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United Kingdom |
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New pumping development strengthens chocking system
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Minimizing wear and fatigue on caisson and risers with cast-in-situ resin chocking.
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SmartShim is a patented chocking system from Furmanite that is designed to prevent costly damage to conductors or caissons created when the lateral force of wave movement causes them to impact against the conductor guides, resulting in fatigue or even fracturing. The shim slips are manufactured from a PVC-proofed nylon and are filled with a special polyurethane cast-in-situ resin, thereby form-fitting to the gap between the conductor and the guides, whatever the dimensions (see picture). Importantly, the shim is engineered with sufficient elasticity to absorb wave energy effects, while holding the riser or caisson firmly in place within the guides.
Installation time on offshore platforms has now been reduced. The cast-in-situ shim system has undergone a new development that adds a high degree of control and flexibility, and makes the service even more efficient – with valuable benefits to operators. This has already been demonstrated on one North Sea platform, where gaps as large as 750 mm – the largest undertaken to date – were shimmed with significant time efficiencies.
The latest improvements to the shim system are: a new pump skid that fully automates mixing and pumping of the resin on-site – a key element in installation – for maximum precision and control, and a speedier process. It also means the process is more environmentally friendly. Precision and elimination of human error in the ratio and mixing process are further benefits of the new system, in which the whole process is monitored from a control panel by a company-trained operator.
Moreover, because (apart from one short length of hose) the pumps and hoses contain only unmixed components, the process can be stopped and started again if necessary without concerns over the resin having begun to cure in the hoses and pump. This provides maximum flexibility and minimum time demands, particularly valuable offshore, where setting up and cleaning downtime can be reduced from every day to once a trip.
The benefits of the improvements were exemplified in the installation of shims on some 10, 20-in. nominal bore risers on one North Sea platform, situated at the plus-10-m elevation guides. Damage was being caused at the guide location due to excessive movement at the wellheads and the existing centralizers not being designed to absorb any shock loading.
Despite the large gaps being chocked (750 mm), as a result of the new developments, installation time was reduced to just two days per conductor, including curing time, as opposed to 4 – 5 days previously.
A full-scale workshop trial was undertaken in advance of this project, including building a mock-up of the conductor and guide to facilitate load tests and prove that the system worked before going offshore. Following installation, a further four risers are due to be chocked on the platform using the system. 
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