If only one gate is unlocked or one button is not pushed, the cyclotron won't start. Once the operator and any other personnel leave that area, he locks different areas that proceed away from the cyclotron. When the cyclotron area is clear of all personnel, all gates are locked, and the door is closed, it can start. The problem is to coordinate all of these buttons, gates and other safety devices such as radiation detectors together without having multiple PLCs and miles of wiring. The safety system must also have the ability to check switch contracts by sending signals to them to make sure they are properly functioning.
Relays There are several ways to create a safety system.
The easiest and least expensive way is with a hard-wired relay system for a system that isn't very complex. However, the technical demands on these types of safety systems are enormous because they must demonstrate fail-safe capability in accordance with established ANSI and OSHA safety standards to obtain the proper approval from the certifying body. Also relays are subject to error functions such as bouncing, contamination, burning or contact welding which compromises their capabilities to maintain a safe system. Another disadvantage of using relays for a safety system is that they may require a PLC and extensive wiring when many relays are used. When more safety devices are added into the system, wiring can become extremely complicated.