[Discussion Thread 31] Is the operating pressure in pressure vessels a definite value?
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This post was last edited by kareale88 on 2019-4-1 10:52 with bg4.png【Discussion Thread 31】Is the operating pressure in pressure vessels a specific value? For example, in the design parameters: the operating pressure of a split collector is ≤1.0 MPa. Is it appropriate to write 1.0 MPa, or is ≤1.0 MPa the correct notation? For example, in the design parameters: the operating pressure of a split collector is <1.0 MPa. Is it appropriate to write 1.0 MPa for the operating pressure, or is <1.0 MPa the correct value? <Does this range value also include -0.1 MPa?>
Working pressure is a range; generally, the maximum working pressure is specified (not the maximum allowable working pressure). Positive and negative pressures should be indicated separately; if negative pressure is not specified, it is assumed that there is no negative pressure condition.
If negative pressure is not specified, there is no default negative pressure condition. Where does this sentence come from?
Is it reasonable to reflect whether negative pressure is present or not within the design pressure? For example, if the design pressure is set at 1.0 MPa, it implies that there is no negative pressure. For example, 1.0 MPa/-0.1 MPa indicates the presence of negative pressure. The operating temperature is considered in the same way as the design temperature.
“The term “work pressure” appears in Chapters 1 and 3 of TSG21, and its meaning here is consistent with that in GB150. Strangely enough, the operating pressure appeared in the regular inspection report of the pressure vessel. Personal understanding: In the absence of negative pressure, the \"operating pressure\" is a fixed value; when negative pressure is present, there are two fixed values for the operating pressure. When subjected to alternating loads from the medium, the operating pressure forms a range, and this range must be specified in relation to the operating temperature. Furthermore, according to clause 3.1.3 of TSG21, the parameter of \"work pressure\" should be provided by the party commissioning the design, rather than being determined by the designer. This value serves as the basis for determining the \"design pressure\". The strange practice in the industry these days is that users simply state they want to purchase a certain device, without any design commission issued; as a result, there are countless drawings with a working pressure of 0.5 MPa and a design pressure of 1.6 MPa.
If the other party only provides a working pressure of <1.0 Mpa, how should the working pressure and design pressure be determined? Is fatigue analysis required?
I agree with the opinion from the second floor; our design also follows this principle
Of course not; this way of writing is likely due to the client’s lack of familiarity with the standards. You can communicate with them to have them specify the exact range of operating pressures and confirm whether there are any changes in the load.
Actually, the device is just a water distributor, and there should be no change in load; it seems inaccurate to specify a working pressure of <1.0 MPa. I’m thinking that the working pressure of 1.0 (or 0.99) MPa can be indicated on the drawings; since there is no safety valve on the housing, it is specified that the user shall install it in the piping system at a specific pressure value. Then, the design pressure of 1.0 MPa is adopted (taking into account the economic aspects related to the use of flanges).
The operating pressure ≤ 1.0 MPa; the design pressure cannot be set at 1.0 MPa