drive side sealing options

Selecting Pump Sealing Options

Specific to Applications

Bob Antion Northeast USA Sales Manager

Metso Slurry Pumps

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85% of Pump Problems come from the Suction Side

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This presentation deals with the opposite side

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And the importance of sealing

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Function of the Shaft Seal

•The basic function of the shaft seal is to prevent leakage at the point where the shaft enters the casing

•With flooded suction the leakage is generally liquid leaving the pump

•With a suction lift the leakage can be air entering the pump

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Types of Seals

•Full flow flushing type•Low flow flushing type•Dynamic seal- expeller•Single mechanical seal- Zero flush•Single mechanical seal- Low pressure flush•Double mechanical seal- High pressure flush

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Full and Low Flow Glands

•Compression packings depend upon the existence of a thin film between the packing surface and the moving shaft for lubrication and cooling. Seal water is used and is distributed by a lantern ring inserted in the packing set. During the break-in period, the gland is adjusted to gain control of the leakage to reduce it to a minimum while maintaining the cooling and lubricating film on the shaft.

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Five Steps to Successful Sealing

•1) Proper selection of the packing material. The packing material must be carefully selected for the application and service.

•2) Proper environment for the packing material. The controls to maintain the lubricating film must be provided. Seal water pressure must be 5-10 psi above discharge pressure of pump and at the flow rate called out in manual.

•3) Proper equipment maintenance. The equipment must be in good running condition.

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continued

A true running shaft with a smooth polished sleeve ensures the longest service

•4) Proper installation. Attention to fit and cleanliness is essential

•5) Proper break-in procedures must be followed .The care taken at start-up can extend the service life of the packing set many times.

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ADVANTAGES DISADVANTAGES

• Fewer pump parts

• Simple system

• Inexpensive

• Additional pump required

• Clear water source required

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Dynamic Seal

•Also called centrifugal seal or expeller seal.•Only works when pump is running and requires static packing seal to prevent leakage when pump is not running.

•No flush water is required and there is no dilution of slurry by flush water.

•There is reduced maintenance of packings•There are limitations based on the ratio of inlet head versus operating discharge head.

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• No Gland Water or additional Pump required.

• Leakage when pump not running

• Limitations based on pumping conditions

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Mechanical seals•Single Seal- Zero Flush

- Doesn’t require flush water.- Depends on slurry to cool and lubricate seal faces.- Seal faces will be destroyed in seconds if run dry.- Can not be used where exposed to particleSize of 1 to 5 micron.

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Mechanical Seals

•Single mechanical seal- low pressure quench-Not suitable for 1 to 5 micron particle range.-Requires clean water supply for water quench.-Doesn’t require resetting after bearing housing adjustment.

-Seal faces easy to replace.-Suitable for light slurry applications

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Double Mechanical Seal•Suitable for all applications.•Requires clean water for quenching.•Doesn’t require resetting after bearing adjustment.•Easy to rebuild and replace seal faces.•High cost keeps it out of many applications.

drive side sealing options

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