Utilizing Innovative Technique in Pipework Maintenance Welding


Ashok Rai – Consultant, Weldwell Speciality Pvt. Ltd.

Pipework users across the entire industrial spectrum occasionally face the problem of having to repair or replace pipe sections or change in-line components such as valves and instrumentation. The conventional approach to these problems involves isolating and emptying the appropriate section. This might necessitate draining a large volume of product and could also cause serious interruption to production. An attractive and economical solution is to freeze the pipe contents upstream of the repair or component replacement zone. Alternatively, freeze both sides of the repair site and simply drain the material between the freezes.

Huntingdon Fusion Techniques, UK have now introduced these advance products in the form of Qwik-Freezer TM and Accu-Freeze™. These products can be used safely on iron, lead, stainless steel, copper, brass and plastic pipes.

Qwik-Freezer™ equipment utilises liquid carbon dioxide (CO₂) to freeze stationary water and other liquids in selected sections of pipe or tubing. The Qwik-Freezer® jacket (orange) is then wrapped around the pipe at a nearby upstream location and the nozzle on the jacket is then coupled to a cylinder of liquid CO₂ by means of a high-pressure hose. Liquid CO₂ is then injected into the jacket. By producing very low “dry ice” temperatures, Qwik-Freezer forms a secure in-line ice plug. This temporarily isolates the liquid in the system and allows repairs or modification to be made without draining or shutting off systems. Simplifies Pipe Repair and Modification for pipes up to 200 mm (8”) diameter.

Accu-Freeze™ is the advanced version which utilises liquid nitrogen technology to generate ice plugs capable of withstanding 140 bar (2000 psi) and can be used on pipes up to 305 mm (12”) diameter. These are now recognised as fast and reliable methods for temporarily isolating sections of pipe so that repairs and modifications can be made.

A typical process starts with simply wrapping copper tubing and placing an insulating jacket around the section of pipe to be frozen. The liquid to be frozen, is brought to a static condition (no flow). The Accu-Freeze™ wrap is placed around the pipe upstream from the section to be repaired. Next, set the recommended surface temperature of the pipe in the digital controller. Accu-Freeze takes over by automatically injecting the liquid nitrogen through the system over the in-line ice plug. When liquid CO₂ is injected into the space between the jacket and the pipe, it immediately expands to form solid carbon dioxide (dry ice) at a temperature of -78˚C (-108˚F) low temperature quickly freezes the contents forming a secure “ice plug” which seals the pipe. The “ice plug” forms only in the section of pipe covered by the jacket so the resulting rise in pressure is very small, and there is no damage to the pipe. The automated system monitors the surface temperature of the pipe and controls the flow of liquid nitrogen to maintain the required temperature. This can dramatically reduce the consumption of liquid nitrogen. These advanced systems also offer the opportunity to control the freeze remotely from a secure location and possibly reducing operator risks where lengthy exposure may be dangerous. Once the plug is formed, maintenance and repair can take place without draining or shutting off the entire system

Major Advantages:

• Saves valuable time and cost of product normally lost draining and refilling a system.

• Avoids complete shutdown of systems and equipment (as in a sprinkler or water supply system).

•Prevents waste of large amounts of liquid. Eliminates handling of wasted liquid.

• Safe and cost effective.

• Standard products to suit pipe and tube sizes. 

* Liquid carbon dioxide and liquid Nitrogen are relatively inexpensive!
Engineers in a wide range of industry sectors have taken advantage of these cost and time savings over the last decade.

For more details & availability contact nivek@weldwell.com

Applications / Usage of ACCUFREEZE – QWIKFREEZE