SFFs ensure safety for nuclear research
After 10 years of construction, CERN’s Large Hadron Collider (LHC) became operational in September 2008. Located near Geneva, the LHC was designed to enable experiments with colliding subatomic particles inside a circular accelerator. Due to technical problems in the cooling system, the particle accelerator shut down automatically last year and is scheduled to restart later this year. The LHC can only be used during the winter months because its electrical power requirements would cause the national power grids in Switzerland and France to break down during the summer.
The LHC is buried in a tunnel 27 km (17 miles) long and 100 m (328') deep underground, where monorail inspection trains keep surveillance. No person or foreign object is allowed inside the tunnel during experiments.
While most commercial plug-and-play devices cannot handle this type of safety application, the Train Inspection Monorail (TIM) from Sick, Germany, is equipped with laser light barriers, encoders, bar code readers, and safety laser scanners to protect people from harm.
Driving at speeds from 3 km/h to 12 km/h (1.9 mph to 7.5 mph), TIM sends live pictures recorded by two safety laser scanners to the supervisory station. Several scanner systems generate reports with information indicating the positions of people or endangered objects. A UE410 Flexi main unit (Figure 1) and other rail-mounted small form factor system boards process signals and position control. The UE410 system controller is based on two dual-redundant Freescale MC9Sxxx microprocessors that are typically used in automotive applications.
This safety controller board is available in a firmware-based version (Flexi Classic) with selectable functions on the front or a software-based version (Flexi Soft). Expansion modules and a diagnostic module for fieldbus coupling to PROFIBUS can be plugged into the side of the basic element. Flexi Soft offers configuration via user-friendly software, as well as modular expandability, expanded sensor functionality, and integration into all leading fieldbus systems.
The I/O and interface modules are clipped on sideways on a DIN rail (see Figure 2). The system doesn’t require a backplane, board guide, or housing. Each board is individually enclosed in plastic with only I/O and power terminals accessible from the outside.
The Flexi modules are 22.5 mm (W) x 96.5 mm (H) x 114.4 mm (D) or 0.9" x 3.8" x 4.5". The modules are certified to Safety Category 4 per EN 954-1 and Safety Integrity Level 3 (SIL 3) per IEC 61508. The emergency stop function corresponds to Stop Category 0 or 1 in accordance with EN 60204-1, which is required to ensure that people will not be harmed in this large underground maze.