Know the Difference: Hydraulic Torque Wrenches, Bolt Tensioners and Induction Bolt Heating

1. Know The Difference: Hydraulic Torque Wrenches, Bolt Tensioners And Induction Bolt Heating Many of us in this industry provide different ways to deliver similar results. Is one method right or another one wrong? Of course, it all depends on your application, manufacturer’s specifications and your mileage may vary. In order to understand how it all really fits together, let’s revisit the basics. Nuts & Bolts 101 or Bolt Theory Think of the bolt and nut as just a tag team. They’re simple mechanical devices which work together to provide the clamping force that will hold two parts together, whether those are steel beams, or sections of a large pipeline. Sometimes the bolt also provides support, but the primary role to deliver that clamping force. So what is the clamping force? The spring tension that is created by tightening each bolt is stretching that bolt ever-so-slightly. The bolt is manufactured with a small amount of elasticity, which naturally wants to return to its normal size and length. That spring tension turns into clamping force. When you combine this with the friction properties of the bolt’s threads, that’s what keeps a bolt from loosening. Yes, the is super simplified, but should give you a basic understanding of how nuts and bolts work. The key is for you is to apply this proper clamping force, and do it in a way that will keep it maintained that way. The idea is to create the right amount of spring tension in the bolt when you tighten it, — and luckily for you — both torque wrenches and bolt tensioners will do this. There’s a big difference in how they get the job done. Torque Wrenches It’s the most common way to apply the load to a bolt: rotational force to the bolt head will pull it slightly closer to the nut. A torque wrench provides that high amount of torque for increased clamping force. As the hydraulic fluid pressure increases, so does the torque applied to the bolt. You’ll get accurate and consistent torque values since we know hydraulic fluid won’t compress. That’s why torque has been the go-to means of controlling clamping force and bolt loading.

2. Hence, standard torque tables point us to the proper amount of torque we use for each specific size and grade of bolt. But if you need to spec the proper torque for a given application, a number of factors need to be considered to ensure the torque applied will result in the correct amount of clamping force. How many times has the bolt been used? Are the bolt and nut truly clean? Any lubricant applied to the threads and nut face? Are you using flat washers? What finish is used on the bolts? Do the bolt and nut match in terms of finish and grade?       Bolt Tensioners This approach actually preloads the bolt, stretching it before you install the nut. You’d use this to achieve the most consistent amount of bolt stretch and clamping force. The proper bolt tensioner needs to be selected for each application, which requires gathering important data, such as: Nut size Bolt diameter Washer thickness and diameter Protrusion length of free stud Bolt load requirement Bolt grade As you might guess, the hydraulic pressure applied to the bolt tensioner controls the amount of bolt stretch. When the bolt is pre-stretched by the tensioner, only minimal torque is needed to tighten the nut. As the tensioner is released, the natural elasticity of the bolt provides the proper clamping pressure.       Too tight! Now what? The bolt is stuck. You need a fast solution, because downtime is typically not an option. Induction bolt heating is a fairly new solution to the age-old problem of that nut isn’t going to budge. Options used to be limited to sledge-hammer force, bloody knuckles and perhaps spraying a solvent oil in

3. there to coax the toughest nuts and bolts loose. Big jobs demand the right tools, and this approach is far superior to an open flame or other heat conduction methods. Induction bolt heating is a safe way to apply heat directly into the stubborn bolt and avoid the problems created with heating the surrounding material. This is a unique AC electrical process that directs heat into the bolt through a coil, which expands the material just enough to change the characteristics of the fitting. It should only take a few minutes to heat the problem bolt. As soon as the bolt cools, the material contracts and will allow for quick and easy bolt removal. See how it works for yourself. Final Thoughts Ultimately, your application will drive which method you’ll use between torque wrenches and bolt tensioners. Certain projects may include some of each. Time is one constraint to consider, because you’ll need to gather all of the proper data points to make bolt tensioners work. Invariably you’ll encounter a tough stuck bolt situation, and hopefully you’ll consider the induction bolt heating method to minimize project downtime. Best of luck, and let us know if you might need some nuts & bolts advice. Author Bio :Dan Johnson is a Des Moines, Iowa consultant and writer who's worked with top American-made construction tool and equipment brands in the upper midwest. His hobbies include metal fabrication, videography, officiating high school football and raising a thick-skulled Rottweiler named Teddy. AMG Bolting Solutions,14545 J. Military Trail,#137 Delray Beach, Florida 33484.Contact No: (561) 306-4547,+1 800-709-2930