Losing time to unscheduled maintenance shutdowns is a problem for any manufacturing plant, but it is especially disastrous for companies whose customers demand consistent and efficient products to help them make their own great products.
Such was the case for Boise Paper Solutions, a manufacturer of papers, containers and newsprint, at their Wallula, Wash., plant. They were losing about $87,000 per year in lost production, makeup lime and maintenance costs due to unscheduled lime kiln shutdowns.
Shortly after joining Boise in 2001, Ron Blood, predictive maintenance and reliability supervisor at the Wallula plant, became aware of a continual build-up problem with calcium carbonate on one of the large induction (ID) fans for a lime kiln.
According to Blood, particulate had a tendency to stick to the fan rotor and this continuous, non-uniform build-up would actually throw the fan out of balance. This high level of vibration resulted in an average of 2.5 unscheduled shutdowns per year at a cost of $33,000 to $35,000 each in lost production, makeup time and maintenance costs.
“When the fan started to vibrate, my coffee would actually shake in my cup as it sat on my desktop,” said Blood. “Shutting down is a serious process though that typically takes three hours to allow the kiln to cool off, and another three hours to conduct the cleaning process. By the time we would get the kiln back in service, at least ten hours of production was lost.”
In addition to lost time and production, frequent episodes of high vibration were causing accelerated wear on the fan bearing, and the staff was often taken away from regular duties to troubleshoot vibration problems.
Searching For An Answer
When faced with finding an answer to this problem, Blood turned to Lord Corp., a manufacturer of vibration, motion and noise solutions. Andy Winzenz, sales manager for Lord, visited the plant and helped confirm the diagnosis.
“Boise’s manufacturing process is dependent on the performance of the fans and their ability to maintain process air flow,” said Winzenz. “As such, when the fan was thrown out of balance because of build-up, the result was untimely and expensive shut-downs.”
After analyzing the problem, Winzenz recommended Lord’s Balancing Systems technology — a permanently-mounted fan balancing system that continuously monitors fan vibration levels. Although Lord has a variety of products for the manufacturing industry, Winzenz recommended the balancing system because of its ability to make rapid balance corrections and withstand the harsh environment surrounding the lime kiln ID fan.
The Lord 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. Typical balance cycle times range from 30 to 120 seconds, depending on operating speed.
Implementing The Solution
Installation took place during a regular scheduled shutdown. Installation involved moving the motor out of the way, pulling the coupling and bearing off the fan shaft, actual installation of the balance ring, reassembly of the bearing and coupling, and putting the motor back in and aligning it. Other work, such as installing power to the controller and then mounting it in a dustproof, waterproof box near the fan, was completed in advance of the shutdown.
Since the installation, the team has endured only one unscheduled shut-down and this was caused by massive particulate build-up and throw-off. Interestingly, Blood said that after the installation, the fan ran so smoothly that the team forgot the fact that build-up was still happening.
“We received a wake-up call several months after installation when a large chunk of build-up flew off the fan,” said Blood. “The resulting vibration was more than the balancer could compensate for, so we had to shutdown and sandblast."
Fortunately though, since the Balancing Systems' technology stores balance history and events, data can be analyzed – aiding Boise’s process of calculating the build-up rate of the particulate in order to better plan for any necessary cleaning and sandblasting.
The Proof Is In The Numbers
No Vibration -- A nickel balanced on the edge of a smooth-operating fan.
Blood states that his coffee not only sits calmly in his cup each morning with the addition of the balancer, but he also is quick to demonstrate the smoothness of the fan operation by balancing a nickel on the edge of a fan bearing. Even more important, the production supervisors have little worries about the fan and can perform their daily functions without the hassle of an unscheduled shut-down.
Finally, the vibration figures speak for themselves. Before installation of the balancer, the fan registered 0.3- to 0.8-inches-per-second within 30 to 60 days of sandblasting. Today, however, Boise reports vibration levels of 0.04- to 0.06-inches per second within the same timeframe thanks to the balancing technology.