Requirements toward safety in production environments have become considerably more demanding over the past decade. Introduction of the 2006/42/EC Machinery Directive by the European Union made machine and plant manufacturers focus their attention on this issue.
They are required to design comprehensive solutions to ensure protection of workers against injuries and the machinery itself against damage while maintaining high levels of productivity.
The new standards led to the necessity for new machinery to undergo strict certification procedures and to elevated performance requirements for the safety components used. Supported by a multitude of new and innovative safety products, they also facilitated changes in the approach toward the conceptual design of safety solutions. No longer is an emergency stop immediately halting all parts of a machine the only safe reaction to violations of the machine’s safe boundaries. Smart safe reactions such as continued operation at a safe limited speed can in many cases deliver the required level of protection while providing better productivity by reducing the time to resuming full speed. In many instances, it enables a more direct interaction between worker and machine, particularly in teaching and adjustment scenarios.
Network Integrated rather than Hard Wired
Traditionally, safety equipment used to be hard wired with dedicated switching circuitry, often logic cast in pure hardware. Although with some effort it is theoretically possible to cover many cases using this method, more and more machine manufacturers have been recognizing the benefits of integrated safety. It is based on safe programmable control hardware and I/O modules using the existing field bus to exchange safety-related data.
At first glance, the older methods may appear less costly. Due to the lower purchasing costs of their hardware components, this may in many cases be true, but not if safety solutions are viewed in their entirety. Wherever the complexity of such systems goes beyond a single emergency stop button, network-integrated safety systems have become the preferred choice. They lower the number of components as well as required cabling and provide more flexibility of safe logic design by replacing hard wiring with configuration and parameter setting. Also, error diagnostics are greatly simplified. Combined with centralized data storage, this results in faster recovery. Maximum availability of plants and machines is provided by network-integrated safety technology through:
- Safety sensors directly attached to the network
- Direct read-out of component information
- Simplified maintenance due to automated component parameter setting across the network
- Safer operating mode switching due to parameter setting during runtime
- Decreased response time, as latency induced by relays is eliminated
- Modular design supported by network structure and safe software
- Increased availability as a result of comprehensive diagnosis
- Reduction of component count and wiring
- Greater variety of safety functions (safe operating stop, safely limited speed…)