If you want something new, you have to stop doing something old.

-Peter Drucker

Reliability engineers and industrial facility operators have long struggled with a lack of hard data to accurately assess the reliability of fiber-reinforced polymer (FRP) piping and other equipment.

Reliability engineers depend on data and systematic approaches to ensure the safe operation of the facilities and processes under their care. These professionals follow codes and standards that describe inspection technologies and methods to monitor the status of equipment to determine fitness for service and predict when maintenance is expected in order to preserve mechanical integrity.

Their work culture is increasingly changing from reacting to emergencies to using scientifically proven methods for predictive maintenance to protect human and environmental health and safety, while avoiding costly unplanned downtime and repairs.

Traditional FRP pipe inspection relies on hunches, intuition and guesswork

Inspection codes and best practices for non-destructive testing (NDT) of in-service steel pipes, including standards for ultrasonic inspection, are well-developed thanks to groups like the American Petroleum Institute (API) and others.

However, while API 570 and API 574 include guidance for inspecting and repairing in-service FRP equipment, assessing FRP and other non-metallic piping still presents unique challenges. 

So how do we handle inspection and Fitness For Service assessment of non-metallic piping including FRP composites, polyvinyl chloride (PVC) or high-density polyethylene (HDPE)? Let’s dive in.

The downside of visual inspection

Traditional inspection of FRP equipment focuses on the state of the inner surface of the corrosion barrier. Assumptions are routinely made about the capability of the FRP material to perform its function, simply based on its appearance. This is despite that fact that no research or published material provides any scientific connection between the visual appearance of FRP and its reliability.

Without data and good information, backed by verified research results, decisions based on a visual inspection of the corrosion barrier rely by necessity on hunches, intuition and guesswork.

Destructive testing compromises the asset

The way to obtain more information — according to traditional theory – is to perform destructive tests of the FRP equipment. However, this approach damages the assets that reliability engineers are trying to preserve.

In the past, it was often not even possible to inspect FRP pipe unless a piece of the FRP was removed. Cutting a piece from process piping and repairing it usually requires that the work be completed according to a piping code such as ASME B31.3.  After the damage has been repaired, a hydrotest is required.  The total cost to the facility can be enormous, considering downtime, engineering, and repairs even before any evaluation of the pipe has started. Finally, any conclusions about piping condition hinge on the specific samples removed; if only one sample is removed, let’s hope it comes from the right place!

Historically, reliable operation has been preserved by repairing or replacing FRP from these subjective inspections, although the maintenance costs have been high and I have seen more than one shutdown extended because of extra time for FRP repairs.

Non-destructive, non-intrusive attenuation-based ultrasound (UAX) provides a better way to thoroughly inspect FRP and other non-metallic piping.

The UltraAnalytix NDT solution for FRP pipe inspection

UltraAnalytix , UTComp’s patented UAX system, uses conventional ultrasonic test equipment to take readings from the outer surface of piping at key locations where chemical attack and stress combine to weaken the pipe. The ultrasonic readings are then analyzed using our proprietary AI algorithm to determine how the pipe has changed and to identify if action is required.

The UltraAnalytix algorithm draws on millions of inspection data points for accurate Fitness for Service evaluations and precise Remaining Service Life forecasting. This provides a reliable, scientific basis for predictive maintenance decision-making to deliver maximum return on asset (ROA).

Compare methods for testing FRP materials

The UTComp method also includes a systematic visual inspection to identify surface damage such as cracks, UV damage, blisters or other deformation in the material as well as signs of corrosion on pipe supports, flanges, nozzles, lugs and other components.

UltraAnalytix NDT advantages

UltraAnalytix NDT evaluation of FRP pipe and other equipment includes:

• Corrosion barrier condition
• Structural changes occurring within the composite structure
• Composite strength
• Composite thickness
• Damage caused by abrasion, corrosion and mechanical loads due to impact, poor supports, earthquakes, hurricanes and other factors.

Furthermore, inspection can be completed while the facility is operating, so there need not be any interruption of production. There’s no need to clean out equipment, store the contents, undertake risky confined space entry or cut test samples out of the asset, compromising structural integrity.

What about cost? Our results show the total cost of UltraAnalytix FRP pipe inspection is less than 10% of the cost of the conventional inspection methods when premature repairs and replacements are included. This means a steep reduction in overall inspection costs.  Based on the engineering results that are provided by UltraAnalytix, we are also seeing that FRP lasts longer than the traditional approaches claim, often at 90% reduction in maintenance costs. This data-driven approach is increasingly being used worldwide to provide accurate and reliable service-life forecasting for FRP assets.

Case study: Non-destructive evaluation of FRP piping at a phosphoric acid plant

The UTComp method also includes a systematic visual inspection to identify surface damage such as cracks, UV damage, blisters or other deformation in the material as well as signs of corrosion on pipe supports, flanges, nozzles, lugs and other components.

How inspecting pipe is different

Inspecting FRP and other non-metallic piping presents unique challenges due to the complex geometry of piping systems, and the properties of FRP that are fundamentally different from metal.

UAX data can be used to accurately calculate pipe thickness, stiffness and corrosion barrier condition anywhere along a piping circuit. Each circuit will likely have distinct components that require slightly different analysis, including: 

• fittings used to alter flow direction, combine or separate flows, or change pipe size
• elbows, tees, butt and wrap joints and socket joints
• spools, spool at joints (SAJ), and repads

In general, inspecting FRP piping requires more UAX readings at more locations compared to inspecting steel. So the first step is to develop an inspection plan that takes these complexities into account.

Inspection plan required for each piping circuit

API 570 requires an inspection plan (IP) for each piping circuit to be inspected. It’s an approach based on Condition Monitoring Locations (CMLs) — specific points along the piping where damage is most likely to occur due to chemical or mechanical forces acting on the pipe.

IPs are created by the inspector using isometric drawings or photographs and UltraAnalytix software so that readings can be assigned to specific CMLs. This allows the inspector to determine the overall condition of a piping circuit by tracking the condition of the material at each CML.

Mapping out the CMLs must take into account the effects of damage mechanisms that would be expected at each location and the potential consequences of a leak. Several CMLs may be required for a particular component such as a butt and wrap joint, and more than one type of inspection may be required at any given CML (for example, UAX + visual + surface temperature readings where hot spots may cause cracking).

Damage mechanisms and failure modes affecting FRP piping

For all FRP equipment, there are three (3) damage mechanisms that can occur:

• Damage to the matrix, or resin, or
• Damage to the reinforcement fibers, or
• Damage to the interface of the matrix and fibers.

These can be expanded to identify that both mechanical and chemical forces play a role in the damage.

API 574 lists several types of damage associated with FRP pipe in service conditions that can be detected by UAX.

These include:

• Flaws due to poor design and/or construction 
• Erosion
• Chalking caused by UV damage 
• Material aging that breaks down the resin or fiber strength over time, and can be accelerated by exposure to some chemicals.
• Deformation or creep
• Star craze  or spider cracks
• Blisters: mechanical resin change
• Liner cracking or mud cracking

Other damage such as flange cracks which can be detected visually — without UAX — can cause mechanical changes to the resin and reinforcement.

Note that only one of the damage mechanisms listed by API – erosion – relates to thickness loss. For chemical process services, API 574 neglects a significant source of thickness loss, which is oxidation of resin. Most other damage mechanisms provided within API documents reduce structural capacity of FRP and do not coincide with thickness loss.

UltraAnalytix validation

UltraAnalytix NDT has been thoroughly tested and validated worldwide. More than 200 industry leaders use UltraAnalytix for FRP asset inspection in chemical processing, oil and gas, pulp and paper, mining and other industries.

It’s the only ultrasonic non-destructive testing method to provide Fitness-For-Service assessments for FRP composites by inspectors who are certified in accordance with SNT-TC-1A practice.

Furthermore, a new Welding Research Council (WRC) Bulletin (WRC Bulletin 601 — “Assessment of Existing Fiber Reinforced Polymer Equipment for Structural Damage”) — published in May 2023, now provides technical background and validation for this quantitative, non-destructive testing methodology.

In the Bulletin, I describe the challenges and solutions involved in determining the condition and fitness for service of aging FRP pressure vessels, piping and other equipment. WRC-601 provides guidance for including new methods for assessing FRP equipment in the consensus codes developed by the American Petroleum Institute (API) and American Society of Mechanical Engineers (API 579-1/ASME FFS-1), which are focused primarily on fitness for service assessments of metal pressure vessels and piping.

WRC Bulletin 601 is the first comprehensive resource that identifies the damage that occurs to the polymer and how to detect it for FRP pipe and other equipment after it is in service, to provide a rational, quantitative basis for determining fitness for service.

– Geoff Clarkson, P. Eng, FEC

UTComp Founder and Chief Technology Officer