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

The head is a component of the container, connected and welded to a cylindrical body. Depending on different geometric shapes, it can be categorized into spherical, elliptical, conical, spherical cap, conical shell, and flat cover types, among which spherical, elliptical, disc-shaped, and spherical heads are referred to as convex heads. The heads that are joined by butt welding are known as socket-weld heads. Containers are used for 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.