What is the reason for the deviation of electric hoist trolley?

When we use electric hoist trolley, we basically talk about whether chain electric hoists or wire rope electric hoists are hung on I-beams or gantry cranes. They can be used up, down, left, and right. The explosion proof electric hoist trolley needs to be installed alone. Unprofessional personnel will have some difficulties in installing the trolley. Improper installation will cause the trolley to wander during operation. If it is lifted crookedly, the heavy objects will fall. Let’s analyze how this is caused.

Track system problems (accounting for about 45%)

Reason analysis:

1. Track installation deviation

   • Track straightness error＞3mm/m.

   • Misalignment at track joint >2mm.

   • Track level deviation＞1/1000.

2. Track surface anomalies

   • Oil stain/rust on track tread (friction coefficient reduced by 30%+).

   • Grooves formed due to wear on the track tread (depth > 1.5mm).

   • Track pressure plate bolts are loose (pretightening force loss >20%).

Solution:

• Track correction: Use laser theodolite to detect, and adjust the straightness of every 6m track segment to ≤1.5mm.

• Joint treatment: Install fishplate and polish it smoothly, and control the misalignment within 0.5mm.

• Surface cleaning: Use metal-based cleaner to remove oil stains, wire brush to treat rusted areas.

• Rail replacement standards: The wear amount on one side reaches 10% of the original thickness or fatigue cracks appear.

Abnormal wheel set (accounting for about 30%)

Reason analysis:

1. Uneven wheel wear

   • The diameter difference between the driving wheel and the driven wheel is >2%.

   • The amount of wear on one side of the rim is >5mm.

2. Wheel alignment failure

   • Wheel horizontal deflection＞1/1000 wheelbase.

   • Vertical deflection＞1/400 wheel diameter.

3. Bearing damage

   • Bearing clearance＞0.5mm.

   • Broken cage causing jamming.

Solution:

• Wheel set adjustment:

  • Use a taper gauge to detect the rim angle (standard 60°±5′).

  • Adjust wheel horizontal deflection to ≤0.5mm/m.

• Bearing replacement:

  • Use C3 clearance grade bearings (axial clearance 0.12-0.25mm).

  • Fill with EP2 grade lithium grease (filling volume accounts for 60% of the cavity).

Drive system failure (accounting for about 15%)

Reason analysis:

1. Motor out of sync

   • Speed ​​difference between dual drive motors＞5%.

   • Brake release time difference＞0.3s.

2. Transmission system failure

   • Reducer gear backlash＞0.15mm.

   • Coupling radial deviation＞0.1mm.

Solution:

• Motor synchronization calibration:

  • Use a stroboscope to detect the speed difference between the two motors and control it within <2%.

  • Adjust the inverter parameters (carrier frequency is set to 2-4kHz).

• Transmission system overhaul:

  • Replace worn gears (when tooth thickness reduction >10%).

  • Coupling alignment adjustment (radial error ≤ 0.05mm).

Other factors (accounting for about 10%)

Special scenario questions:

1. Offset load operation: lifting point offset >5% span.

2. Wind load impact: lateral wind pressure >110N/m² (equivalent to level 6 wind).

3. Temperature deformation: thermal expansion and contraction caused by track temperature difference >30℃.

Targeted measures:

• Install automatic correction system:

  • Install laser displacement sensors on both sides of the track (accuracy ±0.5mm).

  • Real-time adjustment of drive motor torque distribution through PLC.

• Using temperature compensation track:

  • Reserve expansion joints (8-12mm gap for every 30m of track).

  • Use low expansion coefficient steel (CTE＜11×10⁻⁶/℃).

Maintenance management suggestions

1. Daily inspection:

   • Measure wheel-rail clearance every week (standard value 3-5mm).

   • Check track span tolerance monthly (±5mm allowed).

2. Preventive maintenance:

   • Replace reducer lubricant every 2000 working hours (ISO VG320).

   • Full system alignment every six months.

3. Operating specifications:

   • It is prohibited to pull or lift at an angle (stop immediately when the deflection angle is >3°).

   • Control operating speed (≤60% of rated speed under heavy load).

Through systematic investigation and precise adjustment, the deviation of the electric hoist trolley can be effectively controlled within the span range of ≤1/1000. It is recommended to conduct a dynamic load test within 72 hours after the initial installation of the electric hoist trolley, and use an infrared thermal imaging camera to monitor the wheel-rail contact status (the temperature difference should be <15°C). For electric hoist trolleys that frequently wander, it is recommended to install an electronic anti-sway system to improve stability.