Personnel protection has been built into the Rivercircle machine by using three guards that hinge down over the three stations. To prevent anyone from raising them whilst the machine is in a hazardous mode, they are locked in the closed position by pneumatically operated shot-bolts and interlocked with Guardmaster Ferrogard magnetically actuated safety switches, supplied by eja Engineering.

These 2-part switches comprise an actuator, which develops a high intensity magnetic field, and an encapsulated unit containing two reed switches offering a set of N/O safety contacts plus a set of N/C auxiliary signal contacts to monitor the machine and guard conditions. When the actuator is presented to the switch by closing the guard, the magnetic field causes the main contacts to close and, if the guard is opened, the contacts break, thus isolating the machine.

When the machine is switched off, either through its automatic circuit or by hitting the emergency stop button, there is still power for the indicator lights and built-in diagnostics. In the normal way, this could have been provided as a discrete function within the hard-wired system but using the standard features of the integrated Valve Terminal, in which the main supply passes via the PLC, would mean switching off all the electricity.

The solution was found in a separate barrier module which could be readily included in the monoblock configuration and effectively offered an auxiliary 24V power supply. Although of standard design, the barrier module is not normally included with the Festo Valve Terminal and had to be specially ordered. However, it enabled the electrical engineers to segregate the power requirements of the emergency stop and guarding interlocks while killing the supply to the actuator inputs and outputs.

{{GuardmasterTel: Wigan (01942) 255166Enter 473

EJA EngineeringTel: Wigan (01942) 257112Enter 474}}