Bauer Magnum SM 540 Operating Manual page 27

Cavitation
By cavitation or building of a cavity, we understand the immediate coming and going of steam bubbles in a liquid
flow.
Steam bubbles appear when the static pressure of the liquid decreases because of the growing absolute speed
or when the geodesic height sinks to the level where the steam pressure pertinent to the liquid temperature is
reached.
Yet, before material is removed because of the immediate breakup of the steam bubble, cavitation causes an
increasing noise level and a run with disturbances, because the pump efficiency rate and the manometric head
go down.
If, however, the pump is operated over a longer period of time while cavitation is ongoing, the disturbed run of
the pump can cause the pump shaft to vibrate, which again can cause the opening of the slide ring sealing.
Slide ring sealing
The slide ring sealing HJ 977 GN is independent of rotational directions and is, because of its spring alignment,
ideal for material containing solids and highly viscous material.
To function properly, it is important to comply with the given mounting length.
The oil reservoir must always be filled with oil.
After operation the sealing room must be cleaned quickly (rinsed) with a pure liquid (water).
If, for any reason, the cleaning is not done, the sealing might get aggluminated with the dried-up slurry, which
has a negative effect upon a new start. , e.g. dry run, insufficient lubrication, cracks – failure of the sealing
Factors that influence the pump wear
General information
Important influential elements for the safety and the life of the centrifugal pump are operational, i.e. ones that
occur during the pump operation
The pump is laid out for certain performances. If operated outside its capacity, you have to expect operational
conditions, that can have a detrimental effect on its operational safety and life.
One is the operation of the pump with a closed valve.
The problematic zones in such an operational condition are:
•
Increased axial thrust, which means an early wear of the bearing.
•
Premature destruction of the mechanical seal.
•
The spiral exerts an additional hydraulic power on the impeller as a consequence of the asymmetric
hydraulic burden
•
Increased temperature
In extreme cases the pump can become a bomb under such operational conditions and explode.
•
Also a problem is the operation in an oversized pipe network. The pump becomes instable and shows
unfavorable vibrations.
In addition, take care that the pump does not run in cavitation. (decrease in pump capacity and efficiency rate)
The cavitation is accompanied by a disturbed run, a weird cracking sound and in severe cases the vibrations of
the entire pump.
In severe cases of cavitation, the channels of the impeller of the centrifugal pump can be blocked by the steam
bubbles in a way that the delivery stalls completely.
Highly abrasive material
Cleaning
Maintenance
Do not run the pump to its limits (permanently)
Operating manual for BAUER gear pump
of the pumping medium and the insufficient release of heat.
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