Installing door safety switches

Thread Starter

mztrordinary

Joined May 25, 2016
16
Hi guys

I have a project coming up which involves installing 22 door safeties on a machine. The machine doors are all mild steel and i will be installing the following safety switches from the link below. The problem if you could call it that is that the mains electrical panel for the unit is jam packed and hasnt got much more room for expansion so i plan to put these in series with the emergency stop buttons that are on the machine. There are 2 e stops which are running back to a safety relay which in turn is also connected to the machine PLC and once activated need to be manually reset through a reset button. As i do not have access or software for the PLC or drawings for the machine i thought it best to do it the way described unless anyone has an alternative idea as to what will work as well but be slightly different? I also plan to have each door connected to a LED lamp which is to be connected to the aux on the safety switch because the doors are solid all round and the switches will be going inside the machine it gives an indication of which door is open etc. I am just looking for a little advice i suppose is there anything generally wrong with my plan?

Link to switches to be used
https://uk.rs-online.com/web/p/safety-rated-interlock-switches/6233054/

Thanks guys
 

MaxHeadRoom

Joined Jul 18, 2013
20,898
So if any one opens the cause a stop?
So they could be wired in series with the E-stop.
The aux contact could be used as an indicator as you suggest.
Max.
 

Thread Starter

mztrordinary

Joined May 25, 2016
16
Yes Max that is exactly what i want to happen there is a chain conveyor belt running inside the machine which is easily accessed through any of the doors so when they open i want it to activate the emergency circuit
 

MaxHeadRoom

Joined Jul 18, 2013
20,898
Without access to the machine schematics it is hard to say definitively, but based on what is posted so far it appears a reasonable approach.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
20,898
As an after thought, if the system has a start and a stop P.B. say, each into the PLC, it may be worth looking at inserting the various door switches into the Stop P.B. rather than the E-Stop circuit.
Max.
 

shortbus

Joined Sep 30, 2009
7,760
As an after thought, if the system has a start and a stop P.B. say, each into the PLC, it may be worth looking at inserting the various door switches into the Stop P.B. rather than the E-Stop circuit.
Max.
We had a machine at work that when the E stop was used it caused a lot of resetting of things before it could be restarted. But pushing the off button took that into consideration, the way things shut down. I'd think tying the door switches into the stop push button would be better, but then what do I know.
 

MaxHeadRoom

Joined Jul 18, 2013
20,898
We had a machine at work that when the E stop was used it caused a lot of resetting of things before it could be restarted. But pushing the off button took that into consideration, the way things shut down. I'd think tying the door switches into the stop push button would be better, but then what do I know.
Yeah, that was the reason for my second thoughts, if the Safety Relays are shut down, it may require more of a simple start function after the stop.
Max.
 
Devil's advocate:

How do you work on it with the panels open?

I was used to safety switches that were of a variety where when you pulled the panel off it stopped. But you could pull the actuator and disable the safety switch, but when the panel went back on, safeties automatically engaged.

The high voltage that could kill panels had keys to open and were hinged.

Equipment wasn't fancy,.
 

MisterBill2

Joined Jan 23, 2018
6,322
yes Max i dont see why not unless there is something inherantly wrong with this approach?
THAT IS THE WAY IT IS DONE! Door safety switches all in series. And once I tried to add a neon pilot lamp across each one to indicate that it was open, and the ridicule went on for hours because the electrician had never seen such an arrangement. You can't do that with LED indicators, but it will work with neon bulbs. I don't see anything wrong with the arrangement described, although if you had lots of money and extra room there are other ways that will also work.
 

MisterBill2

Joined Jan 23, 2018
6,322
As an after thought, if the system has a start and a stop P.B. say, each into the PLC, it may be worth looking at inserting the various door switches into the Stop P.B. rather than the E-Stop circuit.
Max.

MAX, NO!!! The E-Stop function "shall be different", at least in many auto plants. E-stop de-powers all motion functions, while "Stop" halts the process. E-Stop is for when somebody falls into the machine. So they can all be in series, and I have put neon pilot lights across switches to show which door switch is opened. I used neons because they don't pass enough current to register at the PLC input. It worked well but the criticisms from the unknowing were brutal. The concept of a light across a switch was totally beyond their ability to understand..
 

shortbus

Joined Sep 30, 2009
7,760
MAX, NO!!! The E-Stop function "shall be different", at least in many auto plants. E-stop de-powers all motion functions, while "Stop" halts the process. E-Stop is for when somebody falls into the machine. So they can all be in series, and I have put neon pilot lights across switches to show which door switch is opened. I used neons because they don't pass enough current to register at the PLC input. It worked well but the criticisms from the unknowing were brutal. The concept of a light across a switch was totally beyond their ability to understand..
Kind of late to the game. See posts #9, #10, #11.
 
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