Remote Emergency Shutdown of Hydraulic Excavator New Hope Coal Australia, West Moreton Project The Problem During a desk top emergency exercise a scenario was identified by the production team involving a hydraulic excavator and the operator having medical event that prevented them from shutting the machine down. It was also identified the machine could potentially be in swing mode with an unresponsive operator at the controls. One of the major hazards identified to personnel attempting to provide assistance was unplanned movement of the machine while approaching to activate the emergency stop button under the body. With the equipment running and an unresponsive operator at the controls the level of risk on approach increases. The Solution It was identified a system of shutting the machine down from a remote location would reduce the risk to personnel who were attempting to assist the operator. It was also identified that what ever system was utilised it needed to immobilise the equipment to a point where the operator could not restart the machine from the cab of the machine. The problem was presented to the engineering department and a solution was identified by a member of the team that would allow the personnel assisting to remotely shut the excavator down and immobilise it from a position of safety. It was established the machine already had a relay fitted to that was used to start and shutdown the machine the challenge was to remotely activate the relay to shut the machine down in an emergency situation. It was identified that if normally closed radio controlled contacts were fitted to the coil wires of the turbo timer the machine could run normally, but a radio signal could be used to break the contacts and shut the machine down in an emergency. The radio controlled contacts were fitted to the machine and proved effective in shutting the machine down from a remote location using a small radio signal transmitter. To achieve the required immobilisation of the machine the radio receiver used to break the circuit was set to latch in the open position. The latching of the radio receiver in the open position requires the power supply to be interrupted before the machine can be restarted, this can only be achieved by cycling the main battery isolation switch of the machine. The system is wired to failsafe mode ensuring any faults with the system shuts the machine down The remote shutdown of the excavator allows the machine to be boarded via the emergency access system and full battery isolation established before assisting the operator. The braking system of the machine is a failsafe type when the machine shuts down the slew and traction brakes are automatically applied. Due to the size and portability of the radio transmitter it was decided to have only 2 active radio transmitters one in the possession of the workshop supervisor and the other in possession of the open cut examiner (OCE)/supervisor. The decision to only have two radio transmitters and the positioning of them was to ensure they are available when required, and security of the transmitters to prevent unauthorised shutdown. Testing of the system is carried out on a weekly basis. The excavator driver notifies the OCE/supervisor that the machine has been idled down and is ready for testing of the emergency shutdown. The OCE/supervisor activates the remote emergency shut down, once the machine has shut down the operator attempts to restart the machine. The operator then cycles the battery isolator of the machine in preparation for restarting the machine. The results of the test are recorded by the OCE /supervisor. The system requires basic mechanical and low voltage electrical skills to install. Total cost of the components to install the system is approximately $200 and takes approximately 1 hour to install. Benefits The introduction of the remote shutdown/immobiliser has eliminated the need for personnel to approach the excavator to activate the emergency stop located under the body of the machine. This reduces the risk significantly to personnel who are attempting to respond in an emergency situation. The primary rule of assisting in an emergency is ensuring personal safety and incident controllers have an added responsibility for team safety and ensuring an acceptable level of risk to all in attendance. Once the emergency shutdown/immobiliser is activated the emergency controller can confidently allow assisting personnel to approach the machine for full energy isolation to be achieved. The provision of remote shutdown/immobilisation speeds the response time for personnel to assist the equipment operator who may require urgent medical attention inturn lowering the risk to the causality. The system can be used for shut down of the machine in the event of fire if the operator fails to react and follow the correct procedure. The system is a low cost innovation that primarily provides protection for personal in an emergency situation. Transferability across Industry The remote emergency shutdown system can be installed and utilised on any electric start piece of equipment. The system is currently installed on an hydraulic excavator but the system is being evaluated for installation on other site equipment including bull dozers. The system could also be adapted to fixed installations where remote emergency shut down could be required such as pump stations lighting plants. The components utilised to install the system are all off the shelf items and are readily available. The installation is quick and only requires basic mechanical and low voltage electrical skills.
Posted on: Sun, 18 Aug 2013 04:44:55 +0000
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