Q. What are the benefits of integrating safety and standard control on a single control platform?
Integrated safety control systems enable faster implementation, simplify system configuration, and allow efficient troubleshooting and maintenance. All this, while meeting stringent safety requirements.
During system development, most integrated safety control platforms allow safety control to be managed in exactly the same way as standard control, ensuring consistency in its operability and control philosophy. When projects are tested and ready for final validation, the control memory is locked to the appropriate safety integrity level while the standard control side continues to operate like a regular controller. This, in conjunction with on-line editing and debugging environments, permits a significant reduction in system configuration and development.
Integrated control platforms require less programming than individual standard and dedicated safety PLCs, with users able to develop both the standard and safety control system code concurrently. This allows users to develop single projects and upload them as an integrated package.
The ideal integrated control platform generally employs common hardware and communications networks, and uses a single software package. This streamlines system development and reduces costs in technical support, maintenance and employee training. Integrated control can also save panel space.
Q. How is programming an integrated safety system different from programming individual safety and standard PLCs?
The traditional approach to safety control is to deploy a pair of linked controllers - a conventional PLC coupled with a dedicated safety controller. In designing and developing this kind of system the PLC-based conventional control is first established as the system’s ‘foundation’, while ‘safety’ control is retrofitted.
Integrated safety control systems allow users to develop standard and safety control system code concurrently. The ideal integrated control platform employs single programming software so users manage their safety control system with standard control methods.
Some integrated controllers feature pre-certified blocks of code to simplify certain common safety applications like E-stops or light curtains. In addition, users can develop application-specific code using a library of instructions certified for use within safety tasks.
Q. Can safe and standard devices communicate over one communications cable?
Yes. In fact, most integrated safety control platforms are totally flexible. Users can choose to have standard and safety devices communicating over a common communications network, such as DeviceNet or EtherNet/IP, or they can establish separate networks, splitting standard and safety communications.
Functionally, a single integrated communications network is identical to a twin-safety and standard-communications network architectures. However, users sometimes opt for separate communications systems to maintain consistency through their existing control installation. Most greenfield installations that employ integrated safety control systems deploy a single communications network.
Using a common communications network, coupled with distributed I/O, can improve installation and wiring time.
Q. How difficult is it to interlock integrated safety systems?
Some integrated control platforms leverage ‘Common Industrial Protocol (CIP) Safety on DeviceNet’ for safety I/O connectivity, and ‘EtherNet/IP for safety interlocking’ between separate processors. This allows multiple integrated controllers to share safety data for safe interlocking between different cells/areas.
Ideally, the safety task within one integrated controller can send high-integrity safety messages to safety tasks in other integrated safety processors over EtherNet/IP using the CIP Safety protocol. This enables safety interlocking of controllers over EtherNet/IP. Ideally, the system can also communicate on EtherNet/IP for standard control.
The safety memory of some integrated control platforms can be read by standard logic and external devices such as HMIs and other controllers. This removes the need to set or condition safety data from a dedicated safety device.
Q. How are security and compliance needs met in integrated control systems?
Some systems are equipped with heightened security functionality, providing users with comprehensive local security (project based), or centrally administered security.
From a compliance standpoint, some integrated control system projects are also compatible with auditing and routine source protection software packages. These tools track project changes down to specific user actions. All this is on top of the standard password control for access and lock down of the safety task.
Q. When are integrated safety solutions applicable?
Integrated safety solutions are applicable for all applications where there is sufficient complexity of standard and safety control required. For safety systems with very simple requirements, there are various options in safety relays.
BIOGRAPHY
Gary Milburn has been involved in machine safety for over 20 years. His current role is focused on Rockwell Automation’s wide range of safety capabilities.
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