ISO 13849 Question

With ISO 13849 do two-hand anti-tie down buttons have to go through a safety relay?

This is one of those - what is safe questions.
You are respsonsible for the safety of the machine you are building / modifing.
To Answer with no Idea of what the machine is ---
How long is a piece of string - apart from being twice as long as half it's length

In fairness
- What happens if one button locks on and is mechanically bridged.
does this allow the machine to be operated by the other button and ignore the two button mode.
- can you guarantee no unsafe failure.
- will the operator be able to bypass your setup?

Commonly the twin buttons are used to close guarding
- this guarding will not crush body parts
- the machine can then function with an alternative safety method.

this is not much help - but it is up to you.

Hi RC

If it,s classed as a two hand start then yes it does have to go through a certified device like a safety relay.. the circuit also has to be monitored so generally one safety relay and two standard relays which when there is a fault would stop the circuit being rearmed by nature of the circuit design.... Pilz and A/B both have circuit designs for safety relays and two hand starts in there catalouges

Regards

JV

The first question you have to ask yourself is: "What performance level (PL) is required?" What does your hazard analysis say you need? (You did a hazard analysis, right?).

PLa could be achieved by a couple of switches wired in series. If you need to achieve PLe no way that would work. Even if you use a "safety relay" you still need to consider diagnostic coverage, mean time to dangerous failure of the individual components, and common cause failures.

There are no one size fits all answers. The new safety standards are quantitative rather than qualitative.

Timbert said:

The first question you have to ask yourself is: "What performance level (PL) is required?" What does your hazard analysis say you need? (You did a hazard analysis, right?).

PLa could be achieved by a couple of switches wired in series. If you need to achieve PLe no way that would work. Even if you use a "safety relay" you still need to consider diagnostic coverage, mean time to dangerous failure of the individual components, and common cause failures.

There are no one size fits all answers. The new safety standards are quantitative rather than qualitative.

Click to expand...

I thought/assumed the safety relay he was reffering to was a dual button operation type.
If this was not the case then you are quite right.
the PL you mentioned is in categories here.
(Cat.1~4, 4 being deffinate life threat)
www.pilz.com.au - has some info on the site
I believe that this will be similar world wide.
(Well most of the wise world)