Selection of pressure pipeline grade
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What is the standard for selecting the pressure rating of a pipe? Is it based on the rating of the pipe fitting chosen?
The pressure rating of a pipe is determined based on the system requirements of that pipe. Once it is known how much pressure the pipe needs to withstand, the corresponding pressure rating can be determined
Is it possible for the pressure rating of a pipe to be different from that of the fittings? For example, if a flange is rated at 2.5 MPa, can the pipe have a rating of 1.6 MPa?
I don’t quite understand what the person above meant. In chemical engineering design, there are certainly situations where the pipe grade (including pressure) changes. However, the points where such grading occurs are usually at the fittings (including valves). Moreover, for economic reasons, lower-grade materials are generally used for the fittings, with exceptions for special requirements
Under normal circumstances, the pressure rating of pipelines and fittings should be the same
The selection of the pressure rating for a pipeline is based on the medium, temperature, and pressure
First, the process requirements take precedence, namely the parameters specified in the PFD, including the medium, flow rate, temperature, and pressure. Then, a material is selected, and the pressure rating is determined based on the allowable stress of that material under these operating conditions; for details, refer to the \"Chemical Process Piping Handbook\"
Select according to the usage conditions, referring to the **standards.
First, the process requirements are taken as a basis, namely the parameters in the PFD, including the medium, flow rate, temperature, and pressure. Then a material is selected, and the pressure rating is determined based on the allowable stress of that material under these operating conditions; however, it sometimes happens that higher-grade materials are used when a lower-grade one would suffice, mainly due to considerations related to corrosion and vibration
It is generally one pressure level higher than the actual operating pressure
Generally, the selection of fittings and pipes should have a pressure rating higher than that of the safety accessories.
It is necessary to consider the operating pressure and design pressure of the process; the value should be one grade higher than the design pressure. It’s not acceptable to choose a pipeline pressure of 1.6 MPa while using fittings with a pressure rating of 1.0 MPa – they need to match each other. Likewise, the grade of the bolts also needs to be appropriate