With the extension of the use time, there are various failures in the deceleration opportunity. According to relevant data statistics, 37% of gearbox failures are mechanical seal failures, 31% are bearing failures, 32% are other reasons.

Leakage is one of the common faults of mechanical equipment.

There are two main reasons for the leakage:

First, due to the result of machining, there must be various defects and shape and size deviation on the surface of mechanical products. Therefore, there will inevitably be gaps at the joints of mechanical parts.

Second, there is a pressure difference between the two sides of the seal, and the working medium will leak through the gap. Reducing or eliminating the gap is the main way to prevent leakage.

The function of sealing is to seal the gap between the joint surfaces, isolate or cut off the leakage channel, increase the resistance in the leakage channel, or add a small power element in the channel to cause pressure on the leakage, partially offset or completely balance with the pressure difference causing the leakage, so as to prevent the leakage.

• Seal leakage during reducer operation；

• Stable leakage of sealing surface；

• Aging of oil seal, wear of shaft head, etc；

Faults often lead to leakage of input and output shaft lubricating oil.

• The transmission shaft is installed with shaft sleeve to protect the transmission shaft from wear;

• Adjust the oil seal spring；

• Oil seal end cover adjustment；

• Oil seal rotation and other treatment methods；

However, if the oil seal is seriously damaged and the equipment does not have the condition of long-term shutdown, the above methods can not solve the leakage problem timely and effectively.

The high-speed shaft (input side) of a blast furnace raw material transmission drive reducer suffered from oil leakage. After using it for one month, a new oil seal was replaced in the periodical repair. The reason was that the shaft head was worn and the whole reducer had to be replaced.

Two months later, the low-speed shaft (output side) of the drive reducer suffered from oil leakage, and the oil seal on one side had to be replaced, so the whole reducer must be replaced. Therefore, it is necessary to find a treatment method that not only does not need to replace the whole reducer, but also can effectively avoid oil seal leakage.

1. There are four reasons for the failure of mechanical seal：

1）The quality of mechanical seal is defective；

2）Reducer body defective；

3）Improper selection of mechanical seal；

4）Improper operation, use and maintenance。

2. Existing problems：

1）If the performance of other parts in the reducer is good, but there is only leakage fault, the replacement of the whole reducer will cause great cost waste；

2）At present, most of the leakage faults of reducer are shaft head wear, so the reducer must be replaced; or if the equipment does not have the condition of long-term shutdown, it must be handled in time within 40 minutes；

3）Excessive torque of sealing surface (excessive compression, poor lubricity, dry friction of sealing surface, erosion of sealing surface, adhesion of sealing surface)；

4）Distorted sealing surface；

①The tightness of gland bolt is uneven or too tight, and the clamping stress is too large；

②The sealing surface is not straight；

③Sundries between sealing surfaces；

5）The sealing surface is scratched and scored, which is not well grasped during manufacturing or assembly; the sealing surface enters into particles. It can be mechanically or manually grinded to eliminate nicks or scratches。

3. Improvement measures：

1）Install another oil seal outside the original oil seal, and cut the oil seal into two parts；

2）Making oil seal installation fixture；

3）Careful and careful operation during installation；

4）Adjust compression；

5）Increase sealing oil and reduce sealing temperature；

6）Improve the environment to prevent excessive torque caused by poor lubrication of friction pairs；

7）Assemble carefully to avoid seal seizure；

8）Adjust the gland bolt torque to a uniform and appropriate strength；

9）Change of auxiliary seal structure and material；

10）Rework the sealing surface to be straight；

11）Improve sealing environment and eliminate particles in fluid。

4. Effect analysis：

1）Reduce the safety and environmental protection problems caused by the leakage of lubricating oil；

2）Avoid replacing the whole reducer, save maintenance cost and repair cost。

With the development of material and manufacturing technology, the reliability of mechanical seal has been greatly improved. Now the mechanical seal itself can operate without fault for many years. There are not many cases of gearbox leakage due to the seal itself。

When dealing with the problem of gearbox leakage, it is necessary to comprehensively consider the installation accuracy, operation and operation conditions of the reducer, assembly accuracy of the machine seal and other factors, find out the causes and solve the existing problems.