In the manufacture of air duct heater system, welding is a very important step. Most of the system is transported by pipeline, so the connection between pipeline and pipeline, between pipeline and other parts, except bolt connection, is welded. First weld the flange to the pipe, and then connect the two pipes by bolt connection. Because the pipeline is sweet hot oil, so the temperature and pressure are relatively high, the quality of welding directly affects the quality of the whole system. It can be seen that welding process is an indispensable step in the design of heat transfer oil system.

Welding is a process of local rapid heating and cooling of air duct type electric heater. Due to the restriction of the body around the workpiece, the welding area which can not expand and contract freely will produce welding stress and even deformation in the weldment after cooling.

The air duct type electric heater is composed of body and control system. The heating element is made of stainless steel pipe as protective sleeve, high temperature resistance alloy wire, crystal magnesia powder, which is formed by compression process. The control part adopts advanced digital circuit, integrated circuit trigger, high back pressure silicon controlled rectifier, etc., which can adjust the temperature and constant temperature system to ensure the normal operation of the electric heater.