Innovative visual tension indicator bolts will help theme park rides stay safe for users, while making maintenance easier.
Amusement park and theme park rides must be designed and built for safety first, then thrills. Because of this, the industry is always looking for new ways to assure that the rides are built and maintained properly.
Often bolted joints require a torque wrench for precise tightening and the optimum clamp load. Yet tests have shown that a given torque can produce tensions or clamp forces varying by as much as 5-1 depending on bolt plating, lubrication, thread condition, nut and washer material, and other factors, according to a US Air Force study. A Direct Tension Indicator (DTI) can remove this uncertainty, since it responds only to bolt tension and not to torque.
DTI SmartBolts® were invented by Stress Indicators, Inc of Bethesda, MD to set up the proper bolt tension with no need for torque wrenches, strain gages, wires, electronic or ultrasonic equipment. As for maintenance after installation, there is no need to touch or contact the fastener at all in order to verify its clamp load condition. Yet, the DTI SmartBolt is great for many applications; its color-change scheme is such that it is not designed to show an over-tension condition. The new HR (High Resolution) SmartBolt was developed to transcend this limitation.
The HR SmartBolt is armed with a microindicator element that allows quick-look inspection -- Green is Go! The indicator, located in the center of the bolt head, remains yellow as the fastener elongates while being initially tightened. When about 85% of the design tension has been achieved, the indicator rapidly turns to a bright green at 100%. When tightened beyond design specifications, the indicator darkens until it is nearly black. More importantly, should the bolt loosen more than 10-15%, the indicator returns to bright yellow, warning observers of a problem.
The color-coded system is ideal for critical inspections. Once the bolt is installed, the proper tension may be verified without contact or loosening of fasteners. It also means that loosened fasteners in critical situations may be easily identified and corrected, thereby averting catastrophic incidents.
The HR SmartBolt is an upgrade of the DTI SmartBolt. Besides being more accurate, it is easier to read. However, the original DTI SmartBolts are still appropriate for less demanding applications, such as the fasteners used to join modular electrical conductors, control cabinets, and other less critical equipment...Learn more.
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