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Dry Gas Seals Uses Hydrodynamic Principles
Nov 02, 2017

Dry gas seals The use of hydrodynamic principle, through the sealing end of the opening to create a dynamic pressure groove to achieve the sealing end of the non-contact operation.

As the seal to take non-contact mode of operation, so the sealing of the friction material is basically not affected by the PV value of any impact, especially in high-pressure equipment, high-speed equipment applications, has good prospects.

Dry gas seals working principle

1. Compared with other mechanical seals, dry gas seals in the structure is basically the same. The main difference is that the dry seal of a seal ring above the uniform distribution of the shallow groove, dry gas seal can run in non-contact state is by the operation of these shallow groove generated by the fluid dynamic effect of the sealing surface to separate.

Dry gas seals the end of the groove is mainly single and double rotation of two major categories.

01. Single-swivel groove type can only be used for one-way rotation of the unit, in the required rotation can produce the opening force, such as reverse the negative opening force will lead to damage to the seal. But relative to the double-rotation groove type, it can form a greater opening force and film stiffness, resulting in higher stability and more reliable to prevent end contact. So at very low speed and large vibration can also be used. The most used on the current compressor unit.

02. Double rotation groove type without rotation requirements, positive and negative can be used. The reversal of the unit will not cause damage to the seal. Its use range than the single-round groove width, but its stability, anti-interference ability than the single rotation difference.

Through the repeated tests and comparative studies on the various troughs of dry gas seals, it is finally confirmed that the groove type with the helix design has the largest ratio between the same and the operating parameters.

The following describes the groove type.

The sealing surface is machined with a number of spiral grooves with a depth of less than 10 microns. In the sealed operation, the sealed gas is sucked into the spiral groove in the circumferential direction, and the radial component flows from the outer diameter toward the center (i.e., the low pressure side), and the seal dam restricts the flow of the gas to the low pressure side. The gas is compressed with the change in the shape of the spiral groove, and a local high pressure zone is formed at the root of the groove so that the end face is separated by 3 m to form a film of a certain thickness. In this thickness film, the opening force formed by the force of the film is balanced with the closing force formed by the spring force and the medium force, and the seal is realized in the non-contact operation. Dry gas seals between the sealing surface of the film formed by a certain degree of stiffness, to ensure the stability of the sealed operation. In order to obtain the necessary hydrodynamic effect, the dynamic pressure tank must be opened on the high pressure side.

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