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 products made from pipes. There are many different forms.

The head is a component of the container that is 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 them, spherical, elliptical, disc-shaped, and spherical-headed ones are referred to as convex heads. The heads that are joined by butt welding are known as socket welding 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.