ExxonMobil UK is benefiting from a mechanical pipe connection that is equivalent to a weld, yet requires no hot work. Lokring connections have become commonplace within utilities and process systems that use national pipe size piping with a diameter of three inches or less.

Each Lokring connection is a permanent, metal-to-metal hydraulically formed seal and is therefore completely tamper-proof. The Lokrings are quick and easy to install and are ideal for situations in which welding is difficult or costly.

Exxon is using the Lokring connections at its refinery at Fawley, the largest refinery in the UK and one of the most complex in Europe. The refinery has a modern marine terminal that handles around 2,000 ship movements and 22 MMt of crude oil and other products every year. The refinery processes some 300,000 bbl/d of crude oil and supplies around 13 per cent of all petroleum products in the UK.

Boosting safety and productivity

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ExxonMobil Fawley Refinery Inspection Engineer Derek Savage says “Apart from the obvious safety benefit of not having to strike an arc, Lokring connections give the same integrity as a butt weld – they are leak-tight and permanent– whilst significantly improving the productivity of installations.”

He adds “ExxonMobil Chemical has also developed a ‘golden weld’ procedure, where a single Lokring can be fitted without the need for a hydrotest.

“This has been particularly useful in situations where a hydrotest is impractical or detrimental to process.”

The use of Lokring fittings – which have Lloyds Approval – was adopted from an ExxonMobil chemical fixed equipment network best practice.

All ExxonMobil installers, both staff and contractors, have been trained in the safe installation of the connections by their local Lokring distributor. Each has a unique installer number and certificate of competency. Every connection has a complete quality trail, as all Lokring components are fully material traceable.

A cross section of a Lokring connection

Mr Savage says “By minimising the need for welding, Lokring connections enable many overhead costs relating to safety, personnel, inspection and rework to be eliminated or substantially reduced. Indeed, in 2003, Exxon achieved some $US30,000 ($47,500) of production savings due to a quick repair of a propylene system. Other examples of their use include the replacement of a two inch hexane line from tankage, and the new butyl polymers line, which is being installed using Lokrings.”