What may cause a pump to fail in discharging?

A pump may fail to discharge effectively if the suction lift is too high. This situation occurs when the height from the surface of the liquid being pumped to the centerline of the pump is excessive, resulting in a greater demand on the pump to lift the fluid against gravity. Pumps have a maximum suction lift capability, and exceeding this limit can lead to cavitation, where vapor bubbles form in the liquid, causing a drop in pressure. This can result in poor pump performance or an inability to move fluid altogether.

The other factors do not directly relate to the pump's ability to discharge. For instance, excessive gravity generally refers to the weight of the fluid which does not directly impede a pump's operational capability. Tubercation is a form of corrosion in pipes that can restrict flow but is not a direct cause of pump failure in discharging. Proper lubrication is crucial for pump operation, but it does not specifically relate to the suction lift issue that would significantly affect discharge capacity.