Bolted joints in critical applications need to be regularly inspected and maintained in order to ensure that they function as intended. Loss of preload in bolted connections is a naturally occurring and well-known phenomenon.
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Smart surveillance of bolted joints

An airport may have up to 30,000 runway lights – each secured by up to 12 bolts. These amount to a total of 360,000 bolts, which must be checked several times a year, with the results documented accurately. The cost for having trained personnel doing this works out to millions of Euros or dollars every year. Learn more

Runway Lights

Just in Europe, there are more than a million railway switches spread out over millions of square kilometres. Each switch has several bolts that have to be inspected regularly. This results in huge disruption with 25% of railway delays blamed on switch inspections.
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Railway Switches

An oil platform has about 30,000 – 50,000 bolted joints that have to be checked and documented on time for reclassification. Most of the time, rope access technicians that are flown to the site at a very high cost, perform this task. Read more

Oil Platforms

A wind turbine consists of at least three sections with about 100 bolts for each flange and 3 flanges for the turbine blades with about 100 bolts each – a total of 600 bolts per turbine. Learn more

Wind Turbines

Technology of the future, applied to bolted joints

This is Swedish innovation at its best: advanced technology from StrainLabs and its development partner: the Saab Group.

Bringing it all together: for the first time in the history of bolted joints, the ability to remotely monitor critical bolted connections is a reality – through the combination of advanced LED measurement, remote sensor technology, wireless communication and the Internet of Things.

Strainlabs

Traditional

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JOINT DESIGN

Preconfigured bolts

JOINT DESIGN

Complex procedure to determine torque tightening parameters required in order to achieve design preload. Design variables an inaccuracies are inherent in this process.

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INSTALLATION & TIGHTENING

Simply install bolts and torque until monitor indicates “OK”. Design preload has automatically been achieved and verified.

INSTALLATION & TIGHTENING

Bolts are installed and torque tightened usually using tooling designed to indicate torque, not tension (preload). Installation routine requires repetition to verify torque values have been achieved. However indirect torque values are not as accurate direct preload measurement. Immediate loss of preload associated with joint settlement cannot be identified.

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JOINT LOCATION AND PRELOAD MONITORING

Bolt location and preload data is transmitted automatically to remote user. No equipment shutdown required.

JOINT LOCATION AND PRELOAD MONITORING

Field service evaluation of joints required, both costly and dangerous. Also requiring equipment shutdown.

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INSPECTION

Inspection takes place automatically and proactively, at pre-programmed intervals. Bolt sends a signal when preload level trigger is reached.

INSPECTION

Joint inspection using torque check method is inaccurate and unreliable. Friction conditions in the joint may have changed since first check. As with monitoring, equipment shutdown is required and inspection “at the joint” is costly and dangerous.

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DATA RECORDING

Data is acquired and stored automatically

DATA RECORDING

Field Service evaluation and inspection reports are used to create time consuming reports that are inherently still lacking accuracy.

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JOINT FAILURE

Risk of joint failure is minimized since condition based maintenance programs can now be introduced to bolted joints. Acquired joint data can be used for many types of analysis, including design and maintenance optimization.

JOINT FAILURE

Failures still occur since condition based maintenance is difficult, inspection results are inaccurate and predictive failure signals are not generated or captured.

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