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HFT equipment allows in-situ pipeline repair

Published by
World Pipelines,

Huntingdon Fusion Techniques has launched the Accu-Freeze™ System, which allows pipeline repair to be conducted in-situ. Accu-Freeze™ Pipe Freezing System, available in Europe from Huntingdon Fusion Techniques HFT®, makes it possible to create an ice plug either side of the repair zone to allow work to be carried out without draining the whole system.

Luke Keane, Technical Support at HFT® said: “We recently carried out an installation of an Accu-Freeze™ System in Serbia for a client who was contracted to repair pipework in large blocks of apartments. Working in the plant room, access was pretty tight as the pipes were only 6 – 8 in. from the ground. At one end of the pipe there was a pressure gauge and at the other, a 1000 l hot water cylinder. Ambient temperature in the pipe was approximately 38ºC.

We used a copper coil on the 2 in. carbon steel pipe and had to wrap it about 10 in. along the pipe length, wound tight. We then performed a freeze using the Accu-Freeze™ System connected to a dewar of liquid nitrogen (LN2). Within 50 min. a solid ice plug had been formed, blocking the flow from the cylinder to enable the pipe section to be cut out and replaced. Following the repair work, the ice plug defrosted naturally and the flow continued in the system. Minimum disruption, no system drain down, no air locks and extremely quick!”

Accu-Freeze™ utilises LN2 in a controlled way to freeze stationary liquids in a selected section of pipe or tube. By controlling the surface temperature, Accu-freeze™ can accurately and safely form an in-line ice plug, capable of withstanding 138 bar in diameters up to 12 in. (300 mm).

To form an ice plug, the water or liquid inside the pipe or tube is brought to a static condition and an insulated jacket is placed around the section to be frozen, upstream from the repair zone or a copper coil wound the pipe.

Once the ice plug is formed, maintenance and repair can take place without draining or shutting off the entire system. The controlled ice plug only forms beneath the Accu-Freeze™ jacket or coil, it does not expand outside of this area and does not create enough pressure to affect the integrity of the pipe.

The primary advantages of the patented Accu-Freeze™ System include the increased freezing capability of LN2 and the ability to control the pipe wall temperature throughout the freeze process.

The LN2 injections are automated which reduces the operator’s workload and reduces the amount of LN2 that is consumed, reducing operating costs. Accu-Freeze™ can also be operated remotely, which makes it ideal for use inside ‘hot’ nuclear areas where personal exposure must be kept below certain limits.

Edited from press release by

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