What components are a bolt tensioner made up of?
The complete bolt tensioner is made up of two parts, a load cell and conversion kit.
The conversion kit consists of:
- Nut rotating socket (NRS,NRD) – This fits over the nut and allows you to rotate the nut with a tommy bar
- A bridge – This helps support the load cell over the bolt, and often has grooves cut into it to help with the clearance
- Tommy bar – This simple instrument is used to turn the NRS and threaded insert
- Threaded insert (Puller) - This has a suited thread for the bolt it will be used on, the threaded insert transfers the force that has been created by the cylinder into the bolt
Attaching the NRS to the bridge
The socket can be retained inside the bridge with the help of grub screws.
You can simply hand tighten the grub screws to retain the socket inside the bridge housing.
You must always check that the socket rotates freely inside the bridge body.
Attaching the bridge to the load cell
The bridge can be connected to the load cell, once again using the grub screws already included with the load cell. You can fix the position of the bridge with the load cell by hand tightening the grub screws fully down.
However, to allow the bridge to rotate freely while still attached to the load cell, you can turn back the screws about half a turn to allow this freedom of movement.
Attaching the Threaded Insert
The threaded insert is not really attached to the other components, as it goes through the center of the load cell, and directly attaches itself to the bolt. The threaded insert threads will be suitable for the bolt it’s being used on.
In the case of coated or galvanized bolts, oversized inserts can be requested as a special order from your local Atlas Copco supplier. The tommy bar is of the suitable size to rotate the socket or the threaded insert as and when required.
To sum it up
- The hydraulic bolt tensioner is a combination of a load cell and a conversion kit
- The conversion kit consists of NRS, a bridge, and a threaded insert
- The rotation of the load cell with respect to the bridge can be changed
- One load cell can be used with different conversion kits depending on the size of the bolt and required load
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