Isolation for maintenance

[silva.foxx]

I belive there is an issue, if there is no warning that such is the case on a machine or panel that we have to work on or in.
I've seen isolators that should have been wired to BS7671 by-passed so as to provide power to parts of a machine even when the isolator is switched and locked off.

Does the panel schematics show this setup as it is?

The panel auxiliary equipment should still have mcb/fuse protection for own isolation purposes... is this provided in this case?

s.f

 

[Deleted member 26818]

I thought that were discussing Isolation?
Not main switches on machinery or panels.
To my mind an Isolator positioned adjacent to the device it is intended for, should isolate all power, not just some of the power. The clue being in the name.
A main switch situated on the machine, or the panel is another matter.
Of course parts inside will still be live, the conductors that go to the main switch for instance.

 

[shanky887614]

I thought that were discussing Isolation?
Not main switches on machinery or panels.
To my mind an Isolator positioned adjacent to the device it is intended for, should isolate all power, not just some of the power. The clue being in the name.
A main switch situated on the machine, or the panel is another matter.
Of course parts inside will still be live, the conductors that go to the main switch for instance.

the op is talking about an isolator built in to the front of a control panel.

 

[Deleted member 26818]

Ah yes, so I see.
Crossed wires.

 

[Knobhead]

We always used MCC panels with withdrawable starters which will obviously totally isolate the individual starter once withdrawn, OK so far. At the heart of the MCC would be the marshalling cabinet. The control of every drive would go through it, along with links to other equipment. Short of turning the 11KV incoming to the plant off you had no chance of isolating everything. Even then, there’d be links to other plants.

You just had to get used to testing the bit you want to work on before sticking your pinkies in.

 

[shanky887614]

We always used MCC panels with withdrawable starters which will obviously totally isolate the individual starter once withdrawn, OK so far. At the heart of the MCC would be the marshalling cabinet. The control of every drive would go through it, along with links to other equipment. Short of turning the 11KV incoming to the plant off you had no chance of isolating everything. Even then, there’d be links to other plants.

You just had to get used to testing the bit you want to work on before sticking your pinkies in.

that is like what we do, the difference being we have to work live on some bms/door access or you will shut 10 doors or the whole floor down.

you try telling the already stretched security staff they need to secure 10-15 entraces to stop the loonies getting out

 

[Jamzie]

It should be written on your permit to work that there will be auxiliary live supplies, and that you must test according before performing any work...assuming you have a permit system wherever your working of course . Stick a 'auxiliary circuits isolated elsewhere' sticker on the front.....job sorted

 

[Knobhead]

It should be written on your permit to work that there will be auxiliary live supplies, and that you must test according before performing any work...assuming you have a permit system wherever your working of course . Stick a 'auxiliary circuits isolated elsewhere' sticker on the front.....job sorted

Who is going to issue that permit? Often there will only be one electrical person on a plant, he should be conversant with the systems in use.
If a person needs a note on the permit warning of multiple control systems do you think that person should be working on the system?

All equipment on our plants came under the jurisdiction of a process supervisor. He would make out a permit to me handing over an individual machine or a section to me as shift engineer giving me jurisdiction.
I would then involve other trades as isolation may not be just electrical.
Electric.
Hydraulic.
Pneumatic.
Steam.
Noxious gasses.
Radiation.
Explosion.
Kinetic energy (often overlooked but a killer non the less).

Then there are the environmental hazards that could endanger others, not just the individual.

By handing the plant over it comes under my jurisdiction as the shift engineer. If the work is say a single motor then I will isolate and lock off locally, for larger systems then isolation will be “as required”. As required is what I deem is required to make the job as safe as possible.
One particular job springs to mind, nothing major, change a thermocouple. 77 individual isolations required.
Any of the other tradesmen on shift could ask me to prove isolation but it was also up to them to ensure their own safety.

Go in to an environment where multiple systems are integrated then much of the onus is on the individual. Stray control voltages are often the least of your problems.

 

[Jamzie]

Suppose it depends which avenue you've gone down Tony. I can only refer to heavy industry and power generation, as that's all I've worked in where permits are concerned. As a SAP on a coal station, I used to isolate, prepare and issue permits for apparatus upto 11kV. If there were any anomalies then these had to be clearly stated on the document and verbally read out. I assumed permits were standard affair in industry.....obvious not! Never done a 77 point isolation for a thermocouple though.

 

[Deleted member 26818]

Another problem, is if the person who would issue a permit, is not aware that a particular machine will have live parts when isolated, how will they know to issue a permit?

 

[netblindpaul]

Spin,
They are not competent to issue a permit, if they are not aware of the risks, full stop.
That so called argument is a non-starter.

 

[TailSpin]

Thanks All

for your comments .
This perticular Panel has main isolator on the front with inverter inside with some other circuits which stay alive when isolator is off , they incude panel lights which is fed from a transformer, and cooling fans.
These things are fed from a second multicore cable.
This could bring in another question is it a duel feed Panel ?
and the panel isolator is the local isolator for the motor .
If this is the case I would need a permit to work.
Just to mention the Isolator before this panel will kill both supplies.
I guess I need to be more intouch with BS EN standards for machinery panels,


Regards
John :thinking:

 

[netblindpaul]

Now that does, sound wrong.
All equipment of all sorts in the one panel, should, really be fed from the same incoming supply.
That is all barring interlocks between machines say.
The lighting should be fed from the incoming side of the main isolator in suitable cable to it's own circuit breaker/isolator.
Who CE marked the panel?

 

[Knobhead]

Suppose it depends which avenue you've gone down Tony. I can only refer to heavy industry and power generation, as that's all I've worked in where permits are concerned. As a SAP on a coal station, I used to isolate, prepare and issue permits for apparatus upto 11kV. If there were any anomalies then these had to be clearly stated on the document and verbally read out. I assumed permits were standard affair in industry.....obvious not! Never done a 77 point isolation for a thermocouple though.

I’m only referring to heavy engineering, it’s all I’ve ever done apart for a short spell as production manager.

The permits I issued as AP/SAP would be in addition to the permit issued by the plant supervisor. He hands the section of the plant to me, I in turn would do the MV isolations/earthing required and issue a permit along with the original permit to the work team.
If the work was purely on the distribution system then the plant permit wouldn’t be required as it wouldn’t be affected.

The 77 points of isolation, it was on a coal plant.

 

[Darkwood]

I've worked in many industries subbing in and the most strict one I found was Allied Colloids (Chemical works Bradford) now known as Ciba and was the scene of one of Europes worst chemical fires... You needed a permit and a working pass for any power tool or anything that could create a spark... ..a simple 30min job always took a morning because of the red tape attached. Lost a work collegue their through a skylight - not expected from a company with strict H&S in place. The rest of the companies I work for don't even know what risk is.... Asian, Polish you name it operating machinery with no guards and can't speak the lingo never mind read the warning on the machinery..... I forgot how many jobs I've walked on shook hands - seen the state of the place and walked out and said good luck!