Do E Stops Need a manual reset or not

[thepurple1]

Normally an emergency stop would have been pressed for a reason, the last thing that you want is for something to start atomically with out it being checked by a competent person

 

[TailSpin]

Hi Lenny

Not to familiar with Puwer98 is this again all part of the risk assessment process ? or is there a clear answer lurking in the regulations.

Regards

Tailspin

 

[Wazzajnr]

General consensus and a good rule of thumb is that if there is 1 estop local to 1 fan and it only controls that fan, it should be a twist or pull to release button that drops out the latch on the contactor. Therefore, the machine will not start until you press start again but you have to manually twist or pull the button to release.

If you have several fans or any other machine with multiple estops, then each e/stop should stop all parts of the machine. They should also be twist or pull release and there should be a separate button (Normally illuminated) to reset the estop relay. The buttons should be minimum of dual channel.

This is only a general rule of thumb. Yes, a risk assesment must be performed to decide where estops are required but there are very specific standards written describing exactly how they should operate.
The standard is BS EN 418 if i remember correctly.

Hope this helps

 

[TailSpin]

Thanks again for all your thoughts

Regards

Tailspin

 

[nickblake]

normally stop starts are installed in conjunction with contactors and stop start switched , i worked on one last week which had been wired incorrectly and would operate when the start button was pressed and stop when realeased even when the stop buttot had been pressed not good the only way round it was to install another small contactor so that the supplies were copmpletel controlled but the ES switches

 

[netblindpaul]

BS 7671 doffs its hat to BS EN 60204-1.
The release of an emergency stop button must not re-initate operation of the device in question full stop.
This is also a breach under PUWER98.
The fan motor can have a local e-stop, thus must act on the control system.
It should also have a local isolator to comply with BS7671.
The control voltages etc must comply with statutory legislation.
The e-stops must comply with PUWER98.
It is dubious whether it is acceptable for an e-stop to simply control one device in a system.
For example a machine e-stop would shut down the complete machine, thus an AHU e-stop should shut down the complete system connected to the AHU as this is the button of last resort!
As a parting shot, to be an e-stop under PUWER then MUST be latching end of.
The reset, prior to start, the illuminated reset button and the reference to BS EN 418 could be a red herring dependent upon the macinery in question and the design FMEA & RA carried out by the original designer, which the installer must comply with to ensure that they comply with law.

 

[xraytek]

I have just had a look for 2006/42/EC which are the latest statutory regulations for european machinery, and have found a copy here
Page 16-17 deals with emergency stops and states the following:

1.2.4.3 "Once active operation of the emergency stop device has ceased following a stop command, that command

must be sustained by engagement of the emergency stop device until that engagement is specifically overridden;
it must not be possible to engage the device without triggering a stop command; it must be possible
to disengage the device only by an appropriate operation, and disengaging the device must not restart the​

machinery but only permit restarting."

 

[Guest123]

disengaging the device must not restart the[/LEFT]
machinery but only permit restarting."

That seems to be the winning statement.