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What Is the Principle of Flange Sealing?

Jun. 16, 2020

Threaded Flange

Needle Valve supplier shares this article for you.

In some mechanical equipment, it is often seen that the connection between the two machines is butted through the form of a flange. For example, the connection between the reducer and the motor.

The flange is also called a flange plate or flange plate. The flange is the part that connects the pipe and the pipe to each other, and is connected to the pipe end; it is also useful for the flange on the inlet and outlet of the equipment, which is used to connect the two equipment before. The flange connection or flange joint refers to the detachable connection of the flange, gasket, and bolt as a group of the combined sealing structures. Pipe flange refers to the flange used for piping in the pipeline device, used in equipment Upper refers to the flange of the equipment. There are holes in the flange, and the bolts tightly connect the two flanges. The flanges are sealed with gaskets. The flange can be divided into threaded connection (thread connection) flange and welding flange according to the connection method. Some are also connected by flanges.

Common detachable structures include flange connection, threaded connection, and socket connection. Advantages and disadvantages of flange connection: Flange connection has better strength and tightness. The applicable size range is wide, and it can be applied to equipment and pipelines, so it is the most common application. However, when the flange is connected, it cannot be quickly assembled and disassembled, and the manufacturing cost is high.

1. Flange connection structure and sealing principle

The flange connection structure is a combined part, which is composed of a pair of flanges, a number of bolts, nuts, and a gasket. Therefore, the main problem solved in the design of the flange connection is to prevent the leakage of the medium.

The principle of flange sealing: The flange presses the gasket between the sealing surfaces under the action of the bolt preload force. When the compression force per unit area of the gasket reaches a certain value, the gasket will be deformed It is compacted to fill up the irregularities on the sealing surface, so as to form an initial sealing condition to prevent the medium from leaking. The required pressing force is called the pre-tightening seal specific pressure of the gasket, and the unit is MPa. The specific pressure of the pre-tightened seal mainly depends on the gasket material. The axial force of internal pressure stretches in the working state, which reduces the pressing force. The gasket has sufficient resilience and compensates for deformation. The prestressed seal specific pressure value is not less than a certain value (working seal specific pressure-so that the medium does not leak). The minimum specific pressure that must be retained between the sealing surface and the gasket. ) Maintain a good seal. On the contrary, if the spring back is insufficient, the specific pressure of the pre-tightened seal drops below the specific pressure of the working seal, and even if a gap reappears at the seal, the seal fails.

Conditions to ensure the tight connection of the threaded flange

It can be seen that to ensure flange sealing, the specific pressure actually present on the sealing surface of the flange must not be lower than the specific pressure of the pre-tightening seal of the gasket when pre-tightened, and should be higher than the specific pressure of the working seal during working.