Determination of the operating pressure and design pressure of the container
Thread Content
Dear seniors, I have a question regarding the determination of the operating pressure and design pressure for container-type equipment. Normally, in design work, it is customary to determine these values based on the vapor pressure at the top of the tank. The petrochemical standard GB50160-2008 (2018 edition) also uses the vapor pressure at the tank top to classify tank pressures. However, for many containers that hold liquid media, the static pressure when the containers are filled with liquid is much higher than the vapor pressure at the top. Is it appropriate to still design such containers based on the vapor pressure at the top in such cases? Is it possible that the design pressure at the top and bottom of the container is different?
By definition, the poster should understand that the calculated pressures are different
The design pressure is the same; it’s just the difference in hydrostatic pressure of a liquid column that matters :)
The effect of calculated pressure is different from that of design pressure
There is no operating pressure; it is the working pressure, which represents the highest pressure that can be reached at the top of the container under normal operating conditions. The hydrostatic pressure of the liquid column you mentioned is not within the scope of operating pressures; what you refer to does not qualify as a pressure vessel.
Hydrostatic pressure of a liquid column is not a term used in standard specifications
The static pressure of a liquid column is not only a technical term but also one used in technical specifications; it constitutes a type of load. When this static pressure is less than 5% of the design pressure, it can be ignored.
1. The design pressure refers to the maximum pressure specified at the top of the pressure vessel; together with the corresponding design temperature, it serves as the design load condition, and its value is not lower than the operating pressure； 2. The calculated pressure refers to the pressure used to determine the thickness of the component at the corresponding design temperature, and additional loads such as the hydrostatic pressure of the liquid column should be taken into account. 3. Operating pressure, the highest pressure that may be reached at the top of the container under normal operating conditions. Designers can’t possibly not understand various technical terms; otherwise, problems will arise.
Under normal circumstances, the calculated pressure equals the design pressure; however, depending on the specific situation, it is not necessarily the case that one value is larger than the other. If the static pressure of the liquid column needs to be taken into account, then generally the calculated pressure = design pressure + static pressure of the liquid column. Under normal conditions, (1.05–1.1) × working pressure = design pressure
Regarding the owner’s question, you can adopt a conservative design approach: working pressure = design pressure ÷ (1.05–1.1). The load must be taken into consideration; if there is a maximum allowable working pressure, the operating pressure you mentioned might be higher than the design pressure. If this happens, then there is a problem with the design.
You should speak more politely; after all, the person in question might not work in the design industry, and studying this topic is just a hobby for them