Heat exchanger design pressure
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If the operating pressure on the shell side of a heat exchanger is 1.0 MPa, I design it by using a value of 1.0 × 1.1 = 1.1 MPa. However, today I saw the standards for heat exchangers specified in GB151, and the design pressures listed there are standard nominal pressures for flanges, such as 1.0, 1.6, 2.5, etc. Will using a design pressure of 1.6 MPa directly affect the test pressure for the subsequent heat exchanger? Or should I use a design pressure of 1.1 MPa instead?
For carbon steel flanges, standard flanges with a pressure rating of 1.6 MPa can be used, or custom flanges can also be employed. If it is made of stainless steel, a flange needs to be designed and calculated by referring to the dimensions of carbon steel.
If the design pressure is set at 1.1 MPa, whether flanges with a pressure rating of 1.6 MPa can be used depends on the material and temperature; there is a temperature-dependent attenuation table in the HG/T20592 standard, which can be referred to.
The design pressure of the equipment should meet the requirements of the original design; flanged valves should be selected at a higher grade to correspond to the design specifications! 1.1 and 1.6 are fine.
The design pressure is set at 1.1 MPa, while 1.6 MPa is used when selecting flanges.
There is no issue with the design pressure. Regarding the choice of flanges, I would like to say that whether it’s pipe flanges or vessel flanges, they are selected based on the allowable pressures of 16Mn forgings and Q345R materials at 200°C. For example, if a flange is to be used at a pressure of 1.1 MPa, then using 16Mn forgings or Q345R materials is acceptable at temperatures below 200°C. If stainless steel is used, it may not work at higher temperatures; in such cases, it’s necessary to increase the pressure rating by 2 levels, to 2.5 MPa (even then, it might still not be sufficient at very high temperatures). So what exactly should be done? It’s based on your design pressure, temperature, and material. Go and find the French standard. 1. Design pressure. For 1.1 MPa, you should choose at least 1.6 MPa. Then, under a flange pressure of 1.6 MPa, find your flange material and determine the maximum allowable pressure at the design temperature. If this pressure is greater than 1.1 MPa, congratulations – you can use it. If it’s lower, use the same method and select 2.5 MPa to see if it works well. I wonder if you’re satisfied with this explanation!