MTH has developed proprietary inlet and pumping techniques for reducing the NPSH required by its pumps to handle hot fluids near their boiling point with minimal cavitation. When pumping water at or near 212 degrees F it becomes more and more difficult to draw the fluid into the pump inlet without vaporizing it and causing vapor lock. Even if there is some cavitation in the pump, Regenerative Turbines are well known for having some of the best resistance to cavitation erosion and can often handle vapor in excess of 20% for certain periods of time. Most of our products will handle 4 foot NPSHA, but our 250/260/270 Series can handle down to 2 feet, with some of our 240/280 Series capable down to 1 foot. Please see our Standard Products for more info.
The reduced NPSHR (Net Positive Suction Head Required) provided in our ow NPSH models is obtained by using a first stage centrifugal style impeller with inlet flow paths shaped to maintain a constant fluid velocity. This reduces entry losses to the impeller as well as maintaining efficiency. A multi-vane diffuser is used in conjunction with the centrifugal impeller for balancing radial loads and extracting the maximum pressure from the first stage. Pressure and flow produced by the NPSH inducer assures that the succeeding stages are adequately fed.
NPSH of Water(Net Positive Suction Head) |
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Atmospheric Pressure at Sea Level
(Based on Water) |
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NPSHA (Available)
(Height and Energy of the Water in the supply tank) |
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NPSHR (Required)
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NPSH-A must exceed the pump's NPSH-R rating for the chosen operating conditions to ensure that cavitation is avoided. |
| If the water level of your source tank is 4 feet from the centerline of the pump to the top of the water level, and the water temperature is below 90°F, then you have at least 36.34 feet of NPSHA |
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| When the water is heated up, at between 207°F & 208°F, and the tank has 4 feet between the centerline of the pump and the water level of the tank, there is only 7 feet of NPSHA |
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| When water is boiling (212°F), and the tank has 4 feet between the centerline of the pump and the water level of the tank, there is only 4 feet of NPSHA |
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