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Seal range improves performance

19 November 2007

A new range of non-contacting mechanical seals launched by John Crane improves seal performance on pump applications by reducing operational costs, enhancing reliability, increasing safety and also extending seal life. Designed for non-turbo, large-bore rotating equipment applications, the new Type 2800X dual seals feature patented new technology that provides environmentally-friendly and emission-free sealing.

The 2800X seals have been created for use in a wide variety of performance-critical applications. These include the processing of extremely pure materials where no contamination is permissible, the use of reactive or temperature-sensitive media where local process ‘hot spots’ can cause unwanted chemical reactions, cold applications such as ammonia processing, and air/oxygen-sensitive processes where unwanted oxidation reactions could occur.

The seals feature spiral grooves machined into the mating ring faces of the seal heads. As the pump shaft rotates, a pressurised inert gas is injected between the faces and compressed as it flows into these grooves. The gas expands again as it leaves the spiral grooves and generates a force which separates the faces to create non-contacting operation. This minimises seal face wear, reduces running and repair costs and extends seal life. Because the gap between the seal faces is kept to a minimum, barrier gas usage is also reduced.

A reverse pressure capability ensures that if the barrier gas fails, the process pressure will close the seal faces, preventing any large-scale loss of process fluid to atmosphere. The result is safer and more environmentally-friendly operation, even under breakdown conditions. The system also eliminates the need for any complex barrier fluid system, which simplifies the installation procedure.

This environmentally-friendly performance of the 2800X seals also translates into greater economy for the end user. Figures released by the Fluid Sealing Association show that they reduce the cost of electricity used and the associated greenhouse gas emissions by 92%, when compared to a conventional wet seal rotating at normal pump speeds and pressures.

The patented 2800X design can accommodate both lower and higher speeds and pressures than similar seals and this further extends reliability, while the use of new polymeric components reduces hang-up problems with solid-in-liquid process fluids. The various 2800X seals also incorporate many common components. This minimises spares stockholding and also encourages the re-use, refurbishment and re-cycling characteristics of the seals.

The ability to retrofit the 2800X range into installations currently using John Crane’s 2800, 2800ER, and 2800HP seals enables end-users to upgrade their current sealing arrangements as part of their normal maintenance programs.

Included in the 2800X range are versions that meet and exceed the performance and design requirements of the latest American Petroleum Institute API 682 edition seal standard.

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