The biggest validation of success often comes in the form of repeat business. This is especially true for Lord Corp. and its ability to solve vibration problems for U.S. Steel.
“It goes without saying that efficiency is crucial and downtime is deadly in the steelmaking industry,” said Jim Mays, maintenance manager for the U.S. Steel Fairfield Works in Fairfield, Ala. “Fortunately though, we were able to transfer the knowledge gained at our Gary Works, Ind., facility through the use of a Lord balancer, to fix a similar problem at Fairfield. The implementation at Fairfield has already improved uptime, which lowers our overall costs.”
Lord's solution for U.S. Steel came in the form of the Lord Balancing System – a system that corrects fan imbalance in operating machinery. The balancing system, selected because of its ability to withstand the harsh environment of the steel making process, has proven to greatly minimize the need for off-line balancing techniques at U.S. Steel.
Vibrating Fans = Imbalance
It was the vibration of the basic oxygen furnace, or Q-BOP, ID (induced draft) fans – responsible for pulling the air, gases and materials off the basic oxygen furnace – that was causing the problem at U.S. Steel. Since the furnace heats the steel to approximately 2,800 degrees Fahrenheit, the fans are critical to a successful steel-making process.
The imbalance and high vibration levels were caused by excess build-up of particulate on the fan rotor, resulting in chunks of build-up falling off the rotor. U.S. Steel had to clean and manually balance the fans at least every three months. According to Mays, it typically took between three and five balance attempts to successfully 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 due to high vibration, it would result in a shut-down of the steel making process.
No Downtime For Balancing
Lord's system, which corrects an imbalance in machinery while in operation, 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 system mounts directly to the fan’s shaft. The ring is divided into four chambers that contain a unique high specific gravity balancing fluid. When the balancer’s controller detects an imbalance, it heats up the fluid in the chamber on the heavy side, changing from a liquid to a gas. The gas transfers through a shuttle tube to the chamber on the light side where it condenses and returns to a liquid. This process continues until the controller senses that balance has been restored. A non-contact power supply eliminates the need for maintenance, sending power and data across an air gap between a stationary primary coil and a rotating secondary coil.
Implementing such a system is not as easy as ordering a part. When you are dealing with a 121-inch-diameter, 13-ton, double-wide, double-inlet fan – not to mention a finely-tuned manufacturing process that typically runs like clockwork – any installation procedure must be carefully orchestrated. Mays worked with Lord to design a housing solution for the online balancer, and scheduled installation to take place during a three-day furnace shut-down. Balancing systems were added to the remaining two fans during the next year.
Saving Time And Money
“Our applications and site engineers spent a lot of time coordinating all of the installation details with Mays and his staff at Fairfield,” said Andy Winzenz, product manager for Lord. “We typically install our systems during longer one- to two-week maintenance outages, so we had to make sure there were no surprises when we arrived on-site. Subsequent installations have taken place in as little as 24 hours.”
Since installation of the three balancers, Mays said U.S. Steel averages one scheduled maintenance shut-down and one interim cleaning per year. Since the typical shut-down lasts between eight and 12 hours, the savings are significant. But beyond saved revenue and time from reduced shut-downs, Mays said 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. Additionally, the motor and bearing life has 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,” said Mays.