Contingency measures to mitigate leakage risk

Any breach of pipeline integrity can be extremely costly – with the cost potentially manifesting itself in anything from loss of product, reduced performance, downtime and repair costs, to environmental or safety issues and fines, or a negative impact on corporate image and share price.

Closure of one key pipeline for two months last year after it was damaged by a ship’s anchor, for example, highlighted the massive cost and severe disruption to production that was caused. Such examples underline the high value that contingency repair clamps can offer, to avoid or minimise risk and exposure in the event of a leak.

These clamps can enable leaks to be dealt with immediately, at a cost that is likely to be far less than the potential financial impact of a leak, particularly if the leak forces platform of pipeline shutdown when the cost can very quickly run into millions. However, because the need is not always fully recognised, and further, it can be debatable whether such contingency measures should be covered under capital expenditure or operating cost, potentially expensive risks could be being taken unnecessarily. While self-sealing repair clamps are well recognised for their value as a quick and economic means of repairing a leak without requiring shutdown, the lead time required is less well recognised. Evidently this has to be taken into

account if the clamps are to be used as an emergency measure.

These are not an off-the-shelf item, and stringent regulations and standards mean that they can rarely be produced for fast delivery. If exotic materials are involved, or particularly large diameters or high pressures, the lead time is extended further. While operators may assume that a repair clamp can be prepared in the same time that it will take to prepare the pipe and get a dive vessel for subsea lines, in fact the clamp may well take longer. Contingency measures A far more cost-efficient route, therefore, is to have emergency leak sealing contingency measures in place. Having self-sealing repair clamps held in readiness for immediate application should the need arise (whether the need is an actual leak, or severe wall thinning for example), will serve to mitigate exposure and risk.

This will be all the more valuable where hefty penalty clauses may be in place in the event of a leak, or in world regions where environmental conditions increase the risk. Split sleeve mechanical repair clamps, such as FurmaSeal clamps available from specialist engineering and technical services company Furmanite West Africa, can meet this need, being designed for the emergency containment of pipeline defects. Available in 2 - 48 inch nominal bore and pressure ratings to over 3,625 psi or 250 bar, with higher pressure ratings and special configurations such as tees, elbows, and flanges available on request, these clamps are installed on the pipeline to repair or provide reinforcement without interrupting normal operations. No sealing compound is needed, and no welding required, as the clamps use flouro-elastomer seals.

These are compressed and loaded by bolting around each end of the clamp and between the two clamp halves, producing a highly effective, mechanically-actuated high integrity seal. Cross-asset benefits Moreover, more recent developments from Furmanite mean that the clamps no longer need to be asset-specific (whereas idiosyncrasies in pipeline dimensions have traditionally meant clamps in relevant sizes for each different line were required). This makes holding contingency clamps in readiness a truly viable measure, as these ‘crossasset’ clamps can be held for application on a number of different lines.

The clamps deploy an innovative system of interchangeable inserts and seals, and are able to accommodate variations of more than 30mm in nominal outside diameters, and out-ofroundness, while still meeting the critical requirement that the clamp fit properly to avoid extrusion that would compromise the seal. FurmaSeal subsea clamps Pipelines Bulus Sambo, Furmanite West Africa, discusses developments in contingency leak sealing. Contingency measures to mitigate leakage risk 46 Oil Review Africa Issue Two 2009 A cost-efficient route is to have emergency leak sealing contingency measures in place. Furmanite 24in cross asset clamp.

Based on the FurmaSeal split sleeve fitting and flouro-elastomer seals concept, the circumferential seals are loaded in the axial direction and activated using a separate flange or glanded arrangement at each end of the clamp, which cause radial expansion and compression against the pipe surface. The inserts or segments create an anti-extrusion system to prevent the seals being pushed out of the clamp by the pressure. These slide on tapers to span the annulus between the outside of the pipe and inside of the clamp. As they slide inwards they are able to accommodate the range of pipe diameters allowed for. The near-tangential bolting is tensioned or torqued to load the seal, and virtually eliminates bending and distortion, to ensure that the seal is maintained. The use of two seal sets enables successful installation to be proven by pressurising the interspace between the two seals, without having to subject the pipe itself to additional loading or pressure. It also allows periodic re-testing to confirm the integrity of the seal during the clamp’s lifespan.

Sacrificial anodes are incorporated to provide cathodic protection for this period. Finite element analysis (FEA) and the use of cast steel bodies has enabled optimum use of materials and minimised overall weight, while retaining the shell thickness and bolting requirements necessary to accommodate the high pressures. The advantages of holding contingency leak sealing clamps as a risk reduction measure are increasingly being recognised around the world.

The Azerbaijan International Operating Company (AIOC) operated by BP, for example, has taken steps to ensure that pipeline contingency repair equipment is available for AIOC subsea lines in the Azerbaijan sector of the Caspian Sea. A number of high pressure cross asset pipeline repair clamps are held for use should the need arise on the 185km 30 inch oil pipeline and 28 inch gas pipeline between Central Azeri and Sangachal Terminal and the 18 inch infield gas pipeline between the Central Azeri and Chirag platforms, as well as for the Shah Deniz and Azeri in-field lines including water, gas, condensate and water injection lines. In another instance, leak sealing contingency measures were put in place by an operator in the Middle East with the purchase of a range of self-sealing leak sealing repair clamps for offshore installations. Eight high pressure contingency clamps in 8 and 12 inch nominal bore sizes have been supplied to the operator for use on hydrocarbon pipelines and risers to pressures of 140 bar, for short notice deployment should the need arise. In other cases, the clamps are being used as a preventative measure. In one such example, FurmaSeal high pressure repair clamps are being used on a subsea gas pipeline in West Africa where the line has sustained damage, to prevent any potential leakage.

A number of ten inch clamps in lengths of 25, 39 and 55 inches, and tested to 2,160psi, fitted over the damaged sections will ensure that even in the event of the defects progressing to through-wall damage, no leakage will occur. In another similar case, bespoke subsea sealing clamps designed by Furmanite were installed to reinforce lines where internal corrosion had caused wall thinning. The clamps were purpose-designed and built for installation by divers on the 26 inch crude oil line. Each measuring 1.2 metres in length and designed to a 275psi rating with a 25 year design life, these clamps were engineered to provide the necessary strengthening in three affected areas adjacent to radial butt welds, by encapsulating and sealing the damaged areas to ensure no leakage could occur, even in the event of continued wall-thinning. Using this technology is a highly costeffective route to maintain pipeline integrity, but clearly there remain instances where no such contingency measures are in place, leaving the operator exposed to potential risk.

Where this is down to up-front cost (particularly for smaller operators for example), this obstacle can be overcome by operators collaborating to hold a number of cross-asset contingency leak sealing clamps for use in case of emergency (and replaced by the user), thereby spreading the cost. In other cases, the obstacle may be one of budget allocation, and whether contingency repair clamps fall under capital expenditure or operating costs; an issue that needs to be addressed with joined-up thinking and greater communication between budget holders. Fundamentally, however, greater acknowledgement of the full extent of the risks, and recognition of the value that contingency measures in the form of leak sealing clamps represent, is required. After all, if a leak does occur, the cost of a contingency clamp is likely to be recouped several-fold. ■

Pipelines 48 Oil Review Africa Issue Two 2009 Furmanite contingency repair clamp Furmanite cross asset clamp

 

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