(Power PR circulated the following story by Ed Sullivan on February 17.)
Locomotive, rail and maintenance of way – all reap major benefits from advanced joint fasteners that always stay put, improving safety while slashing maintenance and inspection costs
Despite countless technological advances in other areas, industry continues to be plagued by problems that may seem mundane, yet are often devastating – joint fastener failures. In transportation, such headaches have occurred frequently throughout railroad systems, where fastener failures due to intense stresses have inflicted costly damage and disruption on locomotives, track and maintenance of way equipment.
“On the railroad, most fasteners are very prone to loosening and backing out because they are in one of the worst possible environments . . .
holding joints that are constantly being mechanically agitated and thermally cycled,” says Larry Biess, Director, CSX Transportation Advanced Engineering. “That includes locomotives, cars, track and maintenance equipment.”
“What causes mechanical fasteners to loosen and shear is usually some external force, such as vibration, torsion, shock or thermal cycles,”
explains Bruce Bennett, President of STAGE 8 Locking Fasteners, San Rafael, CA. “In the past, design engineers were forced to use bolts with insufficient stretch due to tight fit or other configuration problems.
Once joint integrity is lost, even the most advanced and durable equipment is likely to fail.”
Critical hot box application
That point is dramatized by several railroad applications. For example, on railroad tracks thermal detectors are mounted via fasteners either adjacent to or flush to the sides of rails at intervals of 18-22 miles.
These detectors contain transducers that measure the heat in rail car bearings and wheels, and then signals the train crew whenever a “hot box” rolls by.
“These detectors perform a critical function,” Biess explains. “We call them end-of-life devices. There are 950-1000 of them on our 22,000-mile rail network. The three to four optical transducers located in each are aimed so that they can ‘see’ excessive heat in wheels and bearings. The devices also let the train’s crew know when wheel or bearing conditions are such that if they proceed any farther there could be an equipment failure and possibly a train accident.”
These hot box detectors are subjected to the extreme vibration of passing trains as well as severe thermal cycles from weather. And when standard or even nylok-type fasteners are used to mount them, those fasteners eventually work loose and lose their aim. “If you lose your aim, the detector is not really doing its job – it’s not a sentinel,”
says Biess. “So there is always that opportunity that if a detector is not functioning properly that we might miss a critical problem on a critical car.”
Heavy vibrations up front
The extensive joint fastener maintenance required by heavy vibrations and thermal cycles is time-consuming and potentially expensive. When maintenance-intensive fastener applications are overlooked, the consequences can be even more costly.
For example, the exhaust manifolds on CSX locomotives are attached to heavyweight GE or ElectroMotive Diesel engines. Those mighty power plants plus the locomotives themselves are continually vibrating and causing the manifold fasteners to loosen and back out of their mounts.
“In effect, the exhaust manifold is a big pipe assembly that is located above the engine, which is vibrating mechanically and going through many heating and cooling cycles,” says Biess. “And so you really can’t use standard locking fasteners. They have to be re-torqued constantly.”
If the proper torque is not maintained on exhaust manifold bolts, the manifold will leak exhaust gases, a Federal Railroad Administration defect that will take a $2 million locomotive out of service – just for want of an effective locking fastener.
Rugged maintenance operations
Efficient maintenance of way is critical to railroad operations, and must be performed within limited timeframes. At CSX a very rigorous part of this is railroad tie removal and replacement, which is done using a TR-10 Tie Exchanger.
“The working head of this equipment extends out on a boom and is held on by four bolts,” Biess says. “In the past, these bolts would loosen frequently. So, the required daily maintenance for the TR-10s was to torque the four bolts before taking the rig out. But the proper torque held only for maybe the first 50 ties, then loosened up. So that situation required continual re-torquing. Otherwise, once the bolts loosened on the TR-10 head, which is moving ties that weighs 300-400 lbs., the head starts to work against the bolts, and eventually they shear. When that happens, you’re out of service until the heads are repaired, or in some cases rebuilt, a very costly predicament.”
The fail-safe fastener
To eliminate problems such as these, STAGE 8 developed the only active mechanical locking fastener. Available in several models, it is designed to stop joint failure and production downtime by preventing thread loosening from even starting.
STAGE 8’S patented GrooveLokTM fastener locking system acts like a small wrench locked onto a bolt head. This locking retainer is braced against a nearby abutment (e.g., frame, casting or protrusion), thereby locking a bolt or nut in place.
If there’s no abutment to brace against to stop loosening, a bridge type or strap retainer can fit over two or three bolts, locking them together, or a retainer can be bent over an edge or frame. For counter-bored applications, the locking fastener system incorporates a secondary counter-bore, a milled slot adjacent to the main counter-bore, into which a locking retainer (i.e. “wrench handle”) is fixed. Once installed, fasteners never need to be re-tightened because loosening never has a chance to start.
Maintaining detector aim
With the transducer-mounted thermal detectors, CSX always required that an inspector visually check the performance of a detector. “However, when our maintenance people began installing the STAGE 8 strap fastener on these detectors, they were able to set their aim, tighten them down – and then forget about them,” Biess explains. “These fasteners give us a very high level of confidence that we’re ending up with a more reliable system of detectors.”
Leveraging detector functionality
Biess adds that the reliability of the locking fasteners will enhance CSX’s future hot box detection program. “In 2006 we are going to begin collecting that data and running it against a computer program that is designed to let us see what the brake and wheel temperatures are on the trains,” he says. “So, we’re going to be using this data for much more than just stopping the trains. We will be learning whether particular cars are having a problem, whether a hand brake has been left applied instead of released . . . things of that nature. And for that reason the data quality is going to be extremely important from every one of the detectors. So, while the STAGE 8 fastener was important to us before, it will be even more useful to us in the future.”
A positive manifold lock
In solving the loosening of the locomotive exhaust manifolds, Biess says the locking fastener has been particularly helpful. “We’ve been using the STAGE 8 locking fastener on exhaust manifolds for several years now, and have never had a failure,” he says. “Once installed, there is just no way for those fasteners to loosen. It’s a positive lock – fail-safe.”
“They create a tangible cost savings just on the periodic re-torquing, and monitoring and scheduled maintenance we used to have to perform just to make certain that these things were all buttoned down,” he says.
“We’ve alleviated all of that. So, I believe it’s safe to say that, after we apply these things, our maintenance personnel are able to concentrate on other matters, because no way were the manifold bolts loosening up.”
Keeping the heads on the TR-10s
To solve the head bolt loosening and shearing problems with CSX’s TR-10 Tie Exchangers, the company developed a special locking fastener design with STAGE 8. “We came up with a program where we modified the working heads themselves,” says Biess. A small slot was milled into the counterbored holes and the Stage 8 bolts were torqued to specs. Then a locking retainer was slipped the over the bolt head. A snap ring was then fitted into the groove on the bolt head to keep the retainer in place. “After we began doing that we found out that we didn’t have loosening on any bolts,” Biess continues. “These locking fasteners resolved a couple of hours of downtime at fairly frequent intervals; and with a production tie exchanger, you have limited time that you are allowed to use it on the track – every hour counts.”
Versatile, secure and cost saving
The STAGE 8 system retrofits existing components, is fully reusable, and has been used in items as small as eyeglass screws and as large as needed for holding generator propellers in a hydroelectric dam. To date, the system has no reported failures in over 10,000,000 installations, ranging from industrial, mining, construction, manufacturing, automotive, and miles-deep oilfield drilling assemblies.
When it comes to fasteners and many other “commodity” items that may be engineered into a product, cost is always a consideration – or should be. Yet, savvy engineers also evaluate cost-performance benefits of components that can make their products better, safer and less expensive to operate. Even though slightly more expensive, the use of specialized fasteners could result in major savings through prevention of premature failures and related service cost. In addition, considering an active mechanical design, like GrooveLok, could eliminate the cost associated with fastener inspection.
For more info on STAGE 8’S patented and trademarked GrooveLokTM technology and products, visit www.stage8.com; email info@stage8.com; call (800) 843-7836; fax (415) 485-0552; or write to Stage 8 Locking Fasteners, Inc. at 64 Louise St., San Rafael, CA 94901. Stage 8 is celebrating 20 years of zero failures.