Head refers to the component used to seal the end of a container to isolate the internal and external media, also known as an end cap. The head of a cylindrical descriptor is usually a rotating shell. According to the shape of the head surface, it can be divided into convex, conical, flat, and composite shapes. Convex head refers to a head with a convex outer surface shape, such as a semi spherical, elliptical, disc-shaped, and non folded spherical head. Some gas cylinders use a combination of convex inward bottom heads, which can ensure strength and meet the requirements of safe use.

The head is a component of the container that is welded to the cylinder. According to different geometric shapes, it can be divided into several types such as spherical, elliptical, disc-shaped, spherical crown shaped, conical shell, and flat cap. Among them, spherical, elliptical, disc-shaped, and spherical crown shaped heads are also collectively referred to as convex heads. In welding, it is divided into butt welding heads and socket welding heads. Used for various container equipment, such as storage tanks, heat exchangers, towers, reactors, boilers, and separation equipment. The materials include carbon steel (A3, 20 #, Q235, Q345B, 16Mn, etc.), stainless steel (304, 321, 304L, 316, 316L, etc.), alloy steel (15Mo3, 15CrMoV, 35CrMoV, 45CrMo), aluminum, titanium, copper, nickel, and nickel alloys.