Relationship between the design pressure of pressure vessels and the maximum operating pressure
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Friends, should the design pressure of pressure vessels be ≥ the maximum operating pressure? I checked some information, but found no clear answer; I would appreciate it if you could offer your guidance. First, according to clause 3.1.9.2 of TSG 21-2016, (1) for pressure vessels equipped with overpressure relief devices, the operating pressure of such devices shall not be higher than the design pressure of the pressure vessel ； (2) For pressure vessels specified in the design drawings with a maximum allowable operating pressure, the operating pressure of the overpressure relief device shall not be higher than that maximum allowable operating pressure. Second, according to clause 3.1.3 of GB150.1-2011, the design pressure is the highest pressure at the top of the vessel, and this value shall be no lower than the operating pressure ； 3.1.6 The specified maximum allowable working pressure refers to the maximum pressure that the top of the container is permitted to withstand at the designated corresponding temperature. It shall also be noted after this clause that when the design documents of the pressure vessel do not specify the maximum allowable operating pressure, the design pressure of the vessel may be considered as the maximum allowable operating pressure.
Work stress is the highest level of work stress. The relationship between design pressure and operating pressure can be found in HG/T20580 and GB/T150.1
GB150.1-2011 3.1.6 Note: When the design documents of a pressure vessel do not specify the maximum allowable operating pressure, it can be assumed that the design pressure of the vessel is the maximum allowable operating pressure. The maximum allowable operating pressure for general equipment may be higher than its design pressure
In GB150.1, clause 3.1.2 provides a specific explanation of working pressure, which refers to the highest pressure that may be reached at the top of a vessel under normal operating conditions. In 20580, the three pressures are also explained separately, which is consistent with 150.
But 3.1.3 explains that the design pressure is the highest pressure at the top of the container – how should this statement be understood?
This post was last edited by Guxi Village on 2018-12-17 at 17:03. Working pressure = maximum working pressure ≤ design pressure ≤ maximum allowable working pressure; there is no standard for this, but it indeed derives from standards. Specifically as follows: The operating pressure, or the maximum operating pressure, refers to the highest pressure at the top of the equipment. This value serves as the basis for the design pressure, which will never be less than the operating pressure; no further explanation is needed for this. The design pressure must be greater than the operating pressure, taking into account other loads such as wind load, snow load, attached loads, and hydrostatic column pressure. Under normal circumstances, there are negative deviations and positive deviations in the material properties of the equipment, as well as a reduction due to manufacturing processes and a margin for corrosion. The thickness indicated on the drawings is the nominal thickness, which may include rounding effects. All these factors combined result in the actual thickness of the material used in the equipment being slightly greater than the calculated thickness. The maximum allowable operating pressure is determined based on this final thickness; therefore, it will be greater than or equal to the design pressure.
When calculating pressure, various loads including the hydrostatic pressure of the liquid column should be taken into account.
What exactly is the original poster trying to say? The operating pressure is at the top of the container, and the design pressure is also at the top of the container; it is only the pressures at the top that can be compared.
You’re right; I equated the calculated pressure with the design pressure. Being precise is indeed the right approach
You make a good point; the material itself is fine, but considering factors such as fittings and welding, it’s generally not specified, and in practice the design pressure is still used as the upper limit.
Yes, the maximum allowable operating pressure can be higher than the design pressure:handshake