JOHN CRANE PROVIDES NEW GAS-LUBRICATED NON-CONTACTING SEAL FOR HIGH TEMPERATURE ENVIRONMENTS

Phil Black - PII Editor 12/03/2009

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John Crane – the world”s leading supplier of engineered sealing systems and associated products – has announced the introduction of the Type 2874NE: a new highly reliable gas lubricated API 682 (ISO 21049) qualified High Temperature non-contacting mechanical seal that utilizes internally pressurized outward pumping spiral groove face technology with high-temperature seal features such as Inconel welded metal bellows and non-elastomeric carbon graphite secondary seals.

This innovative design technology is ideally suited for reliably sealing high-temperature process fluids on rotating equipment. Proven on difficult applications at a number of the world’s largest oil refineries, these seals will extend the Mean Time Between Repairs (MTBR) as compared with conventional seals operating in high-temperature environments.

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.

The Type 2874NE utilizes internally pressurized 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 Fordyce. “The performance of a conventional centrifugal pump can be made to operate with zero emissions and increased safety while increasing pump efficiency and increased MTBR.”

The Type 2874NE seals utilize an all-inconel bellows construction that is resistant to corrosive attack and retains its high strength at higher temperatures. Alloy 718 is the highest strength metal bellows material currently available.

The principles of the Type 2874NE operation are based upon spiral groove technology developed and patented 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 pressurized 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 revolutionary.

Both the Hydrocarbon Processing and Chemical Processing industry will benefit from The Type 2874NE as an innovative solution for shaft sealing of rotating equipment handling process fluids at elevated temperatures or fluids that are incompatible with conventional elastomers.

For more information contact John Crane EAA, Trafford Park, Manchester
Tel: (+44) (0)161 886 5993 Fax: (+44) (0)161 872 1654