What is the tightening torque of the flange and bolt?

The tightening torque of the flange and bolt depends on many factors, including the specification of the flange, the material, the working pressure, the working temperature and the material of the gasket. Therefore, it is impossible to give a uniform tightening torque value. Here are some detailed explanations of flange and bolt tightening torque:

First, determination of tightening torque

Working conditions:

The tightening torque is determined according to the working conditions (such as working pressure, working temperature, etc.) under which the flange connection is subjected.

Under normal circumstances, the higher the working pressure, the greater the required tightening torque.

Flange specifications:

The size of the flange (e.g., nominal diameter DN) affects the size of the tightening torque.

Larger size flanges usually require greater tightening torque to ensure the tightness of the connection.

Gasket material:

The material of the gasket will also affect the determination of the tightening torque.

Gaskets of different materials have different compressibility and resilience, so different tightening torques are required to ensure the sealing effect.

Bolt material and specification:

The material and specification of the bolt will also affect the size of the tightening torque.

High strength bolts usually require greater tightening torque to ensure their tightening effect.

Second, the calculation and selection of tightening torque

Calculation formula:

The tightening torque can be determined by calculating the formula T=KFd(N.m).

Where, T is the tightening torque, K is the tightening force coefficient (0.130.15 for lubricated assembly and 0.180.21 for non-lubricated assembly), F is the pre-tightening force, and d is the nominal diameter of the bolt.

Table lookup method:

For common flanged and bolted connections, the required tightening torque value can be determined by referring to the tightening torque table in the relevant standard or manual.

Experience value:

In some cases, the appropriate tightening torque value can be selected based on experience or actual field conditions.

However, it should be noted that the experience value is for reference only and should be adjusted and verified according to the specific situation.

Third, precautions for tightening torque

Avoid over-tightening:

Excessive tightening may cause bolts to break, flanges to deform, or gaskets to be damaged.

Therefore, a suitable torque wrench or torque wrench should be used during the tightening process and the manufacturer’s guidelines should be followed for tightening.

Prevent loosening:

Insufficient tightening torque may cause the bolts to loosen, affecting the tightness and safety of the connection.

Therefore, it should be ensured that each bolt reaches the predetermined tightening torque value, and its fastening condition should be checked regularly.

Record data:

During the fastening process, the fastening data of each bolt (such as the type of wrench used, the value of torque applied, etc.) should be recorded.

This facilitates future overhaul and reference and ensures the reliability and safety of the connection.

To sum up, the tightening torque of flanges and bolts is a complex problem that needs to be determined by considering a variety of factors. In practical applications, the appropriate calculation method or table lookup method should be selected according to the specific situation to determine the required tightening torque value, and follow the relevant safety rules and operating rules for tightening operations.