Why high discharge head centrifugal pump can not used for low discharge head centrifugal pump ?
The appropriate selection of water treatment equipment is essential knowledge for every designer. As a core component for conveying and lifting, pumps are ubiquitous in water treatment projects. Consequently, the methodology for selecting suitable pumps holds significant importance. Typically, when selecting a pump, we inquire the user's specific requirements for flow rate and didcharge head. If these parameters cannot be determined, it is impossible to make an accurate selection.
Prior to purchasing a pump, many users mistakenly believe that selecting a higher head pump for lower head conditions allows for a wider range of operational heads. This misconception leads to the purchase of pumps with excessively high head capabilities.
In reality, for centrifugal pumps, once the model is determined, power consumption is directly proportional to both the actual head and flow rate. When operating at a lower head, the flow rate increases, resulting in higher current draw and greater power consumption. Conversely, higher head conditions result in lower flow rates and reduced power consumption. To prevent motor overload, the actual calibrated lift of the pump should generally be no less than 60% of its rated capacity.
Using a high head pump in low head applications can lead to motor overheating and potential burnout. In emergency situations, an outlet valve installed in the discharge pipe can be adjusted to reduce the outlet water flow and prevent motor overload. Self-operated control valves or other methods can be used to regulate flow. It is crucial to monitor motor temperature; if overheating occurs, reducing the outlet flow or shutting down the pump promptly can prevent motor damage. Some users attempt to reduce flow by lowering the supply voltage, which actually increases motor load and is counterproductive. Instead, the discharge pipe of a centrifugal pump station should be equipped with a valve to manage motor load. The valve should be closed before stopping the pump and gradually opened after starting to prevent overcurrent during startup.
Proper installation requires positioning the low-lift pump before the high-lift pump, ensuring that the outlet pressure of the low-lift pump does not exceed the inlet pressure limit of the high-lift pump to avoid overpressure leakage.
Therefore, selecting the appropriate head is critical. When purchasing a centrifgual pump, it is essential to determine the required head or discharge pressure to ensure the correct pump selection.
