Pipe Freezing is a method of creating a safe temporary barrier in a pipe system. The use of ice plugs as a barrier means that maintenance and modification work can be carried out without the need to fully shut down a system, which would lead to costly loss of production.

Ice plugging has been used on dimensions from 20mm (tubing) to 30" and can be utilised on all metals used in the petroleum industry. Freezing can be performed on several different flow media, for example:

• Fresh water / sea water
• Oils
• Diesel
• Gels (preferably used in gas systems that are not normally liquid-filled)

Temporary freezing of pipes will not change the microstructure or physiological properties of the metal even at cryogenic temperatures (-150˚C and lower). Ice plugs can be established independently of the pressure on the system fluid. Higher pressure leads to a more compact and "strong" ice plug.

We have performed ice plugging in the field to withstand 600 barg in differential pressure. Ice plug pressure testing has been performed during full scale testing with up to 1000 barg differential pressure.

Freezing of pipes is performed by twisting a copper loop around the sections to be frozen. Liquid nitrogen is then injected through the copper loop so that the flow medium freezes. We regulate nitrogen supply and ensure that temperature exposure is within operational criteria.