Scot hamilton writer9/9/2023 Hydraulic tensioning began in the 1970s, and in the 50+ years since, tensioning has become more common on specific applications, especially high-pressure flanges with large bolt diameters or critical joints across many industries, including oil and gas, wind, subsea, and power generation.īecause tensioning does not place a twisting force on the fastener as applied torque does, we see tensioners used with long threaded fasteners and on rotating equipment such as reciprocating rods.Īnother good use of tensioning is large bolt diameters. To achieve the targeted bolt load, you need to know the area of the tensioner and the amount of force on the fastener, and then adjust the amount of hydraulic pressure. What is Bolt Tensioning?Īs mentioned above, bolt or stud tensioning produces axial load by pulling up on a fastener with what looks like a hydraulic load cell. You also need to take into account friction on bearing surfaces, the bolt diameter, and other variables, which are best examined through experimentation. (And note, K-factor is NOT the same thing as coefficient of friction.) A proper K-factor is critical for understanding what applied torque value you will need. However, the skill levels and training of those who use the torque tools equipment are determinants of how successful and accurate torque tightening will be.Īdditionally, to achieve correct torque-tension relationship, the K-factor is critical. The big advantage to torquing is that is typically more cost-effective than tensioning. Whether the bolt torque is achieved through the use of a manual “clicker” torque wrench, pistol grip torque wrench, or a hydraulic torque wrench, it is the most simple method of achieving axial load. This torque is usually measured in foot-pounds (ft-lbs.) or Newton-meters (Nm). Torquing produces this load through rotational force on a nut or bolt head. Torquing is the most commonly used way to achieve fastener preload with bolted joints. NOTE: For the sake of everyone’s time, we’re not going to talk about tension indicators, hydraulic bolts, or direct tension indicating washers. In this article, we’ll provide definitions of for bolt torquing and bolt tensioning, explain some pro’s and con’s for each, and offer guidelines for the use of each. But really, which is “best” is a loaded question, and depends on… A tensioner sales or service guy would tell you tensioning is the best way to do things. Well, a torque wrench sales guy would tell you torquing is the way to go.
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