What is bolt tensioning and bolt torquing?

What is bolt tensioning and bolt torquing?

Bolts are designed to stretch just a small amount, and this elongation is what clamps the joint together. “Torque” is simply a measurement of the twisting force required to spin the nut up along the threads of a bolt, whereas “Tension” is the stretch or elongation of a bolt that provides the clamping force of a joint.

What is tensioning bolt?

What is Bolt Tensioning. Tensioning is the direct axial stretching of the bolt to achieve preload. Inaccuracies created through friction are eliminated. Massive mechanical effort to create torque is replaced with simple hydraulic pressure. A uniform load can be applied by tensioning multiple studs simultaneously.

How do you calculate bolt torquing?

Calculate required bolt torque

1. normal dry: K = 0.2.
2. nonplated black finish: K = 0.3.
3. zinc-plated: K = 0.2.
4. slightly lubricated: K = 0.18.
5. cadmium-plated: K = 0.16.

Why bolt tensioning is required?

The objective of tensioning is to stretch the bolt, or stud, to a predetermined load, by using force to elongate the shank. Very little turning force is required. It is necessary to have some extra thread above the nut, which is used to attach the pulling cylinder, which is removed after completion.

What is a torqued bolt?

Torque is the amount of energy it takes to spin the nut up along the threads of a bolt. So, as the nut is turned (torqued) along the threads beyond this point, the steel gets pinched together between each end of the bolt assembly causing the bolt to stretch: E-L-O-N-G-A-T-I-O-N.

How does bolt tensioning work?

In bolt tensioning, the bolt is preloaded, stretching it before the nut is tightened. The tensioner is clamped to the bolt’s threads and pushes against the flange in the surface being bolted. This provides a very consistent amount of stretch to the bolt, ensuring clamping force.

What happens to a bolt when torquing?

When using a traditional wrench to tighten a bolt, the torque applied to the nut causes it to slide up the inclined plane of the threads. This dimension is the grip length of the bolted joint.

Which is better torquing or hydraulic tensioning for bolts?

Wherever it is used, torquing achieves a high useful bolt load, at about 70 percent of the bolt’s yield strength. The other 30 percent is lost by torsional stresses. This is a higher yield strength than hydraulic tensioning normally achieves but lower than mechanical tensioning.

How is torquing used to tighten car bolts?

Most people have only ever seen a bolt torqued, usually by a mechanic who is working on their car. By turning the nut, the mechanic tightens the bolt or stud. Torquing is, of course, used in many other applications. Wherever it is used, torquing achieves a high useful bolt load, at about 70 percent of the bolt’s yield strength.

What should my bolt scatter be with tensioning?

With tensioning, you’re typically going to see +/- 10% accuracy. That means your bolt scatter will be lower. If the target was 50 KSI, you’d see values between 45-55 KSI. However, there are some important caveats to note here.

Which is the best method for bolt tightening?

It does this by acting on the bolt directly, so there is no springing back or torsional stress as in the other bolt tightening methods. This allows mechanical tensioning to achieve 90 percent bolt yield strength. Mechanical tensioning is best used in applications where a high bolt yield and high accuracy are both top priorities.