The VLI or Visual Load Indicator is a tension indicator built into the head of a bolt or stud. Reading the dial tells whether or not the bolt has reached its proper fastener load. If the bright yellow tension indicator stripe is hidden on the black face, clamp load remains assured within ±5%. If the yellow tension indicator stripe appears, the fastener needs maintenance. The advantages of VLI are that it gives maintenance personnel a quick visual tension check that can be performed at up to 30 feet away and greater distances with binoculars. VLI also provides indication of tension overload as well as under-load conditions. All fasteners are affected over time in service by temperature changes, joint relaxation, pressure fluctuations, and vibration. Adding this indicator to key wind-turbine fasteners significantly reduces scheduled time for maintenance and fixed costs while improving bolted joint safety and durability. The fasteners are approved by Germanischer Lloyd.
Filed Under: Safety