Cavitation at the pump (3)

In the last two posts: here and here, we have to know what it is cavitation, its effect and the classification of cavitation, namely:
1 Vaporisation - Evaporation.
2 Water ingestion - The entry of outside air into the System
3 Internal Recirculation - Turn on the Circulation System
Next we briefly examine the four classifications:
4 Turbulence - Turbulence Flow
We always want the fluid flow at a constant speed. Corrosion and barriers that exist in the system piping can change the speed of the fluid and any changes speed, the pressure is changed. To inhibit this, needs to be a good piping system design. Among other things meet the following conditions:
The minimum distance between the suction pump with the first elbow at least 10 X the diameter of the pipe. In many settings the pump, attach the suction bells in separate bays, so that the suction side of the pump will not interfere with the other. If this is not possible, some pumps can be mounted on the tub suction (sump) is large, provided that:

         Position the pump perpendicular to the flow direction.
         The distance between the two 'center line' minimum pump suction diameter twice.
         All pumps in a state of 'runing'.
         Upstream piping sections at least have a straight pipe with a length of at least 10 x the diameter of the pipe.
         Each pump shall have a capacity of less than 15,000 gpm.
         Basic adjustment should pump about 30% the diameter of the suction pipe.
         Pump mounting depth relationship with a capacity adjusted to the following table:

capacity	Minimum depth
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

For metrics:

capacity	Minimum depth
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

5. Vane Passing Syndrome
Damage caused by this type of cavitation occurs when the outer diameter of the impeller passing too close to the 'cutwater' pump. The fluid flow velocity increases when the flow through the small path, the pressure decreases and causes local evaporation. Air bubbles are formed and then broke out in a place that has a higher pressure, a little outside the groove cutwater. This is what causes damage to the volute (snail home) pump.
To prevent excessive movement of the shaft, some manufacturers install a bulkhead rings on the suction eye. On the exit side (discharge), the ring can be made to extend out of the side wall of the discharge to the impeller casing.