When British and Norwegian prime ministers Tony Blair and Jens Stoltenberg attended the October inauguration of the 1,200 km Langeled pipeline – the world’s longest underwater gas pipeline, delivering natural gas from Norway into the UK’s national grid – the use of the latest compact connection technology in this major engineering project may not have been a significant focus during the media attention this event attracted. It is, however, part of a growing trend that is seeing the high performance SPO Compact Flange from Vector International used on pipelines, on and offshore, across the globe.

At a time of intense focus on environmental responsibility and close scrutiny of leakage and its environmental impact, not to mention the potentially high associated costs, it is not surprising that attention is increasingly being drawn to compact pressure connection and sealing technology that can help pipeline operators striving for leak-free operation.

The SPO Compact Flange from Vector International is reported to have never, in over 80,000 applications worldwide, leaked in service. “This is a connection technology that offers the zero-leak integrity of a girth weld, coupled with the versatility of a mechanical joint,” Vector Australia Business Development Manager Jim Friel says. “Moreover, it requires minimal through-life maintenance.”

The SPO Compact Flange uses an internal sealring, replacing the gasket of a traditional ANSI flange, which works with the seal faces to ensure face to face mating so that only low seating forces are required to compress the seal faces. It uses radial compression, like an ANSI flange, but importantly, due to a slight convex bevel to the face, combines this with a wedging action. When assembled the flange faces first make contact at the sealring, then at the heel as the pre-tension increases, until full face to face contact is achieved and the bevel is closed, with an environmental seal created at the outer edge.

Significantly, only a small proportion of the bolt pre-load is used to compress the seal. The majority is transferred through the mating flange faces with 90 per cent of the loading on the heel area, creating a static connection which is unaffected by internal pressure or external loads. “Once pressure-tight it will remain pressure-tight, providing a leak-free joint,” Mr Friel says.

Moreover, the design of the SPO Compact Flange is significantly smaller and lighter than conventional flanges – a feature of particular value offshore. Because a traditional flange relies on significant bolt force to maintain the seal, the bolts are larger, requiring bigger nuts, which in turn demands a wider diameter bolt circle to allow for tightening. The wider the diameter of the bolt circle, the more the flange becomes susceptible to bending, so thicker flange sections are required. This tends to result in significant size and weight, particularly at higher pressures, whereas the SPO Compact Flange’s reduced seal diameter and low seating forces requirement enables the size and number of bolts to be reduced. Where a 12 inch Class 2500 ANSI flange will weigh some 730 kg, for instance, an equivalent rated SPO Compact Flange weighs just 155 kg – a substantial 79 per cent weight saving.

Maintenance requirements are also minimised by using SPO Compact Flanges. Where ANSI flanges are known to be prone to leakage and require regular maintenance, SPO Compact Flanges require no periodic bolt tightening, and the internal sealring is protected from corrosion by the outer environmental seal. For long distance pipelines, particularly those running through remote or hazardous regions, ranging from desert to subsea, this is an attractive feature.

The Langeled pipeline, which uses SPO Compact Flanges in sizes from 6 to 28 inches, is one of a growing number of pipelines on which this latest technology is used, with significant interest in the flanges being shown by gas pipeline projects in Australia.

“Given the considerable performance advantages coupled with the minimised maintenance needs these leak-free connections offer, it is not surprising that operators are increasingly opting for this latest technology for onshore and subsea pipelines as awareness builds,” Mr Friel says. “Considering the high level of activity over the coming years in the Australian pipeline industry, interest is already high and is expected to grow.”