Mid Line Weak Link testing accumulation - Is it necessary?

By Gareth Black posted October 28th 2021

Flint Subsea have published previous news articles detailing the rigorous testing of their Mid Line Emergency Weak Link (MLWL) Emergency Quick Disconnect (EQD) devices (Flint Subsea News). In this article, we are going to explain why accumulation is not required during testing of the Flint Subsea MLWL.

Mid Line Weak Link EQD in test tank
Mid Line Weak Link in Flint Subsea's on-site test chamber

Many clients are asking that weak link and safety joints devices are tested with an accumulator in the line to ensure that the pressure stays high throughout the disconnect stroke. This represents the realistic scenario where there is effectively an "infinite" pressure source maintaining pressure regardless of volume changes or leak paths (loss of containment) which might form during the emergency disconnect cycle.

Tackling volume changes first. The Flint Subsea Mid Line Weak Link is pressure balanced throughout the disconnect stroke, including prior to and during closure of the valves. This ensures that there is no volume change in the device throughout and the pressure remains constant. During full pressure disconnect testing, it is possible to stop stroking. The device will stop and remain at full pressure without external interference or additional pressurization. It does not try and “pop” apart or reconnect, which demonstrates that the device is pressure balanced.

Regarding loss of containment, which would require high degrees of accumulation to maintain pressure in the device. The Flint Subsea MLWL is designed so that it does not release until both upstream and downstream valves have closed. Only when this has happened does the unit separate releasing the swept volume of fluid, which for the 2” 10ksi device is only 0.6 liters. Even if the load is removed from the device part way through stroking, containment is not lost. In fact, at no point during disconnection is there a direct leak path, or even potential leak path, from bore to the environment.

With the above taken into account, accumulation is not required during testing of the Flint Subsea Mid Line Weak Link.

This testing is performed at Flint Subsea’s global headquarters in the United Kingdom. Flint Subsea are a global specialist in the supply of Mid Line Weak Link (MLWL) Emergency Quick Disconnect (EQD) systems. Their devices have been certified by DNV to API 17G, ISO 13628-7 and API 6A. The business has been operating since 2013 and are an ISO 9001 certified business. www.flintsubsea.com

Flint Subsea affiliations

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Stanlaw Abbey Business Centre,Ellesmere Port, CH65 9BF,
United Kingdom

Email: enquiries@flintsubsea.com
Phone: +44 1244 886 090

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