Why Safety PLC…??? Even more functionality available in Conventional PLC ?
Safety & Conventional PLC can both control things, while the conventional PLC will probably offer more features, less cost, be more readily available,
Now Concern is requirement of:-
A. Shutdown a system if anything goes wrong.
B. Safely Shutdown a system if anything goes wrong.
Using a Conventional PLC for a Safety Circuit-
Conventional PLC can be programmed however we want. A system can be designed and programmed with any level of complication with a PLC .We can detect any kind of failure and put the equipment in a stopped, safe and controlled manner.
But, the consequence are:-
a- Problems increase with increase in relays and can quickly get complicated
b- Poor diagnostics and poor status indicators
c- Very difficult to do multiple e-stop zones
Using a Safety PLC for a Safety Circuit-
A safety PLC is different from a conventional PLC in many ways, such as:
Redundancy of onboard devices which are continuously monitored by a watchdog timer.
Continuously monitors inputs with a smart circuit to detect failure.
Added safety circuitry between the output switching device and an actual device, which will detect system failure and facilitate a safe shut down by going back to a known state.
Major savings on field wiring, Remote I/O capability with safety, Good diagnostic capability can be easily achieved by Safety PLC.
Definitely, if we see consequence then there is:-
a. cost is higher
b. Requires Safety programming
c. Possibly too complex for applications
d. Understand System & Application, Hazardous study of & System Citification
e. Requires educated maintenance people
Credits - Amit Upadhyay