What are the common malfunctions and preventive measures of vertical low-speed centrifuges?

Vertical low-speed centrifuges (rotational speed generally ≤8000 r/min) are widely used in biochemistry, medicine, food, environmental testing and other fields for solid-liquid separation, sample precipitation and concentration of suspensions. Their structural core includes a vertical host frame, drive system, rotor assembly, control system, refrigeration system (for refrigerated models) and safety protection device. Most malfunctions are caused by improper operation, insufficient daily maintenance, rotor wear/fatigue, and electrical/hydraulic component aging. Below is a detailed classification of typical malfunctions, root causes and targeted, operable preventive measures, combined with the structural characteristics of vertical low-speed models.

 I. Common Malfunctions and Troubleshooting of Core Systems

 1. Drive System Malfunctions (the most frequent fault module)

The drive system consists of a motor, transmission shaft, bearing and brake device, which is responsible for driving the rotor to rotate stably; malfunctions directly affect the centrifugation speed and stability.

- Fault 1: Failure to start, or start with abnormal buzzing and no rotation

  Causes: Power supply phase loss/loose wiring, motor stator winding short circuit/open circuit, rotor jamming due to foreign matter between the rotor and the chamber, brake device not releasing, overload protection of the control system triggered.

  Solutions: Check the power supply circuit and reconnect loose wiring; detect the motor winding with a multimeter and repair/replace the faulty motor; turn off the power and remove foreign matter in the centrifugal chamber; check the brake solenoid valve and adjust the brake release mechanism; reset the overload protection and eliminate the overload cause (e.g., overloaded rotor).

- Fault 2: Unstable speed, speed fluctuation or failure to reach the set value

  Causes: Motor carbon brush wear/poor contact (for brushed motors), drive bearing severe wear, speed sensor (photoelectric/inductive) displacement/damage, frequency converter (for variable frequency drive) parameter drift/failure, rotor unbalance leading to load increase.

  Solutions: Replace worn carbon brushes and clean the brush holder; replace the drive shaft bearing and add high-temperature lubricating grease; recalibrate the speed sensor position or replace the damaged sensor; reset the frequency converter parameters or repair/replace the faulty frequency converter; rebalance the sample and rotor and eliminate unbalance.

- Fault 3: Abnormal noise/vibration during operation (exceeding the normal range)

  Causes: Drive bearing wear/loosening, transmission shaft bending, rotor unbalance (the most common), loose fixing bolts of the motor/host frame, uneven contact between the rotor and the shaft head.

  Solutions: Replace the drive bearing and lock the bearing seat; calibrate/straighten the transmission shaft or replace it; rebalance the sample (ensure equal mass of opposite sample tubes) and check the rotor for deformation/crack; retighten all fixing bolts and add anti-loosening washers; clean the rotor shaft head and rotor connecting surface, and ensure coaxial installation.

 2. Rotor Assembly Malfunctions (core separation component, high safety risk)

The rotor (angle rotor, swing bucket rotor, fixed rotor) is a high-stress component; long-term use will cause fatigue wear, and improper use is prone to serious malfunctions such as deformation and cracking.

- Fault 1: Rotor cannot be installed/locked, or loosens during operation

  Causes: Thread wear/slippage of the rotor and shaft head, damage to the rotor locking mechanism (clutch/locking pin), foreign matter on the connecting surface of the rotor and shaft head, excessive wear of the swing bucket hinge (for swing bucket rotors).

  Solutions: Replace the worn rotor/shaft head; repair/replace the damaged locking mechanism parts; clean the connecting surface and remove foreign matter; replace the swing bucket hinge and lubricate the rotating shaft.

- Fault 2: Rotor deformation, pitting or micro-cracks

  Causes: Overload operation for a long time, sample corrosion (chemical residue on the rotor surface), improper sterilization (high temperature exceeding the rotor material tolerance), fatigue damage from long-term use (exceeding the service life/cycle index).

  Solutions: Scrap the deformed/cracked rotor immediately (prohibited from continued use to avoid explosion); clean the rotor surface in time and remove chemical residues; sterilize in accordance with the rotor manual (e.g., avoid high-temperature dry heat for plastic rotors); replace the rotor when it reaches the rated service life/rotation cycle.

- Fault 3: Swing bucket does not open/close flexibly (for swing bucket rotors)

  Causes: Foreign matter jamming in the swing bucket hinge, rust/aging of the hinge shaft, excessive sample residue adhering to the bucket body, spring failure of the bucket opening mechanism.

  Solutions: Clean the hinge and remove foreign matter; derust the hinge shaft and apply anti-rust lubricating grease (food-grade/lab-grade for experimental use); clean the bucket body and remove sample residue; replace the failed spring.

 3. Control System Malfunctions

The control system includes a touch screen/button panel, PLC, temperature/speed controller and relay, which is responsible for setting and controlling centrifugation parameters (speed, time, temperature); malfunctions lead to parameter setting failure and automatic stop.

- Fault 1: Panel no display, buttons/touch screen unresponsive

  Causes: Power supply failure of the control panel, loose wiring of the display module, touch screen film wear (for touch models), button contact oxidation, PLC power module damage.

  Solutions: Check the panel power supply circuit; reconnect the loose display module wiring; replace the touch screen film or the whole touch panel; polish the button contact or replace the button; repair/replace the PLC power module.

- Fault 2: Parameter setting is invalid, or the machine stops automatically during centrifugation

  Causes: Controller parameter drift, temperature/speed sensor damage, timing relay failure, safety protection switch (door lock/overload) false trigger, program error of the control system.

  Solutions: Recalibrate the controller parameters according to the manual; replace the damaged temperature/speed sensor; replace the timing relay; check the safety protection switch and eliminate the false trigger cause (e.g., loose door lock); reset the control system program or update the firmware.

- Fault 3: Digital display distortion (e.g., speed/temperature jump)

  Causes: Poor contact of the sensor signal line, electromagnetic interference of the control circuit, display module aging, unstable power supply voltage.

  Solutions: Shield and fix the sensor signal line; install an anti-interference filter on the control circuit; replace the aging display module; connect a voltage stabilizer to the centrifuge power supply.

 4. Refrigeration System Malfunctions (for refrigerated vertical low-speed models)

Refrigerated centrifuges are equipped with a compressor, evaporator, condenser and temperature control valve for low-temperature sample separation (0~4℃); malfunctions lead to no refrigeration or inaccurate temperature control.

- Fault 1: No refrigeration, or the refrigeration temperature cannot reach the set value

  Causes: Compressor failure (no startup), lack of refrigerant (Freon) in the refrigeration circuit, condenser blockage by dust, evaporator frost formation, temperature control valve failure.

  Solutions: Repair/replace the faulty compressor; add the specified refrigerant by a professional; clean the condenser dust with compressed air; defrost the evaporator and check the defrosting system; replace the temperature control valve.

- Fault 2: Excessive refrigeration temperature fluctuation, or frosting of the centrifugal chamber

  Causes: Temperature sensor displacement, uneven air circulation in the centrifugal chamber, refrigeration circuit leakage, improper setting of the defrosting time.

  Solutions: Recalibrate the temperature sensor position; clean the air duct in the centrifugal chamber and ensure unobstructed air circulation; check and repair the refrigeration circuit leakage; reset the defrosting time parameter of the control system.

 5. Safety Protection Device Malfunctions

Vertical centrifuges are equipped with multiple safety devices (door lock interlock, overload protection, overspeed protection, rotor imbalance protection) to prevent accidents; malfunctions lead to false protection or loss of protection function.

- Fault 1: Door lock cannot be opened/closed, or the door lock interlock triggers false protection (cannot start)

  Causes: Mechanical jamming of the door lock latch, damage to the door lock proximity switch, loose wiring of the interlock circuit, deformation of the centrifugal chamber door.

  Solutions: Remove the door lock jamming and lubricate the latch; replace the damaged proximity switch; reconnect the interlock circuit wiring; calibrate/repair the deformed chamber door.

- Fault 2: Overload/overspeed protection triggers frequently for no reason

  Causes: Protection sensor parameter drift, rotor unbalance detection module failure, excessive friction resistance of the drive system leading to overload, speed limiter damage.

  Solutions: Recalibrate the protection sensor parameters; repair/replace the unbalance detection module; eliminate the drive system friction (e.g., replace bearings, remove foreign matter); replace the damaged speed limiter.

 6. Sealing and Leakage Malfunctions

- Fault: Liquid leakage in the centrifugal chamber, or seal aging leading to dust/water entering the internal system

  Causes: Deterioration/aging of the centrifugal chamber seal ring, loose connection of the liquid collection pipe (for bottom discharge models), cracking of the rotor sample tube seat, improper installation of the chamber cover.

  Solutions: Replace the aging seal ring (use fluororubber seal for corrosive samples); retighten the liquid collection pipe and replace the sealing gasket; replace the cracked rotor; reinstall the chamber cover and ensure tight sealing.

 II. Routine Preventive Maintenance Measures

The malfunctions of vertical low-speed centrifuges are highly preventable; the core of prevention is to standardize operation, implement hierarchical maintenance (daily/weekly/monthly) and strictly manage the rotor life. Scientific maintenance can reduce the fault rate by more than 85%, extend the service life of the equipment, and ensure the accuracy of sample separation and operation safety. The measures are divided into daily maintenance (before/after use), weekly maintenance and monthly/quarterly regular overhaul, combined with special protection for key components such as the rotor.

 1. Daily Maintenance (5-10 minutes before startup and after shutdown, the most basic and critical link)

 Before use/startup

1. Check the power supply voltage (stable 220V/380V according to the model) and grounding reliability (prevent electric shock and electromagnetic interference);

2. Inspect the centrifugal chamber for foreign matter (e.g., broken glass, sample residue) and clean it with a dry/wet cloth;

3. Check the rotor for deformation, cracks and loose parts; confirm the rotor locking mechanism is intact;

4. Check the seal ring of the chamber cover for aging/falling off; ensure the door lock interlock is sensitive;

5. For refrigerated models: Check the refrigeration system for frosting and the condenser for dust blockage;

6. Calibrate the sample mass: Ensure the mass difference of opposite sample tubes is ≤0.1g (low-speed model) to avoid rotor unbalance.

 After use/shutdown

1. Turn off the power supply and wait for the rotor to stop completely (prohibit forced braking) before opening the chamber cover;

2. Clean the centrifugal chamber and rotor immediately: Wipe off sample residue, liquid and corrosive reagents with a neutral detergent, and dry with a clean cloth (prevent corrosion);

3. Remove the rotor (if not used for a long time), clean and dry it, and store it in a dry, dust-free special rack;

4. Check the sample tube seat of the rotor for damage; replace it in time if cracked;

5. Wipe the chamber cover seal ring and apply a thin layer of silicone grease (maintain sealing performance);

6. Drain the condensed water in the centrifugal chamber (for refrigerated models) and keep the chamber dry;

7. Record the use status: Note the centrifugation speed, time, sample type and equipment operation condition (for fault tracing).

 2. Weekly Maintenance (focus on deep cleaning and partial component inspection)

1. Disassemble the rotor locking mechanism, clean the thread and shaft head, and apply high-temperature anti-seize lubricating grease;

2. Clean the condenser of the refrigeration system (for refrigerated models) with compressed air or a soft brush to remove dust and ensure heat dissipation;

3. Check the wear of the motor carbon brush (for brushed models) and the contact of the brush holder; replace the carbon brush when the wear is more than 1/2;

4. Inspect all fixing bolts (host frame, motor, chamber) for loosening; retighten and add anti-loosening washers;

5. Test the sensitivity of safety protection devices (door lock, overload, overspeed); reset the protection parameters if necessary;

6. For swing bucket rotors: Disassemble the swing bucket hinge, clean and lubricate it to ensure flexible opening/closing.

 3. Monthly/Quarterly Regular Overhaul (focus on core component detection and performance calibration)

 Monthly overhaul

1. Check the drive system bearing for noise and wear; add high-temperature lubricating grease (lithium-based grease) to the bearing seat;

2. Calibrate the speed and temperature of the centrifuge with a standard calibrator; ensure the speed error ≤±50 r/min and temperature error ≤±1℃;

3. Check the electrical circuit for aging, discoloration and loose wiring; wrap the aging circuit with insulating tape and reconnect the loose part;

4. Inspect the seal ring of the refrigeration circuit (for refrigerated models) for oil leakage; replace the sealing gasket in time if leaked;

5. Count the rotation cycle of the rotor and record it in the rotor life management book.

 Quarterly overhaul

1. Disassemble the drive shaft and bearing seat; inspect the bearing precision and replace the worn bearing in time;

2. Conduct a non-destructive inspection (NDI) of the rotor (e.g., magnetic particle inspection) to check for micro-cracks and fatigue damage; scrap the unqualified rotor immediately;

3. Test the motor insulation performance with a megohmmeter; ensure the insulation resistance ≥5 MΩ (prevent short circuit);

4. For refrigerated models: Check the refrigerant pressure of the refrigeration circuit; add refrigerant if insufficient (operated by professional technicians);

5. Reset the control system parameters and update the firmware (if there is an official upgrade); calibrate the overload/unbalance protection threshold;

6. Replace the aging seal ring (centrifugal chamber, liquid collection pipe) and damaged button/touch screen components;

7. Clean the internal dust of the control cabinet with compressed air (turn off the power first) to prevent short circuit of electrical components.

 4. Special Preventive Measures (aimed at improper operation and harsh working conditions)

1. Strictly prohibit overloading operation: Do not exceed the rated load of the rotor (marked on the rotor body); the sample volume shall not exceed the scale of the sample tube (prevent liquid overflow and rotor unbalance);

2. Standardize rotor use and management: Establish a rotor file (record model, production date, service life, rotation cycle); replace the rotor when it reaches the rated cycle (generally ≤10,000 cycles for low-speed rotors); prohibit mixing rotors of different models/specifications;

3. Prevent sample corrosion: For corrosive samples (e.g., acid, alkali, organic solvent), use corrosion-resistant rotors (titanium alloy/PTFE-coated) and clean the rotor immediately after use;

4. Avoid harsh operation: Prohibit opening the chamber cover during rotor operation; prohibit forced braking of the rotor (wait for natural stop); prohibit shifting the speed/temperature parameters at will during centrifugation;

5. Environmental protection and storage: Place the centrifuge in a dry, ventilated, dust-free environment (ambient temperature 5~35℃, humidity ≤80%); avoid direct sunlight and close to heat sources (e.g., electric furnace, heater); for long-term storage (＞1 month), remove the rotor, cut off the power supply, and cover the equipment with a dust cover;

6. Standardize sterilization operation: Sterilize the rotor/chamber in accordance with the manual; avoid high-temperature (＞121℃) sterilization for plastic rotors; use alcohol soaking/ultraviolet sterilization for non-high-temperature resistant components;

7. Professional operation and training: Operators must be trained and qualified to operate; master the basic operation and fault judgment skills; prohibit non-professionals from disassembling the drive system, refrigeration system and control system at will.

 III. Key Safety Reminders for Fault Handling

1. Emergency shutdown: In case of abnormal vibration, noise, smoke or liquid leakage during operation, press the emergency stop button immediately and cut off the power supply; do not continue to use the equipment until the fault is eliminated;

2. Rotor safety priority: If the rotor is found to have cracks, deformation or loose parts, stop using it immediately and replace it with a qualified rotor; the damaged rotor shall be scrapped uniformly and shall not be repaired and reused (to avoid rotor explosion accidents);

3. Professional maintenance for complex faults: For malfunctions of the refrigeration system, frequency converter, motor and PLC, contact professional after-sales personnel for detection and repair; prohibit random disassembly and replacement of components to avoid secondary damage;

4. Record fault and maintenance information: Establish an equipment fault and maintenance record book, record the fault occurrence time, performance, root cause, solution and replaced parts; summarize frequent fault points and strengthen targeted maintenance;

5. Regular calibration and inspection: Send the centrifuge to a qualified metrological inspection institution for periodic calibration (generally once a year) to ensure the accuracy of speed, temperature and separation performance, and obtain a calibration certificate.

 Summary

The common malfunctions of vertical low-speed centrifuges are mainly concentrated in the drive system, rotor assembly and control system, and the root causes are mostly improper operation, insufficient maintenance, rotor fatigue wear and electrical component aging. The core of fault prevention is to implement standardized hierarchical maintenance and strict rotor life management, eliminate unbalanced operation and overload use, and keep the equipment clean and well-lubricated. For refrigerated models, special attention should be paid to the heat dissipation and refrigerant management of the refrigeration system.

By following the above preventive measures and safety operation specifications, the operation stability and sample separation accuracy of the vertical low-speed centrifuge can be guaranteed, the occurrence of safety accidents such as rotor unbalance and explosion can be avoided, and the service life of the equipment can be effectively extended.