What problems will be caused by excessive centering error of horizontal centrifugal pump

Horizontal centrifugal pumps are widely used fluid conveying equipment in modern industrial systems. Whether in petrochemical, electric power, metallurgy, municipal water supply, HVAC and other industries, horizontal centrifugal pumps play an irreplaceable role. However, during the installation of pumps and motors, the accuracy of alignment has a direct impact on the operating stability and life of the equipment. Excessive alignment error will cause a series of mechanical failures, safety hazards and efficiency losses, and in severe cases, even cause the entire machine to be scrapped.

Definition of alignment error and installation requirements
The alignment of horizontal centrifugal pumps usually refers to the coaxiality and angular alignment of the pump shaft and the motor shaft in the horizontal and vertical directions during installation. Alignment is divided into cold alignment and hot alignment, the purpose of which is to ensure that the equipment remains consistent in axis when in operation. Industry standards (such as API 610, ISO 10816) usually require that the radial runout and end clearance errors at both ends of the coupling be controlled within tens of microns.

Abnormal wear and failure of couplings
The most direct consequence of excessive centering error is abnormal force on the coupling, which leads to increased wear, increased clearance and even fracture. The coupling needs to withstand additional bending moment and shear force under non-centering conditions, which not only reduces the life of the coupling, but also may cause the connection to loosen, forming a serious safety hazard.

Early failure of bearings
Horizontal centrifugal pumps usually use rolling bearings or sliding bearings to support the rotor system. The axis deviation caused by the centering error will cause uneven bearing force, generate additional axial load and radial force, which will lead to lubrication film rupture, excessive temperature rise, uneven wear, and eventually cause bearing burnout or jamming. Bearing failure not only affects the service life of the pump, but may also cause sudden shutdown.

Pump shaft deformation and fatigue fracture
Due to the alternating load caused by the centering error, the pump shaft will be subjected to periodic bending stress. This fatigue stress is likely to cause microcracks on the surface of the pump shaft to expand and form fatigue damage during long-term operation. Especially under high-speed operation conditions, the critical speed of the shaft is reduced, and the system is prone to enter the resonance zone, which in turn causes serious accidents such as shaft fracture.

Damage to the sealing system
Horizontal centrifugal pumps are often equipped with mechanical seals or packing seal systems to effectively isolate the pump chamber from the external environment. Excessive centering error will cause the shaft's running trajectory to deviate, resulting in shaft swing and loss of concentricity of the sealing end face. Abnormal contact pressure on the sealing surface will lead to friction overheating, damage to the sealing ring and increased leakage. In severe cases, the leaked medium will corrode the equipment, endangering site safety.

Increased system vibration and noise
When a horizontal centrifugal pump is running in a non-centering state, the vibration level of the whole machine increases significantly, easily exceeding the GB or ISO vibration standards. Vibration not only aggravates fatigue damage to the pump body and foundation, but may also cause secondary structural damage such as loosening of the anchor bolts and stress concentration of the pipeline. At the same time, the mechanical noise emitted by the pump body will also be significantly enhanced, affecting the operating environment and personnel health.

Reduced energy efficiency and increased operating costs
The additional mechanical loss and transmission energy loss caused by the centering error make it impossible for the actual output of the motor to be efficiently transmitted to the pump shaft, resulting in a decrease in the efficiency of the whole machine. In addition, in order to make up for the energy loss, the system is often forced to increase the motor power, increase the operating load, and increase power consumption. This has an adverse effect on the economic efficiency of equipment operation.

Unstable system operation affects process continuity
Alignment errors may cause frequent pump startup and shutdown or operation fluctuations, affecting flow, head and pressure stability, and ultimately disrupting production rhythm. Especially in scenarios with extremely high requirements for continuous operation such as fine chemicals, pharmaceuticals or power plant cooling water systems, alignment accuracy will directly affect system reliability and process quality.