Product category:
Condition monitoring and vibration analysis
News Release from: TEVA | Subject: Lafarge Cement
Edited by the Processingtalk Editorial
Team on 14 December 2006
Balancing system saves downtime at
Lafarge Cement
No company wants to contend with setbacks such as forced shutdowns or increased plant maintenance costs, and this was the problem facing Lafarge Cement when process changes caused fan build-up
No company wants to contend with setbacks such as forced shutdowns or increased plant maintenance costs, which can lead to profit losses However, when Lafarge Cement UK decided to make some production changes, it had to deal with these obstacles
This article was originally published on Processingtalk on 26 Feb 2007 at 8.00am (UK)
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Fortunately, Lafarge found a solution that could accomplish its original production intentions.
In 2005, Lafarge decided to undergo process changes in an effort to increase capacity.
These changes included an increased fan speed from 850 rpm to 890 rpm, using higher alternative fuel tonnages such as tyres and recycled fuel, lowering the preheat tower temperature 10Celsius and adding a second meal chute entry point to the tower design.
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While these changes helped to improve the efficiency and output of the process, the original goal was unattainable because of unscheduled shut-downs caused by vibration.
An unexpected side effect of the modifications was a severe material build-up and associated excessive vibration levels on the preheater ID fan.
The result was build-up on the fan blades, up to 50-mm thick, forcing Lafarge to make several unscheduled shut-downs for cleaning of the rotor.
With zero forced outages in 2004, four forced shutdowns caused by fan vibration and build-up in 2005 certainly caught Lafarge by surprise.
Production losses amounted to 12,000 tonnes of clinker and nearly 100 hours of time was lost.
Furthermore, the outer edges of the fan blades were wearing, and the excessive vibration caused a failure in the motor's white metal bearings in July of 2005.
Lafarge knew that the problems faced in 2005 could not continue and had to find a way to resolve the problem.
Consideration was briefly given to reversing the process changes to see if it would correct the build-up and corresponding vibration problems, however, Lafarge did not want to make any changes that would result in a reduction of output.
"We made the production changes to increase the level of output," said David Pepper, Maintenance Manager at Lafarge Dunbar: "However, there were also some negative effects.
Reversing the changes would have taken us right back where we started, losing valuable time and profits.
We needed to find a way to fix the fan vibration problem and achieve our original objectives".
Lafarge began investigating options to control the fan vibration and solve this problem.
They came across information on the Lord online fan balancing system and contacted the Lord United Kingdom distributor, TEVA, to determine if the system would allow Lafarge to keep the fan running at low vibration levels and eliminate the unscheduled shutdowns that took place in 2005.
After analyzing the balancing system specifications, Lafarge chose to install the Lord Corporation Fan Balancing System during their spring 2006 outage.
As a world leader in the management of vibration, motion and noise, Lord has developed a balancing system comprised of a permanently-mounted device that continuously monitors fan vibration levels and corrects for unbalance while the fan is running.
Although Lord Corporation has a variety of vibration control products, the balancing system was recommended because of its ability to make rapid balance corrections and withstand the harsh environment surrounding the ID fan.
The system is set up to monitor fan bearing vibration levels and the vibration phase angle in order to automatically correct for unbalanced conditions.
This is done while the fan is running at operating speed, eliminating costly downtime to clean and manually balance the fan.
Once levels reach a pre-set high trip point, the system switches on, commanding balance mass inside the shaft mounted system to adjust as needed to counteract the unbalance and reduce the vibration.
The balancing ring of the system mounts directly to the fan shaft and houses counterweight masses that are repositioned to offset the unbalance detected in the fan rotor.
Utilising vibration sensors, the system monitors the fan bearing vibration.
Vibration signals are received and processed by an "Adaptive Influence Coefficient" control system, which then determines the balance adjustments that are required.
The controller relocates the counterweight masses to the desired position to minimise the vibration levels.
This process continues until the controller senses that balance has been restored.
Typical balance cycle times range from 30 to 120 seconds, depending on operating speed.
Lord Corporation developed and patented the actuator coil assembly used in their balancing system.
The actuator coil is traditionally mounted to support brackets located on the bearing pedestal.
The non-contact power supply used in the actuator coil eliminates the need for maintenance, sending power across an air gap between the stationary actuator coil and the rotating balancer ring.
According to Andy Winzenz, Lord Corporation Global Project Manager, they were confident that the balancing system would be a success.
"Lafarge expected the system to end unscheduled plant stops, prevent motor bearings failures, and allow for longer run times between scheduled stops," said Winzenz.
"After evaluating the data associated with the problem we knew it could accomplish these things".
The installation, performed in concert with Lord Corporation's UK distributor TEVA, involved a two-plane balancing system installed on inboard and outboard sides of the fan.
The anticipated vibration offset was approximately 12-14 mm/sec with a 2,888,000 g-cm (4,000 oz-in) correction capacity per balancer plane.
Lafarge also opted for a control set up that only makes balance corrections when initiated by an operator - a manual balance mode.
With balancers installed permanently on the shaft of the rotating equipment and the stationary coil assembly mounted on the bearing pedestal, the system is based on a "Sense-then-Adjust" concept.
The sensors monitor vibration levels which send signals to the controller, and the controller then signals balancers to make an adjustment.
Trim balance corrections are made while the fan is in service which compensates for 1X (Shaft Synchronous) vibration.
Because of the integration of the Lord Corporation balancing system, shutdowns from excessive vibration are a thing of the past.
As of September, Lafarge had identified at least six scenarios when the balancing system was able to make a correction and avoid an unscheduled shutdown.
The balancing system not only allows the fan to run at extremely low vibration levels but it also keeps the plant from having to deal with unscheduled stops.
For Lafarge, what is equally as important as the reduction of downtime is that they are able to continue to increase their output.
"We are very happy with the results," Pepper stated: "The average vibration level is now 1.5 mm/second, which is the lowest it has ever been.
We also haven't had to make any further adjustments to the temperature and fan speeds".
TEVA have been established since 1994, have ISO 9001, and offer high quality Condition Monitoring Products and Services.
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