The pipe's surface melts due to heat being transferred from the coil. The fitting and pipe's constituent components mix when fused and in touch with one another; the polyethene's expansion facilitates this process due to the linear expansion coefficient, which also creates the welding pressure. The upper half of the fitting must be kept firmly against the surface of the pipe for the expansion to decide the incrementation of the welding pressure. As an example, the wrap-around Electrofusion Saddle Manufacturer in India with the bottom half is depicted in the drawings below. https://www.kaizenengineering.co.in/electrofusion-saddle.html 7774001062 / 7774001061 Plot No. 4/6, Sector No. 10 PCNTDA, Near Vishweshwar Chowk, Opp to Shivraj Industrial Premises, MIDC, Bhosari, Pune 411026. [email protected]