Summary of questions regarding pressure vessels

In addition to the pressure vessel itself, it should also include: 1. The welding groove for the first circumferential weld that connects the pressure vessel to external pipes or devices, the first threaded joint in case of threaded connections, the first flange sealing surface in case of flange connections, and the first sealing surface for special connections or fittings； 2. Pressure-bearing cover for the opening part of the pressure vessel and its fasteners ； 3. Welded joints connecting non-compressed components to the pressure vessel body

When selecting steel for pressure vessels, factors such as the operating conditions of the vessel (e.g., design temperature, design pressure, properties of the medium, and operational characteristics), the weldability of the material, the manufacturing process of the vessel, and economic viability should be taken into consideration. Under normal circumstances, material selection is carried out in accordance with the following principles: (1) When the required thickness of the steel plate is less than 8 mm, carbon steel plates should be preferred over low-alloy high-strength steel plates, except for materials used in multi-layer containers ； (2) In applications where stiffness or structural design is the primary concern, ordinary carbon steel should be preferred as much as possible. In applications where strength design is the primary consideration, steel plates such as Q235-A, Q235-B, Q235-C, 20R, and 16MnR should be selected accordingly, based on usage constraints related to pressure, temperature, and the medium involved ； (3) When the required thickness of stainless steel is greater than 12 mm, structures such as lining, compounding, or surfacing should be employed as much as possible ； (4) Stainless steel should be avoided as a heat-resistant steel for applications with a design temperature of 500°C or less ； (5) Pearlite heat-resistant steels should preferably not be used as heat-resistant steels for applications with a design temperature of 350°C or less. When pearlitic heat-resistant steel must be used for heat-resistant or hydrogen-resistant applications, the variety and specifications of the steel materials should be reduced and combined as much as possible ； (6) Carbon steel is used for atmospheric and low-pressure vessels with weak medium corrosion, medium-pressure vessels with relatively thin walls, forgings, pressure-bearing steel pipes, non-pressure components, and other applications where the wall thickness is determined by rigidity or structural factors ； (7) Low-alloy high-strength steel is used for pressurized vessels with weak medium corrosion and a large wall thickness (≥8 mm) ； (8) Pearlite heat-resistant steel is used for resisting corrosion by high-temperature hydrogen or hydrogen sulfide, or as a heat-resistant steel for pressure vessels operating at design temperatures of 350–650°C ； (9) Stainless steel is used in applications where the medium is highly corrosive (electrochemical or chemical corrosion), to prevent contamination by iron ions, or in applications requiring heat resistance or low-temperature performance, where the design temperature is greater than 500°C or less than -100°C ； (10) Austenitic stainless steels that contain no stabilizing elements and have a carbon content of more than 0.03% should not be used in environments that may cause intergranular corrosion of the stainless steel when welded or subjected to heat treatment at temperatures above 400°C. The ignition point refers to the heat of combustion released when a combustible substance is heated and ignited; this heat is sufficient to cause the substance to emit enough combustible vapor to sustain the continuation of the combustion. The lowest temperature required to heat this substance at this point is known as its \"ignition point,\" or flash point. The lower the ignition point of a substance, the easier it is to burn. The flash point is the lowest temperature at which the vapor emitted by a flammable liquid, when mixed with air, can catch fire upon exposure to an ignition source. The flash point is different from the ignition point; the flash point is slightly lower than the ignition point.

Flash point is the lowest temperature at which the vapor generated from the surface of a flammable liquid or solid, in a stable air environment, ignites under the action of a test flame； The flash point is the lowest temperature at which a flammable liquid or solid can release enough vapor to form a flammable mixture with air at the surface of the liquid or solid within its container. The flash point of flammable liquids changes with their concentration. The flash point, also known as the ignition point, is the temperature at which a mixture of vapor and air above the surface of a flammable liquid begins to emit sparks when in contact with fire. The flash points of various oils can be determined using standard instruments. The flash point temperature is lower than the ignition point temperature. The ignition point, also known as the burning point, is the temperature at which a mixture of vapor and air above the surface of a flammable liquid, when in contact with fire, allows the flame to continue burning for at least 5 seconds. It can be continued to be measured in the same standard instrument after determining the flash point. The flash point and ignition point of flammable liquids indicate the likelihood of explosion or fire, and are of great importance for the safety of their transportation, storage, and use. This post was last edited by sus321 on 2009-3-13 13:15]

Flash point: The lowest temperature at which the vapor generated from the surface of a flammable liquid or solid can catch fire under the action of a test flame, in a stable air environment； The flash point is the lowest temperature at which a flammable liquid or solid can release enough vapor to form a flammable mixture with air at the surface of the liquid or solid within its container. The flash point of flammable liquids changes with their concentration. The flash point temperature is lower than the ignition point temperature. The ignition point, also known as the burning point, is the temperature at which a mixture of vapor and air above the surface of a flammable liquid, when in contact with fire, allows the flame to continue burning for at least 5 seconds. It can be continued to be measured in the same standard instrument after determining the flash point. The flash point and ignition point of flammable liquids indicate the likelihood of explosion or fire, and are of great importance for the safety of their transportation, storage, and use.