Dry gas seal
Encyclopedia
Dry gas seals are non-contacting, dry-running mechanical face seal
s consist of a mating (rotating) ring and a primary (stationary) ring. When operating, grooves in the rotating ring generate a fluid-dynamic force causing the stationary ring to separate and create a gap between the two rings. Dry gas seals are mechanical seals but use other chemicals and functions so that they do not contaminate a process. These seals are typically used in a harsh working environment such as oil exploration, extraction and refining, petrochemical industries, gas transmission and chemical processing.
The dry gas seal has spiral grooves, with provides for lifting and maintaining separation of seal faces during operation. Grooves on one side of the seal face direct gas inward toward a non-grooved 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.
The use of these seals in centrifugal compressor
s has increased significantly in the last two decades because they eliminate contamination and do not use lubricating oil. Non-contacting dry gas seals are often used on compressor
s for pipeline
s, off-shore applications, oil refineries
, petrochemical
and gas processing plants.
Dry Gas Seal configurations:
there are many dry gas seal configurations base on their application.
1- Single gas seal
2- Tandem gas seal
3- Tandem gas seal with intermediate labyrinth
4- Double opposed gas seal
Also the dry gas seal can be unidirectional or bidirectional.
issued the first patent
for dry gas seals in 1968 with field applications beginning in 1975. When the technology was introduced, it was aimed at correcting the problems with dry gas film environments by eliminating friction
. Soon, the technology became a common replacement for other lubricated seals. The patented spiral-groove technology of the dry gas seal allows for easy lifting and separation of seal faces during operation. There are three common types of lubrication for these seals: full liquid film, which contains oil and requires light-duty conditions; partial liquid/gas film, which requires a 50 percent balance of liquid to preserve the seal; and dry gas film, which has an absence of liquid that creates hot localized areas that may lead to cracking or damage to the seal. Seal failure results from a flooded compressor with oil or liquid, foreign contaminants and alignment problems.
Seal (mechanical)
A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage , containing pressure, or excluding contamination...
s consist of a mating (rotating) ring and a primary (stationary) ring. When operating, grooves in the rotating ring generate a fluid-dynamic force causing the stationary ring to separate and create a gap between the two rings. Dry gas seals are mechanical seals but use other chemicals and functions so that they do not contaminate a process. These seals are typically used in a harsh working environment such as oil exploration, extraction and refining, petrochemical industries, gas transmission and chemical processing.
The dry gas seal has spiral grooves, with provides for lifting and maintaining separation of seal faces during operation. Grooves on one side of the seal face direct gas inward toward a non-grooved 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.
Design and use
Grooves 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.The use of these seals in centrifugal compressor
Centrifugal compressor
Centrifugal compressors, sometimes termed radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.The idealized compressive dynamic turbo-machine achieves a pressure rise by adding kinetic energy/velocity to a continuous flow of fluid through the rotor or impeller...
s has increased significantly in the last two decades because they eliminate contamination and do not use lubricating oil. Non-contacting dry gas seals are often used on compressor
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
s for pipeline
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
s, off-shore applications, oil refineries
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
, petrochemical
Petrochemistry
Petrochemistry is a branch of chemistry that studies the transformation of crude oil and natural gas into useful products or raw materials. These petrochemicals have become an essential part of the chemical industry today.-Origin of Petroleum:...
and gas processing plants.
Dry Gas Seal configurations:
there are many dry gas seal configurations base on their application.
1- Single gas seal
2- Tandem gas seal
3- Tandem gas seal with intermediate labyrinth
4- Double opposed gas seal
Also the dry gas seal can be unidirectional or bidirectional.
History
John Crane Inc.John Crane Inc.
John Crane Inc. is a subsidiary of Smiths Group, which is a British company listed on the London Stock Exchange.John Crane designs and manufactures mechanical seals , sealing support systems, gland packing, asset management systems, power transmission couplings, bearings and bearing isolators for...
issued the first patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
for dry gas seals in 1968 with field applications beginning in 1975. When the technology was introduced, it was aimed at correcting the problems with dry gas film environments by eliminating friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
. Soon, the technology became a common replacement for other lubricated seals. The patented spiral-groove technology of the dry gas seal allows for easy lifting and separation of seal faces during operation. There are three common types of lubrication for these seals: full liquid film, which contains oil and requires light-duty conditions; partial liquid/gas film, which requires a 50 percent balance of liquid to preserve the seal; and dry gas film, which has an absence of liquid that creates hot localized areas that may lead to cracking or damage to the seal. Seal failure results from a flooded compressor with oil or liquid, foreign contaminants and alignment problems.