The art of tightening nuts on bolts with a spanner is long gone when it comes to large-scale engineering and mining projects. Today’s methods require less effort and are more accurate than ever.
Hydraulic bolt tensioners have turned nut tightening into as close to an exact science as possible, a bolt can be secured to its optimum tension, the weight an application can support can be calculated and a bolt stretched to support more weight.
These powerful tools not only save people the time of performing the task but are faster at doing it and vastly more accurate.
This was born of necessity as recently there has been more focus on accurate records to critically analyse a project’s safety.
Tension product manufacturer Technofast Business Development Manager Joe Kelly said the big advantage in advances in tension technology was improved accuracy.
“Engineers are now saying they can reduce the size of the bolts, because they know the accuracy of the load”, he said.
“With a hydraulic nut, you can get 3-5% accuracy, whereas with a good operator on a hydraulic torque wrench, you‘re taking plus or minus 35%.”
As bolting joints become more advanced and pressures are increased in things autoclaves, where temperatures are raised, instead of the frictional losses you get in traditional torque methods, you eliminate all that by tensioning in a straight line.
“Imaging turning a three-or four-inch bolt. There are huge frictional forces involved in play. But you can eliminate that by just pulling the bolt straight line”.
Tension devices are often used in crushers and draglines in the coal industry with hold-down bolts on the electric motors, the swing and drag and hoist motors.
However, wherever there is critical bolting there is an application for a tension device.
Kelly explained that torsional loads on bolts had to be managed correctly to prevent failures of things such as gaskets.
“If you are familiar with trying to undo a rusty bolt, it gives or bounces back on you. That’s the torsional loads being released and as that torsional load releases over time, the clamping load on the gasket is diminished. Therefore you get failures”, he said.
“(One company) got so frustrated with fact that every time it had a gasket failure or a leaking joint, it was always the gasket that was at fault.”
“By initially doing them up correctly, with the correct design load, he eliminated a lot of his problems with gasket failures.”
“(Tensioners) are small, light, easy to use and require very little training, once the calculations are done to know what pressure to exert.”
“They are very easy to access if you haven’t got a large space. You only need to access to turn them off, let the nut do the job and whole thing’s finished. Fast, simple and accurate, that’s the war cry”.
“There are two types of tension devices – hydraulic nuts and high bolt tensioners. The hydraulic nut stays in position and is basically part of the machine, while high bolt tensioners are basically a service tool”, Kelly said.
“The restriction with high bolt tensioners previously has been you need a protrusion rod through the nut, by which to grip the bolt stretch it.” “Because that’s been an issue, company chairman and founder, John Bucknell has recently invented what we call a CamNut, where you grab the nut rather than the bolt and you stretch the nut”.
Technofast is the manufacturer of high pressure tension products and Technofast considers itself an innovator when it comes to engineering solutions to tension problems.
Its products are exported to the US, the UK, India and Chine, and Kelly said the company is now focusing more on growing the brand within Australia.
Technofast came to life after Bucknell was approached to solve a problem that hampered efficiency in the nuclear industry.
Fixed hydraulic nuts worked well in regular conditions but were ineffective in a high temperature environment, such as in a nuclear reactor.
Bucknell invented the Hi Temp HydraNut, a nut with steel seals that maintained hydraulic pressure under high temperature, which cut down time taken to complete bolting procedures and reduced workers’ exposure to dangerous radiation.