AIA: Bolts That Won't Bolt
Sequa Can Machinery Inc. (East Rutherford, NJ) manufactures different types of industrial machinery, including can-making equipment. The assemblies require reliable threaded fasteners, since critical joints are subject to a variety of different stresses in the shop floor.
"Shock, pressure, vibration, temperature change-all combine to loosen fastener threads, which inevitably come loose at the worst possible time," says Sequa Can Advanced Technology Group Vice President Joe Finan. "The fatal flaw in too many productions lines is failing to protect the critical joints with suitable fasteners."
Finan notes that fastener reliability is especially important for high-speed machines with complex drive trains like those manufactured by Sequa Can. With this kind of equipment, a single loose bolt backing out can trigger a cascade of failures capable of hobbling production for days.
"Companies will spend a ton of money bulletproofing major components, yet neglect the fasteners," Finan says. "It's insane when you think about it because the fasteners hold the components together. If you can loosen the fastener, the physics of your application will. It's Murphy's law."
To safeguard the integrity of its drivetrains and other critical components, Sequa Can uses GrooveLok fasteners from Stage 8 Locking Fasteners Inc. (San Rafael, CA). These fasteners include a retainer that acts like a small wrench locked onto a bolt head, with the retainer, or wrench handle, braced against a stationary object, like a frame, casting or protrusion. This stops any counter rotation of the bolt. The system also works with nuts. In either case, the system includes a grooved nut or bolt and a spring clip to hold the retainer in place.
If there's nothing to brace against to stop the loosening, a special bridge retainer can fit over two or three bolts, locking them in place. A retainer can also be bent over an edge or frame to keep it from moving.
The fasteners do not rely on threads or clamp load to hold them in place, are reusable like other threaded fasteners and can be retrofitted to existing components. According to Stage 8, the fasteners have been used in more than 10 million applications with no reported failures.
Among other specific applications, Sequa Can uses a counter-bore locking fastener arrangement to secure a flywheel weighing several thousand pounds. Stage 8 also manufactures a custom seven-point heptagon retainer for Sequa Can that provides the exact torque needed for a connecting rod assembly. The retainer never has to be adjusted for maintenance.
Stage 8 has used the GrooveLok system with 8-inch fasteners and fasteners as small as eyeglass screws.
According to Finan, an additional benefit of the GrooveLok fasteners is that they are easy to monitor, requiring little more than a quick visual check, as opposed to the use of torque gauges and bolt retightening.
"If you see the clip and retainer locked in place, you know the fasteners retain their full preload," he says. "That speeds inspection and gives peace of mind. Until you remove the clip and retainer, the nut or bolt will not move because they're physically restrained."
For more information on locking fasteners, call 800-843-7836 or visit www.stage8.com.