Line Freezing & Pipe Freeze Plugging Services

Furmanite’s Line Freezing & Pipe Freeze Plugging Services – Keeping Critical Pipe Systems Online and Preventing Unwanted Shutdowns…

For over 80 years, Furmanite has made it our business to keep critical pipe systems online and prevent unwanted shutdowns. As part of this commitment, we are proud to offer Pipe Freeze Plugging also known as Pipe Freeze Stopping. Freeze Plugs are an alternative option to our Line Stopping services and are designed to effectively isolate sections of pipe where valves are unavailable or inoperable. Through a combination of Furmanite’s Hot Tapping , Line Stopping, and Pipe Freeze Plugging services you can be assured that your pipe systems will stay in service 24 hours a day, 7 days a week. Put us to the test and you will see why at Furmanite, “We work best – Under Pressure”.

Pipe Freezing Technology

An effective means of system isolation, freeze plugs are developed within the pipe system through the application of CO2 or liquid nitrogen. The cryogenic process begins with heat being drawn from the product inside the pipe until it reaches a temperature below its freeze point. Once an established freeze plug is formed, the Furmanite technicians will monitor the flow of liquid nitrogen to maintain the proper sized plug based on known system parameters.

In order to establish an effective freeze plug, it is critical that the system has no flow and the freeze plug must be an established distance from any flowing pipe branches or headers. In the event that systems can not be blocked in or flow must be maintained, consider Furmanite Line Stop Services as a safe and effective alternative.

How it works

Pipe freezing involves the use of liquid nitrogen in the controlled formation of a solid ice plug inside the pipeline using specialist equipment and techniques. Once formed, the plug is able to withstand very high differential pressures and provide reliable and effective isolation of the line while modifications or repairs are carried out.

Pipe Freezing Services can be used to perform any of the following routine system modifications

  • Valve Installations
  • Pipe Section Replacement
  • Equipment Isolation
  • Pipe Branch Terminations
  • Pipe Relocations

Pipe Freezing is suitable for use on a wide variety of pipe materials and contents, including:

Typical pipe materials:

  • Carbon Steel
  • Nickel Alloy
  • Copper-based Alloys
  • Kunifer
  • Aluminium Alloys
  • Stainless Steel

Subject to certain qualifications, coated and lined pipes can also be frozen.

Typical pipe contents:

  • Water
  • Acids
  • Coolants
  • Paints
  • Alcohols
  • Oils
  • Liquid Food Products
  • Various Chemicals


Pipe freezing has many applications in a variety of industries, including nuclear and fossil power generation, offshore oil and gas production, refineries and petrochemical plants.

Single or multiple freeze isolations can be applied on-line in pipes up to 48″ in diameter, to allow:

  • Valve repair/replacement
  • Pipe modifications/maintenance
  • Miscellaneous intervention procedures

Typical pipe freezing applications include:

  • Cooling Water
  • Fire Protection Systems
  • Process Systems
  • Fuel Oil Lines
  • Sludge Lines
  • Hydraulic Control Lines
  • Domestic/Utility Water Systems
  • Hydrocarbon Risers
  • Water Injection Lines
  • Drill Pipe Sea Water Ballast
  • Heat Exchanger Lines
  • Boiler Feed and Condensate Systems
  • Lube Oil/Governor Oil
  • Pressure Vessel Cooling Systems
  • Chilled Water Systems

An important aspect of our pipe freezing procedure is the use of the latest Heat Flux Monitoring techniques. The use of Furmanite Heat Flux instrumentation systems offers considerable operational and safety advantages:

  • Growth of the plug is monitored, alerting operators to any problems which may arise due to excessive temperature or flow.
  • Final plug formation is positively confirmed, prior to intervention.
  • The thermal stability of the plug can be constantly checked, providing early warning of any change in conditions that might threaten the integrity of the isolation.

Quality and Safety

Furmanite’s standard pipe freezing procedures specify the use of personal oxygen monitors for all pipe freezing personnel, to guard against the risk of oxygen deficiency due to vented nitrogen gas. The pipe freezing process is fully controlled by formal written procedures which form part of Furmanitefs ISO9001 quality control system. All cryogenic equipment is regularly inspected, maintained and certified, to statutory requirements (and beyond where necessary).


Pipe freezing is widely acknowledged as a safe, reliable and highly cost-effective method of temporary pipe isolation and as a result offers a number of major benefits:

  • No need to drain down systems, thus avoiding costly and time-consuming venting procedures.
  • No need to arrange for the bulk transfer or storage of possibly toxic or corrosive fluids.
  • Cuts losses of expensive liquids, such as treated water and systems inhibitors.
  • Overcomes the problems of handling hazardous materials and enhances safety when working on lines containing contaminated or volatile liquids.
  • In many cases pipe freezing allows maintenance work to be carried out without interruption to continuous process systems.

Controlled isolation

Furmanite’s controlled pipe freeze isolation technique uses gaseous nitrogen and ensures that the equipment is not taken outside its design limits, reducing the risk of embrittlement. The freezing jacket provides an annulus around the pipe into which gaseous nitrogen is introduced, with no direct contact between the gaseous nitrogen and the pipe.




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