Gas lubricated, non-contact seal for high temperature duties
02 March 2009
John Crane has introduced the Type 2874NE gas lubricated API 682 (ISO 21049) qualified, high temperature, non-contacting mechanical seal for rotating equipment. The device utilises internally pressurised, outward pumping spiral groove face technology with high-temperature seal features such as Inconel welded metal bellows and non-elastomeric carbon graphite secondary seals. The design is suitable for sealing high-temperature process fluids on rotating equipment.
According to Jesse Fordyce, Market Manager at John Crane, the industry has long sought a non-contacting, elastomer-free seal that can handle hot hydrocarbons up to 425° Celsius (800° Fahrenheit) and fluids requiring inert secondary seals. The Type 2874NE is an innovative alternative to conventional wet contacting seals supported by various piping plans that provide liquid barriers, buffers, or quenches to the primary seal interface. Instead of using a wet support system, the advantages of non-contacting gas-lubricated technology can be used for reliable operation with a nitrogen barrier.
Spiral Groove Technology
The stationary seal faces (Mating Rings) are micro-machined with a spiral groove pattern, which pumps barrier gas from the inside diameter (ID) of the seal to the outside diameter (OD), thus positioning the process fluid at the outside diameter of the rotating metal bellows. The Primary Rings seal against the un-grooved sealing dam of the Mating Ring. The inner sealing face pair is pressurised on the ID to a pressure differential of 2 bar / 30 psi minimum. The outboard seal faces handle full differential pressure and also pump from the seal ID to the seal OD.
When the pump shaft turns, a band of high-pressure barrier gas is created between the seal faces. This lifts the seal faces and creates a non-contacting dynamic seal. No friction, no heat, no wear, and no cooling requirements provide a sealing technology that is highly innovative.
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