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John Crane has announced the introduction of the Type 2874NE gas-lubricated, API 682 (ISO 21049) qualified, high temperature, non-contacting mechanical seal.

The Type 2874NE is an 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.

The Type 2874NE utilises internally pressurised outward pumping spiral grooves to achieve an effective non-contacting seal.

This spiral groove arrangement places process fluid at the outside diameter of the bellows allowing centrifugal action to keep contaminants free of the welded metal bellows plates and thus keeping the seal head assembly clean and flexible.

The Type 2874NE is an elastomer-free seal outfitted with inert flexible graphite secondary static seals to provide for higher temperature capability and a greater chemical compatibility range.

There are no dynamic elastomers in the bellows design, which helps improve seal reliability.

This rugged seal with pressure balanced design ensures full reverse pressure containment capability in the event of a temporary loss of barrier pressure where seal chamber pressure exceeds barrier gas pressure.

The Type 2874NE will continue to seal the process fluid protecting the barrier chamber and system from exposure to the process fluid.

This is also an important safety feature protecting the environment and personnel against product release.

‘Rotating equipment performance and reliability can be increased through the proper application of the Type 2874NE,’ said Jesse Fordyce, market manager at John Crane.

‘The performance of a conventional centrifugal pump can be made to operate with zero emissions and increased safety while increasing pump efficiency and increased mean time betwen repairs (MTBR).’ The Type 2874NE seals feature an all-inconel bellows construction that is resistant to corrosive attack and retains its high strength at higher temperatures.

The principles of the Type 2874NE operation are based upon spiral groove technology developed by John Crane.

The stationary seal faces (mating rings) are micro-machined with a spiral groove pattern.

The spiral groove pattern 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/30psi 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.

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