Bit of advise with machine safty

[Paul1985]

hi hope you guys can help me out little, my work has asked me to change a couple of things on some machines at work. The one machine it a very old hydraulic break press they want me to fit an emergency stop pedal the stop circuit is n/c 415v. where is the best place to order one from or could i make my own using a limit switch and some bar (we have a fabrication workshop) all the ones i have found are 230v and look really small.

The other machine is a roller to roll steel sheet they only want it to work when holding the forward or revers button what is the best way to do this. its two 415v coil and contactors

thanks

 

[Darkwood]

I hope you can understand that what you are asking can't really be answered on here and should not be either, an Electrical Engineer familiar with the machine and its operations will need to do a risk assessment to possible re-design the control system to allow for safe use and running with a fail safe operation. You cant just add a E-stop or alter the operation of the machine as who-ever does will hold all responsibility for any incidents or accidents that can be attributed to its controls or lack of safety.

This as i have mentioned to many in your shoes is a big deep hole to step in and you do at a great risk as there are alot of regulations and standards to comply to and if the machines need these additions it clear they dont meet them anyway.

My advice is to get a control panel builder and fitter in, do not try undertake this work yourself, and anyone who thinks they can simply add an E-stop on your set up is well out of his depth and you wont be covered even if they have Public Liabilty insurance..... as they by-step all the essential regulations.

 

[Darkwood]

To head you in the right direction you can get E-stop pressure pads or bars that run the length of the machine and are part of a safety relay Selv set-up but just a simple addition can cost upto 1k to upgrade the existing controls etc none of the E-stop products come cheap and you shouldn't be fabricating them yourself a deffo NO NO these systems are made to high standard and are functionally fail safe as they are design to protect life.

As for the dead man controls for the sheet steel roller we can't advice without knowing how it operates at the present and exactly how this is acheived within the controls but if your lucky it may just mean the disconnection of the retaining link of each contactor but should only be done after assessing the set-up as it exists.

 

[Paul1985]

Cheers for the advice. You see We had are insurance and risk assessment guys round and they picked up on these machines and for the break press they give use 3 options 1. foot pedal hold on to run 2. foot pedal to stop 3. fit an emergency stop. i thought just adding another stop switch on a pedal was the best option. the machine its self dose not have a emergency stop at all.

cheers again

 

[Paul1985]

only just read you second post. i will let the guys at work know see what they are going to do. with the rollers that's what i thought but i wondering will that stop the emergency stop from working they are wired like a stop switch in sieres on the overload n/c side. to me on a quick look it just looks like 2 dol starters just forward operating 1 contactor and reverse operating the other.

 

[Darkwood]

Yes i get this alot and unfortunately its not a case of just adding a remote E-stop in most cases by tapping it into the control circuit, it can in some cases mean a rehash of the whole controls as activation of E-stops should stop the machine (in your case, other senerio;s exist) then require a seperate manual reset in most cases to re-energise the control circuit and then the start button can be pressed, so you see a small E-Stop button can seem just a simple addition but in reality can require alot of additions to existing if not a complete re-design.

An Electrician is probably not the best choice to call in unless they are experienced specifically in machine control systems and competent to upgrade them, an Electrical Engineer or Electrical Control Engineer is possibly the person to seek.... post your whereabouts there may be a few on here although most members are not experienced in this area their are a few who are and may even add to this thread.

 

[Paul1985]

I would like to get in to control systems but it seems really hard to get into no where seems to do good courses or companies just want experienced people. you have been very helpful so thank you

 

[Darkwood]

Look up Engineering courses as oppose to Electrical courses then sub section it to contol systems, you wont find it usually without using the Engineering term.

 

[Knobhead]

Brake presses and E-Stops from what I recall don't sit easy. You need to vent the hydraulic pressure immediately to stop the die travel.

 

[SheffSimon]

I would ask to see the risk assessment before I did anything else.

What fixed guarding was recommended etc.

The fitting of electrical controls to make something safer is last on the list of things to do to make a machine safer.

I'm also struggling with "three options" bit to be honest. Sounds like a p*** poor risk assessment.

If you've paid money for this, I would be expecting some firm requirements, not three options.

 

[Paul1985]

no guarding was recommended for both machines which is strange. I havn't paid anything i have not had any thing to do with the risk assessment my manager has and the guys he had in sorted it out, he just come to me and said he has to get these problems sorted.

Any way I did speak to him today and I don't think he knows I told him about some of the problems you guys had mentioned he said he would get back in touch with them im not sure but think he could have just been trying to pass the book to me

 

[cunnishaun]

As an electrical engineer I would strongly recommend the control circuit is altered, by someone who knows what they are doing, to include a safety relay ie piltz. The safety circuit HAS to be separate to the rest of the controls and it has to stop the complete process immediately! That's y a simple "estop pedal" is not efficient! Stick to the rules!

 

[Darkwood]

The guy that came in an risk assessed is most likely just following guidelines for machine safety and putting recommendations i.e. E-Stopping radial drills etc should see the drill cease movement within a set time and if not a dc injection brake is usually requested. Hes not an engineer or experienced in electrics hes a pen pusher with a list of standards for each machine.

Once you get you request then its down to the installer to know the relevant safety standards of E-stops systems or control circuits etc and also to recommend where the assesser may have failed.


Its like trying to rent your house and you are told to repair a hole in the roof by the estate agent but when you get the roofer in he shows you that the roof is structurally unsafe and requires work to reinforce it first, ones a pen pusher with a guidance list the other is the proffesional who knows the requirements.

 

[Darkwood]

As an electrical engineer I would strongly recommend the control circuit is altered, by someone who knows what they are doing, to include a safety relay ie piltz. The safety circuit HAS to be separate to the rest of the controls and it has to stop the complete process immediately! That's y a simple "estop pedal" is not efficient! Stick to the rules!

Ive fitted E-stop foot bars before and is sometimes the better option for machines like rollers or presses where the user works in the mid area where E-stops are difficult to place, they do make them specifically for this purpose.

 

[cunnishaun]

I've noting against foot pedal used in an e stop circuit but to use them in the control circuit effectively as an extra stop button is a no no! In the factory where I work we have approx 100 transfer presses which are fully guard with interlock switches which are designed to knock off the machine when the guard is opened. Or are locked and cannot be opened until the machine has come to a stop. Our e-stop buttons are wired via piltz relays. Better safe than sorry!

 

[Darkwood]

I've noting against foot pedal used in an e stop circuit but to use them in the control circuit effectively as an extra stop button is a no no! In the factory where I work we have approx 100 transfer presses which are fully guard with interlock switches which are designed to knock off the machine when the guard is opened. Or are locked and cannot be opened until the machine has come to a stop. Our e-stop buttons are wired via piltz relays. Better safe than sorry!

I get your angle now but wasn't the way it came across and yes foot pedal machine control common pressure and release is just a start/stop not an E-stop but with single user operation and they are feeding product into rollers, cutters, or presses where the product is large enough to give them enough space to create a hazard then a foot bar E-stop can reduce the risk substantially ... i fitted one to a machine that pulls product into machine and the guy got his watch caught which dragged his hand in .... he crushed 3 fingers but had he not had the E-stop bar he would be looking at losing his arm.....the guards would have stopped his bulk been dragged in but little left of his arm if he couldn't stop it.

 

[Paul1985]

Dose any one have any information on designing e-stop circuit correctly or control circuit PDF files or even books they could recemend. Don't worrie I'm not doing the job but could come in handy with fault finding and just for my own knowledge so I don't end up in a simular situation in the future

 

[Richard Burns]

This guide from schneider may help as a ready reference.

 

[Paul1985]

Cheers I have downloaded that been looking through it.