Hi Hilti. I am designing a pair of M20 anchors: 250mm embedment, HAS-U, HDG, HIT-HY 200.
I am wondering what the installation torque should be? From the HIT-HY 200 tech datasheet page 9 it appears that maximum allowable install torque is 150Nm. Is this correct? I presume not - It seems strange to me that there is just a blanket value for max installation torque without taking into account anchor spacing, embedment, galvanised vs plain material etc.
P.S for my application I believe that a "snug tight" torque of around 70Nm will be more than sufficient. Is there any negative effect of installing anchors at lower torque values?
Hello Henry,
Thank you for your question,
With regards to installation torque for chemical anchors like the HY200, there is no specific requirement as the working principle of "bonding" is not dependent any torque. Once the chemical anchor is installed correctly and cured (correct method of drilling, preparing the hole - including cleaning and correct injection), the anchor is ready to perform as designed.
The torque value given is just a maximum torque which should not be exceeded to avoid damaging the chemical bond to the steel threaded rod or the concrete as well as the potential for concrete splitting failure when installing/using the anchor within minimum spacing/edge distances. If you need to install to higher torque than the 150Nm, we would suggest increasing the minimum allowable spacing/edge and base material thickness in relation to the embedment depth. However, in your case, if you are happy with the 70Nm, that is also fine. No negative effects applying lower than the maximum torque for chemical anchors.
Just for additional information, if it was in the case of mechanical anchors, the torque value given is often a required specific "installation torque" rather than a maximum torque value. For mechanical anchors, it is important that the torque is applied at these exact values to ensure the anchoring mechanism is correctly "activated" or installed.
Hope that helps,
kind regards
Ask Hilti Team
Australia