Introduction to Hot-Air Welding

Among the many important elements of a successful thermoplastic single-ply roof installation, well executed hot-air welding of field seams, head laps, and flashing detail is critical to the system’s overall long-term durability. Professional contractors have improved their command of this process thanks to advancements in both welding equipment and membrane technology, but it still boils down to mastering three basic welding principles: temperature, speed, and welding pressure parameters management.

Installers would use a hand roller to provide enough pressure to connect the heated top and lower surfaces within the seam on a molecular level, with the goal of generating a monolithic roof system. The 1.5′′ welded seam becomes stronger than the next field membrane when done correctly. In the field, there are two basic ways for inspecting seams to ensure weld integrity: Confirm for voids around the edge with a blunt-tipped probe, and destructive cross-seam peel tests can be done to check homogeneity over the whole weld. The upper or lower surface will delaminate, or pull away, exposing the reinforcing scrim if done correctly.

While hand welding is still an allowed installation method, it has been – and continues to be – strongly influenced by external circumstances that can affect the overall quality and durability of the weld. External variables such as fluctuations in ambient air temperature or incoming line voltage, as well as human factors like “how quickly or slow is the technician welding?” or “is the roller pressure delivered consistently across every lineal foot of seam?” are just a few examples. Such conditions, while uncommon, can result in defective, partial bonding that are prone to breakdown over time.

The advancement and development of automatic welders over the last twenty-five years or more has given installers more control over the process and mitigated some of the external influences that could impair hand-weld quality. Roof experts can now control temperature and speed, as well as access other useful features and data, thanks to improved digital technologies. Contractors can specify particular temperature and speed settings and save recipes for easy retrieval after completing test welds at the start of each day. The machines digitally adapt to field conditions to maintain ideal settings, and the machine’s weight delivers steady welding pressure, which is often inconsistent or absent in the hand-welding process. As a result, there’s a better chance of getting consistent, predictable, and repeatable welding results.

Advancements in the industry are continuing to reduce the reliance on traditional hand-welding techniques for most detail work. Installers can automate the welding process over more lineal feet of production than ever before with today’s cutting-edge technology, which is flexible to changing roofing requirements. The industry has gained increased quality control capabilities, as well as improved ergonomics and worker productivity, as a result of this progression.

While equipment manufacturers work to develop the next generation of automatic welders to meet future demands, thermoplastic and membrane manufacturers work to improve formulations and bring new products to market that allow welding in a wider range of temperatures and conditions – a wider “installation or welding window.” All of this, in combination with industry initiatives to increase contractor training and certification programs, will continue to aid in the reduction of warranty concerns relating to weld integrity and the creation of higher-performing roof systems.

Post: Introduction to Hot-Air Welding

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