Let us try to understand about bolt tensioning before we talk about hydraulic bolt tensioner. In engineering point of view, when we talk about tensioning then we mean it is a direct axial stretching force exerted on the bolt to turn till the nut gets fully secured to the bolt. With this approach we can preload the bolt and before installing the nut, it is stretched.
We can use many different kinds of torque tools in order to either tighten or loosen any fastener. The bolt’s stud can be stretched by only one tool and that is hydraulic bolt tensioner. This stud tensioner gets power by hydraulic oil.
You need to take following 4 steps before you put your hydraulic stud tensioner into action:
- First of all, there is a nut ring that you must put over the hex nut. This ring usually remains on the top flange.
- After setting the nut ring in its place, you have to place hydraulic bolt tensioner over the stud and then nut and then the special nut ring till the bolt tensioner rests on the flange.
- After that insert the stud puller, which will stretch the stud of the bolt
- Now you can manually screw stud puller into the threads of stud. Avoid using any tool as it may tighten too much to cause failure of bolt.
Working of Hydraulic bolt tensioner
As hydraulic pressure is added, the stud gets stretched. Now, the hex nut and the joint flange gets separated and due to that reason, it becomes much easier to run the nut down towards the joint flange’s base. The nut is now run down by using tommy bar which is a bolting tool which is manually turned. Now, turn off the hydraulic power in order to release the pressure. Due to release of pressure, the cylinder will return back to its home position. Now the stud is released and you can unscrew the stud puller.
After disconnecting hydraulic hose, you can lift up the bolt tensioner. Now your nut is snugged against the flange and the load cell pressure is released. Now the clamping force got transferred to bolted joint.
Due to this operation, the stud gets stretched and the load gets locked in and the next nut is ready to be tightened as per the sequence.
Now you have understood what the stud tensioning and the working of hydraulic tensioner is. Also, you know when to choose bolt tensioner in place for pneumatic impact wrench or hydraulic torque wrench.