Safety cut out switch install advice

[wade88]

Hi guys,

Im wanting to install a safety cut out switch on one of the machines here at work, its a mixing auger with a screw thread but it has no lid on it, therefore little fiddling hands and silly boys may somehow end up in it, and come out the other end like a curly sausage, which isnt ideal really.

So a lid has been cut and fitted stopping the above from happening, however there are times, when jams, o9r misfeeds occur, and the blockage needs to be dealt with - this unfortunately can only be achieved manually. So short of having the shut the whole machine down, which is simply no practical, i would like to install a cut out switch on the lid to stop the auger from screwing when the lid is opened.

So, after all this drivel, what i would like to know is...how do i wire up one of these switches. It is a 3p, 0.25 HP, wye-delta motor.

 

[davelerave]

usually the safety door switches are wired into the starter on a simple machine

 

[Deleted member 26818]

I take it that you want to be able to replace the lid and have the machine start immediately.
I don't know that such would conform with current practices.
There are many systems about, some use magnets, others use microswitches (which are often subject to tampering or just stop working due to dirt) and there are also optical beam systems.
As davelerave says, often the system is wired so as to interupt the start circuit, usually wired to the stop contactor.
This will entail the machine being manually re-started after the jam has been cleared.

 

[telectrix]

normally closed limit switch on lid wired in series with the stop button on the starter.

 

[davelerave]

yes the machine will have to be manually re-started by a start button

the n/c door switches can't stop/start machine

 

[wade88]

Brilliant, thanks lads

 

[DomCallear]

Beat me to it telectrix...

 

[telectrix]

you could not have the lid switch start the machine anyway, as some numpty's bound to press the switch with the lid off.

 

[Deleted member 26818]

I've seen EM stop switches wired in the line conductor on single phase machines before now.
Twist the knob and away the machine goes.
I've even seen where a momentary EM switch has been installed again in the line conductor. As soon as the knob is released, the machine starts up again.

 

[telectrix]

I've seen EM stop switches wired in the line conductor on single phase machines before now.
Twist the knob and away the machine goes.
I've even seen where a momentary EM switch has been installed again in the line conductor. As soon as the knob is released, the machine starts up again.

bloody frightening, that.

 

[Engineer54]

I've seen EM stop switches wired in the line conductor on single phase machines before now.
Twist the knob and away the machine goes.
I've even seen where a momentary EM switch has been installed again in the line conductor. As soon as the knob is released, the machine starts up again.

That senerio wouldn't meet saftey standards even when i was training!!!

Personally, i would also be including a locking EM switch into the saftey control circuit, if someone is going to have his hands anywhere near that screw feed mechanism....

 

[netblindpaul]

I've seen EM stop switches wired in the line conductor on single phase machines before now.
Twist the knob and away the machine goes.
I've even seen where a momentary EM switch has been installed again in the line conductor. As soon as the knob is released, the machine starts up again.

I see this all the time, I have even seen this on the emergency switching system in a school classroom, that was installed by a LA approved professional electrical company!
Well they were supposed to be!

 

[netblindpaul]

yes the machine will have to be manually re-started by a start button

the n/c door switches can't stop/start machine

Quite correct Sir.

 

[netblindpaul]

Brilliant, thanks lads

Wade,
Is this machine CE marked?
IF so and you modify it then it will no longer comply with its CE marking, and thus will no longer comply with the PUWER98 regulations, this is statute law by the way, so it would be a criminal offence that you had committed by doing the mod if someone got hurt.
There are a few other things to consider, SRPCS and the SIL, or as they used to be called, and the requirements on these remember the possible injury could be a very serious crush or amputation, or even possibly fatal, so your machinery risk assessment should be thorough as should your FMEA.
Modding machinery is a lot more involved and has statute law surrounding it, not like changing a light fitting in a house!

 

[Des 56]

The switch fitted to the muncher to stop the machine and manual restart only
Given that the machine has had this attention,I think an emergency stop very handy nearby should be included (unless one already exists)
The handy emergency stop will only be handy if the muncher hasn't made the operative un handy by the way

 

[wade88]

Wade,
Is this machine CE marked?
IF so and you modify it then it will no longer comply with its CE marking, and thus will no longer comply with the PUWER98 regulations, this is statute law by the way, so it would be a criminal offence that you had committed by doing the mod if someone got hurt.
There are a few other things to consider, SRPCS and the SIL, or as they used to be called, and the requirements on these remember the possible injury could be a very serious crush or amputation, or even possibly fatal, so your machinery risk assessment should be thorough as should your FMEA.
Modding machinery is a lot more involved and has statute law surrounding it, not like changing a light fitting in a house!

Thank you very much for this info mate, that might have just saved me a few problems. I was unaware of this but will take that into close consideration on a lot of things from now on. Cheers for the heads up.

A pad lock it is then!