At U.S. Steel’s Fairfield Works (Fairfield, AL) plant, unbalance and high vibration levels on a basic oxygen furnace were discovered on the fan rotor, which is responsible for pulling the air, gases and materials off the basic oxygen furnace. Excessive buildup of particulate matter caused the problem and resulted in chunks of the particulate matter falling off the rotor. U.S. Steel was forced to stop production and clean and manually balance the fans at least every three months.
According to Jim Mays, maintenance manager at Fairfield Works, it typically took between three and five balance attempts to perform a manual balance on the fan. This often resulted in a violation of the time recommended between starts on the motor, creating high potential for motor failure. Further, when a fan was stopped because of high vibration, it would shutdown the steel making process.
“It goes without saying that efficiency is crucial and downtime is deadly in the steelmaking industry,” says Mays.
U.S. Steel turned to BalaDyne Corp. (Ann Arbor, MI). To solve the problem, a BalaDyne Online Fan Balancer was installed to correct fan imbalance in operating machinery. The online balancing system, selected because of its ability to withstand the harsh environment of the steel making process, has proven to minimize the need for off-line balancing techniques. U.S. Steel previously used the technology at its Gary Works (Indiana) facility.
Defined as correcting an imbalance in machinery while in operation, the system continuously monitors fan vibration levels and phase angle, as well as automatically corrects for unbalanced conditions. This is done while the fan is running at operating speed, eliminating costly downtime associated with manual balancing.
The balancing ring of the BalaDyne system mounts directly to the fan’s shaft. The ring is divided into four chambers that contain a high specific gravity balancing fluid. When the balancer’s controller detects an imbalance, the fluid in the chamber on the heavy side heats up, changing from a liquid to a gas. The gas transfers through a shuttle tube to a chamber where it condenses and returns to a liquid. The process continues until balance is restored.
The BalaDyne technology was developed and patented for the rotary transformer used in the automatic fan balancer system. The noncontact power supply eliminates maintenance, sending power and data across an air gap between a stationary primary coil and a rotating secondary coil.
Implementing such a solution is not as easy as ordering a part considering it is being installed on a 121-inch-diameter, 13-ton doublewide, double-inlet fan. Installation of any solution must be carefully orchestrated. As such, Mays worked with BalaDyne to design a housing solution for the online balancer, as well as scheduled installation in October 1998 during a three-day furnace shutdown. Balancing systems were added to the remaining two fans during the course of the next year.
Since installation of the three balancers, Mays says they average one scheduled maintenance shutdown and one interim cleaning per year. Because the typical shutdown lasts between eight and 12 hours, the savings are significant. In addition to the revenue and time that is saved from the reduced number of shutdowns, Mays says the online balancing technology continuously maintains the balance level of the fans below 0.8 mils, as compared to the previous 1.0 mils low level field balance. Also, the motor and bearing life have been increased, resulting in fewer motor rebuilds at approximately $200,000 each.
“The whole steelmaking process has become more predictable and productive with the online balancer,” says Mays.
BalaDyne Corp, a division of Lord Corp.
(800) 458-0456 Reply 11
www.lord.com
BENEFITS
- The online balancing system continuously monitors fan vibration levels and automatically corrects for unbalanced conditions.
- Shutdowns caused by cleaning requirements dropped from about once every three months to once a year.
- Motor and bearing life have been increased, resulting in few motor rebuilds at approximately $200,000 each.
