Floating Carbon Rings vs Dry Gas Seals in CO2 Compressors: When to Use Which

In centrifugal compressors, two sealing solutions are often compared: floating carbon ring and dry gas seal. Each type has its own role.

Floating carbon ring

Are segmented carbon rings surrounding the shaft, creating a very small clearance to limit gas leakage. Simple structure, resistant to high temperature and speed, but still has a certain amount of gas leakage and requires gas leakage treatment.

Dry gas seal

Uses a gas membrane between two non-contacting seal faces. According to information from Atlas Copco, in field tests, compared to standard carbon rings, dry gas seals emit an amount of CO2 that is only a small fraction, while the short length of the seal helps to compact the compressor size.

Combining both

In practice, many compressors use a combination of floating carbon ring and dry gas seal. The carbon ring acts as a separating seal or auxiliary seal, and the dry gas seal takes on the main sealing task.

Suggested selection

• Requires very low leakage and emission control: prioritize dry gas seal.
• High temperature conditions, dirty media or simple requirements: consider carbon ring.
• Consider total life cycle cost and support system.

Reference source

Atlas Copco (CO2 compressor documentation), compiled from industry practices. The article is compiled and reinterpreted by SNS-VN; brand names belong to their respective owners.