Berendsen has completed the design and manufacture of a hydraulic cylinder and hydraulic power unit to provide the luffing function of a large maintenance crane for a prominent surface mining customer. This project is an example of our whole-of-life approach to design, manufacture and ongoing maintenance to reduce the overall cost of ownership of hydraulic systems and ensure customers extract maximum value from their investment over the lifespan of the equipment.
The project specifications:
This system is part of a large maintenance crane, whose job it is to interchange the high wear components of a massive iron ore cone-crushing unit on a surface mine site. A cone crusher breaks rock by squeezing the material between an eccentrically gyrating spindle. As rock enters the top of the cone crusher, it becomes wedged between the mantle and the bowl and breaks into smaller pieces. As pieces of ore break up and fall lower they are broken again and again until the pieces are small enough to fall through the narrow opening at the bottom of the crusher.
Periodically, the cone must be removed from the crusher for maintenance and a powerful crane is used for this purpose. This system provides the luffing (lifting) power to perform that function. The system comprises two large actuators powered by a custom-specification hydraulic power unit built into a custom-designed enclosure. All of which were designed and manufactured in-house by Berendsen’s world-class Engineering & Design team working closely with our industry-leading manufacturing division in Newcastle.
The design: a focus on ease of access, monitoring & maintenance.
With any system that must perform duty for decades, the focus on designing a system that is not only efficient, but is maintenance friendly, cannot be overstated. This means that the design must take into account more than just the project specifications and deliver the required performance using the most cost efficient and energy-efficient design possible. It must also provide access to key service points and accommodate the removal and replacement of large components such as pump and motor units that may need to be overhauled years down the line. All of this must be considered and worked into a design that achieves the required functions without adding complexity to maintenance routines.
The actuators:
To provide the luffing action required to lift the massive cone from the crusher unit, two large custom-built hydraulic actuators were designed and built in-house. These actuators each have a capacity of 300 tons, to provide the power needed to lift the high wear components for maintenance.
The heavy-duty nature of these cylinders required the use of specific high strength, wear resistant materials in many components. In the design process, the engineering team takes into account the many loading specifications that the cylinders must meet including axial loading, fatigue loading, loading frequency as well as environmental factors that must be considered to determine the factors of safety for the design. These factors of safety influence almost every design decision from material grades to surface coatings, strength of materials and more.
In this case, while medium duty cylinders may use polymer materials in the piston and gland area, these heavy-duty cylinders incorporate fully metallic bronze bearing surfaces to provide the greatest resistance to excessive side loads and to cope with the extreme loads that the cylinders may be subjected to in general. In addition, one of the major failure modes in a luffing cylinder such as this is buckling resistance. Our design team worked around high factors of safety to be able to deal with the buckling loads they may see in service.
The Prime Mover:
The prime mover is an electric motor and hydraulic pump set, which provides power to the system. It is comprised of a 250kW high efficiency electric motor connected to a 500cc closed loop axial piston pump and a 250cc open loop axial piston pump.
The electric motor is specifically a mine spec motor to make it more suitable for a mining application when compared to an industrial spec motor. It features heavier duty bearings, thermistors, space heaters a higher IP (ingress protection) rating for the housings to defend against dust and water entering the unit from the mine environment.
This is rigidly coupled to the pump set by a custom-designed steel bell housing, specially manufactured in-house by Berendsen. This feature was needed to cope with the high power and torque specifications of the prime mover.
The 500cc Danfoss Power Solutions Hydrocraft axial piston pump provides the main winching function of the unit and is hydraulic proportionally controlled. A closed loop pump was chosen for this purpose as it brings down the size requirements for the hydraulic fluid reservoir. Which assists to keep the design within the system dimension requirements given the space constraints. In addition, the closed loop system gives the added benefit of increased efficiency and hydrostatic braking.
The custom-manufactured enclosed housing:
In addition, a custom-designed housing was manufactured to accommodate the prime mover along with its attendant systems and functions, which include such items as hydraulic fluid reservoirs, control valving, filtration, sensing and telemetry. All of this needed to be designed into an enclosure that would facilitate cost effective and timely maintenance of the unit over the course of its life.
As a system that will be used on a working mine operation, the design of the steel fabricated enclosure had to meet many stringent requirements and a regulatory and safety certification and documentation process that included such matters as welding certification, material traceability, and NDT inspection. Accordingly, Berendsen’s engineering project management team compiled all engineering & design inspection test plans and quality process management documents required to deliver on the project’s specifications.
Saving time in production with end-to-end design & manufacturing
The close relationship between Berendsen’s engineering & design team and the manufacturing division played an important part in the speed and high quality of the end result.
Berendsen’s in-house engineering and manufacturing capabilities are an advantage when it comes to designing and building these types of large scale, heavy duty hydraulic systems. The Newcastle manufacturing division is fully equipped with high speed, high precision CNC milling machines and routinely produces specialised components with very precise specifications in a range of materials. Working closely with the engineering team allows us to control the process and streamline our response to critical issues or design changes that are required during the build.
End-to-end, reducing time to delivery and saving time where it counts!
