How Does the Bolt Fastening of Heat Exchangers Perform Correctly?

How do the bolt fastening sequence of heat exchanger tube boxes and tube plates perform correctly?
Generally, diagonal bearing and cross-bearing are adopted for fastening, and a torque wrench is used for fastening according to the design torque value.

Are the material grades of fastening bolts and nuts of the heat exchanger tube boxes and tube plates the same?
Different. The material grade of the fastening bolt of heat exchanger tube boxes and tube plates is higher than that of the nut. The hardness of the bolt material is higher than that of the nut material. If the material is equally hard, it is easy to damage the thread of the bolt, causing the bolt to fail to tighten. Lubricant or anti-seize agent is generally applied during installation.