1. welded joint: two sections of pipelines are connected by welding, which is suitable for high pressure and high temperature environment.

2. Flange connection: The two sections of pipelines are connected together by flanges, which are detachable and suitable for occasions requiring frequent cleaning or replacement.

3. Threaded connection: The two pipelines are connected together by threads, which is suitable for low-pressure small-diameter gas pipelines.

4. Clamp connection: the pipes are connected together by clamps, which are detachable and suitable for medium and low pressure and small diameter gas pipelines.