Fasteners and Sealing
4 Nobody wants a threaded fastener to fail. Paul Stevens reports on some of the latest developments for ensuring that threaded fasteners are tightened correctly and do not lose their tension over time.
4 Personne ne veut qu’une attache à serrer se casse. Paul Stevens rapporte quelques uns des derniers développements pour s’assurer que les attaches sont correctement serrées et ne perdent pas leur tension au fil du temps.
4 Niemand will ein
Schraubverbindungselement, das versagt. Paul Stevens berichtet über einige der neuesten Entwicklungen, mit denen sichergestellt wird, dass Schraubverbindungs- elemente korrekt angezogen werden und im Laufe der Zeit nicht an Spannung verlieren.
Torque management ensures the security of threaded fasteners
W
hile non-threaded fasteners are gaining in popularity for many applications, threaded fasteners are often a better option where close control is required over
the joint characteristics. Consumer products from laptop computers to domestic washing machines feature threaded fasteners, as do high-value goods such as cars. On a larger scale, threaded fasteners are also used in, for example, wind turbine blades and flanged joints for pipelines. Depending on the application, failure of the joint might result in inconvenience for the user, warranty claims or incidents with catastrophic consequences for human life or the environment. To ensure the security of bolted joints, engineers today rely on both equipment that monitors the torque applied to the fastener, and torque-indicating fasteners that can show whether or not the fastener tension remains correct. Assuming that joints have been designed correctly, torque management can help to ensure that joints perform as intended over the lifetime of the application. Torque wrenches apply a torque to a fastener in order to induce a tensile load that clamps the
components together - and keeps them clamped under all anticipated service conditions, which might include temperature fluctuations, vibrations and static loads. Regular calibration to International Standards is vital to ensure torque equipment is operating within defined tolerances. Torqueleader, a manufacturer of torque tools, reports that its United Kingdom Accreditation Service (UKAS) laboratory is capable of recalibrating most hand torque tools, analysers and transducers in accordance with the standards. Furthermore, the UKAS laboratory can calibrate tools from many other manufacturers besides Torqueleader. Crane Electronics (see panel page 43) offers some
of the most advanced measurement technology with its latest product, the IQWrench Opta, which maximises the comfort of the operator. Feedback on the fastening process is important
if the operator is to make each joint correctly. Crane has improved the processing speed of its wrenches to improve the sampling rate, and operators have a choice of visual, audible and physical alarms to indicate the status of the fastening process. Visual indications are provided by multicoloured LEDs on both the front and back
Fig. 1. Rotabolt fasteners feature a Rotacap on the head that locks in position at the correct design tension but spins freely if tension is lost.
www.engineerlive.com 41
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