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The Dry Gas Seals Is Very Small
Jun 02, 2017

Dry air gas seal is a new type of shaft seal for gas seal sealing, which is a non-contact seal.

Dry gas seal principle

When the movable ring of the hydrodynamic groove (2.5 to 10 m) is opened on the outside of the end face, the hydrodynamic pressure groove pumps the high pressure isolation gas having the outer diameter side (referred to as the upstream side) between the sealing end faces, The membrane pressure gradually increases from the slot diameter to the inner diameter, and the opening force formed by the increase of the end film pressure is larger than the closing force acting on the seal ring, and between the friction pairs Forming a thin layer of film (1 ~ 3 micro) m so that the seal work in a non-contact state. The formation of the film completely blocked the relatively low pressure sealing medium leakage channel, to achieve a sealed medium zero leakage or zero escape.

Dry gas seal and the general mechanical seal of the balanced structure of the same type, but the design is different, the surface has a few microns to ten microns deep groove, the width of the wide face. Unlike conventional lubricating mechanical seals, dry gas seals create a stable gas film on both sealing surfaces. The film has a strong stiffness so that the two sealed end completely separated, and maintain a certain sealing gap, the gap can not be too large, usually a few microns. The sealing gap is too large, will lead to increased leakage, sealing effect is poor; and the sealing gap is small, easy to make contact with the two sealing surface, because the dry gas seal friction heat can not be lost in time, the end contact without lubrication, will soon cause Seal deformation, the face of excessive heat caused by sealing failure. The presence of this film, both to effectively separate the end face and the relative operation of the two ends of the surface has been cooled, the two end of non-contact, so friction, wear greatly reduced, so that the seal has a long life characteristics, thereby extending the life of the host The

The grooved sealing surface is divided into two functional areas, the outer area and the inner area, and the gas enters the outer area of the slot. These grooves will compress the incoming gas, form a local high pressure zone at the root of the groove, separate the end faces and form a certain Thickness of the film, in order to obtain the necessary pumping effect, dynamic pressure tank must be opened in the high side. The increased pressure in the grooved seal gap is critical to the work of the dry gas seal, which ensures that the seal can form a stable gas film that is not damaged even in the case of a large axial load. The inner area of the seal (ie, the dam area) is flat and limits the discharge by its throttling action. The opening force of the end face film formation during sealing operation is balanced with the closing force formed by the force acting on the spring and the medium, thereby achieving non-contact operation. The Dry Gas Seals is very small. The main purpose is to ensure that the seal is closed when the seal is not pressed or not working to prevent accidents.

Dry gas seal is a new non-contact seal developed on the basis of a gas dynamic pressure bearing in the late 1960s by fundamentally improving the mechanical seal. In fact, it is mainly through the mechanical seal ring Dynamic pressure tank and the corresponding set of auxiliary system to achieve the sealing end of the non-contact operation. A British company in the late 1970s, the first dry gas seal applied to the offshore platform of the gas transmission equipment and a success. Dry gas seal was originally designed to solve the problem of high-speed centrifugal compressor shaft seal, due to sealed non-contact operation, so the sealing friction material is not limited by the PV value, especially suitable for high-speed high-pressure equipment, seal.





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