Depending on the shape of the head, the head can be divided into spherical, oval, dish, spherical crown, cone shell and flat cover.Spherical, oval, dish and spherical crown heads are collectively called convex Head.

When the container does not need to be opened after being assembled (usually there are no internal parts in the container or although there are internal parts but there is no need to replace or repair), the head can be welded directly to the cylinder, and then it is useful to ensure sealing, save data and Reduce the amount of processing and production. As for the container that needs to be opened many times due to maintenance or replacement of internal parts, the connection between the head and the cylinder should be detachable. At this time, a sealing device is necessary between the head and the cylinder.

(3) Sealing equipment 

Many sealing equipment are required on the pressure vessel , such as the detachable connection between the head and the cylinder, the detachable connection between the container receiving and the outer pipeline, and the connection of the manhole and hand hole cover.Can the pressure vessel be normal and safe? Ground operation depends to a large extent on the robustness of the sealing equipment.

Bolt flange connection (referred to as flange connection) is the most widely used sealing equipment. Its effect is to ensure the seal by bolting and tightening the bolt to make the sealing element compact. Flange is divided into container flange and pipeline flange according to its connected parts.

The flange used for the connection between the container head (or top cover) and the cylinder and between the two cylinders is called the container flange; the flange used for pipe connection is called the pipe flange. In a high-pressure container, a container flange used for the top cover and the cylinder to be welded together with the cylinder is also called the end of the cylinder.

(4) Opening and receiving Due to process requirements and maintenance requirements, various large and small holes or equipment are often opened on the cylinder or head of the pressure vessel to take over, such as manholes, hand holes, sight glass holes, material import and export Receiving and receiving openings for equipment pressure gauges, level gauges, safety valves, temperature measuring surfaces, etc.

Hand and manholes are devices used to view, access, and wash containers. The inner diameter of the hand hole should allow the operator's hand to pass freely. Therefore, the diameter of the hand hole should generally not be less than 150mm. Considering that the length of a human arm is about 650 ~ 700mm, it is not appropriate to set a hand hole for a container with a diameter greater than 1000mm, but a manhole should be set instead.

There are two types of common manholes: round and oval. In order for operators to come in and out freely, the diameter of the round manhole should be at least 400mm, and the size of the oval manhole is generally 350mm × 450mm.

After the hole is opened in the cylinder or the head, the strength of the hole is weakened, and the stress there is increased. This weakening degree increases with the increase of the diameter of the opening, so the number of openings on the container should be reduced as much as possible, and especially large holes should be prevented.For the holes that have been opened on the container, the opening reinforcement planning should also be carried out to ensure the required strength.