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Sunday, August 3, 2008

Vertical Pumps

In the chemical Industry, the term vertical process pump generally applies to a pump with a vertical shaft having a length from drive and to impeller of approximately 1 m (3.1 ft) minimum to 20 m (66 ft) or more. Vertical pumps are used either wet-pit pumps (immersed) or dry-pit pumps (externally mounted) in conjunctive with stationary or mobile tanks containing difficult to handle liquid.

They have the following advantages:

  • The liquid level is above the impeller
  • The pump is thus self-priming
  • The shaft seal is above the liquid level and is not wetted by the pumped liquid which simplifies the sealing task (a safety consideration for highly corrosive or toxic liquid)
  • The vertical wet-pit pump may be the only logical choice.

These pumps have the following disadvantages:

  • Intermediate or line bearing are generally required when the shaft length exceeds about 3 m (10 ft). In order to avoid shaft resonance problem, these bearing must be lubricated whenever the shaft is rotating.
  • Since all wetted parts must be corrosion resistant, low-cost materials may not be suitable for the shaft, column, etc.
  • Maintenance is more costly since the pump are larger and more difficult to handle.
For abrasive service, vertical cantilever designs requiring no line or foot bearings are available. Generally, these pumps are limited to about 1 m (3.1 ft) maximum shaft length.

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