Minerals and metals processing technologies specialist, Outotec, is combining high efficiency hydraulic Enerpac (A Division of Actuant Corp) technology from with ultrasonic bolt load testing to optimise the speed, accuracy and safety of bolting operations in the construction of SAG and ball mills. With Enerpac hydraulic torque wrenches and pumps, each bolt can be fastened quickly and with ease to the required tension, saving time and ensuring precision across the hundreds of bolts required on a construction project.
Peter Nilsson, Global Installation Manager at Outotec in Australia, said that the technique was employed when assembling the critical load-bearing frames. The bolts varied in size from 30-60 mm diameter, with up to 1000 bolts being tightened to the correct tension in each mill. Outotec’s SAG (Semi-Autogenous Grinding) and ball mills part of the metal extraction process for minerals such as gold, copper, platinum, lead, silver, zinc, alumina and nickel.
“Installations can be undertaken anywhere around the world, for a wide variety of safety conscious clients. A recent construction project was at a mine in Bolivia,” said Mr Nilsson. Outotec either constructs and installs the mills for clients, or alternatively supplies the technology and training and work with the client to complete the installation.
Boltstress bolt testing has already been used for approximately two years by Outotec before the precision bolting task was further enhanced by the use of the Enerpac ZU4208TE-Q pump and W-Series torque wrenches and socket accessories. W-Series low profile hexagonal wrenches, weighing 1.4-5 kg, have precisely repeatable torque from 2712 to 20337 Nm. Coupled with the high-speed ZU4208TE-Q pump, they are used for correct power, precision and repeatability in loosening and tightening nuts. The ZU4 Pro Torque wrench pumps were supplied to Outotec for optimum compatibility with Boltstress’ ultrasonic bolt tension measurement for safety and reliability.
Mr Nilsson said that the combined Boltstress and Enerpac technology saved time and gave precision to the bolting operation. “We were one of the first to adopt the Boltstress-Enerpac combination. The advantage of the technique is that our engineers can pre-set all the parameters – the information that needs to go to the tools. The actual bolting job can then be done by a trained operator who doesn’t have to worry about setting up the correct data properties,” he said. The Boltstress G5 bolt loading tool employs ultrasonic measurement of bolt stretch to ensure the correct pre-load is applied, safeguarding joint integrity and preventing bolted joint failure. Ultrasonic bolt tension measurement assesses true joint performance by using real (not assumed) data. It is designed to eliminate costly downtime, potential safety hazards and guesswork.
The Technical Director of Boltstress Ultrasonics, Trevor Robinson, says measuring bolt tension is preferable to relying on tool torque alone, as joint separation has been known to occur, with dire consequences requiring major repair and expensive downtime. The bolt testing and fastening technique is used on all structural bolts where correct tension is required, rather than on a test sample of bolts.
Features of the W-Series torque wrenches include:
- Fast operation from large nut rotation per wrench cycle (30 degree rotation angle) and rapid return stroke. No tools are needed for changing heads
- Innovative pinless wrench construction incorporating quick release cylinder and automatic crank engagement. Robust design with minimal parts for easy on-site maintenance without special tools
- Cylinders and low profile heads engineered for ultra-slim compact low clearance tooling with small nose radius
- Hexagon range 36-115mm (one and seventeen sixteenth inches to four and five eighths)
The wrenches come with a wide range of accessories for safety and efficiency in particular applications, including twin 4:1 Safety Hoses.
Enerpac ZU4T-Series hydraulic torque wrench pumps are the latest energy-saving pumps designed specifically for bolting applications. Their two speed pumps feature higher oil flow and bypass pressure for cooler running that requires 18 per cent less current draw than comparable pumps. The ZU4T’s light weight and compact design make it suitable for applications requiring easy transport. Its universal motor works well on long extension cords or generator-driven electrical power supplies.