FEATURE SPONSOR
MECHANICAL JOINT INTEGRITY CONTROL
Provided that the bolting process is under control, torque provides an acceptable method of bolting control under the majority of circumstances. However, friction under the bolt head and in the threads absorbs the majority of the applied force. Thus, a small change in the friction causes a large change in the applied tension.
Of all the mechanical work that is applied to a joint, surprisingly only 10% is used to stretch the bolt. Everything else, 90% is lost through temperature created by friction. A little more than half of the friction is caused by the underside of the bolt head contacting the first plate of the joint. The remainder is generated by the contact between the mating threads (female and male).
STATE-OF-THE-ART HARDWARE AND SOFTWARE
The USM-3 uses state-of-the- art hardware and software to achieve these measurements with maximum automation and minimises the need for operator interpretation. Offering digital recording and transmission of data, in addition to analogue signal output the USM-3 provides a complete system for measurement, recording and control of fastener tension in the most demanding applications.
The USM-3 can be applied to a bolt to measure in real time while the bolt is actually being tightened using a less accurate method, such as a hydraulic torque wrench. Not only can USM replace existing bolting tools, it can also be used alongside existing bolt tightening tools to supply a second measurement (normally referred to as a redundancy measurement). This serves to provide users, managers or designers with lots of useful information to improve their processes.
By way of contrast, methods that directly measure tension, such as strain gauging, or that measure the extension in the bolt and calculate the tension from a known material constant, bypass the effect of friction the biggest variable in the bolted assembly.
ENORMOUS POTENTIAL The potential for ultrasonic measurement to reduce maintenance times for wind turbines is enormous. In the same way that ultrasonic measurement has been used in other safety critical applications such as aerospace, equipment like the Norbar USM-3 can provide a very precise method of determining the elongation and tension in the fastener due to tightening which could cut maintenance costs and time.
Norbar Click to view more info
www.windenergynetwork.co.uk
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