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Product category: Mechanical fasteners, fixing and joining, and equipment
News Release from: Stage 8 | Subject: Fastener locking system
Edited by the Manufacturingtalk Editorial Team on 16 December 2005

Fastener locking system prevents thread
loosening

For fail-safe joint integrity, US industry is adopting an innovative fastener locking system that can stop joint failure and production downtime by preventing thread loosening from starting.

For fail-safe joint integrity in critical applications, US industry is adopting an innovative fastener locking system that can stop joint failure and production downtime by preventing thread loosening from starting, even in counterbored hole applications "Like David slew Goliath, a single weakness can take down even the biggest, most capable, production machinery," says Joe Finan, vice president of the Advanced Technology Group for Sequa Can Machinery, a leading maker of can manufacturing equipment, based in East Rutherford, New Jersey "The fatal flaw in too many production lines is failing to protect the critical joints with suitable fasteners

Companies will spend a ton of money bulletproofing major components, yet neglect the fasteners.

It is insane when you think about it because the fasteners hold the components together.

Shock, pressure, vibration, temperature change - all combine to loosen fastener threads, which inevitably come loose at the worst possible time, when you can least afford it," continues Finan.

"From the start, you have got to get the critical fasteners right so you are not dealing with the consequences of inadequate joint integrity.

You do not want to bring a multi-million dollar machine to its knees for want of an adequate fastener." Though Finan's advice holds true for most industrial machinery today, itis particularly applicable to high-speed machines with complex drive trains, where a single loose bolt backing out can trigger a cascade of failures.

Since a catastrophe of this sort could hobble production for days, Sequa along with a host of other US manufacturers are leaving nothing to chance.

For critical joints - even counterbored applications - these companies are turning to a unique mechanical fastener locking system designed to prevent thread loosening from the beginning.

This virtually eliminates critical joint failure due to bolt loosening and thus greatly reduces emergency repair, costly production downtime, loss of customer trust, and potential liability.

* Traditional fastening methods fall short - while traditional fastening methods such as prevailing torque, deformed threads, and chemical bonds may be fine for non-critical applications, they are inadequate for production machinery where joint integrity is crucial.

Once a fastener begins to loosen under vibration, jarring, temperature change, or even use of machinery beyond engineered tolerances, joint failure is imminent.

In these situations, relying on maintenance schedules to check and retighten bolts is folly - not only because of the risk of production stoppage and cost of labor, but also due to the difficulty of obtaining equipment access, the risk of over/under-torquing fasteners, and the sheer number of parts to be inspected.

"If you can loosen a fastener at a critical joint, do not use it," says Finan.

"Because if you can loosen the fastener, the physics of your application will.

It is Murphy's Law.

Typical fasteners just aren't robust and do not handle unanticipated events well," explains Finan.

"And, of course, unanticipated events happen with more frequency than we think.

Machinery is run faster and longer than it's designed for, it's overloaded, maintenance is skipped, etc.

Critical joints in production machinery have to be fail-safe in an environment that is never going to be ideal." * A fail-safe fastening system for critical joints - to safeguard the structural integrity of drivetrains and other critical components for Sequa Can Machinery, used in making canning equipment for industries ranging from food and beverage to aerosol and specialty, Finan turned to San Rafael, California-based Stage 8 Locking Fasteners He did this to avoid wasting time, money, or customer trust trying to fix production problems better solved in design.

Stage 8 manufactures the only active mechanical fastener locking system designed to stop joint failure/production downtime by preventing thread loosening from starting.

Essentially, its patented GrooveLok fastener locking system acts like a small wrench locked onto a bolt head, with the wrench handle braced against a stationary object, such as a frame, casting or protrusion.

This stops any counter rotation of the bolt, and thus bolt loosening, until the locking system is removed.

The system works the same way with nuts.

It includes a grooved nut or bolt, an application specific retainer (which serves as the 'wrench socket and handle'), and a spring clip, all which work together.

If there's nothing to brace against to stop loosening, a special bridge retainer can fit over two or three bolts, locking them together, or a retainer can be bent over an edge or frame.

Perhaps the locking system's most appreciated application is with counterbored holes, which normally require tedious torque checking and screw re-tightening with typical fastening methods.

However, once Stage 8's locking system is in place - requiring just a small milled slot adjacent to the counterbore for the retainer to slip into - fasteners never need to be re-tightened.

Thereafter, they can simply be scanned by eye to check for joint integrity, without labor intensive torque gauges or bolt re-tightening.

"If you see the clip and retainer locked in place, you know the fasteners retain their full pre-load," says Finan.

"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.

They literally cannot be defeated, unlike traditional fastening methods.

You won't lose pre-load on any critical joint due to bolt loosening because it's physically impossible for the fasteners to turn.

Loosening never has a chance to get started." Since the GrooveLok fastening system by Stage 8 doesn't rely on fastener threads, clamp load, or anything other than physical restraint to keep nuts and bolts locked in place, no internal or external forces will loosen it until removed.

The system retrofits existing components, is fully reusable, and has been used in items as small as eyeglass screws, to bolts as large as 8" holding generator propellers onto a hydroelectric dam.

To date, the system has no reported failures in over 10,000,000 applications.

"With Six Sigma and other quality measures prevalent today, our engineers need to focus on big issues like defect analysis or designed failure modes," says Finan.

"Not whether commercial bolts will come loose.

Fortunately, the Stage 8 locking system ensures that critical joints stay intact.

This frees our engineers to solve larger problems." For its many canning applications in various industries, Sequa takes advantage of Stage 8's ability to provide application specific locking fasteners in a wide range of sizes, materials, thread pitches, and retainer configurations.

For instance, Sequa used a counter bore locking fastener arrangement to secure a several thousand pound flywheel to canning machinery.

Stage 8 also designed a special 7-point heptagon retainer for Sequa that not only gave them the exact torque needed on connecting rods, but also provided locking on a nut that never has to be adjusted for maintenance.

Sequa highlights its use of Stage 8 Locking Fasteners in sales literature and technical presentations.

"Right up front, we show prospects and customers our attention to detail and quality," says Finan.

"From the smallest component upward, they need to know our machinery will serve them well." If any company has put Stage 8 Locking Fasteners to the test, it's been Grand Island, New York-based Viatran Corp., a leading manufacturer of pressure transducers/transmitters for the oil, auto, and wastewater industries.

In harsh oil field pumping applications where there is 10,000/15,000 lb/in2 pressure, severe shock, and continuous vibration several Viatran level and pressure sensors are protected by encapsulating 'shells' held together by Stage 8 Locking Fasteners.

"The fasteners used to encapsulate and protect the sensors must be back-out proof," says Mike Hallock, Viatran's purchasing manager.

"Every hour of down time costs thousands of dollars in the oil industry." Prior to using Stage 8 Locking Fasteners, Viatran tested typical fasteners such as split washers and chemical bonds, finding that these failed to adequately hold each sensor's encapsulating shell together.

Viatran settled on a lockwire system to encapsulate and protect its sensors in the field.

But this was cumbersome to install, and tended to damage the outside of each sensor on removal for repair.

Consequently, repairs had to be done by Viatran in its manufacturing facilities, adding to overall repair times.

Seizing the chance to improve its product and customer experience, Viatran turned to Stage 8 Locking Fasteners to securely encapsulate its sensors, while speeding repair and maintenance, when necessary.

As part of a 'down-and-dirty' shock test, the transducer was mounted on a fixture with a Weco nut-this was accomplished by fastening the nut on the outside diameter of transducer-and pounded with a 10 lb sledgehammer to simulate the punishment it would receive in field installation.

When customers beta-testing the improved fastening method gave it a thumbs up, Viatran adopted it for its oil field applications.

"Reliability is what we base our reputation on," explains Hallock.

"For the reliability our customers need, we need absolute joint integrity.

That's what Stage 8 provides.

Not a single fastener has failed in the field for 15 years.

That is how we like it." Additionally, since the locking fasteners are easy to install and remove, certified technicians can now do so in the field.

This eliminates the need to return sensors to Viatran's manufacturing facilities for repair, and cuts turnaround repair time by up to a week or more, when necessary.

"If you have got a critical fastening application that is prone to vibration, shock, or other harsh environmental factors, try the Stage 8 locking system," concludes Hallock.

"It is improved our good reputation in the field.

We have had favorable feedback and repeat orders for years and years.".

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