SPC4TM load indicating fastener technology allows installation of a bolted assembly with confidence. Users can monitor the clamp load of any SPC4TM bolted joint whether static or dynamic, by attaching an indicator datum disc located on the end of the fastener and reading the value with a user friendly mechanical indicator.
A fastener is modified by machining a small hole into the head. Minimal modifications to the bolt assures basic bolt design integrity. A gauge pin is inserted into the hole and secured at the bottom. A datum disk is fitted on the top of the bolt head and forms a flat surface with the top of the gauge pin when the bolt is unloaded. When the bolt is tightened, it elongates and the gauge pin is drawn into the bolt away from the datum disk surface. This indicator is calibrated to detect the differential space between the indicating pin and datum head. The differential space is translated into a gauge reading that precisely indicates the fastener’s loading, related to ultimate yield strength.
The benefits of this concept allow the fastener to be loaded many times as long as the stress remains in the elastic range, meeting the criteria of ASTM F2482. An accurate assessment of loading can also be obtained after the joint has been put into service.
These videos illustrate an SPC4 installation on a chemical facility reactor. In this case, the flanges are titanium and extremely sensitive to elevated load which has the potential to plastically yield the flanges. The flanges must be held to a target of 11% fastener stress. By utilizing and monitoring the elongation of the fasteners, the operators can easily achieve the desired load without the inconsistencies associated with torque and friction. For the first time in the history of this unit, it is operating at maximum efficiency and producing more product that ever anticipated due to accurate preload and subsequent monitoring with SPC4.
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