A beginner in instrumentation is asking questions regarding the connection flanges between instruments and equipment
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I have a very basic question. I work in the electrical field, but my colleague who specialized in instrumentation has left, and now I’m doing the instrumentation work with no one to guide me. I remember my colleague mentioning that the pressure rating of the flanges used in instrumentation should be one level higher than that of the flanges on the pipelines. I’m not sure if this is true. For example, in the case of this double-flange differential pressure level gauge, regarding the process connection specifications, the pressure rating is PN25. This rating should be either the same as the pressure rating of the flanges on the tower to which it is connected, or one level higher; there may also be other requirements.
It should be no lower than the pipeline pressure rating; as for whether it should be the same as that rating or one level higher, this is determined by taking into account the actual operating conditions, your own preferences, and the requirements of the client.
Don’t listen to nonsense from others – 150LB flanges and 300LB flanges are not the same; it’s essential that they be of the same grade and made from the same material. The material can be of a higher grade though. If you’re not sure, consult the plant piping engineer; and if you work for a large company or organization, there will be a piping grade table available. Follow the data in the table
The SH3104 specifications require a pressure rating that is not lower than that of the pipeline; in addition, the pressure requirements and other aspects have already been taken into account in the specifications provided by the design institute. Therefore, you must submit the application in strict accordance with the design specifications in order to match the flange grade of the equipment itself
The material of the instruments should be no lower than that of the pipes and equipment. The pressure rating must not be chosen arbitrarily; as mentioned on the 3rd floor, you can’t use a higher standard than specified by the American standards.
If the process design is good, then following the flange rating specified in the process is the right approach; as long as it can handle the pipeline pressure, that’s sufficient. If the flange rating required by the process is too high, it may not be suitable for use
Thank you all for your guidance; as a beginner, I don’t understand many basic things.
““Not less than” will do. Regarding the pressure rating of instrument flanges, manufacturers usually determine it based on the highest pressure tolerance within the same installation dimensions. So to achieve a result that is “not lower than” the target, it will be “higher”.