Integrating wireless and functional safety
The growth of wireless applications in industrial automation results from recognised benefits of efficiency and improved operator safety. The move from electro-mechanics to electronics enables them to monitor and control unintended movements of the machine or unexpected changes to the process. Monitoring this functional safety is enhanced by integrating wireless
Functional safety is the part of the overall safety of equipment that depends on the system or equipment operating correctly. This includes its inputs, the safe management of likely operator errors, hardware failures and environmental changes.
The increasing use of mobile wireless controls and variable speed drives requires monitoring of all related functions of the machine. (Category 2 according to EN ISO 13849-1). This includes both stop functions and for motion functions, as required in the current European Machine Directive 2006/42/CE.
The more advanced wireless remote control systems integrate monitoring of the stop function. (up to Performance level e and Category 4 according to EN ISO 13849-1). Also motion function (Performance level c and Category 2 according to EN ISO 13849-1). This is without the need for additional safety devices.
Requirements for hoisting equipment and cranes
The EN15011 (Cranes – Bridge and gantry cranes). The standard states that electronic and programmable component control circuits must meet at least Performance level c and Category 2 in accordance with EN ISO 13849-1. Constant monitoring of the components ensures safe operation.
In addition, the EN13557 (Cranes – Controls and control stations). This standard requires circuits to meet Performance level c and Category 3 in accordance with EN ISO 13849-1. This specifies the minimum safety level needed for the stop function of a wireless remote control system.
Finally, the EN13135 (Cranes- Safety – Design). This standard requires the machine manufacturer to address the need for safety devices for overload protection of hoisting machines and limiting of motion
The increasing importance of wireless remote control systems in machine safety applications results from the revision in progress of standards. IEC60204-1 (Safety of machinery-Electrical equipment of machines- Part 1: General requirements). Also, the creation of the new international standard IEC 62745 (Safety of machinery – General requirements for cable-free control systems of machinery). Standard IEC62745 defines how wireless remote control systems must meet the minimum requirements of machine design and safety.
OEMs and end-users can better accommodate migration to wireless remote control systems by establishing clear differences between general stop function and emergency stop function. This enables certain maintenance to take place during a functional stop without stopping the entire machine or production line.
Accessing more information enables operators to avoid and manage unexpected machine stops. This is particularly important when the load is in a critical state. The operator is alerted if the communication signal between the device and base station drops too low.When valid frames are no longer transmitted or received, the system stops automatically.
An alarm can be set to warn the operator when the battery charge falls to a low level, and avoid system power loss. A ten-minute warning is suitable.
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