Girth Gear Monitoring System (GGMS)

The problem of misalignment of girth gear, sooner or later, affects to every rotary kiln. This is because it is directly related to the kiln shell. In case of sudden temperature change on the shell circumference close to girth gear, e.g. due to brick lining failure or coating collapse, some thermal crank at the kiln shell can appear. This crank changes the geometrical position of girth gear, which is directly attached to the kiln shell. Correct operation of meshing between girth gear and pinion is at risk. To monitor this misalignment two basic parameters has to be constantly controlled – axial run-out and radial run-out.

The problem described above is one of the main maintenance challenges for industrial rotary equipment. The periodic thermal crank, near the girth gear gradually increase the vibration level at, rapid wear and components damage at the station.

It became obvious that geometrical position in real time has to be monitored to improve equipment control possibilities. To implement very early warning system.

The basis of the system is non-contact indictive sensors with high reading frequency which precisely measure the distance only to ferrous materials. No oil and grease have any influence to the measurements. Precise results are possible without kiln stoppage, arduous cleaning process and the measurement itself can by applied directly on the teeth.

The system is composed of two linear, non-contact inductive distance measurement sensors, one high temperature resistant position sensor, industrial computer with the software and screen.

During kiln normal operation, both axial run-out and radial run-out parameters are constantly measured. The operator from the CCR level has the direct access to the raw data readings, calculated values of radial run-out and axial run-out and exact orientation of the deviation on the shell circumference. All the results are stored in logs at local hard drive, which allow to analyse the trend lines in relation to production parameter and kiln operation condition.

Installation of the sensors very close to the girth gear are the subject of vibrations (especially at a time with not a perfect alignment). It may seem a high influence on the accuracy of the measurement. However, since this vibration are cyclical, with relatively high frequency, and have relatively small amplitude, there is no significant effect on the calculated value of run-out.

Ambient temperature difference for the sensor itself can also create some measurement error and become an accuracy problem. This issue was solved by method of calculation of the parameters. All output data base on differential values not on direct (absolute) ones, so most of thermal component errors are eliminated.

High ambient temperature was problematic especially for sensor which work as a marker of shell rotation. This marker was placed as a hatch line position, which create an imaginary line along the length of the kiln shell. High temperature resistant sensor was used.

As the excessive severe vibrations on the girth gear station very often occurs periodically, the main goal is to locate the cause of the problem. The measurements of both parameters’ axial and radial run-out are performed and the period of higher deviations is recorded. Then all the production and kiln condition parameters can be collected.

Installation of GGMS as a permanent monitoring equipment resolves many problems with condition monitoring not only for the girth gear but also for other kiln components. It is a very early warning system that informs the kiln operators long before the mechanical problem and any damages will appear. With a real-time monitoring system in place operating condition in relation to girth gear alignment are precisely controlled.