To replace or to wrap – the standardisation of composite repair

Corrosion, erosion and mechanical damage have long tormented pipework and pipeline maintenance engineers. For years the only credible solutions to damaged pipework were to cut out the section and replace it with new or welding sections, usually stopping production. In addition, the hot work required to complete the replacement prohibits use in many sensitive environments and the metallurgical problems caused by welding often add up to a costly, complicated solution.

As the pressures placed on pipe maintenance engineers have increased so has the use of mechanical clamps and composites. Composite repairs have become increasingly popular as an alternative to replacement, and particularly mechanical clamps, as they offer increased versatility, can be used in areas where clamps cannot and are often more cost effective. However, composite repairs have been an unknown in many industries for many years.

Although composite technology is widely used and understood by sectors including automotive and aerospace, and is well established in the glass reinforced plastic (GRP) pipe industry, its use for the repair for steel pipe had been based upon experimentation rather than mathematical design. This, compounded by inconsistent application standards, has led to composite repairs historically operating with varying degrees of success, and confidence in this technology not obtaining the same acceptance experienced by mechanical clamps.

Standards

The publication of two international standards in 2007 has changed all of this and this technology sector is growing rapidly. These standards are:

• ISO/TS 24817 – Composite repairs for pipework – qualification and design, installation, testing and inspection; and
• ASME PCC-2 Article 4.1 – Non-metallic composite repair systems for pipelines and pipework: high risk applications.

Now all aspects of composite repairs are governed by these standards, from the prequalification of materials and repair systems, to the design of a repair specific and ‘fit for purpose’ for the individual pipe defect that it is to repair, including the training and validation of applicators.

Here are some key considerations for the asset owner to be aware of with respect to compliant composite pipe repairs:

1. A repair is only compliant if the materials used have been tested in accordance with the above standards, on the substrate material requiring repair.
2. Composite repairs can be compliant on pipe with thinned wall and through wall defects, however, some products are only compliant to repair thinned wall defects but not through wall defects.
3. Each repair must be designed specifically for the application it is intended for.
4. If a pipe is suffering from an internal effect such as erosion or corrosion then the defect size at the end of its life must be estimated and a repair designed for the end of life condition. It is therefore essential that even if a pipe is only suffering from wall thinning that the repair must be, and designed for, ‘through wall’ if the defect will grow to become through wall within the life of the repair. This ensures the repair is fit for purpose throughout its life.
5. The two standards do differ in several ways, including treatment of temperature, geometries and repair life. In the majority of cases a repair can be designed to be compliant with both standards.
6. Repairs can be designed for a 20 year life and for the majority of complex geometries including bends, tees, reducers and even flanges. Tank repairs are also possible and made economical by ISO/TS 24817 allowing patch repairs.
7. Method statements should be supplied for each repair and this should include details of the repair design.
8. All compliant repairs must be applied by manufacturer trained and validated applicators and, as with ASME IX coded welders, it is the individual not the company which is validated.
9. Applicators validations lapse after 1 year unless they have completed 10 compliant repairs over that time.
10. At the end of their design life repairs are no longer compliant and should be removed or revalidated.

Application quality is a major part of these standards because, as with welding, even the best material in the world applied badly will not perform as required. The standards recognise that repairs must be applied to a certain standard, assumed in the design, i.e. the same manner as the compliance testing from which much of the performance data used in design is derived. They therefore require all training to be validated and pressure tests are required to test that an applicator can produce work to the required level.

SuperWrap

Harrogate, UK-based Belzona Polymerics Ltd has been at the forefront of this quiet revolution, participating in the development of the ISO standard as well as being a founding member of ACoReS (Association of Composite Repair Suppliers). Having provided composite repairs to industry for over 50 years and continuing to develop innovative and market leading technology, Belzona has designed repair systems to meet the rigours of the compliance testing for both through and thinned wall defects and be a truly versatile, fit for purpose, solution to pipe repair problems. Belzona has taken a different approach to many of its competition, developing systems designed to be as robust as possible to survive 20 years in an industrial environment, rather than looking just at pressure retention and pipe strengthening.

Based upon epoxy technology, using the highest quality, refined resins and performance enhancing fillers, in combination with high density treated glass fibre reinforcement, Belzona SuperWrap is easy and quick to apply while developing the highest possible adhesion to the pipe. This technology also means that the repair is chemically resistant to a broad range of chemicals and offers outstanding corrosion protection once applied.

Qualified for both through wall and thinned wall defects, Belzona SuperWrap has been extensively tested at pressures in excess of 250 bar and can be used in a huge variety of environments, on almost any geometry and over a wide range of temperatures. Further impact and accelerated weathering testing has ensured that Belzona SuperWrap is a robust fit for purpose repair with a wide range of potential applications.

In addition to product development and compliance testing Belzona has embarked upon an extensive training and validation program for hundreds of installers and supervisors in many key markets around the world.

The system is applied by first applying a paste grade product to the blasted substrate. This paste grade product, Belzona 1871, is designed specifically to offer maximum adhesion to the substrate throughout the full temperature range of the system. On to this, the high density glass reinforcement, wetted with a low density resin, is spiral wound onto the repair adding strength to the repair. Further paste grade product is then applied on top of the reinforcement layer. This process of paste grade, reinforcement, paste grade layer is repeated as required and the repair finished with a final layer of paste grade to give a robust impact resistant repair. Because this system uses a higher density glass reinforcement than most, typically only two or three spirals are required, significantly cutting application time when compared to other systems.

Applications

Belzona’s ISO/TS 24817 and ASME PCC-2 Article 4.1 compliant solution, Belzona SuperWrap, has been popular with many oil, gas and petrochemical clients and in this growing market, with its simple but effective application, the product is going from strength to strength. Additional interest has also been generated in other sectors including the water/wastewater, steel, paper and marine industries.

An example of what a composite repair system does and how it can benefit an asset owner is easily demonstrated with this case history. A produced water line on an offshore platform was holed and suffering wall thinning due to bacterial corrosion. The line obviously needed repairing and returning to service in the quickest possible time. The steel pipe was grit blasted to enable the repair to gain optimum adhesion and a Belzona SuperWrap composite repair was then applied by a factory trained Belzona SuperWrap supervisor. The total application took just 2 hours and the line was put back into service within 2 days; this time could have been substantially reduced with the application of heat.

This SuperWrap application was the first of many to be applied on this offshore oil platform, enabling it to return to production in a fraction of the time of the only other viable solution being considered, to replace the line. Other repairs on this line involved complex geometries such as bends and tees, and all were applied quickly and safely in this challenging environment. Several other lines on this platform were also repaired online, enabling the thinned wall defects to be rectified at a minimum of cost and inconvenience.

Clear benefits

The performance of composite repair technology is such that the client achieves a compliant, fit for purpose, permanent repair. The benefits are clear: reduced down time, reduced installation cost and long term solutions, all resulting in cost effective reliability for the asset owner and operator.