A boiler end cap is a component of a boiler pressure vessel, typically used at both ends of pressure vessels. It also refers to the closed end of pipe-made welded pipe products. There are many different forms.

The head is a component of the container that is connected by welding to a cylindrical body. Depending on different geometric shapes, it can be classified into spherical, elliptical, conical, spherical cap, conical shell, and flat cover, among which spherical, elliptical, disc-shaped, and spherical heads are referred to as convex heads. The heads formed by butt welding and plug welding. Containers are used in various equipment such as storage tanks, heat exchangers, towers, reactors, boilers, and separation equipment. Materials include carbon steel (A3, 20#, Q235, Q345B, 16Mn steel, etc.), stainless steel (304, 321, 304L, 316, 316L, etc.), steel (15Mo3, 15CrMoV, 35CrMoV, 45CrMo), aluminum, titanium, copper, nickel, and nickel alloys.