Rank: Forum user 
|
Is there a legal minimum distance that an isolator switch can be located from the equipment? In order to improve and make or Lock Out Tag Out more effiecent we are considering relocating some of the isolator switches to one central location (on the equipment) so we can attach multiple hasp cable LOTO device to multiple isolators.
The equipment is designed to have 3 x augers, 1 x pump, that all make up the function of 1 piece of equipment but the isolators are located on opposite sides of the equipment. When isolating with 3 people working on the equipment we currently have to apply 4 padlocks per person to machine meaning there is 12 padlocks in total. If we centrally located the isolators next to each other (all labelled) then a cable lock out device would be attached each operator could fit 1 padlock each to isolate all 4 of the switches (1 padlocks per person rule always required!)
This does not involve moving the isolators miles out of the way but i'm worried that there is a requirement for a minimum distance that we would be not be in compliance to if we made this change.
Any machinery boffins out there???
|
|
|
|
|
|
Rank: New forum user
|
There is a difference between an isolator and an emergency switch.
According to BS7671 (IEE Wiring Regs) the isolator need not be adjacent. It could even be in another room provided it is lockable in some way. The isolator is primarily there so that an electrician can access and work on live parts safely - it can also be for someone to work on mechanical moving parts safely.
Machinery which has accessible moving parts must have an emergency switch or stopping device. This must be "readily accessible" to the person using the machinery.
Without seeing the arrangement, I suspect the augers will each need an emergency switch within reach - normally a red mushroom button - and then you could quite safely put the isolators in a common location.
Why should you trust me? I lecture on the regs for the IET.
|
|
|
|
|
|
Rank: Forum user
|
Thank you Mike,
Appreciate your help. I'm aware of the emergency stop and isolator difference and we do have E-Stop faciltiy at close proximity to operating areas. This issue is related to LOTO procedures.. so i'm very thankful for your assistance with the location of the isolators.
Thanks again,
|
|
|
|
|
|
Rank: Super forum user 
|
Peeps, we are straying away from 7671 here into the realms of PUWER98 & BS EN 60204-1, the "equivalent" of 7671 for machinery, obviously EAWR89 is also relevant. You may also need to consider the Machinery Directive, and the Low Voltage Directive, under which there are a plethora of standards which can be “used” for compliance.
Whilst I agree with MikO wrt the location of isolation devices and the equipment they control, you could take this one step further and isolate at the circuit protection device at the origin of the circuit, as an MCB and other protective devices are classed in 7671 as suitable for isolation are they not.
One has to be careful of the suitability of emergency stop devices for LOTO function. They are not acceptable. Also, I personally do not like them being called emergency switches, sorry. Emergency switching to me is emergency switching of energy sources, i.e. electricity, hydraulic, pneumatic energy etc.
An emergency stop will not isolate the source of energy unless it is configured in a similar manner as an emergency switching system as defined in BS4163.
To my mind an emergency switch for electrical energy would be a switch disconnector, suitably coloured Red & Yellow. This would be robust enough to operate as an isolator & a functional switch.
I would question why there are so many sources of electrical energy supplied to a single piece of equipment?
Perhaps a better design for the future would be suitable, remembering that I have not seen the equipment! I was taught “Design for Maintenance” was a key factor when I was designing equipment and plant layouts!
HTH
Paul
|
|
|
|
|
|
Rank: Forum user
|
Hi Paul.
I need to clarify something here as I think theres been a mix up. Underno circumstances have the E-Stops been included as any part of the LOTO process. This is quite clear and fully understood in our procedures.
The issue relates to the requirement to break open equipment and remove guards for cleaning and maintenance/repairs of items of equipment. There are a number of mechanical hazards, augers and pumps that need to be isolated and LOTO prior to work commencing.
My question is related to isolating switch location of each individual mechanical hazard on this piece of equipment. There are 3 augers each with their own isolator switch and a pump with its own isolator. The main isolator at the main panel is not in the same room as the equipment but it all mechanical devices can be isolated at the machine. Are you saying that when this machine needs to be isolated for repairs, clean the LOTO should always be at the main panel? Is it not acceptable to control from the switches (yellow/red switch) at the equipment?
Thanks,
|
|
|
|
|
|
Rank: Super forum user
|
safetyman2010,
No I am not saying that it is necessary to isolate at the main panel, but it could be an option for you?
The main panel you refer to, is this the electrical distribution board for the area being served, or is it the main control panel for the piece of equipment?
I am not fully aware of the equipment layout you have however, it seems to be an assembly of separate but interlinked individual pieces of machinery?
Or, are these local isolation devices just that, local to the motors/machinery for LOTO use? With the equipment all supplied from a single machine control panel?
If all of these electrical supplies to the local motors originate at a machine control panel, which in itself has a single point for isolation of electrical energy, then surely this would remove the need to re-locate the individual isolators as this single point at the control panel could be utilised for LOTO?
This would remove all electrical energy from the complete machine control system.
One word of caution, IF the motors are driven by inverters or variable speed drives etc. then should they be commanded to run whilst the local isolator is in the LOTO state, this can cause damage to the drive electronics depending upon the design of the internals.
This could be avoided by upstream isolation as described above.
This will all depend on how the units are configured.
HTH
Paul
|
|
|
|
|
|
Rank: New forum user
|
Safetyman2010,
We have similar issue in the lift industry. Our rule of thumb is that the main isolator must be within easy reach of the lift machine room doorway usually within 1M. A secondary isolating switch maybe required adjacent to the main control panel if you are not able to reach of the main isolator when standing in front of the control panel. And finally an Emergency stop button as previously described within easy reach of any rotating parts, this could mean 2 / 3 E stops.
With the addition of secondary switches you always have the possibilty of isolating and following LOTO procedures for individual pieces of equipment. It can also give an engineer piece of mind if they are working on a piece of equipment that is a distance away from the isolator that has been tagged out.
|
|
|
|
|
|
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.