Dry Gas Seal
Dry Gas Seals are non-contacting, dry-running mechanical face seals that consist of a mating (rotating) ring and a primary (stationary) ring. When operating, lifting geometry in the rotating ring generates a fluid-dynamic lifting force causing the stationary ring to separate and create a gap between the two rings.
Machined-in lift profiles on one side of the seal face direct gas inward toward an extremely flat portion of the face. The gas that is flowing across the face generates a pressure that maintains a minute gap between the faces, optimizing fluid film stiffness and providing the highest possible degree of protection against face contact. The seal's film stiffness compensates for varying operations by adjusting gap and pressure to maintain stability.
Grooves or machined ramps on the seal direct gas inward toward the non-grooved portion. The action of the gas flowing across the seal generates pressure that keeps a minute gap, therefore optimizing fluid film stiffness and providing protection against face contact.
Dry Gas Seal (DGS) is nowadays recognized by markets as the most reliable sealing device for Centrifugal Gas Compressors. After decades the DGS technology has proven to be effectively reliable and has better performance than other shaft sealing methods as outlined in API 617 and API 692.
Nevertheless, to achieve optimum performance DGS needs to be clean and dry, and has positive pressure all the time. Guidance on dry gas sealing systems for centrifugal gas compressors is available in API Standard 692.