Introduction: Gas flame heating with oxy-propane is the most commonly used methods of applying preheat during in-service welding. Propane by itself does not give a hot enough flame for heating of high pressure gas pipelines, but can be used on low pressure pipelines/pipework. Gas flame heating is relatively cheap in terms of equipment needed, and it is versatile for site use.The disadvantages are:

• The welder has to stop working whilst heat is being applied.& bull; There are increased safety considerations due to the naked flame being used in close proximity to other personnel (i.e. welders and inspectors).
• Possible overheating may occur which leads to the integrity of the pipe will be comprised and the pipe must be replaced.
• Replacing an overheated pipe can cost in the region of £500,000.

Objectives:

To evaluate induction heating techniques to assess the suitability to improve welding process within National Grid.

Expected Benefits: To maintain preheat using induction heating for in-service hot tap welding and include it into business as usual.