How to deal with the failure of industrial gearboxes?

Industrial gearboxes are key components of industrial equipment transmission systems and are widely used to achieve functions such as speed change, torque change, clutch, and power distribution. A typical industrial gearbox is mainly composed of key components such as the box body, box cover, gear shaft, gears, and bearings. During service, the above components may be damaged and fail, causing operational failures or safety hazards.

As industrial equipment develops towards high power and long-term safe service, the reliability control of key components of gearboxes has become the focus of equipment manufacturers. Timely understanding of the service conditions of industrial gearboxes, failure modes of key components and corresponding protection measures can guide the damage prevention and delay the occurrence of failure of industrial gearboxes, thereby extending the service life of industrial equipment.

Industrial gearboxes may encounter a variety of failure modes during long-term operation. Common damage and failure of industrial gearbox components include case failure, gear failure, shaft wear or fracture failure, bearing failure, etc.

(1) Box damage failure and protection

The gearbox housing is mainly used to support and contain key components such as gears and carry lubricating oil. The failure modes of the housing are mainly:

a. Box cracks: The heat dissipation speed at the riser position is slow during casting, which often causes defects such as coarse structure and leads to a decrease in mechanical properties. The corners of the box structure are often accompanied by stress concentration, which is very prone to stress corrosion cracking in an environment with external corrosive media.

b. Seal failure: Aging or damage of seals causes lubricating oil leakage, affecting the lubrication effect.

c.Box deformation: Long-term uneven force may cause box deformation and affect the meshing accuracy of gears.

In order to effectively prevent box failure, we should start from the structural design and processing technology. On the one hand, we should add enough fillet transition to relieve stress concentration, introduce reinforcing ribs to improve box rigidity, etc. On the other hand, when formulating the casting process, we should focus on the riser position of the casting. For example, by adding cold iron to quench, we can effectively avoid the formation of coarse grains, so as to obtain good comprehensive mechanical properties. In addition, by optimizing the box coating process, we can effectively prevent the erosion of corrosive media and achieve box life extension.

(2) Gear damage, failure and protection

Gears are the most critical components in the transmission system and are also the components most prone to damage and failure. The main forms of gear failure are:

a. Plastic deformation of gears and tooth root fracture: During heavy-load transmission, the soft tooth surface of the gear pair will inevitably produce plastic deformation due to yielding, causing tooth shape deviation, and further development will cause fracture at the root position where stress is concentrated.

b. Tooth surface pitting: Tooth surface pitting is a form of tooth surface failure, which mostly occurs at the pitch line on the tooth root surface. The relative sliding speed of the gear pair at the pitch line is low, the conditions for forming the oil film are poor, and poor lubrication is prone to occur. The direct contact of the gear meshing surface produces a large friction force that directly causes tiny cracks, and the extrusion effect of the infiltrated lubricating oil causes small areas to peel off, forming pitting on the tooth surface.

c. Tooth surface adhesion and peeling: In heavy-load transmission, the local high temperature environment in the gear tooth meshing area will cause lubrication failure, resulting in direct contact and adhesion of the two metal surfaces. In the subsequent relative sliding, tooth surface bonding failure will occur and the soft tooth surface material will be carried away by the furrows.

d. Continuous tooth surface wear: In an environment with insufficient lubrication and high dust content, tooth surface wear is difficult to avoid. Dust and metal chips generated by wear will cause abrasive wear between tooth surfaces. When the tooth surface wear reaches a certain degree, it will cause abnormal vibration of the gearbox and eventually lead to transmission failure.

To prevent gear failure, damage should be reduced during the design and processing stages. Reasonable manufacturing processes should be selected, fillet transitions should be increased at locations prone to stress concentration, heat treatment carburizing and nitriding should be used to increase tooth surface hardness, sufficient lubrication environment and lubricant cleanliness should be ensured, and if necessary, the viscosity and heat dissipation of the lubricant should be increased according to specific service conditions to achieve good lubrication.

(3) Shaft wear and failure protection

During long-term operation, gear shaft wear is inevitable. The main manifestations of shaft failure are:

a. Shaft wear: Wear directly causes the original mating surface to become loose, which manifests itself as abnormal vibration and noise. In severe cases, it can also cause lubricating oil leakage and unbalanced loading.

b. Plastic deformation of gear shaft: The gear shaft needs to withstand large torque during service, and under the action of strong torque, the gear shaft tends to undergo elastic-plastic deformation.

c. Gear shaft fracture failure: Even in a low stress state, long-term alternating loads can cause fatigue damage to the material and cause the gear shaft to fracture and fail.

Reasonable selection of materials and processing technology is particularly important for improving the fatigue strength of gear shafts.

In addition, inclusions must be strictly avoided during the hot working process, as this is often the root cause of brittle failure of gear shafts in the later stage.

(4) Bearing failure and protection

Bearings are important parts in industrial gearboxes, used to support rotating bodies and reduce friction coefficients. Bearing failure is an important source of gearbox failure, especially under low-speed and heavy-load conditions, where it is difficult for bearings to form good lubrication conditions, thus causing a series of failure problems. The main failure forms of rolling bearings are:

a. Rolling bearing failure: The rolling elements and inner and outer rings roll through point contact, resulting in large contact stress, which causes failures such as wear and contact fatigue. In addition, the cage of the rolling bearing is also one of the most vulnerable parts. The axial load and impact load generated during improper installation and overload operation often cause deformation and failure of the cage, fracture of the pillars or desoldering.

b. Failure of sliding bearings: The failure forms are mostly fatigue spalling, abrasive wear, etc. Bearing wear often occurs when lubrication is insufficient. Foreign hard particles directly cause plow-shaped scratches on the bearing surface. In addition, when the lubrication conditions are seriously deteriorated, micro-area welding of the friction surface will cause adhesive wear. Clearance is a key parameter to consider when installing bearings. Increasing the clearance appropriately can ensure the lubrication and heat dissipation of the bearing, but too much clearance will weaken the bearing's ability to resist impact loads.(Author: SGR, Angie Zhang)

Email:export@sgr.com.cn

WhatsApp:+86 188 1807 0282

Related Video: https://www.tiktok.com/@gear.reducer/video/7418523981113855263