the essential criteria for dry gas seals is a clean and dry gas. the design does need to consider all operating scenarios of the equipment (i.e. normal start-up/shutdown, emergency shutdown, normal operation, etc.). consider source of gas and destination of gas for extended periods of time. position of seal faces and source of gas during downtime.
there are some interesting and suitable applications (pumps - no kidding!, compressors, etc.) in which dry gas seals are being used.
good luck!
-pmover
John Crane and Flowserve are the two largest suppliers for compressor seals although there are other designs. AP-614 Chapter 4 covers the support systems for these seals, and API-617 has some generic cross sections of gas seals. Gas seals come in different "flavors" including unidirectional and bidirectional and different configurations such as single, double, tandem, and tandem with an intermediate labyrinth for inert gas injection. Due to the complexity, I strongly favor cartridge seals which are available on most all multistage compressors, but may not be available on integrally geared units by some manufacturers due to space and impeller overhang considerations. Concentrate on the seal support system and keep the seal environment controlled, and these are the best technology process seals currently available.
