Safety relay Implementation

[Rocboni]

I presume redundancy is only required on the motor control circuit for which the guard is operating for instance dual redundancy on the final elements of a bucket elevator where the safety relay is monitoring the inspection/clean out hatch but not required on say a airlock or blower which is blowing material away from the elevator as they pose no hazard although they would stop as part of the control circuit.

I really need to turn my attention to risk assessment, SIL SIF, RRf etc, they are quite difficult to understand.

 

[Bobster]

SIL and SIF is to do with process safety, PL is machinery safety. Both are similar but have different standards to follow. They also use a lot of the same terminology and abbreviations.

ISO13849-1
BS 62061

Depends on your MTTF and diagnostic coverage on devices, this will indicate if parts or the entirety of the safety loop needs to have redundancy.

Not only does redundancy come into play, common cause failure needs to be taken into consideration for higher performance safety circuits.

 

[Rocboni]

I’m only going to be working with enclosed conveyors and farm machinery really so, the risk is quite low

 

[Bobster]

Still plenty of high risk machines and applications on a farm.

Dependent on the farm and what you're conveying. ATEX may come into play also.

 

[Rocboni]

I Would say it should with the dust involved but nothing explosion proof is never installed.

 

[Bobster]

As has been said with all electrical work, fine until it goes wrong.

However ATEX and machinery safety is statuary.

 

[Rocboni]

Agreed, surely the motors etc that come with the new elevators should come Atex approved, on all the farm and grain handing equipment ive never seen one atex motor, I have noted that the rotation sensors and belt alignment sensors are atex approved,

 

[Bobster]

Depends if the motors are deemed to be in the safe zone or not.

Just because the sensor has an atex rating, it likely unless supplied through a barrier comply with atex regulations.

Atex is a whole other subject. If not more involved than safety.

I know enough to get by, but I'm no means an expert in that. We have other people in my office I can ask.