Regarding the material selection for flange nuts and bolts
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At room temperature, for valves with a WCB body, according to the valve manual, bolts made of 35CrMoA should be used along with nuts made of steel grade 45. However, the drawings provided by the company specify bolts of 35CrMoA paired with nuts of 35CrMo. . . . Today I was confused because of this issue; my supervisor told me to follow the standards, but then the senior manager intervened and changed things back. I just want to know if 35CrMoA can be paired with 35CrMo What are the impacts? What is the difference from the scheme using 45 nuts?
The type with A is high-quality steel; it is common to use 35CrMoA in combination with 35CrMo.
Yes, it’s essentially just about using better materials in their place. Generally, the tensile strength grade of the bolt material is one level higher than that of the nut material, which helps to prevent leaks at the flange interface more effectively! I specialize in the design of low-temperature and ultra-low-temperature valves; I hope this is accepted!
You’re right, thank you, for answering my little question