The reasons and treatment methods for oil leakage in the reducer of the explosion protection manual hoist trolley are as follows:

1、 Analysis of Oil Leakage Causes

Oil leakage caused by pressure difference between inside and outside

Reason: During the operation of the reducer, the friction heating of the moving pair or the increase in ambient temperature cause an increase in internal pressure. If the breathable cap is blocked or the breathable hole is too small, the pressure inside the machine cannot be balanced, and lubricating oil leaks from the gap under the pressure difference.

Typical scenario: In a high-temperature environment or after prolonged continuous operation, the breathable cap is blocked by dust and oil stains.

Unreasonable structural design

Inspection hole cover plate issue: The cover plate is too thin and is prone to deformation after tightening the bolts, resulting in uneven joint surfaces and oil leakage.

Casting defects: Failure to conduct annealing or aging treatment during the manufacturing process, failure to eliminate internal stress in the casting, and deformation resulting in gaps during use.

Missing oil return groove: There is no oil return groove in the box, and lubricating oil accumulates at the shaft seal, end cover, etc., leaking under pressure difference.

Outdated shaft seal structure: In the early days, oil groove and felt ring shaft seals were used, but the compensation performance of felt was poor and the seal was prone to failure; The oil return hole in the oil groove is prone to blockage, causing the oil return function to fail.

Excessive refueling volume

Reason: During operation, the oil pool is violently stirred, causing lubricating oil to splash and accumulate at the shaft seal, joint surface, etc., resulting in leakage.

Typical scenario: Failure to refuel according to the dipstick scale, resulting in the oil level exceeding the upper limit.

Improper maintenance process

Joint surface treatment: During maintenance, the dirt on the joint surface is not completely removed, or the sealant is improperly selected or unevenly applied.

Sealing installation: The sealing direction is reversed, aging parts are not replaced in a timely manner, or the oil seal lip is damaged or the outer edge is deformed.

Bolt tightening: Incorrect tightening sequence or insufficient torque can cause uneven stress on the joint surface, resulting in gaps.

Aging of seals or assembly issues

Aging of seals: Seals such as oil seals and O-rings age and wear out after long-term use, losing their sealing performance.

Excessive roughness of the shaft neck: The surface roughness of the shaft neck is too high (such as Ra>1.6 μ m), and the lip cannot fully fit, resulting in leakage.

Poor oil return: The oil groove on the shaft is blocked by oil stains, and the lubricating oil cannot flow back to the oil pool, accumulating at the shaft seal.

2、 Oil leakage treatment methods

Balance the pressure difference between inside and outside

Improve breathable cap: make an oil cup style breathable cap with enlarged breathable hole diameter to 6mm for easy ventilation; Thicken the inspection hole cover plate to 6mm and weld an oil cup type breathable cap to avoid frequent opening of the cover plate causing oil leakage.

Regular cleaning: Regularly clean the internal filter of the breathable cap to prevent dust and oil from clogging.

Optimize structural design

Add a return oil groove: A return oil groove inclined towards the inside of the machine is opened at the center of the bearing seat, and a notch is opened at the straight mouth of the end cover facing the return oil groove, allowing excess lubricating oil to flow back into the oil pool.

Improve the shaft seal structure:

Half shaft output: Remove the coupling, machine a groove on the outer side of the shaft seal end cover, and install the skeleton oil seal (spring side inward); If the distance between the end cap and the inner end face of the coupling is ≥ 35mm, an oil seal for equipment can be added.

Whole shaft output: Design a detachable end cap, saw the oil seal into an open shape, connect it with adhesive, and install it into the end cap to simplify the installation process.

Control fuel volume

Add oil according to the standard: The oil level should be between the upper and lower limits of the dipstick (usually 1/2-2/3 of the height of the dipstick) to avoid excessive oil level during shutdown.

Regular inspection: Regularly check the oil level and promptly remove excess lubricating oil.

Standardize the maintenance process

Joint surface treatment: Thoroughly clean the joint surface, use anaerobic sealant (such as Loctite 510), control the thickness of the adhesive layer at 0.3-0.5mm, and assemble after 24 hours of curing.

Seal installation: Ensure that the oil seal lip faces the oil chamber side and the radial runout of the shaft neck is ≤ 0.05mm; replace aging seals to avoid lip damage or outer edge deformation.

Bolt tightening: Tighten the bolts diagonally in stages, increasing the torque by 30%, and finally reaching the required torque in the manual (such as 35-40N · m for M12 bolts).

Replace or repair seals

Replace seals: Choose the appropriate material according to the working conditions (such as nitrile rubber NBR for ordinary working conditions, fluorine rubber FKM for high temperature/corrosion working conditions).

Repair the shaft neck: For minor wear (≤ 0.2mm), use electric brush plating to repair or install the shaft sleeve; Severe wear/scratches require replacement of the shaft or gearbox core.

Polishing the shaft neck: Use 1000 grit fine sandpaper to polish the shaft neck, ensuring that the surface roughness Ra is ≤ 1.6 μ m.

Adopting new sealing materials

Static sealing point repair: Use polymer composite materials (such as emergency repair agents for oil surfaces in surface engineering technology) to block leakage points without disassembling equipment, saving time and effort.

Maintenance of dynamic sealing points: Regularly wipe the oil stains on the shaft to prevent leakage caused by coal dust adhesion.

The main equipment produced by Hebei Makita: stage electric hoist, electric chian hoist, wire rope electric hoist，Hand chain hoist, lever hoist, pneumatic hoist and other lifting equipment