How to program a Siemens safety PLC?

[Yardern]

Have never used a safety PLC (like S7 CPU 416F)
What are the differences of programming between a safety PLC & a normal PLC?

Could somebody give an explaination?

Thanks

 

[panic mode]

the difference is that in this case you are directly affecting safety of the people. take a training before you do anything.
you need to understand difference between categories (learn about
redundancy, monitoring, start interlock, restart interlock etc.) and proper wiring. all blocks of safety logic are already defined and certified. you just need to use them properly.

 

[Doug_Adam]

I don't use Siemens for safety, although we use it for normal control.
We have decided on Pilz safety PLCs.

One reason is that when the decision was made was that S7s did not have pre-programmed safety functions like the Pilz did. For example, the pre-programmed safety functions could handle E-stop push buttons, light curtains, safety gates, monitored safety contacts and other devices. With these, there is a much lower chance of stuffing up.
I believe the S7 now has some of these types of functions available.

As to the difference between normal programming and safety programing (my point of view only):
1, Messing up safety can kill someone, messing up normal programming usually only results in damaged machinery.
2, Safety devices need a higer level of monitoring and cross checking, so you need a good method of programming to ensure you don't accedently leave out any of these (Hence why I prefer pre-written safety functions to roll your own)
3, You must ensure that only authorised persons can modify the safety code, and not without permission. I would not even allow myself to modify safety code without the permission from management, and I believe I know what I'm doing.

Above all, know your local standards, and know how build hard wired safety circuits before you start playing with a safety PLC.

Hope this helps,

Doug

 

[jwall]

Safety PLC's are meant to monitor a process, and enure the controls are functioning properly

The standard operation is discrepancy faults. Inputs come in channel a and B. The hardware can be set to see if they should always be matching, or flopped. If they ever are indescrepant, a signal is sent to the process plc controller about the fault, and the line is supposed to stop. Its meant as a data validator, in ways.

They also ensure all modules are active, and not in any fail state.
They can monitor input/output sets, known as a readback, to enure devices are turning on and off.

The main reason to use them, is to be in compliance with the CSA Standard, of maintaining Control Reliability. CAT 4 is a industry cliche that is thrown around in field of PLCS. It comes down to being able to detect physical problems, that could ordinarily be missed by a standard plc, jeopodizing the safety of the operator and equipment.

 

[Amr Hassan]

for siemens i think u have to buy a library for the f system

also i know that there is a software which works with the cause and effect diagram , ucreate the cause and effect diagram and the software generates the safty blocks