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New Version ofAVAS Released for2011                                                             Français

The latest version of UNIVIB's chatter-avoidance system, the "Advanced Vibration Analysis System" or AVAS" for short, has just been released.

AVAS is a chatter-avoidance system which comprises a number of software modules for monitoring and analysing the vibration of rolling mills, roll grinding machines and tension levellers used in the processing of steel and aluminium and other strip metals. Since its inception 20 years ago, systems have been installed at major steel and aluminium plants across the world.

For the latest release, many new features have been added to all of the modules to make them easier to use whilst providing even more functionality. The most significant are described below:


Alarm logging:
In response to a request from a number of users, the alarm-handling capabilities of the system have been completely overhauled. A new alarm log screen has been added to the Mill Module and Grinder Module that logs all events and alarms that occur during rolling/grinding.

Alarm Display
The three most severe/most recent alarm messages are prominently displayed next to the alarm indicator lamps in the top right corner of all user screens

System configuration tool:
A new system configuration tool has been added that allows the authorised system administrators to easily modify the configuration of the system. They can, for example, select the upper and lower limits of the bandpass-filtered frequency bands and alarm threshold levels without having to edit the registry as was the case in previous versions of the system. The tool also allows administrators to "map" or allocate messages of their choice to various alarms or alarm combinations. This provides important information to the mill/grinder operator about why the system is alarming and can even recommended, in simple English, actions to be taken.

Stability Indicator:
A thermometer-type indicator at the side of the mill speed window has been added to indicate more-stable and less-stable speed ranges for the mill installed with the current back-up rolls. If the operators try, wherever possible, to run the mill at speeds that lie in the green zones (as in the example below) they will minimise the rate at which marks are worn into the back-up rolls as a result of the interaction of any exciters with the 5th-octave mode resonances of the mill. The indicator is derived from about the resonant frequencies of the mill that is gathered and input to the system during on-site commissioning along with the difference in diameters of the back-up rolls that is communicated from the mill controller.

Sensor connection monitoring and alarming:

Hardware options now include
(1) magnetically mounted sensors or (2) sensors and fully-submersible disconnect boxes that are permanently attached to the back-up roll chocks and that enable the sensor cables to be disconnected when the back-up rolls are changed.

The connection is monitored so that, if the mill operators forget to re-connect when the new back-up rolls are installed, a warning is issued via the alarm logging and alarm messaging display described above. This increases the reliability of the data provided by the monitoring system.





Chock temperature monitoring:
Chock temperature monitoring is available as an option in the latest release of AVAS. If this option is ordered, dual-purpose sensors are supplied that are magnetically mounted to the chocks. The temperature signals are monitored along-side the vibration signals and a new screen has been developed for the display of the measured temperatures. Alarms can be set to occur if the temperature of either an individual chock or of one chock relative to another increases above a pre-set threshold.


Signature analysis:
The latest release of the AVAS Grinder Module includes signature analysis so that the system can track sources of vibration that commonly have harmonic content, such as wheel imbalance and eccentricity. The levels of these tracked signatures are displayed in the main monitoring window.

Waterfall display:
New for 2011, the band-pass filtered vibration levels can be displayed in a waterfall display so that the user can see how the levels vary on a pass-by-pass basis. This provides a visual indication of whereabouts along the length of the roll barrel the vibration has been at its highest (so the grinder operator knows where to inspect the roll most closely).

Integrated with Chatter_Detect System:
The latest version of the AVAS Grinder Module is now fully integrated with UNIVIB's Chatter_Detect system. This means that after each regrind, the roll can be readily subjected to a surface inspection to check for chatter marks that are often invisible to the naked eye but but may still affect the rolling process. With the roll data now automatically transferred to the Chatter_Detect system, the inspection time is reduced significantly, to no more than a couple of minutes. The application of the system in the field is proving invaluable in ensuring that all ground rolls sent to the mill are free from chatter marks.