If you’re a rotary dryer user, you might experience various issues over time, leaving you feeling frustrated. Don’t worry, let us point out these potential problems and provide solutions.
Unusual noise, vibration, or overheating in a rotary drum dryer are common warning signs of a malfunction and require prompt investigation to prevent equipment damage or even safety incidents. Below are some common causes and solutions for these issues, which we hope will be helpful.
Abnormal Noise
Causes of Abnormal Noise
Bearing damage This is one of the most common causes. Poor lubrication, wear, contamination, or improper installation can all lead to damage to the bearing raceways and balls/rollers, resulting in high-pitched, rattling, or dull rumbling noises during operation.
Gear Meshing Problems
Improper Lubrication: Gear oil is missing, deteriorating, or the wrong type.
Wear or Damage: Tooth surface wear, pitting, or broken teeth.
Improper Meshing Clearance: Excessive clearance produces a knocking sound, while too little clearance produces a squealing sound.
Poor Alignment: The drive gear is not parallel to or offset from the centerline of the cylinder gear ring.
Problems with the rollers or rollers
Poor lubrication: The roller bearings or roller tracks are dry-grinding due to lack of oil.
Uneven wear: The roller or roller surfaces are worn into grooves, out of roundness, or deformed.
Foreign objects: Material, bolts, tools, etc. are trapped between the rollers and rollers.
Drive Component Problems
Coupling Damage: Worn or broken elastic blocks, worn or misaligned metal coupling teeth, and abnormal noise.
Belt Slippage: Loose, worn, aged, or oily belts cause slippage and squealing; belt breakage or joint problems.
Chain Looseness: Poor engagement between the chain and sprockets causes noise.
Internal Cylinder Problems
Loose or Falling Lifting Plates: Loose bolts or cracked welds can cause components to rock and strike the cylinder walls.
Foreign Objects in the Cylinder: Large, hard objects or fallen liner plates rolling and impacting the cylinder.
Worn or Falling Liners: Excessive wear or loss of the liner plates protecting the cylinder.
Mechanical Interference: Friction or collision between the cylinder or transmission components and surrounding fixed structures, such as the frame or protective covers.
Abnormal Noise Troubleshooting Steps
Safety First： Shut down the machine, disconnect the power supply, lock out the machine, and ensure it is completely stationary and cool.
Preliminary Location: While the machine is running, if it is safe to do so, attempt to determine the approximate source of the abnormal noise: the drive end, the middle section of the cylinder, the tail section, the roller support area, etc. Pay attention to the sound characteristics: sharp, dull, periodic, and continuous.
Visual Inspection:
Check all lubrication points: oil level/grease level, oil color, and leaks in bearings, gears, gear rings, and roller bearings.
Inspect the meshing areas of gears and gear rings for wear, pitting, or broken teeth.
Inspect the rollers and rollers for smooth surfaces, dents, wear steps, or cracks.
Inspect the outer surface of the cylinder for obvious signs of friction or deformation.
Check the tension, wear, and damage of the drive belt and chain.
Check the condition and alignment of the couplings.
Check the foundation anchor bolts and equipment connection bolts for looseness.
Check the protective covers for deformation or looseness that could cause friction.
Manual Turning: Under safe conditions, manually turn the cylinder to feel for any sticking points and listen for any unusual internal friction or clashing sounds.
Internal Inspection: Open the manhole door and inspect the attachment of the lifting plate, lifting plate, and liner for looseness, loss, or severe wear. Inspect the cylinder for any foreign objects.
Precision Inspection: Use tools such as a listening rod, vibration analyzer, and infrared thermal imager to help locate the source of abnormal noise and determine the condition of internal components such as bearings.
Vibration
Common Causes
Mechanical Imbalance:
Uneven material distribution, dropout or severe wear of the lifting plate, cylinder deformation, and severe and uneven scaling within the cylinder. Rotating components such as couplings, pulleys, and gears are inherently unbalanced or installed eccentrically. Couplings between the motor and reducer, and between the reducer and the cylinder drive shaft, are out of alignment.
Foundation Issues:
Loose anchor bolts.
Insufficient or damaged foundation.
Deformed/cracked equipment base.
Roller and Roller Problems:
The roller is out of round, the roller ovality is excessive, or the surface is uneven.
The roller axis is not parallel to the cylinder axis.
The roller bearing is damaged.
Drive Component Problems:
Damaged coupling, failed elastic element, worn teeth, loose and broken bolts.
Uneven tension and varying degrees of wear on multiple belts; uneven chain pitch and excessive wear.
Vibration Troubleshooting Steps
Check fasteners: Thoroughly inspect and tighten all anchor bolts and equipment connection bolts, including the roller base, reducer base, motor base, and coupling bolts.
Check foundation: Inspect the foundation for obvious cracks or signs of settlement. Tap to check for hollowing sounds.
Check alignment: Recheck the alignment of the coupling between the motor, reducer, and drive shaft. Use a laser alignment tool or dial indicator to accurately measure and adjust.
Check rollers and rollers: Measure the diameter of each roller and check for uniform wear. Check the surface wear of the rollers and the surface wear and ovality of the rollers. Check the condition of the roller bearings. Check that the roller axis is parallel to the cylinder axis and that the contact marks between the roller and roller are centered and uniform.
Inspect transmission components:
Check couplings for wear and damage, and tighten bolts.
Check belt tension for consistency and appropriateness, and replace any belts showing uneven wear.
Check chain tension, wear, and lubrication.
Cylinder Inspection: Visually inspect the cylinder for obvious warping and deformation. Inspect the outer surface of the cylinder for uniform scale buildup. Inspect the lifting and lifting plates for loosening, severe deformation, or uneven wear, and for severe and segregated scale buildup on the cylinder wall. Clean any large aggregates or foreign matter from the interior.
Vibration Analysis: Use a vibration analyzer to measure the vibration amplitude, frequency, and spectrum of key points: bearing housing, reducer, and motor. This helps accurately diagnose fault types such as imbalance, misalignment, bearing failure, and gear failure.
Overheating
Abnormal overheating and causes
Bearing Overheating:
Lack of oil, excessive grease leading to poor heat dissipation, incorrect grease type or deterioration, or contamination. Bearing Damage: Wear, fatigue spalling, retainer fracture, improper installation, overtightening or loosening, seal failure. Equipment overload.
Bearing overheating:
Lack of oil, excessive grease leading to poor heat dissipation, incorrect grease type or deterioration, or contamination. Bearing damage: Wear, fatigue spalling, retainer fracture, improper installation, overtightening or loosening, seal failure, or excessive equipment load.
Gearbox overheating: Lack of oil, improper oil level, insufficient or excessive oil. Incorrect or deteriorated oil, incorrect viscosity, oxidation failure. Exceeding the rated load.
Temperature Control Failure: Heat source temperature out of control, malfunction of temperature measuring instruments such as thermocouples or RTDs, or incorrect or faulty thermostat/PLC settings.
Insufficient Exhaust: Insufficient induced draft fan air volume, small damper opening, clogged bag filter, or obstructed exhaust ducting prevents timely exhaust of hot and humid air, leading to increased temperature accumulation within the drum.
Changes in Material Properties: Temperature settings too high when handling heat-sensitive materials; low moisture content or insufficient feed volume, causing the material to remain in the high-temperature zone for an extended period of time.
Troubleshooting temperature runaway
Safe Shutdown: Immediately shut down the machine if overheating is detected, especially if smoke or a burning smell is present! Allow the equipment to cool thoroughly.
Locating the Heat Source: Use an infrared thermometer or spot thermometer to measure the temperature of key locations, such as the bearing seats, motor housing, reducer housing, and various locations on the outer surface of the cylinder, to identify the main hot spots.
Lubrication Inspection: Check the oil level in all bearings and refill or replace the lubricant with the required lubricant. Check the reducer oil level and oil quality (e.g., color, viscosity, presence of metal shavings, emulsification), and replace with new oil if necessary. Check the lubrication system, such as the oil pump, piping, and distributor, for proper operation.
Motor Inspection: Check whether the motor current exceeds the rated value. Check the power supply voltage and three-phase balance. Check the wiring terminals for tightness and burn marks. Check whether the cooling fan is rotating normally and the air duct is unobstructed.
Check the reducer: In addition to checking the oil, listen for any unusual noises or periodic shocks during operation. Check the cooling water flow, pressure, and temperature. Check the heat sink for cleanliness.
Check the temperature control system: Calibrate or check the cylinder temperature sensor for accuracy. Check the thermostat and displayed temperature for accuracy and the correct setpoint. Check the heat source actuator for operation as instructed.
Check the ventilation system: Check whether the induced draft fan is operating properly and the damper opening is appropriate. Check the dust collector for excessive pressure drop and blockages that require cleaning.
Check the exhaust duct for unobstructed flow and for any material buildup or valve closures.
Summary
Establish and strictly adhere to a regular schedule for lubrication, tightening, vibration inspection, and temperature monitoring. Detailed documentation of abnormalities will aid in failure mode analysis. Maintain a stockpile of critical wear parts: bearings, seals, belts, and commonly used lubricants. For complex vibration analysis, precision alignment, electrical faults, or internal damage, promptly seek assistance from the equipment manufacturer or professional maintenance personnel.
By following these troubleshooting steps, you can usually pinpoint the root cause of abnormal noise, vibration, and overheating in your rotary drum dryer, implement appropriate repairs, and restore normal operation. PALET, a professional rotary dryer manufacturer, is happy to share its experience and technology in rotary drying. We hope this information is helpful.