Operating conditions

pressure

The pressure of a pressure vessel can come from two aspects, one is that the pressure is generated (increase) outside the vessel, and the other is that the pressure is generated (increase) inside the vessel.

The maximum working pressure usually refers to the highest pressure that may appear at the top of the container under normal operating conditions.

The design pressure refers to the pressure used to determine the thickness of the vessel shell at the corresponding design temperature, that is, the vessel design pressure marked on the nameplate. The design pressure value of the pressure vessel shall not be lower than the maximum working pressure; When the liquid column static pressure of the pressure component reaches 5% of the design pressure, the sum of the design pressure and the liquid column static pressure shall be used for the design calculation of the part or component; the pressure vessel equipped with a safety valve shall not be designed Lower than the opening pressure or burst pressure of the safety valve. The design pressure of the vessel should be determined according to the corresponding regulations of GB 150.

temperature

Metal temperature refers to the average temperature of the pressure component of the container along the thickness of the section. In any case, the surface temperature of the component metal must not exceed the allowable use temperature of the steel.

The design temperature refers to the highest or lowest temperature that the shell wall or component metal may reach under the corresponding design pressure under normal operating conditions. When the temperature of the shell wall or component metal is lower than -20℃, the design temperature shall be determined according to the lowest temperature; otherwise, the design temperature shall be selected according to the highest temperature. The design temperature value shall not be lower than the highest metal temperature that the component metal may reach; for the metal temperature below 0℃, the design temperature shall not be higher than the lowest metal temperature that the component metal may reach. The vessel design temperature (that is, the design medium temperature marked on the vessel nameplate) refers to the design temperature of the shell.

medium

There are many types of media involved in the production process, and there are also many classification methods. Classified according to the state of matter, there are gases, liquids, liquefied gases, simple substances and mixtures, etc.; according to chemical characteristics, there are four types: flammable, flammable, inert and combustion-supporting; according to their degree of toxicity to humans, they can be divided into extreme hazards ( I), high hazard (Ⅱ), moderate hazard (Ⅲ), light hazard (IV) level four.
易燃介质：是指与空气混合的爆炸下限小于10%，或爆炸上限和下限之差值大于等于20%的气体，如一甲胺、乙烷、乙烯等。

Flammable medium: refers to gases whose lower explosion limit is less than 10% mixed with air, or the difference between the upper and lower explosion limits is greater than or equal to 20%, such as monomethylamine, ethane, ethylene, etc.

Toxic media: The “Pressure Vessel Safety Technical Supervision Regulations” (hereinafter referred to as “Containment Regulations”) divide the toxicity of media into four levels according to GB 5044 “Classification of Occupational Exposure Toxicant Hazards”. The maximum allowable concentrations are as follows: extreme hazard (level I) <0.1 mg/m3; high hazard (level II) 0.1 ～<1.0 mg/m3; moderate hazard (level Ⅲ) 1.0 ～ <10 mg/m3; mild hazard (level 1V) ≥10 mg/m3.

When the medium in the pressure vessel is a mixed substance, the composition of the medium and the classification principle of toxicity or flammable medium shall be determined by the process design department of the design unit or the production technology department of the user unit to determine the degree of toxicity of the medium or whether it is flammable medium.

Corrosive media, petrochemical media have corrosion resistance requirements for pressure vessel materials. Sometimes because of impurities in the medium, the corrosiveness is aggravated. The types and properties of corrosive media are different, and the corrosiveness of the media is also different due to different process conditions. This requires that when selecting materials for pressure vessels, in addition to meeting the mechanical performance requirements under the conditions of use, it must also have sufficient corrosion resistance, and take certain anti-corrosion measures when necessary.