Commercial & industrial faults.

[Knobhead]

Here’s one to start me off

This nearly resulted in the death of an electrician!

Day 1
Lost one phase to a large storage shed DB. Immediately heads off to where the “Plumbers from Hell” are digging a trench for a new 6” main, low and behold the raged remains of cable dangling out of the side of the trench 2 phases still live. Sorted! Test at the main sub, one fuse blown, so isolate and get them to widen the trench (hand digging this time not the back actor).
Day 2
2m of new cable 2 scotchcast joints, bobs you uncle job done. Replace all fuses and restore supply, test at shed still one phase down Back to sub all fuses OK
One of my joints must be faulty! Isolate again cut the cable before my joints. Strip cable as for a third joint so I could spread the cores to test safely. Restore supply test again, still one phase down Time to go home!
Day 3
Arrive on shift and got talking to Albert the electrician going off shift. “I diverted that cable 20 years ago, it feeds a DB in the compressor house now, the storage shed is fed from there”. Visit to said DB, blown fuse to storage shed! Joint No.3! Now full supply to shed.
Day 4
Attempt to kill Albert

20 years and he’d never got around to changing a label

 

[Darkwood]

Hi tony, Im thinking the above should never have happened from your procedures to safely isolate, i come across miss labled supplies constantly and to assume the cable you isolated is actually the correct cable without confirmation is a tad worrying, i assume after isolation of the 2 remaining fuses the supply will have been checked in the shed as well as the damaged cable, followed by a continuety test to confirm cable is the one and the same. After the repair an insulation test will also have picked up the error or mismatched lableling too, had their been a serious accident then the liability would have been wholy rested on your shoulders irrespective of the poor lableling, i would take this one as a big lesson learned.

 

[Knobhead]

Continuity checks were not possible for the conductors, as it would have meant a major power outage on a plant that was running. The point of origin was a board fed by 2 X 1200A feeders. To do a continuity check I would have had to expose the busbars. This board was from the 1950’s so not up to modern standards, built like a tank but safety wasn’t such a consideration then.
Practical means of testing need to be born in mind.
Knowing what this plant was like it’s a wonder the fuses had been down rated from 450 to 150A. I found one 16mm cable with 800A fuses!

 

[WDMDL]

I went to look at a job today, which I've had to turn down - it's out of my league.
Evidently a phase went down before Christmas and the relevant fuse was replaced.
But just after new year there was a surge and a lot of fried IT equipment followed by a total power failure.

My friend works at the place, his boss asked him to investigate (He's 17th Edition but not 2391).
Some building works had taken place and the submain cable to their distribution equipment had been visibly damaged.
It was looking like that was the cause and a new length of cable would have to be jointed in.
After isolating and carrying out continuity tests he found the Neutral was open circuit.
Cutting the cable after the visibly damaged part, he tested again found that the neutral was actually open circuit on the supply side of this.
Following the cable back towards the intake house, he could not believe what he saw...

Someone had made a branch joint into the cable.
Now I've done plenty of Scotchcasts, Raychem shrinks and a few Birketts in my time, but I've never seen anything like this!
They had jointed a 4c70mmsq XLPE SWA branch into a 4c19/.064" PILC main cable (just over 35mmsq).
Now I'm not sure how the conductors were joined, but whoever did it obviously didn't realise the lead sheath was there for more than just keeping the paper insulation dry.
And the joint enclosure?
A bit of neoprene sheet cable-tied around the lot!
Looks like the actual failure occurred because the paper insulation got too wet and started arcing between the conductors. The connections themselves hadn't failed.

Not surprised a few things blew up with the Neutral down though... the generator they're running off at the mo is showing 85A L1, 55A L2, 20A L3 so quite out of balance!
PIRs? What are they?
If one had been done in the past 10 years I'm sure the Zdb would have been found to be way too high and investigated.

A 200m run with 300A fuses per phase too...

Out of interest, what's the copper equivalent CSA of the lead sheath?

I have a few pictures but need to upload them somewhere first.

Simon.

 

[Knobhead]

Once did a Scotchcast breach joint in to a paper lead with PVC. Nice job, all armours and sheaths bonded all tested perfect. It was a couple of weeks before it was made live due to rerouting the original cable. Test again, all OK so made it live.
A couple of weeks later, bang one phase supply fuse blown. Test again all OK so made live again. Foreman is now giving me earache about the joint, so chop the joint out and replace it with a new breach and a through. Test again all OK so made live again. A couple of weeks later, bang, the same phase supply fuse blown again. This time shorted to earth, but not a good short. Set up the CAT signal gen and started to follow the cable with the detector. Noticed a bit of ground that had been disturbed but the signal carried on. Out of curiosity I set to with a shovel where the ground was disturbed and low and behold there’s the cable just 6” down with a plastic bag wrapped around it! Our wonderful plant operators had been cleaning up a few months before and had used a front-end loader shovel instead of digging by hand as they had been told to do. On damaging the cable there was no bang so they wrapped it and buried it. Being summer all was fine until the rain started then the cable would blow but the heat of the fault would dry out the insulation. So two more through joints later we were back in action. It had got to the stage where we thought of replacing the cable but no one seemed keen to pull in ½ mile of 50mm 4c.

 

[vaughant]

I think the above show that it`s more often human intervention rather than actual installation problems that give us the most grief!!!
I`m mainly control and you get some crackers in that field,not really as dangerous as above but baffling nonetheless,like one day when I got called to a job as a trade just out of my time by an old boy who no matter what,couldn`t get his machine started,there were two other long established sparks there too,both scratching their heads.
No drawings for the machine and all relay controlled,oh great!!!
After much deliberation and wire pulling,embarrassing I know,we determine that K25 needs to be energised,we can find no voltage to the coil of the relay.
It`s getting near our 2pm handover now and the older boys have given up,but it`s bugging me so I keep tracing wires which lead off to a tool replacement table (machine is a pittler drill).It looks like this drill table hasnt been used for 50 years but there is a small bit of conduit going into it,which appears to power a lamp,but using a torch I count 4 seperate cores. After removing the 20 or so siezed M8 bolts,I get behind a guard and follow the unmarked cables up to a sort of mechancial counter.
It`s after 2 now and the others are in their cars going home and I decide to check out this counter,which reads 23437 or some sort of random number,but I`m a bit reluctant to press it.
The operator comes in and we have a chat about whats happenned and he says hes off to get a tea,hangs his bag by the tool table,so I decide to try it again,electrical fairies and all that and it fires up!!!
Confused, I go off to inform the operative it`s running and notice the counter at 00000.He tells me he resets it the start of each shift to know how many bits he`s done,although it`s actually for tool life that never really requires resetting,unless of course it goes over 23400,you get a few more,but then it randomly cuts out!!!!!FFS!!!!!!
The guy had been off for 3 months on the sick and as they only did a few hundered parts a shift,his constant resetting meant it never went over that amount!!!He`d ran the machine for 30 years continually and had just done this from day one,never thought to mention it.
Oh and he had the electrical diagrams,he kept them safe in his locker just incase they got lost!!!
Gotta love production!!!
A good operator in this game can be your best friend,he runs the machine everyday and probably cleans up 50% of the problems before you get there but this also poses problems as very often you can become too reliant upon them and sway away from basic principles,getting this to start needs that etc,it`s awkward when you`ve got management/foremen etc breathing down your neck and the operators telling them he know`s its this as it happenned 20 years ago!!!
I`ve even been in a position where management have told me to replace a particular item beacause an operator told them that was what`s wrong,say a 3 phase motor etc and it`s taken me to physically prove to them the motors good for them to accept that I need more time to investigate,strange how management seem to think you dont want to make the job easy and that your somehow trying to find a more difficult outcome,crimes of the past I suppose!!!

 

[Smudge]

Part of our factory set up involves using a lade system to use river water for the cooling side of some heat exchangers for our refrigiration plant. Our on call electrician was called out to a problem with the pump supplying this in the early hours. He found that the local isolator had failed and the pump was single phasing. A simple fault easily rectified. A report was written against the job by said electrician, although he did not go into detail about remedial action taken, just that the fault had been sorted.

6 months went by, and one of the fitters comes shouting and swearing at me, soaking wet. He was going to work on the fridge plant, so he isolated the feed pump as he has been trained, locked it off and then went to begin his tasking. He split the inlet pipe of the heat exchanger just as the isolated pump automatically started up, ultimately flooding the boiler house and soaking a now very upset fitter.

The electrician hadn't replaced the faulty isolator, but had bypassed it by jointing the phases straight through and replaced the lid. He had written on the isolator, 'isolate elsewhere' which the fitter did not see. His excuse was...'we didn't have a spare isolator in the stores, and the shift men were hassling me about the system being down, so i done what was necessary to get production running again.'

This is an approved electrician with nearly 40years experience that prides himself on being 'old school'.

Disciplinary hearing continues...

 

[vaughant]

^^^^^ don't see a lot wrong with what he did other than it should have been documented better that the isolator was no longer in use but again it's proving a lack of communication causes major issues.

 

[Darkwood]

Ruddy nora ...... this bring back memories, this thread was started 2yrs ago on sat' strange how it keeps rearing its head up.

 

[stef]

Should have removed the operating gear of the isolator and properly taged it out or remove the switch completely and use a temp terminal box. Although, no local isolation which is required by the regs...

That refers to Smudge's post of course.

 

[vaughant]

Should have removed the operating gear of the isolator and properly taged it out or remove the switch completely and use a temp terminal box. Although, no local isolation which is required by the regs...

That refers to Smudge's post of course.

Not sure if you've done much in a production environment but it's often the case that a temporary repair will be done when production requires it and then the correct repair is followed up at a convenient or safe time,some systems are essential and could actually cause more problems if switched off in the eyes of the regs.
As for local isolation you must be joking whether it's regs dependant or not I could probably give you over a hundred examples just where I work alone!!!!
often in industry what's right and what's done are two very different things.
In the above case the main problem is a lack of a correct communication system,there should have been a correct labelling system and the right people informed before the fitter tried to isolate the pump.
You should still test after isolation anyway plus realistically a decent electrician will always isolate further back if possible,I wouldn't be happy about a fitter locking off thinking that's ok without consulting the spark first.

 

[Knobhead]

When a process is making money every ones happy. But once it’s broken down it’s costing money, you’re priority is to get it up and running again. It’s all right saying what should be done, you try and convince a production manager that’s jumping up and down on your neck!
I’ve resorted to all kinds of tricks, the important thing is that whatever I’ve done is recorded and put right as soon as practicable.

 

[netblindpaul]

As long as it's not downright dangerous Tony!
I have been asked to bypass critical/essential safety switches in the past & refused, not popular with the client, but, my line manager would not give the written go-ahead, so, customer had to wait for spares.

 

[Knobhead]

Give me some credit Paul!

 

[snowhead]

I've linked out safety switches before to allow machines to run till the end of a shift.
The only condition was I stand by the machine, if I move the machine was locked off.

Things change tho', now I won't leave a D.B cover off even if the terminals are shrouded and I've got the switchroom key, there are too many people about nowadays who start screaming dangerous.

 

[Smudge]

The spark in question ended up getting a wrist slapping. I personally think he was lucky. To defeat the local isolator on a machine that is automatically controlled and filling out a report on the work saying that its 'fixed', IMO is lack of awareness of potential increase of hazards.
Like has been said, his failure to communicate properly could have led to a much more severe result. Although you can't predict the actions of other tradesmen (in this case the fitter), all reasonable precautions should be taken to prevent an increases to hazards to persons, livestock and property...I'm sure I've read that somewhere...

 

[stef]

Wrist slapping is generous in this case, could get the sack for gross misconduct.