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Inducer & Cavitation

Inducer

inducer
Inducers are used in the event of the danger of cavitation

  • They increase the pressure in the inlet area of the impeller
  • Inlet heights of hot fluids can be kept low
  • Cavitation noise is reduced or avoided
  • Installation heights of systems can be minimised

Cavitation

Definition:
Cavitation (lat. cavus = hollow) denotes the formation and the sudden collapse of steam-filled voids (steam bubbles) in flowing fluids.

Kyffhäuser Pumpen ArternHow and where does Cavitations occur?

Steam bubbles occur in places where the pressure drops to the evaporation pressure of the temperature of the media.

In centrifugal pumps, a pressure drop occurs in the suction line, the danger zone in this case is the impeller inlet.

Resulting voids (steam bubbles) are swept along with the flow and get into areas of higher pressures, where they suddenly collapse (cavitate).

kavitation_npsh

What are the consequences of cavitation?

  • Drop in the characteristic supply curve and the efficiency of the pump to the point of complete stoppage of the flow.
  • Increased noise to the point of loud rattling
  • Rough running with loud surges
  • Damage to the impeller (pitting by implosions) and other internal parts of the pump

Areas subject to the risk of cavitation

  • Pumping of seasoning from the whirlpool
  • CIP inlet
  • Vacuum evaporation 


How can cavitation be prevented?

  • Short, adequately dimensioned suction lines
  • Large inlet height before the pump
  • Accurate maintenance of the temperature regime

See Chapter NPSH


NPSH

Kyffhäuser Pumpen Artern

Definition:
The net energy level in the inlet cross-section of the pump is referred to as NPSH (Net Positive Suction Head).
The net energy level is the difference between the energy level and the evaporation pressure level.

What is NPSHerf.?

NPSHerf. is the minimum energy level required in the inlet port of the pump to limit cavitation, for a pump with certain parameters (speed, flow rate) and certain media.

What is NPSHvorh.?

NPSHvorh. is the net energy level in the inlet cross-section of the pump generated by the system.
The net positive suction head of the system is calculated as follows:

How can cavitation be avoided?

NPSHerf. < NPSHvorh.

Maximum installation height of the pump

kavitation_max_hoeheIn the event of a positive value for ze, the pump must be installed below the inlet-side fluid level by at least the distance ze.