AS NZS 4871.4 pdf download – Electrical equipment for mines and quarries Part 4: Mains powered electrical mobile machines
Machines and accessories shall be of rugged construction and be designed in a manner thatwill facilitate inspection and maintenance. They shall be well constructed, based on soundengineering principles and suitable for their intended use.
Every machine shall be provided with an isolating facility by means of which all power tothe machine can be isolated for the purpose of carrying out electrical work.
The main switching device shall be manually operated and capable of being locked in theisolated position.
The isolator shall be either in a separate compartment or remote from the machine to isolatethe supply cable.
The main isolating device shall isolate all electrical circuits within the confines of themachine unless such circuits are ELV or for equipment operating in hazardous areas,allcircuits are classified as intrinsically safe.
2.3 ISOLATION FOR MECHANICAL MAINTENANCE
Every machine shall be equipped with an isolating device by means of which all power tothe machine can be isolated for the purposes of carrying out non-electrical work on themachine. The main isolating device shall isolate all electrical power circuits that may effectmovement.
On the load side of the isolating device,functional switching devices may be used forindividual drives or groups of drives.
Machines shall be provided with a lighting system that is appropriate for the machinesoperation.
2.5AUTOMATIC GAs MONITORING sYSTEM
Where an explosive gas monitoring system is provided，the following requirements andrecommendations apply:
(a)The trip mechanism should isolate the power supply to the machine.
(b)The monitor should give a visual warning that a predetermined concentration of
explosive gas has been reached.
(c)The monitor should be configured to cease operation of parts of the machine when the
explosive gas concentration setpoint has been reached.
A lockout mechanism that will prevent the restoration of power to a machine until thetrip mechanism is reset should be fitted.Following an explosive gas trip it should notbe possible to apply power to the machine until the explosive gas concentration hasfallen to safe levels.
(e) There should be a visual indication of the gas level.
A system to override the trip mechanism may be provided to allow the safewithdrawal of the machine for repair and maintenance.Only functions necessary forthe safe withdrawal shall be enabled.
(g)Access to the override or reset mechanism should be restricted to authorised
l The relevant regulatory authority may require gas monitoring systems to be fitted to the
Some regulatory authorities may require audible and visual warning when a predeterminedgas level is reached.
2.6 MACHINE CONTROLS2.6.1General
Controls on all machines shall be located so they are within easy reach of the operator.
Consideration should be given to sound ergonomic principles for location and means ofoperation.
Where dual-driving cabs are fitted to machines, a control direction device shall be fitted andset to give control to one driving cab and to immobilize the controls in the second drivingcab.
Where two or more machines are connected together to operate in tandem—
(a)one machine shall be the master from which all controls (for all machines) are to be
centralized——other controls not required for safety shall be neutralized;
(b)the control system shall be designed to fail-to-safety; and
(c)the emergency braking in each machine shall operate all machines connected in
Where more than one control station is fitted to a machine, or where multiple machines areconnected together, the operating logic between each of the control stations shall be subjectto a risk management process.
2.6.2 Emergency stop device
Machines shall have an accessible emergency stop device(s) located for easy access duringall modes of operation.
Emergency stop devices shall comply with the requirements of AS/NZS 48220.127.116.11.3 Dead man control
Where ‘dead man control’is required its operation shall stop travel movement and bring themachine safely to rest. The dead man system shall be subject to functional safety analysis,refer to AS/NZS 4871.1.