MICRO SWITCH ON A MACHINE DOOR

[stillp]

i dont know if we are looking at this too deep , i only asked as i was given a switch to try to fit and it was a simple 1 amp 230v door contact switch.
The machine has a stop start old metal type beside the door so to try it i diverted the stop wires through the switch....it worked fine but was the wrong way round, you had to have the door open to work the machine....the green start had to be pressed manually to restart the machine , so if it basically did the job although its hard to get to the contactor it can not be too much a load..and all connections are covered...

That's the way door contact switches work!
What you need is a door interlock switch from one of the global electrical switchgear manufacturers such as Schneider, Rockwell, Siemens, etc. You will need to know the coil rating of the motor starter in order to get a suitably rated switch - "1A 230V" is not sufficient unless you know the utilisation category of the switch and the coil rating of the starter.
If you don't understand anything I've said then you really need professional advice, since this is a machine safety issue.

 

[bhm1712]

If this is in a work environment the company should have relevant safety standards and safe systems of work in place. Based on these, the machine must be assessed to see what category of safety is required. Once this has been assessed, an appropriate safety circuit must be designed and fitted to the machine which will provide protection which meets the required category of safety.

If this is not done, as the competent person ( which i presume you must have been deemed if your working on this?) then the responsibility lies with you as well as your company.

However, from your apparent lack of knowledge of machine safety i would suggest you leave well alone unless you dont mind the risk of causing death, serious injury and the associated criminal proceedings afterwards.

 

[bernardgreen]

i dont know if we are looking at this too deep ...

You can never look too deep when it is a safety matter. If the switch you fit fails to protect life and limb due to negligent design and install then you will be liable and could be facing legal action if some one is injured or killed if the machine runs when the door is open.

 

[WELLSIANA]

the machine would not be able to start with the door open as the stop circuit would be broken the the same as hitting the stop button...it could not be reset until the door is closed...i do take on the injury side but you would do well to have a death unless you physically offered your neck and wrists and even then you would have to be at a fantastic angle as its about 3 inches deep...its not a large machine although i take accidents happen it would have to be long odds...as for the botched e stop system well at present and since the day dot it has had no safety other than the stop / start button...if the door is fitted with a break device which shuts it off and is locked that has to make it safer as such....we are not in some massive works factory here just a small car panel shop

 

[Spark123]

Not for the squeamish:
http://www.youtube.com/watch?v=ylUSEGjl6Ig

 

[bhm1712]

the machine would not be able to start with the door open as the stop circuit would be broken the the same as hitting the stop button...it could not be reset until the door is closed...i do take on the injury side but you would do well to have a death unless you physically offered your neck and wrists and even then you would have to be at a fantastic angle as its about 3 inches deep...its not a large machine although i take accidents happen it would have to be long odds...as for the botched e stop system well at present and since the day dot it has had no safety other than the stop / start button...if the door is fitted with a break device which shuts it off and is locked that has to make it safer as such....we are not in some massive works factory here just a small car panel shop

Unfortunately that wouldnt wash in a court of law. It doesnt matter whether its a small car panel shop or a 400,000 square foot factory. You dont understand the ins and outs of a safety circuit. It doesnt matter whether the machine has been without safety since the year dot. YOU ARE NOW MODIFYING IT. A stop circuit is NOT a safety circuit. Using a simple switch to close the stop circuit, inline with the stop button does not meet any safety category as required by the machine safety directive. If the switch failed open and somebody used the stop button to stop the machine instead of just opening the door to stop it, they could go in and be in contact with the blade when somebody inadvertently pressed the start button. Due to the switch failing open, then the machine would start.

 

[bhm1712]

health and safety legislation applies to large and small business alike. I wouldnt be touching this machine in the way you plan to. I have had the unfortunate experience of witnessing a colleague and friends thumb and index finger ripped off to the stub because somebody had messed with the machine safety circuit. He was clearing a jam of cardboard from around a conveyor belt drive shaft. Due to somebody having linked out the safety key switch (to go in the machine the key had to be removed, and put around your neck on a chain) the conveyor system was remotely started by the warehouse management system whilst my friends hand was under the belt and pulling card out from around the drive shaft. Different circumstances from yours i admit, but it goes to show that accidents can happen even if you think they cannot, or are unlikely to occur.

 

[WELLSIANA]

they are not relying on the opening of the door to stop it......the door is closed permantly and only has access to the blade wheel...its locked...the stop start is used to operate the saw....but should the door be openend by mistake the machine would shut off...and if left plugged in and working on the machine of which anyone should know better of course it would still break the stop circuit so the machine could not be used....

 

[bhm1712]

you still dont get it do you?!!!

OK IN BIG LETTERS

SCENARIO: MACHINE BLADE REQUIRES CLEANING, OPERATOR STOPS THE MACHINE WITH THE BUTTON. OPENS THE DOOR, GOES INTO MACHINE WITH HANDS ON THE BLADE

ISSUE: DOOR SWITCH HAS FAILED WITH THE CONTACTS OPEN - SO THE SWITCH IS ACTUALLY IN THE SAME STATE AS IT WOULD BE WITH A CLOSED DOOR.

RELEVANT EVENT: SOMEBODY PRESSES THE START BUTTON, MAYBE EVEN BY ERROR OR ACCIDENT. MAN HAS HAND CHOPPED OFF BECAUSE THE MACHINE STARTED

 

[bernardgreen]

If you fit a safety switch to the cover of a rotating saw then it is almost certain that to comply with safety requirements you will need to fit an electrical lock to prevent the door being opened when the blade is rotating. After the stop button is pressed the saw will continue to rotate, during that time the door MUST be impossible to open.

The fact that some one has decided it is necessary to fit a safety switch suggests they have started having concerns that locking the door with a key is no longer a safe way to prevent injury.

 

[WELLSIANA]

The door switch to fail and someone to open the door to work on the blade and someone switch the start button on which is 6 inches away from the door.....yeah i get it !!!! could you give me some odds on that and do not forget that someone should be competant so hence should have turned it off and unplugged it......and got a key ...!!but thanks for all your interesting views.

 

[bernardgreen]

It is the Health and Safety people you and the machine's owner will have to satisfy.

I repeat the question in a more detailed way " If the existing system of the door being locked with key was acceptable in the past then what has changed to require lock AND a safety switch being fitted ?" Did someone run the machine with the door open ? Is that person still working there ? Is that the person who the switch is intended to protect. ? Are there others at risk from that person's negligence in leaving the door unlocked ?

 

[bhm1712]

The door switch to fail and someone to open the door to work on the blade and someone switch the start button on which is 6 inches away from the door.....yeah i get it !!!! could you give me some odds on that and do not forget that someone should be competant so hence should have turned it off and unplugged it......and got a key ...!!but thanks for all your interesting views.

I dont really find it very funny that you are finding all of these views a bit of a laugh or a bit silly....You have time and time again failed to realise that this is real world stuff. Accidents happen for the strangest of reasons and course of events. Look at Chernobyl - what where the chances of all of those events occuring which lead to the explosion? what were the chances of the series of events which lead to piper alpha?? all of those people involved probably said the same as you - "what are the odds of that"

Go ahead, fit your simple 230v micro switch because you wont listen to our advice anyway. I hope for your sake that nothing happens but remember, people here have been doing stuff like this for years - i have for the last 10 years in the high speed manufacturing sector for pharma and tobacco, and these silly little failures and incidents do happen.

 

[ban-all-sheds]

The door switch to fail and someone to open the door to work on the blade and someone switch the start button on which is 6 inches away from the door.....yeah i get it !!!! could you give me some odds on that and do not forget that someone should be competant so hence should have turned it off and unplugged it......and got a key ...!!but thanks for all your interesting views.

WELLSIANA wrote "i am only just starting out on commercial work after 35 years in domestic."


I suggest you go back to domestic.

 

[bhm1712]

I just read the other post about E-stops.

Wellsiana - it seems as though you are not qualified to do the job you have now got. How did you manage to get taken on? I would imagine the company is just another one of those small one or two man bands who have no regard for H&S legislation and prefer to ''do it the old fashioned way''

Thats all well and good, as years ago thats how it was, but today we cannot work in the same ways. You should walk away from this company before the preverbial hits the fan. It sounds like the company has no safe system of work, health and safety responsible person/s, risk assessments, standard operating procedures, standard maintenence instructions, PPM, etc etc.....

This is all stuff which must be carried out or in place. As Bernard has already said, if they are now asking you to fit some form of safety devices, then it must mean either something occurred, somebody complained, or the HSE is already looking at the place.