Turbulence cavitation 3-1.4

Turbulence Cavitation 1-3.4

Cavitation means that cavities or bubbles are forming in the liquid that we’re pumping. These cavities form at the low pressure or suction side of the pump, causing several things to happen all at once:

  • The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.
  • We experience a loss in capacity.
  • The pump can no longer build the same head (pressure)
  • The pump’s efficiency drops.

The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.

We always prefer to have liquid flowing through the piping at a constant velocity. Corrosion or obstructions can change the velocity of this liquid, and any time you change the velocity of a liquid, you change its pressure. Good piping layouts would include :

  • Ten diameters of pipe between the pump suction and the first elbow.
  • In multiple pump arrangements locate the suction bells in separate bays so that one pump suction will not interfere with another. If this is not practical, a number of units can be installed in a single large sump provided that :
    • The pumps should be positioned in a line perpendicular to the approaching flow.
    • There must be a minimum spacing of at least two suction diameters between pump center lines.
    • All pumps are running.
  • The upstream conditions should have a minimum straight run of ten pipe diameters to provide uniform flow to the suction bells.
  • Each pump capacity must be less than 15,000 gpm..
  • Back wall clearance distance to the centerline of the pump must be at least 0.75 of the suction diameter.
  • Bottom clearance should be approximately 0.30 (30%) of the suction diameter
  • The minimum submergence should be as follows:
    FLOW
    MINIMUM SUBMERGENCE

    20,000 GPM

    4 FEET

    100,000 GPM

    8 FEET

    180,000 GPM

    10 FEET

    200,000 GPM

    11 FEET

    250,000 GPM

    12 FEET

The metric numbers are :

FLOW
MINIMUM SUBMERGENCE

4,500 M3/HR

1.2 METERS

22,500 M3/HR

2.5 METERS

40,000 M3/HR

3.0 METERS

45,000 M3/HR

3.4 METERS

55,000 M3/HR

3.7 METERS

See cavitation

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Posted

  • On February 17, 2018