Working alongside high-voltage lines places special demands on the safety standards of the machines used. In order to sufficiently protect line workers, reliable voltage-free areas on the machine are required, through which the worker is separated from the ground and safe working is possible.
Altec Inc., an American manufacturer of cranes and aerial work platforms, offers the TA55 Series of telescopic articulating lifts provided with the necessary equipment for working in high-voltage areas. The telescopic articulating lifts have insulated components attached to the work cage. In addition, a tip is attached to the work cage, which enables the worker to lift loads to working height. This makes the TA55 telescopic articulating lift ideally suited for working on high-voltage lines.
For its use specifically in Australia, WIKA Mobile Control supplied an overload protection system with safety cut-off function for these telescopic articulating lifts. This includes additional monitoring of the tip and the work cage including safety cut-off according to a safety level corresponding to EN ISO 13849 of PLr d. The system for the TA55 telescopic articulating lift consists of an HMI (vSCALE D3), controller hardware (qSCALE S9 trueSafety), robust sensor technology and certified RCL-C library.
“When we talked to EWP operators and depot managers about their specific needs, job site safety was their priority,” says Chitra Ranganathan, Altec’s Australia Market Manager. “Altec’s customer-focused product development process led us to work with WIKA Mobile Control to develop the load management feature with real-time display.”
The visualization via the user-friendly HMI vSCALE D3 fulfills a variety of functions: from display of the system load and sensor comparisons, to diagnostic functionalities and various setting options. The qSCALE S9 trueSafety control system with an integrated rated capacity limitation (RCL) core collects and processes data to determine the machine position, load detection of the work cage, load calculation of the suspended load on the tip, and load limitation of the system depending on the detected load on the tip and work cage. In the event of an overload, the control system takes over the safe cut-off by directly controlling redundant valves. Various other control functions provide an additional level of safety. These include:
- Safe bridging function with checking of status and time control
- Advanced diagnostics of redundant and certified input signals and outputs
- Test function to validate the correct operation of the valves at system start-up
- Control of the valves to block the movements in case of an overload of the boom
- Control of the valves for blocking the movements of the tip on the working cage
- Control of the signal transmitters for the system and communication with the visualization unit
Load detection on the work cage is completed by the use of additional hardware and software components. These include a redundant load cell with CANopen signal transmission (fSENS KMD), two certified 300 bar pressure sensors (pSENS, PL d) and qSCALE RCL trueSafety, the certified RCL-C library.
In addition to the functional implementation in the system, WIKA Mobile Control also supplied the required documentation of the safety cut-off, including the calculation of the necessary safety chains. The performance Level PL d (according to ISO 13849) and compliance with other international standards ANSI/AS/NZS were successfully accepted by an Australian certification body. As a result, the customer benefited from the full service of a system integration from WIKA Mobile Control.