Dry gas seals are used to seal centrifugal compressor shafts in harsh industrial environments without the need for lubricating oil. Gas seal failure can occur due to various reasons, and the design of the gas seal is critical to its function. John Crane Inc. patented the spiral groove design in 1968, which reduced friction without the need for liquid lubrication. There are two other types of lubrication used in these operations: full liquid film and partial liquid and gaseous film.
A gas seal, often referred to as a dry gas seal, is used to seal the shafts of centrifugal compressors. Its main advantage is that it does not require lubricating oil to operate and is therefore less likely to contaminate the sealing process. Dry gas seals are used in harsh industrial environments where workers are exposed to many chemicals, such as in petrochemical processes, mining and refining, oil drilling and gas transmission. Gas seal failure can occur due to a variety of reasons including compressor flooding, shaft misalignment, or particle contamination.
The design of the gas seal is critical to its function. It was created to trap noxious odors, chemicals and gases inside centrifugal compressors, carrying pipes that carry gases from one processing site to another. The spiral grooves on the outside of the gasket facilitate lifting and handling during industrial use. The grooved part of the gasket conducts the gas to the non-grooved part of the gasket. This action traps the gas between the two parts, increasing the internal pressure.
This pressure leaves a small gap between the grooved and non-grooved faces of the gasket, improving the resistance of the fluid film. The resistance allows for maximum protection against any contaminants touching the gas seal faces. The resistance of the fluid film can be adjusted according to the industrial design or the nature of the compression system.
Dry gas seals have an interesting and varied history. John Crane Inc., a British turbomachinery manufacturing and maintenance company, was the first to register the dry gas seal patent in 1968. The company patented the aforementioned spiral groove design, which has become very popular in petroleum and petrochemical applications. Before the company introduced the new model, the industry relied on lubricated seals to seal and maintain centrifugal compressors. Lubrication was messy, made the seals harder to handle, and sometimes led to contamination of the compressor contents.
Despite its drawbacks, lubrication is required to reduce friction between the gas seal faces. John Crane Inc.’s innovation was the use of a dry gas film, which reduced friction without the need for liquid lubrication. There are two other types of lubrication used in these operations: full liquid film, which carries various types of oils and is intended for use in light machining operations, and partial liquid and gaseous film, which uses one part liquid and one part gas to maintain the integrity of the seal.
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