Rank: Guest 
|
Posted By James Dudding
Hi all,
I have come across an interlock gate switch which only stops the machinery when it is in automatic mode. The user can move certain parts of the machinery in manual mode with the interlocked gate open. This doesn't seem right to me, are there requirements with interlock switches that they must stop the machine in all operating modes?
Thanks
James
|
|
|
|
|
|
Rank: Guest
|
Posted By Mike Draper
Not necessarily, James.
Some machines require limited operational capability during setting up and maintenance activities, although it is usual to restrict access to such functionality only to authorised and trained individuals. This may include the use of key controls and permits.
|
|
|
|
|
|
Rank: Guest
|
Posted By Pete Longworth
This is a normal situation with power presses. Usually a power press will have an inch control which allows the ram to be lowered and raised while setting, attaching or removing die sets. On some of the older presses the ram had to be brought down using a metal bar in the fly wheel, but usually an inch control is used. As previously mentioned, these are key controlled, to by-pass the interlock guard.
|
|
|
|
|
|
Rank: Guest
|
Posted By James Dudding
Thanks for the responses so far.
This particular interlock is like this so that one person can work in the guarded area whilst another operates the machinery in manual mode. There is no permit or key system, you simply turn the control from auto to manual and it can run with the interlock gate open. I don't believe that interlock switches are supposed to be wired like this? Shouldn't the person within the guarding have control of the machine e.g. by hold to run device or similar?
Thanks
James
|
|
|
|
|
|
Rank: Guest
|
Posted By David Bannister
James, is it possible for the person inside the guarding to be injured by the operating machine? How likely is this scenario? How bad would it be?
Why does the operator need to be in this position? Can the task be done another way? For each of these questions seek a truly authoritative viewpoint.
Finally, ask the Operations Director (or equivalent) how they would be able to answer these questions in Court.
The answers to these questions should point you in the direction of what is to be done.
|
|
|
|
|
|
Rank: Guest
|
Posted By Tabs
"one person can work in the guarded area whilst another operates the machinery in manual mode"
This is blatantly unsafe and should be corrected immediately. It is almost certainly going to be found to be gross negligence in any court to allow it to continue to be used.
My advice is to have it modified as soon as you can, and to take it out of service if possible until such time. If not possible, issue and record an instruction that manual operation must not be used.
Control of any moving part should rest solely with the person setting the machine. No communication system is robust enough to allow the kind of setup you describe.
If I sound paranoid, it is because I have seen too many three-fingered setters.
|
|
|
|
|
|
Rank: Guest
|
Posted By Brando
Agree with Tabs.
Our machines ( which include bottle filling machines and blow moulding machines ) have auto and manual settings but they only allow basic setting up procedures and inching of the machines when the guards are open.
Brando
|
|
|
|
|
|
Rank: Guest
|
Posted By Andrew Dickenson
hi
firstly please allow me to introduce myself, i am a control systems engineer (new to this forum) and couldnt help but show interest in these threads.
i'm thinking that perhaps a new perspective may help.
initially there's the obvious safety flaws in that someone can be in what we call the guarded "safe zone" whilst someone else can operate, albeit "inch" the machine, this control design is terrible and really needs looking at urgently.
depending on the age of the machine it could well be as simple as a software change on some plc's!
in normal design practice we would specify castell interlocks to prevent the machine being used in any other mode other than "inch" when the guards are removed.
hope this helps
andy
|
|
|
|
|
|
Rank: Guest
|
Posted By Pete48
There is an court report in the current SHP that clearly indicates the importance of proper controls and how easy it is for people to operate unsafely if badly designed machinery is in use. (employee fined for endangering fellow employee)
I agree with the other comments about the lack of safe design.
I am so old these days that I come from the generation that was taught that if ever I entered a protected zone one better have either the Kastell key in my pocket or the fuses from the machine supply! Unless that is one was on inch-patrol; but that should be set up so that it could only be operated locally to the actual work site and was limited to the area required to be inched; the person doing the inching had to operate the control and not allow anyone else to do so. on pain of instant dismissal.
I still have all my fingers and thumbs even if my brain is now somewhat depleted:)
Of course these days we have all this electronics which can make some design elements much simpler I am sure.
But surely the principles remain constant? "no access to dangerous motion and no dangerous motion during access".
|
|
|
|
|
|
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.