Purging system cuts argon costs

Gas supplier BOC worked with Huntingdon Fusion Techniques to reduce argon consumption in the welding involved in multi-million pound liquid gas facilities currently under construction in the UK.

The multi-million pound facilities currently under construction near Milford Haven underpin a major project to receive gas in liquid form from Qatar and distribute it throughout the United Kingdom via a 128km long pipeline link between the port and a terminal near Gloucester.

A receiving station will transport liquified gas from the ships to massive storage tanks each holding 160,000m3.

Handling the liquid and transporting the gas places the total project among the biggest global engineering achievements being currently undertaken.

An integral part of the project involves welding of large diameter stainless steel pipework which is used between the unloading jetties and the storage tanks.

Two leading engineering construction companies are currently undertaking the fabrication work.

It became clear during the early stages of the welding operations that consumption of argon, used as a protective gas to purge air from the weld zone and prevent contamination of the stainless steel joints, was extremely high.

To reduce gas consumption, gas supplier BOC worked with Huntingdon Fusion Techniques (HFT) in nearby Burry Port.

An innovative and more eco-friendly solution was developed and the HFT Argweld Quick Purge system was selected to reduce gas wastage.

The benefits were noted immediately.

Gas consumption dropped by 90%, saving over GBP 2500 per month for the contractors.

To date since the initial contact Huntingdon Fusion Techniques have supplied 15 complete quick purge systems to the fabricators.

The liquid methane transit and storage pipework is all fabricated from stainless steel to grade 316 and to pipe standards between schedule 10 and schedule 100.

With pipe diameters ranging from 200 to 750mm and typical lengths of 10m the demands on handling and welding to meet the stringent joint acceptance levels impose particularly high-quality control standards for which specific procedures have been developed.

The original welding procedure called for gas purging of the pipe diameter prior to and during welding to be undertaken using proprietary foam dams.

The engineers noted that the dams were taking a long time to locate in position and to remove after welding but of even more concern was the very high consumption of argon gas during the purge process caused by leakage.

Specialist weld purging company Huntingdon Fusion Techniques (HFT) was contacted and technical staff examined the problem.

Within a matter of hours HFT staff had identified a potential solution and drove across to Pembroke with a selection of purge systems which would allow the fabricators to carry out controlled tests.

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