Essential Bolting Tools

October 30 2020

Introduction

The necessity of using right bolting tool for right fit is very essential to prevent the bolted joints from loosening, from leakages and thus prevents from major hazardous accidents.

Let us first understand some of the key bolting concepts before identifying the essential bolting tools for bolt tightening.

1. What is Bolted Joint?

Bolted joint, is one of the oldest and most common type of joint in many industries like construction, machinery equipment and piping industry. The joint consists of fasteners that holds two or more parts securely. Bolted joints come under the category of temporary joints which means the joint is not permanent. Few industries prefer bolted joints over permanent joints with a benefit of mainly easy serviceability and weight requirements.

2. Why Joints fails?

For bolted joints, appropriate bolt tightening techniques and right bolting tools are crucial for the safe operation of many types of equipment. However, if not taken enough care for selecting the method required for assembly and appropriate tool while assembly, it may lead to failure of joint.

Failure of Bolts and Bolted Joints

The bolt preload being insufficient to resist the forces acting
Failure of the bolts due to Fatigue
The bolt being directly overloaded by the force acting
Excessive bearing stress within the joint itself

Joint efficiency is mainly depending on its bolt clamping or tightening force, which is generated by applying the torque on the bolt. It is a known fact that addition of a gasket in a joint is to prevent the leakage but it may work effectively as long as there is a sufficient clamp force generated by the bolts.

3. Necessity of Bolt tensioning

Bolt preload or Bolt tensioning refers to the stretching or elongation of a bolt that is needed to clamp two or more parts together. For a bolt to hold two components together securely, a certain amount of preload tension is required.

4. The Importance of Torque Control

It might appear that more torque may always be a better choice when it comes to tensioning a bolt, but it is not the case, as too little torque will not provide enough clamping force and too much torque causes the bolt to break.

Using the right bolting services and the right bolt tightening techniques are key for applying the right amount of torque on a given task.

5. Determine the preload Torque

Several factors affect the required preload torque calculations of a bolt. To calculate the amount of preload required, it is important to know that the material of a bolt and its grade, the amount of load it can withstand, the loss of torque due to friction and other aspects of the load.

In General, Preload is specified as a percentage of the bolt tensile yield strength. It can be calculated using either a mathematical equation or an online bolt torque calculator. The joint may fail, if it doesn’t meet the preloading conditions.

In simple words, to determine how much torque is needed for achieving an efficient bolt joint, it mainly depends on the Material and its properties of the bolt with which it is made up of and the application of the joint.

6. Tools required for bolt joints

The Bolting tools required for bolt tightening can be classified by their bolting techniques. The popular bolt tensioners and torqueing tools are as follows.

Tensioning tools:

Bolt tensioners – Hydraulic bolt tensioners are suitable for all bolting applications. It can be operated with single stage or multi stage.

Hydraulic nuts - the technology of Hydraulics replaces the conventional hexagonal nuts to provide accurate and uniform bolt loading. Using array of hydraulic nuts on a bolted joint gives a better uniform bolt load across all bolts, which greatly improves the efficiency of the joint. This type is suitable for tightening large diameter bolts without damage that may occurs when conventional wrenches are used to loosen the fastener.

Torque tools:

Torque Wrenches – These torques wrenches are operated either manual or powered. Powered wrenches operate with the help of either Hydraulically, pneumatically or electrically operated.

Nut Runners - Nut runners are the tools used for tightening of the nuts by pneumatically, electrically, or with the help of hydraulic power. Pneumatic nut runners are operated by compressed air. Whereas, Hydraulic nut runners are powered by hydraulic fluid and operates with either single stage or double stage cylinders.

7. Torque Tightening vs Bolt Tensioning

To identify, which method of tightening is suitable, it is important to know its application. Below is Key difference of torqueing and tensioning methods.

While tightening large bolts use of Hydraulic or Mechanical tensioning is preferable over torque tightening

Content Source :- ABS Group

Image Source :- HYTORC Twitter