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re-wire
May 9, 2012 13:28:06 GMT -5
Post by Wheldale on May 9, 2012 13:28:06 GMT -5
Do mines ever get re-wired? Ie, as cables have a life span do older mines have them renewed?
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rac
Shotfirer.
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re-wire
May 9, 2012 13:45:37 GMT -5
Post by rac on May 9, 2012 13:45:37 GMT -5
Do mines ever get re-wired? Ie, as cables have a life span do older mines have them renewed? never heard of it unless upgrading capacity or other problems/faults. praps a case of if it aint broke dont fix it. |
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re-wire
May 9, 2012 14:10:40 GMT -5
Post by John on May 9, 2012 14:10:40 GMT -5
Do mines ever get re-wired? Ie, as cables have a life span do older mines have them renewed? No, never, armoured cables have a life span longer than us.The only time a cable will be replaced, is if it ever breaks down and the fault is not visible, then it's replaced and the faulty one sent to a cable workshop who locate the problem, cut the cable at that point and add a cable coupler. The only other time to replace cables would be if you're upgrading, say to carry more power, 100 to 3oo amp, or upgrading from 3.3Kv to 6.6Kv or 11Kv and the old cables aren't rated for those voltages. My first pit had cables dating back to the 1930's at least!! If a cable develops a fault, say phase to earth, you can usually find it by walking it, generally blows a hole in it. We'd cut it, and add a FLP 2 part cable coupler, fill each section with compound, and couple the two sections together. Do an insulation test, and if all's well, repower it up. Two elecs can joint a cable in about 90 minutes or so, then wait for the two part compound to cool off. |
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rac
Shotfirer.
Posts: 87
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re-wire
May 9, 2012 15:15:12 GMT -5
Post by rac on May 9, 2012 15:15:12 GMT -5
 Do mines ever get re-wired? Ie, as cables have a life span do older mines have them renewed? No, never, armoured cables have a life span longer than us.The only time a cable will be replaced, is if it ever breaks down and the fault is not visible, then it's replaced and the faulty one sent to a cable workshop who locate the problem, cut the cable at that point and add a cable coupler. The only other time to replace cables would be if you're upgrading, say to carry more power, 100 to 3oo amp, or upgrading from 3.3Kv to 6.6Kv or 11Kv and the old cables aren't rated for those voltages. My first pit had cables dating back to the 1930's at least!! If a cable develops a fault, say phase to earth, you can usually find it by walking it, generally blows a hole in it. We'd cut it, and add a FLP 2 part cable coupler, fill each section with compound, and couple the two sections together. Do an insulation test, and if all's well, repower it up. Two elecs can joint a cable in about 90 minutes or so, then wait for the two part compound to cool off. armoured cables sent to a cable workshop? never heard that one john trailing cables yes.in my experience if an armoured cable failed and could'nt be jointed it was just replaced with another then lost/scrapped.mind you with the scrap price of copper now it would be worthwhile salvaging and weighing in.90 mins to joint a cable hmm bloody good going what type of coupler is that?not a 3.3kv/6.6kv half coupler surely
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re-wire
May 9, 2012 16:00:03 GMT -5
Post by John on May 9, 2012 16:00:03 GMT -5
Pits I worked at sent them to central workshops if we couldn't locate the fault by eye.
90 minutes is long enough to make an end off on a double wire armoured cable, the old red sheathed ones, 3.3Kv 300 amps, that's each, not the complete pair... Most time is lost locating the fault, unless someone saw a flash.
First time I put a plug on a 6.6Kv cable, was at Boulby, kept getting called out the workshops, but still managed to complete it in a shift. Now they were big couplers!! But once you've made one off, the rest are straight forward.
We used to "race" each other at Brit Gypsum, still could never beat our elderly elec though!! He could nearly do two to my one, and we used to make a hell of a lot off at that mine, both armoured and trailing cable ends. We even used to repair our own trailing cables off down there.
On copper costs, I'd say with the high price now, if the NCB was still operating, they'd probably go back to aluminium cables once more, jeeze they were stiff!! Hated them.
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re-wire
May 9, 2012 16:30:16 GMT -5
Post by Wheldale on May 9, 2012 16:30:16 GMT -5
Couple of years ago I had my house re wired. I thought the mines electrics would just be like twin and earth! ;D
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re-wire
May 9, 2012 17:15:42 GMT -5
Post by John on May 9, 2012 17:15:42 GMT -5
Couple of years ago I had my house re wired. I thought the mines electrics would just be like twin and earth! ;D That would have made our job real easy.... Highest voltages I've worked with U/G was 11Kv, although when I was leading hand, I was authorised to enter the switchyard and control room , there was 66Kv in that yard and the boss warned me, "stay on the marked paths if you go out there, NEVER stray from them" I never went in the yard....  I did a weekly in the control cabin to make sure nothing was amiss. U/G has many safety circuits, has to have in that environment. There's some sophisticated gear underground these days, even the shearers are sophisticated, tons of electronics in them, whereas when I did my apprenticeship there was only one electronic component in a shearer, the pilot circuit diode. Now Joy is using electronic motor speed control for haulage, and cutting head motors for load control. Even the AFC has load controls for motor efficiency these days. Soft start conveyor motor control instead of the old fluid couplings. I often wonder what electricians will be working on in another hundred years time. |
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rac
Shotfirer.
Posts: 87
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re-wire
May 10, 2012 8:06:58 GMT -5
Post by rac on May 10, 2012 8:06:58 GMT -5
Pits I worked at sent them to central workshops if we couldn't locate the fault by eye.
90 minutes is long enough to make an end off on a double wire armoured cable, the old red sheathed ones, 3.3Kv 300 amps, that's each, not the complete pair... Most time is lost locating the fault, unless someone saw a flash.
First time I put a plug on a 6.6Kv cable, was at Boulby, kept getting called out the workshops, but still managed to complete it in a shift. Now they were big couplers!! But once you've made one off, the rest are straight forward.
We used to "race" each other at Brit Gypsum, still could never beat our elderly elec though!! He could nearly do two to my one, and we used to make a hell of a lot off at that mine, both armoured and trailing cable ends. We even used to repair our own trailing cables off down there.
On copper costs, I'd say with the high price now, if the NCB was still operating, they'd probably go back to aluminium cables once more, jeeze they were stiff!! Hated them. agree with you there john re the aluminium cables terribly stiff especially if in a cold enviroment,did'nt help having to go up a size to get the same current carrying capacity as copper.dont know which was worse the solid core (blue sheath) or the stranded (yellow sheath) neither of them good at jointing with having to shape the cores etc.they stopped using it in n/derbys area due to a high failure rate of 300a couplers. |
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re-wire
May 10, 2012 8:29:00 GMT -5
Post by John on May 10, 2012 8:29:00 GMT -5
It interacts with other metals and forms an oxide, when that happens it forms a high resistance joint, that's why you had failures. Aluminium is used a lot here stateside by elec utilities for overhead lines, although installed by me, the service feed from the meter/isolator box on the pole is aluminium, we are supposed to use a special paste when terminating it due to it's highly reactive qualities.
Aluminium armoured cables were just showing up when I left the NCB, so never had to joint one....
When I worked in NSW collieries in Oz, all termated cables using pins and to be sweated, the law didn't allow grub screw termination.
Straight jointed armoured cables could be crimped connections then sealed with either epoxy compounded boxes or straight two part mix. Last I used was one made by 3M, Scotch, it came in a two part clear sealed bag we put inside out shirts to warm up while we jointed the cable, when warmed up and ready, we broke the seal between both sections and kneaded the resins together, then the whole envelope was put into what I can only describe as a "grease gun"!! and we pumped the resin into the joint box. That was rated over 6.6Kv as the main system was 6.6Kv. Only time I've used that type of joint box.
We were at one point allowed to Scotchcast trailing cables as a temporary repair on fixed points of trailing cables, ie the shearer cable that was inside the flexible gate end cable carrier.
I had one nipped one night after the face was pushed over, it blew out through the sheath. I opened the cable up and it was "repairable, just need some insulation removing from around a couple of cores then some conductive tape over the top of that, then a Scotchcast around it to seal the temp joint. No idea why the Inspectorate banned them, they were perfectly safe, never heard of anyone getting hurt by them. They were perfectly acceptable on outbye pump cables etc. There was no way you could put a Scotchcast on the "used" part of a trailing cable, they were just too rigid.
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re-wire
Oct 14, 2012 15:02:52 GMT -5
Post by tonys on Oct 14, 2012 15:02:52 GMT -5
No, never, armoured cables have a life span longer than us.The only time a cable will be replaced, is if it ever breaks down and the fault is not visible My first pit had cables dating back to the 1930's at least!! Around 1985 the company I worked for sent some cables for testing at BASEC, installed in the 30's we were hoping to squeeze a bit more life out of them. The report went along the lines of "good for another 50 years". They were in our main crushing plant, always cool and nothing ever got desturbed. As for Scotchcast! I hated the stuff after the first time I used it, pulling the bag seal apart the bag split! |
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re-wire
Oct 14, 2012 15:14:37 GMT -5
Post by John on Oct 14, 2012 15:14:37 GMT -5
No, never, armoured cables have a life span longer than us.The only time a cable will be replaced, is if it ever breaks down and the fault is not visible My first pit had cables dating back to the 1930's at least!! Around 1985 the company I worked for sent some cables for testing at BASEC, installed in the 30's we were hoping to squeeze a bit more life out of them. The report went along the lines of "good for another 50 years". They were in our main crushing plant, always cool and nothing ever got desturbed. As for Scotchcast! I hated the stuff after the first time I used it, pulling the bag seal apart the bag split! |
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Mick
Shotfirer.
Posts: 163
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re-wire
Oct 16, 2012 9:58:39 GMT -5
Post by Mick on Oct 16, 2012 9:58:39 GMT -5
Had a trailing cable blow on 04s at wheldale i was only 6ins from ware it went,it blinded me and had to be taken out of pit.
It turned out that the cable had been damaged before and the tag not been changed,so what should have been a 100 yrd cable turned out to be a lot shorter.
I was off work for 2 weeks,mines inspector was told and i had you go to a meeting with him and management.
Was told later that the power was not tripped,and some of the lads down the face got a belt as well.
The story was sent round some of the pits,i know there was a notice put up at Manor coll at Wakefield because some of my mates asked about it.
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re-wire
Oct 16, 2012 10:21:01 GMT -5
Post by John on Oct 16, 2012 10:21:01 GMT -5
Only ever saw one cable "blow out" was the shearer gate end to mid face section, I was advancing a shield and never spotted the cable had formed a loop until the shield trapped it, wasn't much of a flash as both the GEB and transformer E/L circuits tripped power pretty quickly, that was an 1100 volt cable too.
Same pit, and one of the longwall transformers had been brought to the surface, the 11Kv circuit breaker had ionised for some reason. I have never seen so much soot inside an FLP chamber in my life! It was thick on the sides, bottom, top and inside door.
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