Testing emergency stop circuit ?

[tomodo]

Hi im working on 3 emergency stop circuits at work all stopping the same motor , each has 4 emergency stops on it so a total of 12. The last two on every circuit do not stop ( the conveyor system ) when the button is pressed. I was testing for incoming voltage on them (24v DC ) but had no neutral or earth to test with..... is there any other way of testing for voltage? Thanks

 

[Plonker 3]

Have you proved continuity of all the conductors between the EM stops?

They are all wired correctly aren't they?

 

[Plonker 3]

They are all the same aren't they?(N/O or N/C)

 

[shanky887614]

sounds like the emergency stops are wired back to a control panel that runs the motor.

it helps if you explain what kind of system it is.

it could be in singles with the line passing through the stop before the motor (breaking the circuit)

or via a panel that then turns the pumps off via contactors etc

(lol I put earth instead of line)

 

[tomodo]

Not yet can only test when the place is shut so not had long at it. Just found it weird how its the last 2 on every circuit ( a total of 6 ) that doesnt work......

 

[tomodo]

Its a big control system all goes back to an emergency stop panel which then in turn goes back to the main conveyor panel ....

 

[shanky887614]

why not start by checking if the stop is faulty, a quick 30sec continuity test on back of unit would rule this out.

could be damaged cable if there in series

 

[Plonker 3]

Have you checked there is voltage on both sides of each switch?

 

[tomodo]

I was trying to earlier but there was no earth or neutral to test voltage between ...

 

[tomodo]

Its just surely if there was no volatage on the last 2 emergency stops then the previous 2 emergency stops wouldnt work either as they have to go through the last 2 emergency stops to work

 

[Plonker 3]

Take a flying lead with you to test for voltage. Check continuity of each switch is working correctly as has already been said.

 

[Darkwood]

Have these stops that don't work been added at a later date?
Are you sure they are E-Stops and not functional stops for part of the machine?
Are they all marked up as E-stops?

What actual control function do the E-Stops do - are they just dropping out a master contact directly or is there a safety relay feature?
What kind of machine is this or what is the motor doing?
What is your background 'Electrically' are you maintenance running a routine check or are you experienced in Electrics and as your testing these then specifically control systems?

 

[Darkwood]

Its just surely if there was no volatage on the last 2 emergency stops then the previous 2 emergency stops wouldnt work either as they have to go through the last 2 emergency stops to work

What if the last 2 are additions and wired in parallel instead of series?... I can give you many reasons for your query but answer my other post first please.

 

[tomodo]

Im part on a maintenaince team in a factory only been qualified for a year or so and did commericial installs for most my apprentiship so not too much experience on control systems... :/ all e stops were added at the same time ive had a look through the drawings but need a bit more time to test i think . Theres basicly 6 motors running a conveyor line working together. The e-stops are there for to stop the conveyor line running in case of an emergency.

 

[Darkwood]

Due to your experience you should not be going beyond a functional operation check then hi-light your findings, the minute you go deeper you become the responsible person of the control system as you are the last one to mess with it.

This brings up a very big question 'Why hasn't this been found before?'... E-stops should be frequently checked by regular maintenance and operator checks, to say 3 lines all have the same issue shows massive H/S breaches or you have got something wrong here.

As you can't answer my other questions and as your in training according to your profile (update if out of training) you should really be asking your competent person in charge of looking over you and not on here first, he will know the machines and advice accordingly where we have to guess.

Do all the E-stop work the same and look the same and are they marked up accordingly all as E-Stops?

You have qualifications in Electrical Installation so what are you doing dipping your toes into Electrical Engineering grounds... I would tread carefully here if you or your company involve yourself into area's your not competent in and an accident occurs you could be liable without a leg to stand on.. Ill reiterate that you only really should do a functional test and report it for the attention of a competent Engineer to actually fault the issue, as you suggest the E-Stops have been added all at the same time it would require someone with control system regulation knowledge and risk assessment training to see if the upgrade meets requirements.