How to classify pressure vessel?

- Aug 10, 2018-

Pressure vessel classification according to various methods

A pressure vessel is a sealed container that is internally or externally subjected to gas or liquid pressure and has high safety requirements.

The pressure vessel is primarily cylindrical and a few are spherical or otherwise shaped. Cylindrical pressure vessels usually consist of parts and components such as cylinders, heads, nozzles, flanges, etc. 

The higher the working pressure of the pressure vessel, the thicker the wall of the cylinder should be.


Pressure vessel classification

Classified by pressure level:

Pressure vessels can be divided into internal pressure vessels and external pressure vessels.

The internal pressure vessel can be divided into four pressure grades according to the design pressure (p), which are divided as follows:

Low pressure (code L) container 0.1MPa≤p<1.6MPa;

Medium pressure (code M) container 1.6MPa≤p<10.0MPa;

High pressure (code H) container 10MPa ≤ p < 100MPa;

Ultra high pressure (code U) container p ≥ 100MPa.

Classified by the role of the container in production:

Reaction pressure vessel (code R): used to complete the physical and chemical reactions of the medium.

Heat exchanger pressure vessel (code E): used to complete the heat exchange of the medium.

Separation pressure vessel (code S): used to complete the fluid pressure balance buffer and gas purification separation of the medium.

Storage pressure vessel (code C, which can be used to store gas, liquid, liquefied gas, etc.).

In a pressure vessel, if there are more than two principles of process function at the same time, the variety should be classified according to the main role in the process.

Classified by installation method:

Stationary pressure vessels: Pressure vessels with fixed installation and use locations, process conditions and fixed operator.

Mobile pressure vessel: It is not only subjected to internal pressure or external pressure load during use, but also subjected to impact force caused by internal medium sloshing during transportation, as well as external impact and vibration load caused by transportation, so it is structural, use and safety. There are special requirements for them.

The several classification methods described above only consider a certain design parameter or use condition of the pressure vessel, and cannot comprehensively reflect the danger degree of the pressure vessel.

The degree of danger of the pressure vessel is also related to the medium risk and the product of the design pressure p and the full volume V. The larger the pV value, the greater the explosion energy when the container ruptures, and the greater the hazard, the design, manufacture。

The higher the requirements for inspection, use and management.

Security Technology Management Classification:

The Pressure Vessel Safety Technology Supervision Regulations adopts a comprehensive classification method that considers both the pressure and volume of the vessel and the danger of the medium and the role of the vessel in the production process to facilitate safety technology supervision and management.

This method divides pressure vessels into three categories:


1. The third type of pressure vessel

A third type of pressure vessel is one of the following:

High pressure vessel

Medium pressure vessel (only the degree of toxicity is extremely high and highly hazardous);

Medium-pressure storage container (only flammable or toxic to moderately hazardous medium, and pV product is greater than or equal to 10MPa?m3);

Medium pressure reaction vessel (only flammable or toxic to moderately hazardous medium, and pV product is greater than or equal to 0.5Pa?m3);

Low pressure vessel (only for the degree of toxicity is extremely high and highly hazardous medium, and the product is greater than or equal to 0.2MPa?m3);

High-pressure, medium-pressure shell-and-tube waste heat boiler;

Medium pressure neodymium glass pressure vessel;

a pressure vessel made of a material having a higher strength level (referring to a lower limit of the tensile strength specified in the corresponding standard, 540 MPa or more);

Mobile pressure vessels, including railway tankers (medium is liquefied gas, cryogenic liquid), tank cars [liquefied gas transport (semi-suspension) vehicles, cryogenic liquid transport (semi-trailer) vehicles, permanent gas transport (semi-suspension) vehicles] Tank container (medium is liquefied gas, cryogenic liquid), etc.;

Spherical storage tank (volume greater than or equal to 50m3); cryogenic liquid storage container (volume greater than 5m3).

Cryogenic liquid storage container (volume greater than 5m3) 

2. The second type of pressure vessel

A second type of pressure vessel is one of the following:

Medium pressure container

Low pressure vessels (only for highly toxic and highly hazardous media);

Low pressure reaction vessels and low pressure storage vessels (flammable media only or moderately hazardous media);

Low-pressure shell-and-tube waste heat boiler;

Low pressure glass pressure vessel.

3. The first type of pressure vessel, the low pressure vessel other than the above, is the first type of pressure vessel.

It can be seen that the domestic pressure vessel classification method comprehensively considers the influencing factors such as design pressure, geometric volume, material strength, application and medium damage degree.

For example, because of the characteristics of the medium or the function of the container, that is, according to the potential hazard, the low pressure container can be divided into the first type or the second type or even the third type of pressure container.