Safety control function reconfiguration using standard HMIs

Wednesday, 31 May, 2017

The reconfiguration of safety control functions can be carried out using standard human machine interface (HMI) products such as control panels, industrial PCs and mobile devices.

ABB’s AC500-S safety programmable logic controller (PLC) allows operators of equipment such as harbour and factory cranes, elevators and airport passenger bridges to select, modify and amend their safety control functions.

Operators of these industrial applications need to reconfigure their safety control functions to adapt to changed application conditions and to optimise machine productivity. These reconfigurations, known as safety actions, are often performed using mechanical or electromechanical mode selector switches connected to the digital safety inputs of a safety PLC.

ABB allows standard HMI to interface with an ABB AC500-S safety PLC to carry out these safety actions.

Standard HMIs that support at least two different Ethernet-based communication protocols can be used. ABB recommends Modbus/TCP and ABB ETH. A mean time between failures (MTBF) greater than 22.5 years is required for standard HMIs to satisfy PL d (ISO 13849-1) requirements. HMIs with lower MTBFs may only satisfy PL c (ISO 13849-1) requirements.

Benefits of using standard HMIs include cost savings on safety I/O channels and mode selector switches. The ability to select from a wide range of HMI products offers the user independence from any one vendor, a larger range of input options and greater flexibility to adapt the connections and layout of the HMIs.

The method allows connecting to high- and low-level safety systems remotely. One example is in the selection of a crane, allowing it to be controlled remotely using the emergency stop located on the operator desk. A network links the AC500-S safety PLC in the control room with the safety PLCs at the cranes. The user in the control room can select, using standard HMI equipment, which of the cranes will stop if the emergency stop button is activated on the remote operator control station. Pressing the remote emergency stop button on the operator’s desk will therefore stop the selected crane only. Independent of the remote emergency stop function, all cranes still have their own local emergency stop controls.

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