TXM Plant, leading supplier of Road Rail Vehicles, required a solution that met Any Line Open (ALO) requirements for an excavator working “in the dig” on track renewals. The solution required a reliable Movement Limiting Device (MLD) that could be retrofitted to the machine. TXM collaborated with GKD Technologies, providers of effective and innovative safety control products designed to safeguard personnel and mobile machinery, who supplied an upgraded version of their 2RCi (rated capacity indicator), the 2RCi Plus.
TXM fitted the 2RCi Plus to a life-expired machine to conduct trials in a test environment. The first trial was successfully completed at TXM’s Wigan depot on 28th July 2020, with all functionalities successfully achieved.
The 2RCi Plus technology is based on proven GKD technology employed on 1000’s of RRVs and excavators across the globe. The system uses sensors on the machine slew, boom and dipper, combined with pressure sensors in the hydraulic system. This forms the basis for the data used by the rated capacity indicator to reliably calculate the safe weight loading and position of the machine’s dipper arm.
To meet the ALO high-performance standards, the 2RCi Plus had to be designed, so “that there would no credible single point failure that would cause the system to fail to an unsafe condition”. This was met by having dual verification, with two sets of sensors working on separate control modules.
This system was also unique in having ‘virtual wall’ functionality, effectively allowing the creation of a 3D safe working zone that the machine cannot move outside of. When the system detects that the machine is getting close to the virtual wall, the system stops the machine from breaching the virtual wall.
Enhancements to hydraulics
Some ALO solutions have suffered from slow operational speeds. The 2RCi system utilises ‘Proportional Control Valves,’ which permits the machine to work at normal speeds until it comes close to the slew limit / virtual wall. When proximity to the wall is detected, the proportional control reduces the speed of operation of the machine until it physically stops when the wall is reached. This allows for a smooth and controlled operation of the machine, and for full productivity to be achieved.
The virtual wall is set by placing the excavator dipper at the edge of the safe slew (or rotation) position, and a button on the control screen is then activated.
- The system can be pre-programmed with the virtual wall dimensions by entering them into the screen.
- The virtual wall can be set at either side or both sides, to permit island working. Safe height limits can also be set.
- To meet ALO requirements, the system is complete with a supervisor key – once this is activated and removed, the system cannot be turned off, or have the set parameters changed.
- An orange beacon is illuminated on the exterior of the top of the cab to indicate that the safety control solution is active.
The travel/ tracking function for the excavator is also fitted with an overlaid control system. When the machine is set in ALO working mode, the excavator can only travel forwards or backward irrespective of the Operator engaging one or both travel levers. The Operator cannot make the machine turn one track individually; to make the machine turn on its tracks the ALO system needs to be disengaged by the insertion of the key.
Machine controller override
The Machine Controller also has a fob with a button that is synchronised to the system. If for any reason the Machine Controller wishes to stop the operation of the machine, he/ she simply pushes the button on the fob which instantly ‘freezes’ the entire hydraulic system of the machine. The engine still runs on the machine, and the lights/ alternator, etc. continue to function, however, the Operator is unable to move the machine by utilising the controls. By depressing the fob button again, the Machine Controller then re-instates the functions back to the Operator, and the machine continues to function within its ALO parameters.
Repositioning of the machine
Once the machine has completed its excavation of the immediate area, it can travel backward and forward along in a straight line in ALO mode, suited for longer excavations in a straight line. If the machine needs to periodically change its direction of travel e.g., excavating on a curve, the ALO key can be given by the Machine Controller to the Operator, inserted and turned.
This allows the Operator to control the direction of travel on the excavator tracks and position the machine at the new desired angle. Once the new position is achieved, the key is turned, removed and given to the Machine Controller. The excavator is then back in ALO mode and defaults to its previous ‘Virtual Wall’ settings.
Successful collaboration between TXM Plant and GKD Technologies has delivered a reliable, efficient solution for ALO working on track renewals. TXM will continue to work with GKD to develop and deliver innovative solutions for our customers with safety, reliability and production enhancing solutions at the forefront.
Coming soon: The 2RCi Plus safety system is being overhauled to the Series 2LHS+! The new Series 2LHS+ is a highly flexible height, slew and load system with full envelope control. It increases safety during lifting operations and is highly adaptable working on a variety of machines, including wheeled and tracked excavators, whatever their boom configuration.