Archive for category: Slewing Drive Knowledge

Slewing drive is also called slewing reducer and slewing spur gear drive. Slewing drive oil leakage often occurs during the operation of the equipment, but there are many reasons for the oil leakage, and the solutions are also different. So what should I do if the slewing drive leaks gear oil? The following is a brief introduction by the slewing drive manufacturer on the cause and solution of the oil leakage of the slewing drive.

Reasons for gear oil leakage in slewing drive

1. The pressure difference between the inside and outside of the slewing drive

In a closed drive, each pair of gears meshing and friction will generate heat. According to Boyle Mario’s law, as the operating time increases, the temperature in the slewing drive box gradually rises, and the volume in the reducer box No change, so the pressure in the box will increase accordingly, and the lubricating oil in the box will be splashed and spilled on the inner wall of the reduction box. Due to the relatively strong oil permeability, under the pressure in the tank, where the seal is not tight, the oil will seep out from there.

2. The design of the slewing drive itself

The designed reducer has no ventilation hood or no breather plug on the peephole cover; the shaft seal structure design is unreasonable, and the oil groove and felt ring shaft seal structure is adopted. The compensation performance of the felt is extremely poor, which causes the seal to fail in a short time. ; Although there are oil return holes on the oil ditch, it is very easy to block and the oil return effect is difficult to play.

During the manufacturing process, the casting has not been annealed or aging treated, and the internal stress of the casting has not been eliminated, resulting in deformation and gaps resulting in oil leakage; there are defects such as sand holes, slag inclusions, pores, cracks, etc.; oil leakage caused by poor processing accuracy, due to deceleration The existence of factors such as low machining accuracy of the matching surface of the chassis body, improper tolerances, and non-conforming assembly requirements may cause the reducer to leak oil.

3. Excessive lubricating oil

During the operation of the slewing drive, the oil pool is greatly agitated, and the lubricating oil splashes everywhere in the machine. If the amount of lubrication is too much, a large amount of lubricating oil will accumulate on the shaft seal, joint surface, etc., resulting in leakage.

4. Insufficient installation accuracy

Oil leakage caused by poor installation accuracy. The reducer bears a huge dynamic load when it is started. Once the installation accuracy of the reducer does not meet the standard requirements, the base bolts of the reducer will be loosened, which will aggravate the vibration of the reducer and make the seal ring at the high and low speed shaft holes of the reducer. The wear is intensified, causing the lubricating oil to flow out. At the same time, when the equipment is overhauled, due to incomplete removal of dirt on the bonding surface, improper selection of sealant, reverse installation of the seal, and failure to replace the seal in time, oil leakage may also occur.

5. The lubricating oil model is wrong

Generally, the slewing drive often uses HJ-40, HJ-50 mechanical lubricants, and can also be lubricated with HL-30, HL-20 gear oils and HJ3-28 rolling machine oils. In short, the lubricating oil of the reducer should be selected according to the load, speed, temperature and other conditions. It is wrong to blindly pursue the viscosity of the lubricating oil, the better.

The solution to the leaking gear oil of the slewing drive

1. Improve the breathable cap and inspection hole cover

Aiming at the problem of oil leakage of the slewing drive caused by the pressure difference, it can be solved by improving the vent cap and the inspection hole cover. Although the reducer has a vent cap, the vent hole is too small, and it is easy to be blocked by dust and oil. In addition, the inspection hole cover must be opened every time the oil is refilled, and opening once will increase the possibility of oil leakage, causing leakage in places that did not leak. To this end, an oil cup-type vent cap can be made, and the original thin inspection hole cover is changed to 6mm thick, and the oil cup-type vent cap is welded to the cover plate. The diameter of the vent is 6mm, which is convenient for ventilation and makes the machine The internal and external pressures are balanced. When refueling in the future, you can directly add oil through the oil cup without opening the inspection hole cover to reduce the chance of oil leakage.

2. Unblock the lubricating oil return channel

The oil spilled on the inner wall of the box should flow back to the oil pool as soon as possible, and do not store it in the shaft head seal to prevent the oil from gradually leaching out along the shaft head. For example, an oil seal ring is designed on the shaft head of the reducer, or a semicircular groove is glued to the upper cover of the reducer at the shaft head, so that the oil splashed on the upper cover flows to the return pool along both ends of the semicircular groove.

3. Improve sealing materials

(1) Slewing drive shaft seal with output shaft as half shaft Improved belt conveyor, screw unloader, impeller coal feeder and other equipment. The output shaft of reducer is half shaft, which is more convenient for modification. Disassemble the reducer, remove the coupling, take out the shaft seal end cover of the reducer, machine the groove on the outer side of the original end cover according to the size of the supporting frame oil seal, install the frame oil seal, and the side with the spring is inward. When reinstalling, if the end cover is more than 35 mm away from the inner end surface of the coupling, a spare oil seal can be installed on the shaft outside the end cover. Once the oil seal fails, the damaged oil seal can be removed and the spare oil seal can be pushed into the end cover. Eliminate the time-consuming and laborious processes such as disassembling the reducer and disassembling the coupling.

(2) The output shaft of the reducer shaft seal of the entire shaft is improved. The output shaft of the reducer of the entire shaft transmission has no coupling. If the above scheme is modified, the workload is too large and unrealistic. In order to reduce the workload and simplify the installation procedure, a split-type end cover was designed, and an opening-type oil seal was tried. The outer side of the split end cover is machined with grooves. When installing the oil seal, first take out the spring, saw the oil seal into an opening, and sleeve the oil seal on the shaft from the opening, butt the opening with adhesive, and then install the opening upward. Put on the spring and push in the end cap.

4 Using polymer composite materials

Polymer composite materials are based on high molecular polymers, metal or ceramic ultra-fine powders, fibers, etc., which are composited under the action of curing agents and curing accelerators. Various materials complement each other in performance and produce a synergistic effect, so that the comprehensive performance of the composite material is better than that of the original composition material. With strong adhesion, mechanical properties, and chemical corrosion resistance, it is widely used in the repair of mechanical wear, scratches, pits, cracks, leakage, casting sand holes, etc. of metal equipment, as well as various chemical storage tanks , Chemical anti-corrosion protection and repair of reaction tanks and pipelines.

For the leakage of the static sealing point of the slewing drive, the polymer composite material and technology can be used to control the leakage on the spot. There is no need to disassemble, and the polymer composite material is used to control the leakage externally, which saves time and effort, and the effect is immediate. Oil resistance and 350% stretch, overcoming the influence of the vibration of the reducer, has well solved the problem that the company has not been able to solve for many years. If the static seal point of the reducer leaks oil during operation, the oil surface emergency repair agent of surface engineering technology can be used to stick the plug, so as to achieve the purpose of eliminating the oil leakage.

5. Improve the maintenance process

During the overhaul of the slewing drive, the process regulations must be carefully implemented. The oil seal must not be installed reversely, the lip must not be damaged, the outer edge must not be deformed, the spring must not fall off, the joint surface must be cleaned, the sealant must be evenly applied, and the amount of oil must not exceed the scale of the oil dipstick.

6. Do a good job of cleaning

The static sealing point of the slewing drive can generally be leak-proof through treatment. However, due to the aging of the seals, poor quality, improper assembly, and high surface roughness of the shaft, the dynamic sealing points will cause small leakage at individual dynamic sealing points. Due to the poor working environment of cement companies, the dust sticks to the shaft and it is almost greasy. Therefore, it is necessary to wipe off the oil stains on the shaft after the equipment is stopped.

What to do if the gear oil leaks in the slewing drive From the above-mentioned reasons and treatment methods of oil leakage, the common oil leakage problems can basically be solved. We should pay attention to the maintenance and regular maintenance of the reducer when using the slewing drive in daily life, which can better prevent the occurrence of oil leakage, and at the same time extend the operating life of the slewing drive to ensure its good working condition.

In the current transmission mechanism, the application range of slewing drive is very wide, including the application of products such as high-altitude lifting platforms, fire trucks, marine cranes, and log transfer machines. In a complex application environment, the slewing drive device will inevitably fail due to various reasons. The editor below has sorted out some common faults and solutions of the slewing drive device and hopes to be helpful to everyone.

Common causes of failures of slewing drive devices

1. Rotary drive string shaft

(1) Shaft tandem caused by broken teeth causing the input shaft to lose its axial restraining force;

(2) The slewing drive driven gear is not tightly fastened to the shaft, resulting in insufficient bearing interference, resulting in a series of shafts, and the steering problem of the slewing drive is affected;

(3) Gear machining deflection;

(4) Gear helix angle error;

(5) Tooth thickness error, uneven wear of tooth surface and premature wear, deformation of tooth back.

The rotary drive oil temperature is too high

(1) The lubricating oil used by the rotary drive is unqualified or has been used for too long;

(2) Too much lubricating oil is used in the rotary drive;

(3) Damage to the slewing drive components, including severe pitting of gears, broken teeth, damage to the bearing cage, inner and outer rings, balls, as well as bearing seizure or severe shaft deformation;

(4) The outside of the rotary drive is covered by debris or dust. When things are piled around or the surface of the machine body has not been cleaned for a long time, the cover of debris or dust may cause incomplete heat dissipation of the reducer and increase the oil temperature;

(5) The cooling device fails or is blocked. If the cooling device is blocked or the cooling device is broken due to long-term work without cleaning the internal pipeline, it will cause the temperature of the rotary drive oil to rise;

(6) Overload operation of rotary drive.

Oil leakage of rotary drive

The oil leakage of the slewing drive: the driving shaft seal ring, the driven shaft seal ring, the slewing drive box, the sight hole cover, the oil drain hole at the bottom, and the oil leakage of the breather. Possible reasons include the fixing bolts are not tightened; there is iron filings on the joint box surface and the closure is not tight; the rotary drive housing is deformed and does not fit tightly and leaks oil; or the ventilator has too much oil.

The slewing drive is overheated or there is noise in the bearing part

(1) Insufficient lubricating oil. When the lubrication oil level is insufficient or the reducer cannot reach a reasonable height due to oil leakage, it may cause high temperature or noise in the bearing part of the reducer;

(2) The bearing cap or seal part is rubbed. When the bearing cover or the sealing part and the connecting part are worn due to improper installation, improper bearing cover or long-term use, the bearing temperature of the reducer may be high or there may be noise;

(3) The bearing is damaged or worn. This item mainly includes damage to the cage of the bearing, wear or deformation of the inner and outer rings, wear or fall of the balls, these reasons will make the reducer unable to work normally;

(4) The bearing clearance is too large or too small. The above symptoms may be caused when the gap between the ball of the reducer bearing and the inner and outer rings, the gap between the bearing inner ring and the shaft, and the gap between the bearing and the end cover increase due to long-term use;

(5) The key handle of the helical gear is loose. The looseness of the helical gear key handle will cause the lack of tight fit between the gear and the shaft, resulting in overheating or noise in the bearing;

Large vibration of the rotary drive body

The possible reasons for the vibration of the slewing drive body include: the anchor screw is loose; the coupler is damaged; the motor screw is loose; the bearing is severely worn; the gear is damaged; the shaft is deformed and out of balance. These conditions may be due to loose screws or coupler failures, bearing wear and other reasons caused by long-term operation.

The bearing of the slewing drive device is broken

The slewing drive bearing cracks mainly occur in the driving shaft bearing. The main reason is that when the driving shaft moves, axial sliding will occur between the bearing inner ring and the rollers, causing the bearing inner ring to move axially, causing the inner bearing rollers to move first. Damage to the bearing.

Damage to the slewing drive gear

Rotary drives have different reasons for broken teeth, gear pitting, spalling, and wear. It can be roughly divided into insufficient contact fatigue strength of the gear; gear material defects, poor precision, inadequate lubrication, impurities in the lubricating oil, and errors in the center distance of the gears.

The slewing drive device has abnormal noise

Possible causes The reducer is overloaded; the load of the working machine is unbalanced; the lubricating oil is deteriorated; the gear tooth surface is worn or the manufacturing quality is poor; the bearing clearance is too large or too small; there is adhesion on the tooth surface; there is debris in the box.

After understanding the causes of common failures of the slewing drive device, the editor briefly introduces the repair methods of the slewing drive device failure. You can check the fault according to the specific situation. If you can’t solve it by yourself, you still need to contact the manufacturer for repair.

Solutions to common failures of slewing drive devices

1. Rotary drive string shaft

It can improve the strength and manufacturing accuracy of the gear, and reduce the roughness value of the gear and shaft. Improving the installation accuracy and tightness of the driven gear and the shaft is mainly to achieve a reasonable interference fit.

2. The rotary drive oil temperature is too high

(1) The staff can perform a detailed inspection on the actual load of the slewing drive and adjust it to the specified value, or it can be replaced with a larger power slewing drive.

(2) Use lubricating oil to remove excess oil in strict accordance with the prescribed amount of oil; or replace the lubricating oil.

(3) Remove the debris and dust around the rotary drive, replace the cooling device to remove the blockage.

3. Oil leakage of rotary drive

(1) The sealing ring gland adopts an open structure or an easily disassembled structure.

(2) Install gaskets and fastening bolts on the sight hole cover.

(3) The oil return hole at the input shaft bearing should be appropriately enlarged.

(4) Replace the deformed drive housing.

(5) Correctly install and correct the oil level of the ventilator.

(6) An annular oil groove is cast or machined on the box surface of the rotary drive base, and there are multiple oil return holes communicating with the annular oil groove. When the reducer is working, once the oil penetrates into the joint box surface, it will enter the annular oil groove, and then flow into the oil tank through the oil return hole, and the lubricating oil will not leak along the box surface to the outside of the reducer housing.

(7) Apply a layer of sealant (such as D05 silicone rubber sealant) on the surface of the box to effectively prevent oil leakage at the surface of the box.

(8) Improve the ventilation cap and inspection hole cover. The internal pressure of the reducer is greater than the external atmospheric pressure is one of the main reasons for oil leakage. If you try to balance the pressure inside and outside the machine, oil leakage can be prevented. Although the reducer has a vent cap, the vent hole is too small, and it is easy to be blocked by dust and oil. Moreover, the inspection hole cover must be opened every time the oil is refueled. Once opened, the possibility of oil leakage will increase once, so that the original place does not leak. Leaks also occurred. The vent hole can be enlarged to equalize the pressure inside and outside.

4. The slewing drive is overheated or there is noise in the bearing part

(1) Check the rotary drive oil level and add lubricating oil;

(2) Tighten the bolts of the bearing and the connecting part, and check the installation of the seal;

(3) Check the bearing and replace it immediately if it is damaged;

(4) If the clearance is not suitable, adjust the bearing clearance, and replace the bearing if it cannot be adjusted;

(5) If the key handle of the helical gear is loose, send it for repair in time;

5. The vibration of the rotating drive body is large

The fault can be eliminated by tightening the foot bolts and the loose screws of the motor; repairing the coupler; replacing the bearing; replacing the gear.

6. The slewing drive bearing is broken

Increase the interference between the inner ring and the shaft, or add a retaining ring on the outer side of the inner ring of the bearing to prevent axial movement.

7. Rotary drive gear damage

Gear damage can be strengthened or the viscosity of the regular lubricant can be used to reduce the loss of lubricant and prevent rust. Clean the gear to keep the surface free of impurities, replace the gear that cannot be repaired, and pay attention to daily maintenance.

8. The slewing drive device has abnormal noise

When there is abnormal noise, you can replace the new lubricant to adjust the bearing gap, check the bearing and do the cleaning work, or replace the new parts in time.

The above is the sorting and summary of the common failure causes and solutions of the rotary drive device. I hope it will be helpful to everyone.