mechanisms and failure modes.

Accurate evaluation involves relating the equipment’s current strength or stiffness to its “as new” stiffness and operating requirements such as the design pressure. The UltraAnalytix system does this by calculating three main values:

• Percentage of design stiffness (PDS)
• Thickness of the FRP
• Depth of damage to the corrosion barrier

While conventional ultrasonic testing can be used to measure thickness and find cracks and other defects, UltraAnalytix quantifies the condition of the material, calculates remaining service life, and provides fitness for service assessments that allow owners to make informed decisions about their FRP assets.

Get UTComp’s free FRP Assessment Guidebook for more information.