TurnaSure DTIs achieve and retain specified clamping forces in bolts.
TurnaSure DTIs not only provide critical bolt tensions above the required minimum, they also help ensure those tensions are permanently retained.
A 2014 study conducted at a bolting specialist laboratory using structural bolts implanted with ultrasonically monitored chips recorded measured initial tensions and long-term remaining bolt tensions in two groups of bolts:
- One group using tightened using the calibrated wrench method
- One group using DTIs with feeler gauge verification
All test assemblies on which TurnaSure DTIs were installed provided loads above minimum with no relevant long-term relaxation. Notably, test assemblies also included TurnaSure DTIs which had not been quenched and tempered (through-hardened) to investigate any potential differences between types. No differences in long-term relaxation were found. Some of the bolts tightened by calibrated wrench were under- tensioned in the first place and therefore failed the test for that reason.All TurnaSure DTIs gave loads above minimum with no relevant permanent relaxation. Some of the bolts tightened by calibrated wrench were under tensioned in the first place and therefore failed the test.
Provides Assurance of Slip Resistance
Connections deemed slip critical must not slip
. Engineers have taken into account the slip factor for the joint surfaces in their planning and the bolts have to provide the needed level of clamping forces. DTIs assure these clamping forces are present after bolt installation.
No loosening of bolts due to vibration
The high clamping forces DTIs provide has been shown to reduce the tendency of the assemblies to loosen when subjected to in-service vibration or load reversals.
Better fatigue resistance
DTIs assure a given preload force in the bolts, and when the varying loads under fatigue conditions do not exceed these induced clamp load values, the magnitude of the variation in the load experienced by the bolts is significantly reduced. This guards against fatigue failure in bolts.
Minimizes the affects of prying action
Studies have shown that the presence of a DTI inhibits permanent loss of bolt pretension when the connection is subjected to high prying forces. The DTI introduces a spring or shock absorbing affect.
Improves structural rigidity
DTIs benefit structural rigidity and integrity by ensuring properly clamped connections. Properly tensioned fasteners will absorb energy and dampen a structure against wind or snow loads or seismic loading.
TurnaSure DTIs are the most accurate by far
Each production lot of DTIs provides highly consistent performance. Independent 3rd party testing shows clamp load variation on the order of 1% at one standard deviation. No other DTIs are more accurate.
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