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ENSURE YOUR DESIGN SPECIFICATIONS ARE IMPLEMENTED ON SITE

Specifying Hilti’s HST3 expansion anchors along with our intelligent, cordless impact wrench means installed as per design

Over-torqued and under-torqued anchors are among the most common causes of failed jobsite inspections

Torque: hard to see; easy to neglect. Applying the right torque is critically important to achieve the performance of a torque-controlled expansion anchor.  Put bluntly, if an anchor is not set with the manufacturer’s recommended torque, it is only a matter of time before defects creep in. In fact, the American Construction Inspector Association (ACIA) ranks over-and under-torqued anchors as the number-two reason for failed jobsite inspections.

There are many reasons why anchors are not installed as per the manufacturer’s recommendations on job sites. Foremost among them is speed: with scheduling pressure constantly increasing, finding the time to carefully torque and check every single anchor is practically impossible. Furthermore, experienced jobsite professionals with the necessary specialized training are not always on hand.

What are consequences of incorrect torquing?

What are consequences of incorrect torquing?

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    Implications of over-torqueing an anchor near the concrete edge

    A correctly torqued anchor vs. an anchor which has been over-torqued near to the concrete edge. Near the edge over-torqueing may result in concrete splitting.

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    Implications of over-torqueing an anchor away from the concrete edge

    An anchor over-torqued away from the concrete edge may result in the cone being pulled too far into expansion sleeve

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    Implications of under-torqueing an anchor

    An under-torqued anchor results in the cone being in the incorrect position i.e. it is not drawn far enough into the expansion sleeve, to achieve the required loads.

Implications of over-torqueing an anchor near the concrete edge

Over-torqueing results in the cone being pulled too far into expansion sleeve. This generates high forces during setting which may be powerful enough to cause spalling at the concrete edge (when concrete splits or breaks away in chips), reducing the load carrying capacity of the base material. 

If the damage to the concrete is visible, then remedial works can be carried out. However remedial works can be very labor-intensive, as fixing points may need adjusted and the position of the steel fixture changed accordingly. Worse yet, is when the damage to the concrete is not visible i.e. hidden under a steel plate and therefore the flaws remains undetected and unrepaired. 

Now with the HST3 anchor installed with the AT system, you can significantly reduce the risk of structural defects caused by improper torque.

Implications of over-torqueing an anchor away from the concrete edge

Over-torqueing an anchor always results in the cone being pulled too far into expansion sleeve, generating high splitting forces. However, when the anchor is located far from the concrete edge, the splitting forces can be absorbed by the surrounding concrete without any damage to the concrete.

However, if the anchor is significantly over-torqued, then the steel bolt can be damaged by high torsional moments. The result is a clear drop in the steel capacity under tension, shear, or combined tension and shear forces. As with spalling, the biggest problem with anchor damage is that it can go undetected. Applying torque to gauge the condition of the anchor could worsen any existing damage. 

The adaptive torque system from Hilti is protects compatible anchors from unseen damage.

Implications of under-torqueing an anchor

An under-torqued anchor can be just as problematic as an over-torqued one. Under-torqueing results in the cone being in the incorrect position i.e. it is not drawn far enough into the expansion sleeve to achieve the required load capacity 

This means that the cone will only be pulled into the correct position when the external load is applied. The maximum load or resistance values may only be achieved once the anchor has been pulled slightly from the intended position. The result is an installation with unforeseen displacement, as illustrated. 

Loose anchors are extremely easy to avoid when using an AT-ready impact wrench.

The AT system is made up of four components:

  • Hilti HST3 expansion anchors (in M8, M10 and M12 diameters)
  • SIW 6AT-A22 cordless impact wrench with intelligent 
  • SI-AT-A22 data processing module which slides in between the impact wrench and its battery. This number-cruncher processes data from sensors within the impact wrench to confirm that the nut is being hit with the right torque for the right amount of time. 
  • Documentation software so that a record of the  HST3 installation can be transferred from the SI-AT-A22 processor module to a computer. This raw data is used as proof of the installation method



Hilti AT-ready tools are equipped with the on-board intelligence to confirm if an anchor has been torqued to as per the instructions for use.

WHAT ARE THE BENEFITS OF THE ADAPTIVE TORQUE SYSTEM

Design and Specification

The AT System gives you assurance that the anchor has been set to the manufacturer's recommendation.

No need to 'design in' additional safety factors to compensate for anchors which are underperforming due to incorrect torque.

Installation and Torqueing

Reduce the amount of unplanned design work during the construction phase due to incorrect installations.

The AT system workflow meets the need for a high-productivity solution.

Site Inspection

The report generated by the AT System proves the method of installation by the installer. 

Results in a reduction of risk due to incorrectly torqued anchors and fewer opportunities for structural defects to emerge over time.

The right solution, Hilti's Adaptive Torque System

The right solution, Hilti's Adaptive Torque System

The anchor setting trifecta: SafeSet

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Safety. Productivity. Approval. SafeSet is Hilti’s proven methodology for consistently high-quality anchor installation at lightning speed.

The SIW 6AT-A22, along with the SI-AT-A22 module, fulfills all SafeSet criteria because they save time and reduce costs while also removing scope for installation error.
 

Discover how Profis anchor design software can help you

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Find out how to design and install anchor systems

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Design your own cordless system with Make It Fit

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