Production • Processing • Handling
Prior to installing the repair it is also necessary to perform a design evaluation in accordance to the relevant industry guidelines to determine the overall length and number of layers of material applied. Tis design process was conducted by the qualified technicians at site. Te stages of the repair are:
● Wetting out of the fabric. ● Applying a base coat to prime the steel surface. ● Hand lay up of the fabric and cutting to suit the repair geometry.
● Continual visual inspection of the layers of material as they are applied to ensure of no dry spots, sagging of the cloth, foreign debris in the repair, etc.
● Once the total number of material layers have been applied a peel ply material is applied over the complete repair area. Tis serves a number of purposes including: holding of the complete repair in position, allows excess resin to drain through and out of the repair and prevents any ingress of foreign matter into the repair .
● Once cured (up to 8 hours) the peel ply is removed. A final visual and depth measurement inspection of the repair is completed. A final corrosion coating is then applied to the complete repair area.
Utilising both materials and personnel on-site the separator was back in production within 36 hours from the original shut down and the complete field back in operation.
42-in suction line repair Inspection of a 42-in suction line at a storage terminal, identified a 90-ft section of serious external corrosion due to a breakdown of the originally applied corrosion coating in the region where the pipeline passed through the main bund wall. Initially it was not possible to determine the depth extent of the corrosion and initially manual excavation and coating removal was conducted to allow initial detailed NDT inspection to take place. Once it was determined the corrosion was within safe limits (in this instance below 80 per cent wall loss) the operator permitted blasting of the complete work area to take place prior to the composite repair installation. Although nearly the complete circumference of the pipe was affected the area of significant concern was between 3 to 9 o’clock where the corrosion extended for the complete 90-ft length. In this instance the line could not be isolated and no hot work was permitted. In addition there was very limited access to either side or beneath the pipe. Due to the memory matrix within a composite repair sleeve it is possible to install the sleeve using
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a ‘spool feeder’ technique which providing you have access from one side only requires 2-ins of clearance around the remaining pipe circumference. In total over 90 repair sleeves were installed to
cover the complete corroded area and to reinstate full load carrying capacity back to the pipeline. A suitable corrosion coating is then applied and the bund wall reinstated.
Corrosion repairs on risers Corrosion underneath holding clamps and at the splash zone are often encountered on offshore platforms. In these particular instances due to the high
service pressure +750 psi, commercial and technical considerations and for ease of installation a full cured composite sleeve is the most suitable composite repair option as a wet wrap system would have to be of a significant thickness and hence would necessitate a large volume of product which impacts all of the above factors. In addition the composite sleeve provides a fixed
and controlled final repair thickness and a structure that allows the riser repair clamp to be reinstated over the installed composite sleeve once the repairs have cured (the repair sleeve will cure within 2 hours from the start of the installation). Te overall length of the repair sleeves can be cut to accurately fit the axial length to be repaired and as previously discussed can be used to bridge girth welds where applicable. Once installed the complete repair area including the holding clamps are sealed with a suitable corrosion coating.
Conclusion As shown composite repairs are a viable repair solution for a wide range of applications including: high pressure pipelines, pipework, risers and complex geometries within a wide range of operating facilities and environments. In general a composite repair will provide a long term repair solution providing many benefits in terms of health and safety (no hot work, heavy lifting equipment etc) with associated technical and commercial benefits. In addition some repairs have now been utilised within the industry for over 20 years and have a significant amount of test and user reference data to support their use and application. ●
Enter 56 or ✔ at
www.engineerlive.com/iog
Andrew J Patrick is Vice President – Clock Spring Company, LP, Huntingdon, Cambridge, UK.
www.clockspring.com
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