Precautions Before Starting an Industrial Centrifugal Fan

I. Basic Mechanical Inspection

1. Fan Casing and Appearance

• Check the fan casing, inlet, and volute for deformation, cracks, dust buildup, or foreign objects.
• Ensure all flanges and inspection doors are properly sealed and all connecting bolts are tightened.
• Remove any tools, welding slag, fabric, or other foreign objects left inside the fan.

2. Impeller Inspection

• Manually rotate the impeller to ensure it turns smoothly without jamming, friction, or abnormal noise.
• Check that the impeller does not contact the casing or inlet.
• Make sure the blades have no corrosion, deformation, cracks, or excessive dust accumulation.

3. Bearings and Lubrication System

• Oil lubrication: Ensure the oil level is within the specified range and the oil is clean, without emulsification or contaminants.
• Grease lubrication: Ensure sufficient grease is applied and there is no leakage.
• Check the bearing housing for oil leakage and ensure cooling-water pipes are unobstructed for water-cooled bearings.

4. Coupling / Belt Drive

• Check that the coupling alignment is correct and the flexible elements are in good condition.
• For belt drives, ensure proper belt tension and check for cracks or aging.
• Make sure the protective guard is complete and securely installed. Never operate the fan without the guard.

5. Foundation and Supports

• Ensure all foundation bolts are securely tightened and the base is stable.
• Check that vibration isolators are in good condition and properly positioned.

II. Ductwork and Valve System

1. Dampers and Control Valves

• For normal centrifugal fan startup, close the inlet damper and start the fan under low-load conditions to reduce starting current.
• Check the outlet valve according to process requirements. Do not keep the outlet completely closed for extended periods, as this may cause excessive pressure buildup.

2. Ductwork Inspection

• Ensure the ductwork is not collapsed or blocked.
• Check flexible connections for twisting or damage.
• Ensure expansion joints are correctly installed and all supports and hangers are secure.

3. Pressure Relief and Bypass System

• If the system has bypass ducts or pressure relief valves, confirm that they are in the correct position to prevent abnormal system pressure after startup.

III. Electrical and Instrumentation Inspection

1. Motor Inspection

• Check that motor insulation is qualified and electrical connections are secure.
• Ensure reliable grounding of the motor casing.
• Check that the cooling fan is functioning properly and that there is no debris around the motor.

2. Power Supply and Control

• Ensure the voltage is within the rated range.
• Check that control cabinet indicators and protection devices, including overload, overtemperature, bearing temperature, and vibration protection, are functioning properly.
• Make sure the emergency stop button is reset.

3. Monitoring Instruments

• Check the wiring of vibration sensors, temperature probes, pressure gauges, and other instruments.
• Confirm that the instruments display normal zero or initial readings.

IV. Safety and Site Preparation

1. Clear the area around the fan to ensure sufficient space for maintenance and emergency evacuation.
2. Confirm that no personnel are working around the fan or ductwork, and issue a startup warning.
3. Ensure fire-fighting equipment is available to prevent fire caused by abnormal friction.
4. For explosion-proof applications, check sealing and anti-static grounding. Keep flammable and explosive materials away from the fan.

V. Pre-Startup Trial Operation

1. Jog Test — Very Important

• Briefly jog the motor and confirm that the impeller rotates in the same direction as indicated by the rotation mark.
• Never proceed with normal operation if the rotation direction is incorrect.

2. Communication

• Ensure clear communication between control-room and on-site personnel.
• Make sure the fan can be stopped immediately if abnormal noise or severe vibration occurs.

3. Cold Weather Conditions

• Check the fluidity of the lubricating oil in low-temperature conditions and preheat it if necessary.

VI. Conditions Under Which Startup Is Prohibited

Do not start the fan if any of the following conditions exist:

• Friction, jamming, or abnormal impact noise occurs during manual rotation.
• Insufficient lubrication or serious oil leakage is present.
• The protective guard is missing.
• The rotation direction is unknown or incorrect.
• The ductwork is seriously blocked.
• Protection devices are not functioning or grounding is missing.
• Foreign objects remain inside the fan casing.

Additional Operating Reminder

After starting the motor, wait until the current drops back to the normal no-load level. Then gradually open the inlet damper to increase the load step by step.

After startup, continuously monitor vibration, temperature, and noise. If any abnormal condition occurs, stop the fan immediately and inspect it.