Technical Specifications for Inspection and Maintenance of Electric Forklift Motors in Winter

Low-temperature environments in winter (especially below -10℃) can cause decreased insulation performance of motors, lubrication failure, and shrinkage deformation of metal components, directly affecting motor starting efficiency and service life. The following provides a systematic motor maintenance plan covering four aspects: "Inspection Process, Maintenance Operations, Key Indicators, and Precautions," balancing principle and operability.

I. Core Inspection Process (Full Cycle: Before/During/After Operation)

(1) Pre-Operation Inspection (Daily Mandatory, Duration: 5-8 Minutes)

• Appearance and Physical Condition Check: Clean ice, snow, dust, and oil stains from the motor housing. Focus on inspecting whether the cooling fins are blocked (blockage rate ≤5%) and if the housing has cracks, deformation, or collision marks. Check the tightness of the motor junction box and whether the waterproof gasket at the wire inlet is aged or cracked to prevent condensation from seeping in and causing short circuits.
• Electrical Connection Check: Tighten the motor's three-phase terminals with a torque wrench (torque value as specified by the manufacturer, usually 6-10N・m) to eliminate loosening caused by metal shrinkage at low temperatures. Inspect the terminals for oxidation; if green rust or blackening occurs, polish to metallic luster with fine sandpaper, apply conductive paste (thickness: 0.1mm), and re-tighten. Measure the motor winding insulation resistance using a 500V megohmmeter: the insulation resistance between the stator winding and the housing shall be ≥1MΩ, and between the three-phase windings shall be ≥2MΩ. If not, shut down the motor for drying treatment.
• Rotation Flexibility Check: Manually rotate the motor output shaft; it should rotate without jamming or abnormal noise, with uniform rotational resistance (maximum resistance ≤5N・m). If jamming or abnormal noise occurs, focus on inspecting the bearing condition to determine if lubrication failure or ball wear exists.

(2) In-Operation Monitoring (Real-Time Attention, Shutdown Immediately for Abnormalities)

• Temperature Monitoring: Real-time monitor the motor housing temperature via the forklift instrument or a dedicated thermometer. During continuous operation, the temperature shall be ≤80℃ (stator winding temperature ≤105℃, measured by thermocouple). If the temperature exceeds the threshold, shut down the motor and cool it to below 40℃ before re-operation to avoid accelerated insulation aging.
• Operating Status Monitoring: Monitor the motor operating noise; the noise level during normal operation shall be ≤75dB (measured at 1 meter). If whistling, knocking sounds, or increased vibration occur (vibration acceleration ≤2.8m/s²), investigate issues such as bearing wear, rotor imbalance, or uneven air gap. Observe changes in motor current: no-load current shall be ≤30% of the rated current, and full-load current shall not exceed 110% of the rated current. If there is abnormal current fluctuation, check the compatibility of the electronic control system or whether the load exceeds the limit.

(3) Post-Operation Re-Inspection (Weekly, Duration: 10-15 Minutes)

• Temperature and Insulation Re-Test: Within 30 minutes after operation, re-test the motor housing temperature (shall be ≤60℃). After the motor cools down to room temperature, measure the insulation resistance again (the value shall be consistent with that before operation without significant decline).
• Sealing and Protection Check: Inspect the oil seal at the motor shaft extension end for leakage (no oil dripping is qualified). If leakage occurs, promptly ｒｅｐｌａｃｅ it with a low-temperature adapted oil seal (temperature resistance range: -30℃ to 120℃). Clean the heat dissipation channels to ensure no dust or ice/snow accumulation on the cooling fins, maintaining heat dissipation efficiency.

II. Targeted Maintenance Operations (Winter-Specific, Performed on Schedule)

(1) Lubrication System Maintenance (Monthly or Every 50 Operating Hours)

• Grease Replacement: Completely remove old grease from motor bearings (residual amount ≤10%), and fill with winter-specific low-temperature grease (recommended model: Lithium-based grease NLGI Grade 2, dropping point ≥180℃, pour point ≤-35℃). The filling volume shall be 1/2-2/3 of the internal bearing space (excess will cause high-temperature carbon deposition). For motors with grease fittings, inject grease through the fittings while rotating the output shaft to ensure uniform coverage of balls and raceways.
• Bearing Condition Evaluation: If the bearing has been used for more than 2000 hours, or if grease deterioration (blackening, caking) or excessive bearing clearance (radial clearance ≥0.1mm) occurs, directly ｒｅｐｌａｃｅ the bearing (ｓｅｌｅｃｔ deep groove ball bearings consistent with the original model, precision class ≥P6). After replacement, perform a running-in test (30 minutes of no-load operation with stable temperature and no abnormal noise).

(2) Insulation Performance Enhancement Maintenance (Quarterly or When Ambient Humidity >70%)

• Winding Drying Treatment: If the insulation resistance is below the standard value, dry the motor windings. Prefer the "low-temperature hot air drying method" (hot air temperature: 40-50℃, wind speed: 0.3-0.5m/s, drying time: 4-6 hours) to avoid insulation layer aging caused by high-temperature baking. Measure the insulation resistance every hour during drying; it is considered qualified when the value stabilizes above the standard and remains unchanged for 1 hour.
• Insulation Protection Enhancement: Spray three-proof paint (complying with IP65 protection class) on the motor junction box and winding ends, focusing on covering terminals and weak insulation areas to improve moisture and condensation resistance. Inspect the motor grounding device to ensure the grounding resistance ≤4Ω, preventing electric shock risks in case of insulation failure.

(3) Low-Temperature Adaptability Adjustment (Completed Before Winter, Annually)

• Air Gap Inspection and Adjustment: Due to potential differences in thermal expansion and contraction between the motor stator and rotor at low temperatures, measure the air gap (the average three-phase air gap shall comply with the manufacturer's specifications, usually 0.2-0.5mm, maximum deviation ≤0.1mm). If the air gap is uneven, adjust the end cover bolt positions to avoid friction between the rotor and stator (rubbing).
• Heat Dissipation System Optimization: Clean dust from the motor cooling fan blades and inspect the fan motor operating status to ensure the fan speed meets the standard (usually 2800r/min). If the operating environment temperature ≤-20℃, install a motor insulation cover (made of flame-retardant insulation material) to reduce heat loss during startup, ensuring the cover does not block the heat dissipation channels.

III. Key Performance Indicators and Judgment Standards

IV. Safe Operation and Precautions

• Power Off Operation Specifications: Before all inspections and maintenance, disconnect the forklift's main power supply, pull out the motor wiring plug, wait for the capacitor to discharge (usually 5 minutes), and hang a "No Switching On" sign to prevent electric shock.
• Tool and Material Requirements: Use explosion-proof lighting equipment (when combustible dust is present in the operating environment). Tools such as thermometers and megohmmeters must be calibrated (error ≤±2%). ｓｅｌｅｃｔ grease, conductive paste, three-proof paint, and other materials from regular manufacturers; strictly prohibit the use of expired or mismatched materials.
• Environment Control: Perform maintenance operations indoors at ≥5℃ to avoid hand frostbite or tool operation errors at low temperatures. If emergency outdoor treatment is required, set up a temporary insulation shed, and limit the operation time to no more than 30 minutes.
• Recording and Traceability: Establish a motor maintenance file to record data such as insulation resistance, temperature, and current during each inspection, as well as maintenance content and replaced component models. If the motor experiences three consecutive instances of decreased insulation resistance or excessive temperature, conduct a comprehensive disassembly and inspection to evaluate whether motor replacement is necessary.