68 wwwenerpaccom Tensioning Tensioning requires longer bolts 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 Tensioning requires longer bolts and a seating area on the assembly around the nut Tensioning can be done using detachable Bolt Tensioners or Hydraulic Nuts What is Load Loss Load loss is a loss of bolt elongation depending on factors such as thread deflections radial expansion of the nut and embedding of the nut into the contact area of the joint Load loss is accounted for in calculation and is added to the preload value to determine the initial Applied Load The preload depends on Applied Load and Load Loss load loss factor INCORREC T CORREC T L Minimum 1 X D Preload residual load Applied Load minus Load Losses GLOSSARY OF TERMS Applied Load The load applied to a bolt during tensioning which includes an allowance for Load Loss Bolt Tensioning A method of controlled tightening which applies preload to a bolt by stretching it axially Breakout Torque The amount of torque required to loosen a tightened bolt Usually more torque is required to loosen a bolt than was used to tighten it Elastic Range The range on a bolts stress strain curve where stress is directionally proportional to strain Load Loss The losses in a bolt which occur on transfer of load from a tensioning device to the bolt assembly these may arise from phenomena such as thread deflection and embedding of the nut to the contact area of the joint and is calculated as a factor of the length to diameter ratio of the bolt Load Scatter The spread of differing loads in a sequence of bolts after they have been loaded It is mostly due to the elastic interaction of the bolts and the joint member as subsequently tightened bolts further compress the joint previously tightened bolts are subject to some relaxation Plastic Range The range on a stressstrain curve where the tensile load applied to a bolt results in permanent deformation Preload The load in a bolt immediately after it has been tightened Proof Load Proof load is often used interchangeably with Yield Strength but is usually measured at 02 plastic strain Tensile Point The point at which the tensile loading on a bolt causes the bolt to rupture Torque Tightening The application of Preload to a bolt by turning of the bolts nut Ultimate Strength The maximum tension which can be created by tensile load on a bolt Yield Strength The point at which a bolt begins to plastically deform under tensile loading NOTE Bolt is used as a generic term for a threaded fastener