Dry gas seals are known as mechanical seals but use other chemicals and functions so that they do not contaminate a process. These seals are usually used in a harsh working environment such as oil exploration, and other petrochemical processes. The dry gas seals comprises of hard-face mating ring etched circumferential spiral groove style and a primary (stationary) ring in softer material. The stationary ring is radially restrained but can rotate in the axial direction. Under the static and depressurized condition, the springs behind the stationary ring keep the seal faces closed and in contact. In the static and pressurized condition, the sealed gas penetrates across the faces at the tip of the groove. The sealing dam can maintains similar pressure supply among the seal faces which also support the hydrostatic lift that result in low startup torque, less parasitic power and lower heat generation.
The advancing shallow spiral glues the grooves during change period which enhances the sealed gas to center around the dam to originate gas film pressure that will motivate the separation of the faces. They become non-contacting during processing. The special geometry of the spiral grooves provides a uniform hydrostatic and hydrodynamic pressure distribution and maintains the actual seal face gap for gas film stiffness. These features help in quick liftoff, even during low-speed operation (10 fps [3.05 m/s]) for pressures less than 50 psi (345 kPa gauge) and allow the seal faces to adjust rapidly to the changes in the process conditions.
Dry Gas seal Contamination
The running space between the primary (stationary) and mating gas seal rings’ is typically about 3 to 4 Microns, about1/20th the diameter of human hair. When the foreign material like solid or liquid into a narrow seal running gap can Cause degradation of seal performance and eventual failure of the seal. The external materials within the running gap of these result in increased shearing force between the primary and mating ring. The seal component then overheat that will lead to some mechanical seal failure like mating ring cracking O-ring deterioration.
On The Final Note
The above explanations of the dry gas seals are major points to note when studying the totality of gas seals. Indeed there is various gas seals contamination which can be seen in our other post. To ensure you acquaint yourself with the necessary information regarding dry gas seals listed on our blog.