As core equipment for high-pressure water supply, industrial pressurization and building water supply and drainage systems, self-balancing multistage pumps feature stable operation, high head, no axial force and long service life, and are widely applied in industrial and mining enterprises, municipal engineering, water conservancy and water supply industries.
However, during long-term continuous operation, affected by multiple factors such as installation deviation, foundation settlement, component wear, off-design working conditions and pipeline stress, the equipment is prone to abnormal vibration and excessive noise. If not inspected and handled in a timely manner, it will gradually cause hydraulic performance attenuation, seal leakage, bearing burnout, impeller wear and other component damages. In severe cases, it will lead to equipment shutdown and system outage, directly affecting the stable operation of the entire water supply system.
Based on practical experience in on-site operation and maintenance, fault overhaul and commissioning of self-balancing multistage pumps, this paper systematically sorts out the troubleshooting scheme and rectification and optimization technology for vibration and noise abnormalities from ten core dimensions, including vibration source positioning, foundation verification, drive system diagnosis, rotating component detection, operating parameter optimization, pipeline stress check, preventive maintenance, professional technical support, standardized safety operation specifications and full-cycle monitoring, providing standardized technical support for the long-term and stable operation of equipment.
1 Accurate Vibration Source Positioning (Dual-Dimension Inspection of Spectrum & Operating Conditions)
The vibration and noise faults of self-balancing multistage pumps are mostly compound-induced, which cannot be accurately located by simple visual inspection. It is necessary to adopt professional detection methods ofvibration spectrum analysis and acoustic positioning, and conduct comprehensive judgment combined with real-time operating data of equipment. During the operation, key operating parameters such as bearing temperature, motor current fluctuation and pump abnormal noise are continuously monitored, with focus on checking the assembly accuracy of the equipment connection system. The coupling alignment deviation is strictly controlled, with both radial deviation and angular deviation not exceeding 0.05mm to avoid mechanical vibration caused by excessive misalignment. Meanwhile, the pre-tightening force of foundation bolts is fully checked to eliminate low-frequency vibration caused by loose bolts, uneven stress and virtual connection from the source.
2 Stability Verification and Reinforcement of Equipment Foundation
Insufficient stiffness, settlement and cracking of the pump concrete foundation and voids between embedded steel plates and foundation are latent core causes of long-term pump vibration. Professional rebound modulus detection shall be carried out for the equipment foundation. For conventional C30 concrete foundation, the rebound strength must be no less than 30MPa to ensure qualified bearing capacity. Check the bonding part between embedded steel plates and concrete foundation carefully; if the crack width exceeds 0.1mm, high-pressure grouting filling treatment must be implemented in a timely manner to prevent crack expansion and foundation looseness. For foundations with insufficient stiffness and settlement deformation, the secondary grouting process can be adopted for reinforcement. Non-shrinkage special grouting materials are selected with the water-cement ratio controlled at 0.14~0.18 to ensure grouting compactness and overall foundation stiffness, and completely eliminate foundation resonance.
3 Comprehensive Fault Diagnosis of Drive System
Abnormal operating conditions of motors, couplings and transmission mechanisms are important fault sources inducing pump vibration and noise, which require full-dimensional accuracy detection and performance verification. For motors, focus on detecting insulation performance and winding parameters: the normal insulation resistance of equipment shall be ≥100MΩ, and the inter-phase DC resistance deviation of stator windings shall be ≤2% to avoid electromagnetic vibration caused by motor inter-turn short circuit and insulation aging. For couplings, check keyway wear; the coupling must be replaced integrally when the keyway wear depth is greater than 0.2mm to prevent operation jitter caused by excessive transmission clearance. For belt transmission structures, accurately measure the diameter deviation of V-belt pulley groove bottom with the error controlled within 0.1mm, so as to avoid abnormal noise and vibration caused by belt slipping and uneven transmission.
4 Precision Detection and Replacement Standards for Core Rotating Components
Wear and precision failure of rotating components such as impellers and bearings are the main internal causes of mechanical noise and high-frequency vibration of self-balancing multistage pumps. As core wear-resistant parts, bearings shall be inspected in strict accordance with national standard clearance values. Taking the commonly used 6205 bearing as an example, the standard clearance range is 0.03~0.06mm. If the measured clearance exceeds twice the national standard value, the bearing must be replaced immediately to prevent vibration caused by bearing stalling and eccentric operation. Impellers shall undergo regular dynamic balance test with the residual unbalance ≤0.05g·cm to avoid high-speed rotation vibration caused by impeller eccentricity and scale wear. Meanwhile, strictly control the core assembly clearance: the clearance between the inlet edge of the first-stage impeller and the guide vane is maintained at 0.3~0.5mm, complying with the assembly standard of multistage pump stage clearance, so as to avoid hydraulic impact noise and clearance vibration.
5 Optimization of Operating Parameter Matching
Long-term operation of equipment deviating from the design high-efficiency working conditions will cause hydraulic pulsation, cavitation vibration and fluid noise, and greatly reduce operating efficiency. The flow-head characteristic curve can be accurately matched through a variable frequency speed regulation system to keep the actual operating point of the equipment in the high-efficiency range, with the working condition deviation ≤±10% of the design parameter, avoiding adverse working conditions such as overload, low pressure and low-flow pressure holding. For working scenarios with severe pipeline pressure pulsation and loud fluid noise, a pressure stabilizing tank with a volume no less than 5% of the rated pump flow can be installed to effectively offset pipeline pressure fluctuation, eliminate hydraulic resonance and fluid abnormal noise, and optimize the stability of equipment operating conditions.
6 Pipeline System Stress and Modal Check
Stress concentration, non-standard support layout and pipeline resonance of pump inlet and outlet pipelines will easily transmit vibration to the pump unit and aggravate equipment faults. Finite element analysis software is adopted for pipeline modal analysis to ensure that the first-order natural frequency of the pipeline is more than 1.2 times the equipment operating frequency, completely avoiding pipeline resonance. The pipeline layout strictly complies with GB50316 industry specifications: the hanger spacing of horizontal pipelines is ≤15m, and the support spacing of vertical pipelines is ≤3m to prevent pipeline suspension and stress deformation. Meanwhile, standardize the pipeline elbow specification with the elbow curvature radius ≥1.5 times the pipe diameter (D), reduce vibration and noise caused by fluid turbulence and local resistance, and lower the additional stress of the pipeline on the pump body.
7 Construction of Graded Preventive Maintenance System
To fundamentally reduce the incidence of vibration and noise faults, a three-level standardized maintenance system of daily inspection, weekly inspection and monthly inspection shall be established to realize early fault prediction and disposal. Daily inspection focuses on monitoring bearing operating temperature, which shall be lower than 75℃ under normal working conditions to prevent bearing overheating failure. Weekly inspection detects equipment vibration values with the motor vibration velocity ≤4.5mm/s to capture slight vibration abnormalities in a timely manner. Monthly inspection verifies the equipment cavitation performance, and the net positive suction head (NPSH) of the impeller shall be ≥1.1 times the required NPSH to avoid cavitation vibration and erosion damage. For vulnerable core components such as mechanical seals, double-end seal structures are preferred, with the flushing liquid pressure 0.1~0.2MPa higher than the pump outlet pressure to ensure stable seal operation and reduce equipment jitter and abnormal noise caused by component faults.
8 Professional Fault Detection and Remote Technical Support
For intractable vibration, low-frequency abnormal noise and latent faults that cannot be solved by conventional inspection, professional pump industry technical teams can be relied on for accurate detection. A professional Brüel & Kjær 4396 vibration analyzer is equipped to complete high-precision vibration spectrum analysis and accurately locate vibration sources. Laser alignment equipment is adopted to calibrate transmission accuracy with an alignment precision of ±0.001mm, completely solving vibration problems caused by misalignment. Meanwhile, based on the industrial Internet of Things remote diagnosis platform, real-time collection of equipment operating data and intelligent fault early warning are realized with a technical response time of less than 2 hours, which can quickly dispose of various abnormal working conditions and ensure stable equipment operation.
9 Standardized Safety Operation Specifications
All vibration inspection, equipment maintenance and component replacement operations must strictly implement safety operation specifications. Before maintenance, strictly implement the LOTO (Lockout/Tagout) energy isolation system to completely cut off the equipment power supply and medium pipeline and eliminate potential safety hazards caused by residual energy. Explosion-proof tools with ExdⅡCT4 explosion-proof grade shall be used throughout the operation to adapt to industrial flammable and explosive working scenarios. Meanwhile, ISO Class 4 professional hearing protection equipment shall be worn to control the on-site noise exposure value within 85dB, fully ensuring the personal safety of maintenance personnel and realizing safe and compliant construction.
10 Full-Life Cycle Intelligent Monitoring and Operation Maintenance
To realize predictive maintenance of equipment and eliminate sudden faults, a full-life cycle intelligent monitoring system is recommended. High-precision vibration sensors with a sampling frequency of 10kHz and 0.2-class precision pressure transmitters are arranged at key positions of the pump unit to collect core operating data such as equipment vibration, pressure, temperature and flow in real time. Build an equipment vibration trend database based on the SCADA system, set an abnormal vibration fluctuation threshold (acceleration >80m/s²), and realize automatic early warning of abnormal working conditions. This upgrades the maintenance mode from passive overhaul to active prediction and predictive maintenance, greatly reduces the equipment failure rate and extends the full service life of self-balancing multistage pumps.