Maximizing equipment performance and ensuring stable production is still the most urgent need for steel enterprises. The main line equipment failure of rolling mill will seriously affect the operation efficiency and production safety of rolling mill, and become a painful difficulty in the process of "intellectual transformation" of steel enterprises.

1 Complex working conditions, bearing cage prediction is more difficult

According to SKF statistics, since 2021, 92% of the mill gearbox bearing failures diagnosed in the steel industry are bearing cage fracture problems (including warning and no warning). In addition, through the diagnosis and analysis of 57 typical gearbox fault cases in the past 10 years, the bearing cage problem accounted for as high as 58%.

The main function of the bearing cage is to separate the rolling element, uniform load and guide the normal operation of the rolling element, as a non-major force component, its hardness and strength are much lower than other bearing components. In the application environment of steel rolling, the complex conditions such as alternating load, abnormal impact and variable speed make the bearing cage easily damaged.

By analyzing the operational characteristics of rolling production, SKF has found that there are many challenges to achieving predictive maintenance of rolling mill gearboxes.

· The source of the fault signal is difficult to distinguish -- affected by complex working conditions, there is a lot of interference from the impact signal, and the strength of the damaged signal is attenuated during transmission, so the received effective signal is very weak;

· The prediction accuracy of traditional monitoring methods is low - most sampling techniques cannot ensure effective collection of cage fault signals, and can not assess the damage and the severity of damage;

Failure to estimate residual life - most analytical methods often have short warning times to interpret deterioration trends and adjust spare parts and maintenance strategies in a timely manner.

The gear box of rolling mill is the core equipment of steel rolling production line. Bearing failure will lead to long time shutdown, huge loss of output and sharp increase of maintenance cost.

2 Successful practice to solve predictive maintenance problems

In 2021, SKF successfully detected a number of gearbox bearing cage failures on the 2050 hot rolling finishing mill gearbox of two large steel mill customers in China, helping customers to reduce unplanned downtime and avoid the escalation of failures.

In the case of a steel mill, SKF online monitoring system issued an abnormal vibration warning on the operating side of the input shaft of the gear box of the F4 finishing mill, and reported the abnormal vibration induced by the fault characteristic frequency of the gear box bearing cage. After the expert diagnosis confirmed the bearing cage damage, and gave the equipment to maximize the surplus life time advice, as expected, the equipment can continue to operate stably with the disease for about 4 weeks, before the planned shutdown to replace the bearing, for customers to obtain sufficient spare parts preparation time.

3 There is a good way to predict ahead of time

Insight, capture effective signals

The quality of data is the premise of accurate monitoring. Based on a comprehensive consideration of the process characteristics of steel rolling production, equipment structure, equipment loads and forces, and typical equipment failure modes, SKF mill gearbox predictive maintenance solutions have the following three application characteristics:

(1) The front-end sensor is closer to the bearing bearing area;

(2) The data sampling time of the hardware acquisition unit is highly synchronized with the rolling production;

(3) Isolation of impact signals during rolling production.

The above characteristics ensure that the signal acquisition process of the rolling mill gear box is efficient and the signal accuracy is high, and it can effectively deal with the influence of the gear box low speed variable load and impact signal interference.

In-depth analysis to improve prediction accuracy

SKF's proprietary acceleration envelope technology (gE) effectively filters low-frequency and high-amplitude vibration components, utilizes a complete bearing database and powerful damage frequency calculation capabilities, and combines professional monitoring solutions based on rolling production to efficiently capture the transient impact signals that occur in the early stage of bearing failure, and can identify the bearing cage damage false earlier and make accurate prediction.

Professional diagnosis, estimated residual life

In addition to accurate prediction, estimating the residual life of equipment is also crucial for steel mills. With the rich experience of the diagnostic analysis experts, SKF uses the Protean diagnostic rules in the system analysis software to effectively track the deterioration trend of bearing cage damage, confirm the severity of cage breakage combined with field noise and production load, evaluate the residual life of the equipment and develop spare parts and maintenance strategies.

4 Conclusion

SKF intelligent monitoring system allows the potential risks of equipment to be hidden, uses data to guide production, helps steel mills to better predictive maintenance, and always guards the safe and stable operation of production. SKF will lead the industry in the performance of rotating equipment knowledge, technology and data into the digital model of equipment maintenance management, so that SKF's experience and diagnostic capabilities become part of the digital platform of steel enterprises, accelerate the metallurgical industry intelligent operation and maintenance construction, enabling gold enterprises to accelerate the "intelligent manufacturing" transformation and reform, towards the goal of high-quality development.