Re: "326" Water Pump Shaft Failure
The pump doesn't cavitate. If it did, there'd be evidence of spalling on the impeller vanes. When a pump cavitates, areas of low pressure are created which causes the fluid to boil in localized areas. When the fluid "flashes" or boils, tiny pieces of metal are carried away from the vanes. Pumps which have been cavitating to any great extent look as if they are severely corroded, due to the spalling.
Vane type pumps, since they are not positive displacement, will "churn" the fluid if it is running at moderate to high speed and the flow rate through it is diminished. This can happen if there is a blockage in a closed system (like an engine's cooling system), or flow through a hose is shut off (such as on a fire pump). If the fluid is recirculated through the volute with low or no flow, it will become heated, sometimes to the point of inducing cavitation even though the impeller is not running at a high rate of speed. The best way to combat this situation, which can occur frequently in a fire pump, is to maintain flow by opening the pump drain partially................
The pump doesn't cavitate. If it did, there'd be evidence of spalling on the impeller vanes. When a pump cavitates, areas of low pressure are created which causes the fluid to boil in localized areas. When the fluid "flashes" or boils, tiny pieces of metal are carried away from the vanes. Pumps which have been cavitating to any great extent look as if they are severely corroded, due to the spalling.
Vane type pumps, since they are not positive displacement, will "churn" the fluid if it is running at moderate to high speed and the flow rate through it is diminished. This can happen if there is a blockage in a closed system (like an engine's cooling system), or flow through a hose is shut off (such as on a fire pump). If the fluid is recirculated through the volute with low or no flow, it will become heated, sometimes to the point of inducing cavitation even though the impeller is not running at a high rate of speed. The best way to combat this situation, which can occur frequently in a fire pump, is to maintain flow by opening the pump drain partially................
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