Regular assessment of in-service fiber-reinforced polymer (FRP) assets provides critical information about their Fitness For Service (FFS) that enables asset owners to:
- maintain uninterrupted operations
- ensure personnel safety
- efficiently plan repairs and maintenance, and
- budget for capital expenditures.
However, while 200+ consensus codes and standards currently provide guidance on the design and construction of FRP equipment, a gap still exists in consensus guidance to assess FRP equipment once it is in operational service.
Fortunately, work is under way to close this gap, as detailed below.
Development of a proposed new part for API 579
Work is now under way by the ASME/API Fitness-For-Service Joint Committee (FFSJC) project team on a new part for API 579-1/ASME FFS-1 for evaluating FFS of FRP assets.
The new part will include in-service FRP composite equipment for the first time. (Currently the standard focuses primarily on FFS assessment of metal pressure vessels and piping).
Technical documentation for the new part includes Welding Research Council Bulletin 601, which provides reliability engineers with a technically valid, quantitative and repeatable process for evaluating in-service FRP assets.
Once approved, Part 16 — “Assessment of Fiber Reinforced Polymer Equipment” — will provide FRP asset owners with something they’ve never had before: a consensus-based set of engineering tools to reliably assess in-service FRP equipment quickly, safely and non-destructively.
The proposed new part includes the following FRP testing and evaluation methods:
External visual inspection
External visual inspection is the first step in determining Fitness for Service of FRP composite assets. A systematic process/program includes:
- Support Structure: Structural support of the vessel such as the concrete pad or steel structure and any anchors.
- External Condition: The condition of the outer surfaces associated with the vessel, including insulation, cladding, vessel shell and roof, and paint and coatings.
- External Components: The presence and condition of overflows, pressure relief, vacuum relief, venting, external attachments, and seal pots.
- Pipe and Nozzle Connections: All flanges and connections to them.
Acoustic Emission (AE)
Acoustic emission tests identify imperfections in FRP and composite materials by detecting mechanical vibrations generated by material defects such as cracking and debonding.
Acousto-Ultrasonic (AU)
Acousto-ultrasonic (AU) testing combines aspects of AE and ultrasonic testing by introducing ultrasonic pulses to stimulate stress waves which are then analyzed to detect variations and damage in the material.
Attenuation-Based Ultrasonic (UAX)
Attenuation-based ultrasound involves transmitting ultrasonic pulses and analyzing how the signal changes or weakens as it passes through the material being tested. Analysis of these changes in the ultrasonic signal is used to identify cracks, voids and other defects that may affect the performance of the material. (UTComp’s UltraAnalytix NDE system is a UAX method that uses a proprietary algorithm to quantify polymer condition to assess fitness for service and remaining service life.
UltraAnalytix NDE (UAX+)
UltraAnalytix NDE is based on several standard practices for where to obtain data, external inspection, and other standards, including API 653 and 570. When used together, these provide all of the requirements for the proposed Part 16 update to API 579 assessment. All inspection processes included in the UltraAnalytix system are aimed at detection and evaluation of the condition of FRP using the primary damage mechanism of visco-elastic creep.
A comparison of non-destructive evaluation methods follows in the table below:
Non-Destructive Evaluation (NDE) Methods for FRP
Comparison of NDE methods for determining Remaining Strength Factor of FRP for completion of Assessment as per proposed Part 16 update to API 579-1/ASME FFS-1: