The persistent bolting problem in wind turbines and most other construction is that it requires so many different tools. That means erecting a wind turbine and its tower might make use of hydraulic, electric, manual, and sometimes pneumatic tools. To make matters worse, the pumps and tools are heavy and their hoses can pose a safety hazard. Then there is the noise from working in a steel drum. Try warning someone of a safety hazard when workers above and below are making a racket. That is the opinion of Dominic Ortolani, Application Engineer with Norbar, a manufacturer of precision, high torque bolting equipment.
There is good news, he says. Most manufacturers are constantly asking for feedback from the field on how to make their tools better. “Then we take the ideas to our engineers, asking how can we make it more compact, for example, yet still maintain accuracy and high torque,” says Ortolani. While electric torque multipliers are not new, demand for them has increased recently thanks to improvements in accuracy, reliability, and capability. In seven ways, he says, electric bolting tools are solving construction problems.
1. Relatively compact. “We are finding that one recent electric-torque multiplier can fit into areas that other previous customer tools could not. And they’re finding more uses for multipliers where they were using hydraulics before,” says Ortolani.
2. Accuracy. Ortolani says accuracy refers to the precision with which the tool delivers torque. “For example, the EvoTorque 2 electric-torque multiplier delivers torque to within 3% of its setting. We calibrate the tools to 3%. Accredited calibration labs use traceable equipment, so you can see when the tool was calibrated and the equipment it was calibrated on. This ensures the maintenance of accuracy. Also, there are real cost savings involved when you can cut job time by 50% or more,” says Ortolani.
All EvoTorque2 units have what Ortolani call joint-sensing technology. “It means as the wrench torques down on a bolt, it is sensing the type of joint, by its hardness or the softness and the rate of torque rise, and adjusts accordingly to maintain a proper speed and accuracy, so it does not overshoot or undershoot the torque target,” he says. This is important because there’s a manufacturer’s recommendation for almost every bolt application that says: “Don’t over-tighten this because it can do more damage than good.”
3. Simplicity. The operator must input the torque specs for the anticipated work and that allows applying several values, such as a torque figure alone, or a torque value followed by an angle of rotation. “With torque targets set, a user puts the tool on the bolt and pulls the trigger. You have one electrical cord and it is considerably quieter than hydraulic tools. Hydraulics, on the other hand, require pumps and hoses that make operating one tool a two-man job,” says Ortolani.
4. Low noise. This is a bigger deal than you think. “Consider the safety risk that comes with noise. If you have guys in multiple areas up tower, everything echoes and bounces off the walls. If a safety event occurs on the deck above you, it’s likely you will not hear them. Using a quieter tool makes it easier to hear in case something does happen,” he says.
5. Quality assurance. Data reporting on all of maintenance cycles is a more frequent requirement. “Every time a user tightens a bolt, quality-assurance requirements call for recording the data for later examination. Should the maintenance or construction team ever get audited, they would like to have a file telling that a particular tool was calibrated on this date, used by this worker in this tower, and on this bolt. That report would also show that things have been done by the book.”
6. Higher torque values. As the towers are built larger, such as with offshores towers, the torque requirements also increase. “The bolts and structures are getting larger, so we’re constantly trying to adapt. Highest construction torque requirements now range from 15,000 to 20,000 Nm.
7. Improving on current practice. Typically, after tightening a bolt, the technician marks the bolt position by drawing a line on it and its contacting surface. “The line tells that the line is where it was last tightened to. Later in a maintenance cycle, after reapplying the torque, a worker can see how the bolt moves and decide whether that is OK or not so good,” says Ortolani.
“We have a solution for that practice as well in the EvoTorque2. It will measure a pre-tightened bolt and record the degree of rotation so you don’t over-torque the joint. You don’t want to hit the nut with full-speed torque because the bolt’s going to move no matter what. So we developed technology that senses and measures the pre-tightened value without slamming into it. That tells how the bolt and joint are performing over time.”
What’s more, construction personnel might have recorded data on paper. “And as people sometimes do, they may write down the wrong number. That error could cause problems. So automatic data recording is a useful feature,” he says. An EvoTorque 2 can store 3,000 readings. “So when torquing a bolt, the tool is recording actual torque output, and other details to the second. Even if a worker takes 20 minutes per bolt, that will be recorded.”
Users are always trying to eliminate cords and use more compact or lighter tools. Electric is the way to go and as batteries improve, they will allow more innovation.