New oil shear brake technology eliminates crane downtime and maintenance for this high volume anodizer.
Operating 24 hours a day, five to six days a week, there is literally no convenient time for downtime for Linetec (Wausau, WI). The Wausau plant employs a computer-controlled hoist system to guide material through the anodize process, eliminating any chance of manual variations in pre-cleaning, etching, anodizing, coloring or sealing – thus ensuring a consistent and durable finish on every load.
But any system is only as strong as its weakest link – which in this case was the dry brakes used to accurately stop and position the hoists. They required weekly maintenance and monthly overhauls – and still they periodically experienced failures which brought the anodizing process to a standstill. However, oil shear brake technology from Force Control Industries (Fairfield, OH) slashed the downtime and eliminated the failures – resulting in unprecedented productivity for Linetec.
There are eight cranes in this plant – each with a 3 hp trolley motor and a 15 hp hoist motor. Every motor performs roughly 2000 moves per shift. Previously, dry Stearns brakes were mounted on each motor for stopping and positioning. Since these brakes have a sacrificial wear surface (the disc) each one had to be checked weekly.
In addition, each was rebuilt on a quarterly basis – requiring disassembly, replacement of the disc, and solenoid, check the gap, reassemble everything, and get it running again. Conservative estimates of 7.5 minutes per each crane for weekly maintenance and 30 minutes each for quarter meant that the shop was spending 124 hours per year on preventative maintenance.
This was calculated as follows: Weekly maintenance requirements of 7.5 mins/brake times 16 brakes times 46 weeks per year (calculated at 50 weeks less the quarterly maintenance) equals 92 hours per year. Add to this the quarterly maintenance of 30 mins/brake times 16 brakes times four quarters equals 32 hours. This is a combined total PM time of 124 hours per year.
In addition to the time, the plant was spending another $8000 per year on maintenance parts. And keep in mind that these figures are “best case scenarios” because they do not account for any breakdowns or repairs.
All of this work was accomplished without removing the brakes from the motors, meaning scissors lifts were required to reach the motors, which are nearly 30 ft in the air. At that height the ambient temperature is elevated throughout the year – especially in summertime when the heat routinely registers in the triple-digit range.
Most maintenance work – whether inspections or preventative maintenance like rebuilding of brakes – was scheduled for the weekend when the plant was idled. But unscheduled failures while the plant was operational created problems of another sort.
“If the brakes failed when the line was running, we’d have to shut down production, then go get a scissor lift and the necessary tools and materials” said maintenance supervisor Jon Brubacher. “Then we’d do the rebuild – disassemble, replace disc, replace the solenoid, reassemble, check the gap and get it running again. It was quite time consuming, and the line is down throughout the entire process.”
Downtime is calculated at $1500 per hour, so these costs escalate to uncomfortable levels (perhaps bordering on unacceptable levels) very quickly. So when Bob Rhode from Linder Electric suggested an alternative braking technology, Brubacher was intrigued.
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