Proper Alignment through Proper Torque and Tension Methods TorcUP
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Proper alignment of any bolted joint can be achieved by the use of either torque or tension methods of bolting. While both methods of securing the joint produce the same end result, the debate continues about which method delivers the most accurate and consistent bolt load value. If the proper bolt loads are not achieved during installation, the integrity of the joint will be compromised leading to misalignment and, if not checked, ultimate failure of the joint. These two methods of bolting are used in wind turbine installation and maintenance, through the use of hydraulic torque wrenches and hydraulic bolt tensioners. The method used is typically determined by the turbine manufacturer and can include the use of one or both of these techniques.
To begin, look at the function of a bolt. The purpose is to hold or clamp two surfaces together. In order for the bolt to successfully achieve this function it has to be installed properly which means applying the correct torque or tension to the bolt. The bolt can be thought of as a spring as it is stretched by either turning a nut through the use of torque or by stretching the bolt through the use of tension. If the bolt is not stretched enough the joint will be loose and ultimately fail. If the bolt is stretched too much the bolt will be weakened and can ultimately fail. The correct amount of torque or tension applied will result in the bolt being stretched to a point where it will try to retract to its original shape and keep the proper tension on the joint. Hydraulic torque wrenches have been commonly used in the wind industry for many years in applications where torque requirements exceed the limits or safe use of manual torque tools. The basic principal of a hydraulic torque wrench is that the torque output is determined by the amount of hydraulic pressure that is applied to the tool. The unit of measure for torque is usually expressed in ft/lbs or Nm. The higher the pressure applied, the higher the torque output of the wrench. Most hydraulic wrenches operate at pressures up to 10,000 psi. These wrenches come in two basic designs and multiple sizes. The square drive design employs the use of a socket attached to the wrench and the low profile design is used ........
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20 January 2012
