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It is well documented that applying heat prior to, during and after welding high-strength steels can minimize the risks of weld failure due to hydrogen-induced cracking. However, preheating and post-heating the metal using an open flame from a propane torch can pose quality and safety challenges in extremely cold environments.

Open flame preheating of pipe is a very common practice in pipeline construction, but can be very inconsistent when trying to ensure uniform preheat temperatures. Another issue, especially on projects in cold climates, is that water vapor produced during the combustion of propane condenses on the cold pipe internal diameter away from the heat zone, creating frost and water — a potential source of hydrogen contamination when welding.

Regarding safety challenges, propane lines may become stiff and break in cold weather, a potentially dangerous situation that can result in propane fires. In addition, there is the logistical challenge of transporting the large propane tanks to the work sites, which can be in remote locations with harsh conditions, especially in the northern climate pipeline industry.

One way to address these issues when preheating for welding in sub-zero temperatures is to use induction heating — a noncontact method of electrically heating conductive materials. Induction technology provides faster, safer and more consistent heating when compared to using a propane torch.

Induction heating drives and keeps moisture out of the weld to help prevent hydrogen-induced cracking and it offers the welding operator the ability to monitor and control the temperature. Induction heating also eliminates many of the hazards posed by propane.

Miller offers induction heating systems that are easy and quick to set up and use. Induction heating with these systems has proven successful on even the harshest jobsites in Canada and Siberia, where temperatures can dip to -40 degrees Celsius.

Topics that will be discussed in this presentation include the background on induction heating; the benefits of induction heating including productivity, quality and safety improvements; and how induction heating compares to other preheating methods in cold weather applications. In addition, examples of welding successes on pipeline applications will be presented.