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Post by welderpaul on Feb 22, 2013 14:15:32 GMT -5
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Post by John on Feb 22, 2013 14:35:25 GMT -5
Looks like an ancient Victor flameproof light fitting, they were rated 120/240 volts, my memory says edison screw, but it's been a long time since I saw one and changed the bulbs.
I do recall one that had been wired to 240 volts, the only one underground that had, and I was on lamping up with another apprentice on days. We replaced the bulb with one from the box we had, put the top back on and powered up.....It was the brightest light in the pit for about five minutes!!!
All the others were 120 volts..
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Post by welderpaul on Feb 22, 2013 14:46:30 GMT -5
Cheers John - i knew you would know ;D
What era...1970's?
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Post by John on Feb 22, 2013 14:54:58 GMT -5
Cheers John - i knew you would know ;D What era...1970's?
Belmos also used to make flp light fittings, chances are it may be their design.
I still have my old Belmos "popeye" a brass box spanner with a couple of allen keys set into it, it was nicknamed a "popeye" after the cartoon character, looked like his pipe. The box spanner end fitted all the light fitting flange bolts. I think they were 1/4 BSW. |
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Post by John on Feb 22, 2013 15:08:16 GMT -5
I put the lamp in photoshop to read the etching on the glass, I've never seen words etched in any light fitting that said tested to....the rest was off the photo...It could predate the 1950's.
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Post by welderpaul on Feb 22, 2013 15:15:49 GMT -5
Did you ever have to test them for their 'flameproofness'? Presumably they were airtight to prevent gas entering the body?...
Were the cables in a conduit, or were they connected up with SWA?
How did earthing work in a mine..connected back to an earth rod on the surface or earthed in the mine?
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Post by John on Feb 22, 2013 17:18:35 GMT -5
Did you ever have to test them for their 'flameproofness'? Presumably they were airtight to prevent gas entering the body?... Were the cables in a conduit, or were they connected up with SWA? How did earthing work in a mine..connected back to an earth rod on the surface or earthed in the mine?
FLP gear is not air tight, far from it, the door/lid gaps allow the equipment to "breathe". The flamepaths are designed to cool burning gases in the event of an internal explosion.
The definition of an FLP chamber is one that will withstand an internal explosion, (of a predetermined mix of methane and air) without distortion or destruction.
FLP lights had FLP sockets on them with swa cables terminated into plugs. The plugs were usually filled with compound. The plugs had removable pins, and when plugged into the lamps had two studs with a nut to tighten the plug onto the lights socket.
Usually, most collieries had two large earth "mats" in two locations, made up of copper bars riveted together...Don't ask how big, never saw one, they were buried at depth somewhere near the main surface substation.
They could be disconnected to test for conductivity in accordance with the M&Q Act.
All underground earthing was done via the main feeders armouring. They were double wire armoured cables.
I think in the last few years there has been a rethink on earthing systems at collieries in the western world, as one underground gas explosion was proven to have been caused by a lightning strike on the surface. Taking into account that mine was over 1000 feet deep, it mystified the investigators.... Turned out a roof bolt carried enough charge to discharge the lightning strike into active workings where a build up of methane had taken place.
There was another incident in Australia where a conveyor structure was charged by lightning, OK, it was the main drift belt, but regs were introduced where the conveyor structure had to be bonded throughout it's length and earthed at various points to the underground electrical earthing circuit, ie main feeders.
So we are still learning!! |
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Post by smshogun on Feb 8, 2014 14:56:46 GMT -5
I can possible help with the earth ring John as many were updated with the rising quantities of mechanised equipment being installed.
Earthing ran back to the main power house and everything there was bonded, the earthing ring was the ring of copper earth spikes knocked into the ground to provide the earth.
Earth spikes were standardised because copper was expensive and it was easier to have one standardised design to buy in, they were copper rods 8" outside diameter with a 5 1/2" inch bore and came in a variety of lengths, to make your own you ordered a 7 yard length which later became 7 metres, you had a design from area to form your ring.
You cut them to length + 3" to ensure they weren't too short, you soldered on a spike to one end which was essentially a point and on the other end you soldered on a cap which had a series of grooves in it.
You bored a hole to the prescribed depth and excavated around the top, but in practice they excavated an area first and bored your holes to the pattern designated in the plan, you dropped your earth rods in to give you a circle of earth rods, you connected them by dropping in 2" x 1/2" copper strap into the grooves in the caps to form a solid and continual earth bond between your ring of copper earth rods, they were then soldered to the caps using oxy acetylene.
You repeated this and ran a second ring of copper strap around the now inserted earth rods to give two continual earth bonding rings.
Where they met you had to overlap them to form one ring, you did this by overlapping the copper strap by 12" either side and bending it 90 degrees, these two bent flanges were drilled and 1/2" brass bolts were inserted to hold them solid. You repeated this with the second ring, you now had your termination points for connecting to the main power house.#
Copper earth strap was run to the power house in one length and the tail was left for connecting to the new earth ring, the bolts were undone and the new copper strap was cut to fit and drilled, it was tinned and so were the bent flanges on the inside, the earth strap was coated in flux over the tinning and the bolts tightened, the whole assembly was then heated to solder the new earth strap to the flanges of the ring while a second man tightened the brass bolts while the solder was still molten.
The earth ring was tested by a specialist who drove a stake into the ground a prescribed distance from the new earthing ring and he tested it, the whole lot was buried and could remain for a century or more. |
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