The industrial flange connection design

Flange design involves creating a connection system for flanged joints, which includes three key components: gasket design, bolt (or stud) design, and the flange body design. The most widely used method for flange design is the Waters method, which is adopted in GB 150. Below are the main points involved in this design approach:

Gasket Design
Gasket design serves as the foundation for flange connection design. It’s important to select the right type and material of the gasket based on the design conditions and the type of medium involved. The size of the gasket—its inner diameter, outer diameter, and thickness—must be determined, followed by calculations of the gasket’s clamping force in both the pre-tightened and operational states. The gasket’s ability to seal effectively during these conditions is critical to the success of the flange connection.

Bolt/Stud Design
The selection of bolts (or studs) is guided by the design conditions. The required bolt area is calculated to ensure that it can provide the necessary clamping force for both the pre-tightened and operational states of the gasket. The actual bolt area used should not be smaller than the calculated value. The key principle in bolt design is determining the smallest possible bolt center circle diameter. This can be achieved by selecting appropriate bolt specifications and determining the optimal number of bolts required.

Flange Body Design
Flange body design can be divided into two main cases: internal pressure and external pressure. Flanges that bear external pressure can be designed using the same calculation method as for internal pressure, with slight differences in calculating the operating torque.

- Narrow-Face Flanges: These flanges can be calculated using two methods: as loose flanges or as integral flanges. In most cases, loose flanges are used, but for certain conditions, they can be simplified as integral flanges. Loose flange calculations are relatively straightforward, as the thickness of the flange can be determined in a single step.

- Integral Flanges: Designing integral flanges requires more complex calculations. Initially, the dimensions of the flange cone neck and flange ring are assumed based on the structural requirements. The torque and stresses on the flange are then calculated. If the stresses exceed allowable limits, adjustments to the flange dimensions are made, and the process is repeated until the stresses are within acceptable limits, ensuring a balanced and safe design.

- Wide-Face Flanges: For wide-face flanges, the design is generally calculated using a simplified model resembling a "simply supported beam." This method provides a more straightforward approach for evaluating the flange's structural integrity.

By following the Waters method and considering these key elements, flange design ensures a secure and effective connection for various piping systems under different pressure conditions.