Infastech Engineered Fastening has come up with a simple but sophisticated solution to equipment maintenance.
Not only is conveyor maintenance expensive, but it can also be a safety concern, as it often requires maintenance staff to work at height using scaffolding and fall arrest equipment.
Aside from the obvious distress caused when a company is faced with a safety incident, these incidents are also another financial cost.
Equipment like that used in mining operations has a wide range of moving parts, and is subject to vibration and unpredictable, rugged conditions. This makes it especially vulnerable to fatigue failure. Traditional solutions include the use of adhesives, locknuts, lock wires, and lock washers to prevent thread loosening, but these methods aren’t always reliable.
“For example, the application of adhesives can be inconsistent and ineffective in high or low temperatures,” said Glenn Heffernan, general manager of Infastech Engineered Fastening. “Adhesives are also single use and require cleaning off and reapplication, which adds to the cost of maintenance.”
Furthermore, in constantly moving equipment such as conveyors, the last few threads of typical locknuts tend to wear down and deform, making locknuts another single-use product that cannot safely be used again.
Vibration and other stressors can also deform the entire locknut, requiring maintenance crews to cut them from the bolt, meaning both the locknut and the bolt need to be replaced.
To provide a solution to this problem, Infastech Engineered Fastening has produced a new fastening nut, called Spiralock, with extreme resistance against wear and tear.
“Most nuts will come loose over time if they are being used in high vibration environments,” Mr Heffernan said. “In the mining industry there are some conveyor belts that are a kilometre long that depend on crews ensuring nothing has come loose. With Spiralock, this isn’t a problem.”
The solution has transformed the standard internal thread profile into a self-locking female thread form with the addition of a unique 30-degree wedge ramp at the root of the thread. This wedge ramp allows male fasteners to spin freely relative to the female threads until clamp load is applied. At that point, the crest of the standard male threads is drawn tightly against the wedge ramp, creating a continuous spiral line of contact along the entire length of the thread engagement. And as clamp load increases, the wedge ramp pushes against the male thread from all sides, eliminating the radial clearance that allows fasteners to begin self-loosening under vibration.
Mr. Heffernan says Spiralock fills a gap in the market for industries that need the dependability of a nut that won’t come loose.
What makes Spiralock a more stable solution?
Load distribution Research by Massachusetts Institute of Technology, Lawrence National Laboratory and others has confirmed that joints using Spiralock threads carry load much more uniformly than joints with standard 60-degree threads.
The research showed that the percentage of load on the first engaged thread produced with a Spiralock tap is significantly lower – 24 per cent versus 64 per cent – with five threads of
engagement.
Because the uniform thread loading provided by Spiralock reduces load concentration at the first
engaged thread, joint reliability is improved by minimising the likelihood of thread stripping.
The Spiralock thread form also generates higher radial thread loading compared to standard threads, taking advantage of the material hoop strength and lowering the chance of shear failure.
Testing performed on 1/4”-28 Spiralock fasteners in conjunction with NAS624-32 bolts has also shown that Spiralock can enhance fatigue life 300 per cent over standard fasteners. This is because the even load distribution with Spiralock consistently reduces the stress concentration that leads to fatigue failure.