Does the flange grade on the pipeline need to match the flange grade of the equipment?

It also depends on the material and temperature; with different materials and temperatures, even if the pressure rating is the same, the maximum allowable operating pressure for that flange can vary.

The pipe flanges connected to the equipment must be of the same grade as the equipment’s flanges; otherwise, a connection cannot be made. The number of bolt holes and their spacing also need to be identical

The pressure transmitter on the pipeline is connected using flanges; does the pressure rating of these flanges need to be the same as that of the flanges on the equipment (under the same temperature and material conditions)?

In the same system, the design pressure is a value. It is also normal for individual devices and pipes in a single system to have different design pressures. This is determined by taking into account various factors such as relevant parameters, installation conditions, and seismic intensity.

The pressure is selected because the pressure at the inlet and outlet of the equipment is definitely different. Choose the higher value in the system, not the lower one. For the first one, not only stress should be considered, but also the water hammer effect of the medium. Additionally, in some devices, the outlet pressure is several times higher than the inlet pressure. But when it comes specifically to equipment manufacturing, exporting products designed for domestic use is no problem; however, the situation is different when it comes to connecting pipes, as this involves dealing with the pressure that the pipes must withstand. Perhaps the output pressure is twice as high as before; in that case, a flange size of 40 might be a bit too small. The decision you mentioned was certainly made by the design institute after fully considering the overall stress conditions. A pressure gauge of 63 is appropriate for the pipeline. However, for pipe fittings in general, including pressure gauges, they should be one grade higher than necessary; just as for pipes with a weight of 40 kilograms, the elbows should be one grade thicker than the pipes themselves. A pressure gauge with a rating of 63 is suitable. If allowed, it could be one level higher. But the pressure gauge itself has an overflow safety range, so it’s fine to choose 63 as well.

This post was last edited by lijie2007521 on 2022-7-6 at 13:02. Many factors need to be considered when selecting the pressure rating of pipe flanges and the pressure rating of equipment: temperature, pressure, natural conditions, seismic intensity, extreme conditions, and so on. But generally, it should not be lower than the design pressure of the entire system. However, some devices take many factors into account, resulting in a pressure rating that is higher than that of others. In other words, the design pressure refers to a value for pipes, while the equipment and components do not necessarily belong to the same pressure class.

A consistent design pressure for flanges and equipment is determined during system design. And the same execution standards are applied. All flanges follow this standard and design pressure

The pressure of standard fittings is usually higher than the designed pressure; whoever designs them will set it at a higher level rather than a lower one, which serves as a form of double safety measure. As for the pressure rating of flanges, whenever there are flanges on other equipment and matching flanges need to be connected to them, those flanges must be compatible with those on the equipment – otherwise, connection will not be possible. The corresponding pressure rating and type of sealing surface also need to be identical.