An online conference for Everybody in the Midstream Pipeline Industry
The use of composite repairs for restoring integrity of pipelines has been expanding since the late 1990s. The first efforts to standardise their use commenced in Europe in 1999 and this work acted as the starting point for both ASME PCC-2 Article 401 and 402 and ISO 24817. These standards are now used as the basis of the majority of composite repairs installed on pipelines globally. The standards set a large number of requirements to ensure the repairs restore integrity. To illustrate this burden it is noted that PCC-2 Article 401 is about four times the average length of the other 33 articles in the standard that cover traditional repair methods. It is difficult for someone unfamiliar with composites to ensure such a large number of requirements are complied with, particularly when their nuances are difficult for a non-expert to appreciate.
The main areas covered by the standard are:
The first point to note is that the guidance was written to cover all pipes – including those in plants and refineries as well as pipelines. This can create some confusion given the construction codes may have different design philosophies.
The second point to note is that the standards differentiate between repairs to two distinct types of defect – Type A and Type B. Type A defects are defined as those that are not leaking nor expected to leak during the life of the repair (typically caused by external corrosion and discovered before they go through-wall). Type B defects are those that are leaking or, critically, are expected to go through-wall during the life of the repair (typically defects caused by external corrosion but discovered after the pipes had started to leak or those caused by internal corrosion). For pipelines, the standards are intended only to be used for repairs to Type A defects.
The qualification requirements define a repair system as the combination of the repair materials, pipe substrate and method of surface preparation used. The adhesion between the repair materials and pipe is dependent on all these variables and not just the repair materials. This point is probably the one most commonly overlooked, with surface preparation methods readily changed on site to suit what is available or considered acceptable, whereas this is NOT allowed by the standards.
A range of design approaches are given but they are all driven by pressure requirements. This works well for pipes in plants but clashes with the philosophy of design for pipelines where wall thickness requirements may change with the routing and location of the line. Designing in full compliance with the standards may therefore change the design philosophy of a pipeline and unintentionally reduce the pressure capability of the line (reducing the factor of safety imposed as part of the original design).
For pipelines, the design methods are only applicable to defects, such as corrosion and wall thinning, where burst strength is the major concern and the methods are not sufficient on their own to define repairs to defects, such as dents or cracks, where fatigue performance is the main issue.
Requirements for training of installers are given as are requirements for installation controls. These are intentionally restrictive to ensure expected performance is achieved. These requirements may not be enforced at site because they can be inconvenient, but this could lead to repairs not performing as intended; the requirements need to be clearly understood and complied with.
These points will be expanded on in the presentation to give the listener a greater understanding of the requirements within the standards and what constitutes best practice.
Dr Hill studied long term performance of composite materials for his PhD at Cambridge University in the UK. He has over 20 years of experience with pipelines and has sat on the ISO 24817 committee and ASME PCC-2 401 work group since their inception.
TEAM, Inc. is a global leading provider of integrated, digitally-enabled asset performance assurance and optimisation solutions. The company deploys conventional to highly specialised inspection, condition assessment, maintenance and repair services that result in greater safety, reliability, and operational and economic efficiency for clients' most critical assets.
A professional team of experienced engineers, technicians, and client support personnel backs each service armed with the best on-the-job safety and service training, equipment, and technical support in the industry. Through locations in more than 20 countries, TEAM, Inc. unite the delivery of technological innovation with nearly a century of progressive, yet proven integrity and reliability management expertise to fuel a better tomorrow.
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