What are the effects of a large flow pump operating at low flow for a long time?
, large flow pumps are widely used in electronics, electricity, chemical industry, metallurgy, medicine, food, electroplating, environmental protection, fire protection, municipal administration, water purification, textile printing and dyeing, mining and mineral processing, civil construction and other industries due to their good performance, high efficiency, long life and large flow. In actual operation, the flow of large flow pumps can be infinitely adjusted by various methods. Under normal circumstances, the pump works reasonably under the rated point condition, but sometimes due to some reasons, the pump runs under the small flow condition point, which will cause the following negative effects.
1. The pump body temperature rises. Since the actual flow of the pump is extremely small, that is, the useful work done by the pump is extremely small, and most of the shaft power is converted into heat energy and transmitted to the liquid in the pump, causing the entire shell to heat up. The radial thrust increases. At a very small flow rate, unreasonable continuous operation, excessive shaft bending and deflection, rapid wear of the bearing ring, and even excessive shaft fatigue, resulting in shaft breakage. When running at a small flow rate for a long time, the flow rate and the pump outlet pressure will change regularly and periodically. This phenomenon is called surge. When surge occurs, there are vibrations and sounds, which have adverse effects on the pump.
2. The internal reflux of the pump increases significantly, the cohesive heat increases, the temperature of the liquid in the pump increases, causing the pump body to heat up, affecting the mechanical properties of the pump parts, and also deteriorating the cavitation performance of the pump, further affecting the suction conditions of the pump.
3. The radial force of the pump increases, which worsens the force on the rotor of the pump. Because the pump deviates from the design operating point when working in the small flow area, the flow velocity of the liquid in the vortex chamber decreases, but according to the speed triangle analysis, the outflow velocity of the liquid in the impeller increases instead, so that the liquid cannot converge, forming an impact, continuously increasing the pressure and generating radial force.
4. The efficiency is reduced and the power consumption increases. When designing the pump, the efficiency point is generally near the rated operating point. If a large flow pump is running at a small flow operating point, its operating efficiency will drop quickly. Generally, the smaller the flow of the same pump, the lower the efficiency, so it is very uneconomical to operate under small flow conditions. Generally, it is necessary to re-equip a suitable small pump at this time.
5. The vibration and noise increase, causing environmental pollution, damaging pump parts, and affecting the service life of the pump. At the design operating point, since the direction of the liquid flow is consistent with the direction of the blades, the shedding loss, impact loss, and vortex loss are relatively small and close to zero. However, when the pump is working in the small flow area, due to the deviation from the design point, the shedding loss, impact loss, and vortex loss of the pump flow components are further increased, and these losses are accompanied by a large amount of hydraulic noise and mechanical vibration.
