Manual Reset of E-stops

dowthebow

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Hi,
In the EU, Do I have to Manually reset e-stops or can this be done from a HMI?
I have a machine that gets regular brown outs and this is picked up as an E-stop by the Pilz components. The machines are manned remotely so every time this happens we need to get a man to site.
I would like to avoid this but I'm not sure if an E-stop can be reset remotely?
I see something around resetting the e-stop seperately to restarting the machine, but nothing about having to reset locally.
Any CE marking experts out there??
Thanks in advance...
 
dowthebow said:
Hi,
In the EU, Do I have to Manually reset e-stops or can this be done from a HMI?
I have a machine that gets regular brown outs and this is picked up as an E-stop by the Pilz components. The machines are manned remotely so every time this happens we need to get a man to site.
I would like to avoid this but I'm not sure if an E-stop can be reset remotely?
I see something around resetting the e-stop seperately to restarting the machine, but nothing about having to reset locally.
Any CE marking experts out there??
Thanks in advance...
Click to expand...

Reading the relevant BS EN standard that applies to the equipment in question would be a starting point, but E-Stops are latching for a reason and that is to force a human intervention.

If you have an issue with power brown outs stopping your process you would be better looking at a solution to solve that rather than run the potential of re-starting a machine that's had a legitimate E-Strop

For instance how would you differentiate between a true E-Stop and a power issue ?
 
Last edited:
I think an e-stop should be reset manually anywhere in the world: even if the local laws and standards are lax, you would just sleep a bit better.
 
I routinely use a PLC output driven from a HMI PB to reset safety relays, its pretty routine. The reset function can't override the non-safe condition so it really doesn't matter where it originates from. But what I do NOT do is restore hazardous motion power in the same action. That requires an additional step, usually a hard wired PB to activate a MCR.
 
tragically1969 said:
Reading the relevant BS EN standard that applies to the equipment in question would be a starting point, but E-Stops are latching for a reason and that is to force a human intervention.

If you have an issue with power brown outs stopping your process you would be better looking at a solution to solve that rather than run the potential of re-starting a machine that's had a legitimate E-Strop

For instance how would you differentiate between a true E-Stop and a power issue ?
Click to expand...

A true E-stop would latch the e-stop and therefore not be resettable.
The issue with brown-outs is supply related and out of my control.
 
BobB said:
In Australia E-stops have to latch and be manually reset.
Click to expand...

Agreed, I think that is probably the case world wide.
I'm talking about a supply failure, which is seen as an E-stop by a pilz safety relay, but in reality no E-stops were pressed or latched
 
I believe the OP is saying that an E-stop has not been pressed but that the system is in a safe condition because of a return from a power down condition. I believe the condition that needs to be considered is a safety reset not an unlatching of the estop.

The reset button isn't a safety device so it could be an hmi as long as the safety system can't allow an automatic start condition when all estops are unlatched if the input to the safety system is stuck on. The safety reset must require an off-on-off on of the reset input and the safety system can only be reset if all devices are in the safe state.

Of course a full safety analysis must be done to determine the risk of remote start. I'm assuming that this is remotely operated equipment so the unattended operation is accounted for in the safety analysis anyway but If there is ANY chance of a person being inside of the safety barrier remote reset start should not be allowed.
 
Yes a safety reset is perfectly allowable from the HMI.

The resetting of it (after twisting the mushroom) is not a safety function.
 
janner_10 said:
Yes a safety reset is perfectly allowable from the HMI.

The resetting of it (after twisting the mushroom) is not a safety function.
Click to expand...

I disagree. If an E-Stop is momentary then a machine can unexpectedly restart after a shutdown situation clears or a spin timer times out. A perfect example would be a high temperature switch closing after sufficient cool down time.

Latching E-Stops aren't 100%, but they are a step in the right direction. I can't think of a good reason to not use latching E-Stops. Even in the case of the original poster, unless he can completely guarantee that there is absolutely positively no one working on that machine when he hits reset, he stands a chance of tearing some poor *******'s arm off.
 
Last edited:
Can't the HMI trigger the PLC to toggle a relay on/off for the reset to the safety relay instead of the reset button being a physical button that toggles to the safety relay?
 
kvogel said:
I believe the OP is saying that an E-stop has not been pressed but that the system is in a safe condition because of a return from a power down condition. I believe the condition that needs to be considered is a safety reset not an unlatching of the estop.

The reset button isn't a safety device so it could be an hmi as long as the safety system can't allow an automatic start condition when all estops are unlatched if the input to the safety system is stuck on. The safety reset must require an off-on-off on of the reset input and the safety system can only be reset if all devices are in the safe state.

Of course a full safety analysis must be done to determine the risk of remote start. I'm assuming that this is remotely operated equipment so the unattended operation is accounted for in the safety analysis anyway but If there is ANY chance of a person being inside of the safety barrier remote reset start should not be allowed.
Click to expand...

This is exactly what I was asking, Thank you
 
Tom Jenkins said:
I disagree. If an E-Stop is momentary then a machine can unexpectedly restart after a shutdown situation clears or a spin timer times out. A perfect example would be a high temperature switch closing after sufficient cool down time.

Latching E-Stops aren't 100%, but they are a step in the right direction. I can't think of a good reason to not use latching E-Stops. Even in the case of the original poster, unless he can completely guarantee that there is absolutely positively no one working on that machine when he hits reset, he stands a chance of tearing some poor *******'s arm off.
Click to expand...

We are talking about different things, I am referring to the Safety Reset, as in the tradition blue button wired through a n/o contact that then goes to the Safety Relay to reset the safety function, NOT the actual E-Stop
 

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