One critical factor in achieving optimal pump performance is ensuring your pump’s inlet pressure is sufficient for your pump’s requirement. Inlet pressure is the pressure at the pump suction, and it is essential that the fluid pressure at the pump suction, or Net Positive Suction Head available (NPSHa), is high enough to match or exceed the Net Positive Suction Head required (NPSHr) on the pump. However, various factors can cause low NPSHa, which can affect the pump’s performance and lead to issues such as cavitation. You can check the pump manufacturer’s performance curve to track what the NPSHr is for the pump that is having these issues. Let’s explore several ways to increase the inlet pressure in a system for your pump including making adjustments to the system, using booster pumps, checking and fixing suction line leaks, and adjusting the NPSHr for your pump.
Make System Adjustments
If the pressure at the pump inlet is still insufficient, increasing the height of the storage tank, reservoir, or feed pipe can be an effective solution. By increasing the hydrostatic head, the height increase can help to increase the pressure at the pump inlet and provide a greater force on the fluid. This can help to overcome any frictional losses from the pipe, valves, or other structural items in the suction line. And, although it would cost more, another way to increase NPSHa is increasing the diameter of the supply pipe.
Decrease the Size of the Impeller
If changing system structures are cost prohibitive or downright impossible, and alternative would be to reduce the impeller diameter. Reducing a pump’s impeller diameter will decrease the amount of NPSHr the pump requires to run efficiently, thus the requirement for NPSHa is less. However, it is important to note, that even though the NPSHr is reduced in the pump, the total dynamic head and flow rate will be reduced as well.
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Install a Booster Pump
Commonly used in water municipalities or other industries that require high head and pressure, booster pumps can be used to increase the inlet pressure by increasing the flow rate of the liquid being pumped. A couple of great products for this solution would be the Grundfos Hydro MPC or the Barmesa HMV series. The MPC system consists of multiple pumps that work together to provide the desired pressure and flow rate. The MPC is perfect for a system that requires a high level of pressure to meet the NPSHr requirements of a pump at the end of the line. However, the Barmesa HMV series is a single pump designed to be installed directly into your pipping system with the same diameter with the outlet and inlet at the same level resulting in minimal system changes. The HMV series is perfect for a system that needs higher fluid pressure and flow, but doesn’t require an exorbitant
Conclusion
All the steps listed above are common steps that can be taken to increase suction pressure, but we highly recommended consulting our pump and application engineers to help you decide on the best steps to take to reduce cavitation in your system. Contact a Southeast Pump engineer.
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