In fields such as industrial production, water treatment, and mining, multistage centrifugal pumps serve as core fluid-conveying equipment due to their advantages of high head and large flow rate. If a pump fails to start, it will not only cause production line shutdowns and operation interruptions, but also may lead to secondary damage to the equipment, resulting in unnecessary economic losses. Combining practical experience, Changsha Zoomlian Pump Industry, a professional pump manufacturer, systematically sorts out the core causes of failure to start in multistage centrifugal pumps in this paper, together with clear troubleshooting logic and typical manifestations, to help technicians quickly locate problems and efficiently resolve faults.
The power supply is the core power source for pump startup, and its abnormality is the most common external factor leading to startup failure. Typical symptoms include no response after power-on or circuit breaker tripping. First, use a multimeter to detect the supply voltage—if it is 10% lower than the rated value (e.g., the voltage of a 380V motor is below 342V), the motor will fail to drive the pump shaft due to insufficient starting torque. Second, inspect the wiring: check if the three-phase power connections are loose or disconnected. For star-delta starting, ensure that the wiring corresponds to the motor winding terminals (star connection corresponds to the winding ends, while delta connection corresponds to the start and end of the windings) to avoid excessive starting current (more than three times the rated value) caused by wiring confusion, which triggers thermal relay protection. Meanwhile, check if the grounding line is intact. Reset the circuit breaker and thermal relay after tripping, and replace fuses with accessories of the same specification if they are blown.
After ruling out power supply factors, if the pump emits a buzzing sound but does not rotate, or manual turning is heavy, focus on checking for mechanical seizure. In scenarios such as sewage treatment and mine drainage, the impeller is prone to being entangled and stuck by foreign objects like stones and fibers, requiring pump body disassembly for cleaning. Bearing damage (ball wear, bearing housing deformation) or dried lubricating grease can cause shaft system "seizure", which necessitates bearing replacement and refilling with suitable lubricating grease. In addition, pump shaft bending, friction between the impeller and pump casing, and excessive coupling coaxiality deviation can also hinder operation, which should be addressed by shaft alignment and adjusting coupling deviation.
Failures caused by improper startup operations are mostly characterized by immediate tripping after startup or idling without output. When starting a multistage centrifugal pump, the outlet valve must be closed (to reduce load). If the valve is fully open, the motor has to overcome the full resistance of the pipeline, which is prone to overload shutdown. The phenomenon of "air binding" will occur if the pump body is not filled with liquid (air exists inside), so it is necessary to open the exhaust valve to release all air before startup. Avoid multiple startups and shutdowns in a short period to prevent motor overheating and protection triggering—it is recommended that the interval between two startups be no less than 5 minutes.
If the above troubleshooting steps show no issues, focus on core component failures. Burned motor windings (insulation layer damage, short circuit) or broken rotor bars will result in no response after power-on. Use a megohmmeter to test insulation performance and replace the motor if necessary. Seized mechanical seals or overly tight packing glands will increase shaft system resistance, accompanied by water leakage—adjust the tightness of the packing or replace the seals. Impeller wear, excessive balance precision deviation, or loose connection between the pump shaft and motor shaft will lead to power transmission failure, requiring impeller maintenance or tightening of connecting parts.
Improper type selection or installation deviations are likely to cause long-term pump startup difficulties and need to be fundamentally investigated. If the actual head far exceeds the rated head, the pump will fail to start due to overload—re-calculate the working conditions and replace it with a suitable model. During installation, unstable foundation fixing, air blockage or backflow in the pipeline, and air leakage in the suction pipeline will damage the working conditions—reinforce the foundation, optimize pipeline layout, and repair air leakage points. The coupling coaxiality deviation should be adjusted to within 0.05mm to avoid hindering power transmission.