Some questions regarding the operating pressure and design pressure of reaction vessels
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This post was last edited by jmdc on 2019-6-16 09:36. Some questions regarding the operating pressure and design pressure of reaction vessels: 1. Enameled vessels usually come equipped with jackets. The operating pressure and design pressure of the inner cylinder of such vessels are generally 0.2 MPa and 0.4 MPa respectively, while the operating pressure and design pressure of the jacket are typically 0.5 MPa and 0.6 MPa. Since the jacket pressure is higher than that of the inner cylinder, why is the wall thickness of the inner cylinder much greater than that of the jacket? 2. The operating pressure and design pressure of the inner cylinder of an enamel kettle are generally 0.2 MPa and 0.4 MPa respectively, yet 6 kg of nitrogen pressure is often used in production – isn’t this considered overpressure use? 3. If the operating pressure of the reactor is -0.098 MPa, is it acceptable to use -0.1 MPa as the design pressure? Is it acceptable to use a pressure of 2 kilograms of absolute pressure for the hydrostatic test of negative-pressure containers? Are the maximum internal and external pressures that the container can withstand the same? 4. Why are generally two sets of values provided for working pressure and design pressure in the design data sheet of enamel kettle drawings? 5. At the junction between the inner cylinder and the jacket of the reaction vessel, should the design calculations be based on the jacket or on the inner cylinder? 6. What should be the design pressure for a reactor with a working pressure range of -0.098 MPa to 0.01 MPa?
I can only tell you what I know, because many things can only be inferred and are not clear. 1. For the content in question, it is necessary to meet the requirements of external pressure calculations. These calculations take into account not only the diameter but also the length over which the external pressure acts. In your case, the jacket is subject to an internal pressure of 0.6 MPa, while the inner cylinder is subject to an external pressure of 0.6 MPa. Generally, the inner cylinder will be thicker; this is considered normal according to conventional practices. 2. It is estimated that 6 kilograms of nitrogen represents only a utility-grade pressure level, and it will not be the operating pressure. Firstly, the operating pressure for 6 kilograms of nitrogen cannot be 0.6 MPa; Secondly, the pressure inside the container after the material is pressed in depends on how the system is configured. 3. I’m not sure if the reactor you’re referring to has a jacket; if it doesn’t, a pressure of -0.1 Mpa is fine. For the hydrostatic test, an internal pressure of 0.1 Mpa is sufficient, as a external pressure hydrostatic test cannot be carried out. 4. I don’t know what intention you have in mind. 5. Calculate based on the pressure inside the jacket. 6. I’m not sure whether this pressure range involves alternating conditions; the design pressure can be set at -0.1/0.05. If alternating conditions are present, fatigue calculations are required.
The thickness of the inner cylinder of an enamel-lined reaction kettle needs to take into account two factors: one is the thickness calculated based on external pressure (which is also relevant for non-enamel-lined equipment), and the other is the requirement that the equipment remains unchanged after multiple high-temperature enamel coating processes.
1. The design criteria are different; the jacket is subjected to internal pressure, leading to strength failure； 2. The cylinder fails due to instability when subjected to external pressure. 2. The nitrogen pressure used for pressing is the pressure inside the tube; it’s not as high inside the reactor, nor is such a high pressure necessary. 3. For externally pressurized containers, the design pressure is taken as the smaller of the difference between internal and external pressures and 0.1 MPa; for reactor cylinders, this value is usually 0.1 MPa, which is determined using a specific formula for hydrostatic testing
The design thickness is related to factors such as the inner diameter of the cylinder and the material used； Overpressure use is not permitted; if the inner cylinder is a pressure-bearing component, it must be equipped with a relief device, so that pressure can be released in case of overpressure ； I have never seen calculations done using upper and lower connecting rings; as for the two sets of data, please provide the drawings – this situation has not been encountered with reaction vessels.
1. Because it is calculated that the thickness required to withstand external pressure is greater than that required to withstand internal pressure. 2. During material compression, PV remains constant; the volume of material fed in does not cause significant changes in the pressure inside the tank. 3. -0.1 is the limit; it cannot be lower, but it is possible. Through internal pressure testing, the relevant stresses can be verified. The external pressure is much greater than the internal pressure; it’s almost impossible for them to be equal. 4. Usage conditions are determined. 5. Unless the cylinder is very long and the jacket is very short, requiring it to be divided into 2 sections, the same thickness will suffice. 6、-0.1/0.1.