|
Post by shropshirebloke on Mar 1, 2011 16:54:18 GMT -5
I'd also assumed that the CO2 was expanded by electrical heating from a shotfiring battery (see my earlier posts, # 17 & 30). I'd wondered then how much current would have been required to fire a round of say half a dozen shots.
Subsequently I discovered that the battery was just used to ignite a "heating powder" charge at the outer end of the shell - this provided the rapid heating needed to expand the CO2 quickly enough for the shell to provide an effective shattering effect.
Maybe the modern system for surface use dispenses with the heating powder and just depends on electrical heating - obviously on the surface a suitable power supply would be much easier to arrange?
|
|
|
Post by erichall on Mar 2, 2011 6:04:52 GMT -5
Must admit that I can't say exactly how the heating took place. Time does many things with the memory. I do know, however, that the exploders used were the same 6-Shot Batteries used for conventional firing, as well as the 'Little Demon' Single shot Battery.
|
|
|
Post by shaunmg on Mar 16, 2011 6:47:09 GMT -5
Maybe the modern system for surface use dispenses with the heating powder and just depends on electrical heating - obviously on the surface a suitable power supply would be much easier to arrange? Nothing has changed regarding the heaters; they are still manufactured to the exact specification at the site that has been operation since the 30s in Faversham Kent. Much has changed regarding the tubes, restraining methods and refilling operation, but not the heaters. I visited the Faversham factory about 18 months ago for the second time. It is an old First World War munitions factory and nothing has changed since it was built, it is like stepping back in time. There are a couple of men and about 6 or seven women working there. We buy our heaters direct from the factory Although I was a shotfirer myself, I had no experience of cardox when working underground. It is only in my present business I gained the experience. The modern shells we use do not have wings or pawls as they call them. The fizzing as described by Eric is due to insufficient co2 in the tube either by faulty filling or leaking. After filling we weigh them and submerse both ends of shell into water to check for leakage. If we still get a fizzer, as we call them, then we handle with care, as the shell becomes very hot and will burn bare hands I have some amazing pictures of the factory, if I can fathom out how to reduce size I will post them
|
|
|
Post by John on Mar 16, 2011 7:20:35 GMT -5
Photo sizing can be done in Photobucket, then just C&P the IMG code from under the photo and paste it directly into your post here.
|
|
|
Post by Sam from Kent on Mar 18, 2011 18:26:22 GMT -5
WHERE IN fAVERSHAM ARE THEY? I LIVE NEAR THERE AND WOULD BE INTERESTED TO SEE IT
|
|
|
Post by johnnyfitter on Jan 16, 2015 18:21:50 GMT -5
I was an Apprentice Fitter at Rossington Colliery from 1961 until 1966.
Rossington Used Cardox explosives for most of the period I worked there. All shells once fired had to be returned to the surface to fitted with a new fuse and bursting disc, they were then refilled with Co2 with a compressor. The Co2 in each shell was contained as a solid gas. We had about 15 coal faces in the early 60's, most of which were hand filled, so most of the coal had to be bored and fired. It was a military operation, with each face using several hundred shells each day.
There a whole department and workshop dedicated to the job.
Sometime just before I started at the pit they had installed three Armstrong Airbreaker compressors.
The compressor was sited at a different side of the pit to serve it's own area. Each compressor was fitted with a 120 (maybe 150) HP motor. It was a six stage compressor. The LP stage outputted at something like 45 psi and stage No. 6 outputted at 12,000 PSI. (This piston was only around 3/4” dia and was fitted with (I think) 22 piston rings. The output stage of the compressor was fitted with a Fuse Tube. This was a copper tube, machined to a size that allowed it to burst at a pre-set pressure, thus protecting the system, and it was not uncommon to have to replace fuse tubes at least every 3 months for some reason.
They always ran very hot, and it was never a pleasurable experience working on them. You burnt your fingers a lots and got very sweaty in an already hot pit.
The whole of the pit was connected with the special air mains so that whichever district was shot firing other compressors could always kick in if needed..
The mains consisted of 1” OD x 3/8” bore, High tensile steel pipe. It had a 1” NF thread on each end, and the end of each tube was machined with a grove to allow a copper washer to seal when pipes were screwed together using a 1” socket.
I used to work with the Guy responsible for maintaining the Airbreaker Compressors. His name was Ron Davis and he was build like a sumo wrestler.
In 1961 I worked with him installing new air mains to the West Side of the pit. We installed around 30 pipes per shift and we got paid a bonus of 3 pennies per yard on top of our wages.
Every joint thread had to be run down with a 2” NF die nut. The range end was propped up on to a short length of timber into a 'V' notch cut in the end.
I would run the socket onto the free end by hand while Ron cleaned to other end of the range. I would place a copper washer into the socket and tamp it down gently to the pipe end.
I would then hold my end high in th air above my head as Ron screwed the free end on to the range end. When the ends met the piper were screwed together using two pairs of 24” Stiltsons until Ron could not get any more on them.
The nuts on the Stiltsons normally lasted about 1 month before we had to fit new ones. That was how tight they had to be, and how strong Ron actually was.
No one ever wanted to undo a pipe that Ron had tightened, and I don't recall ever one of his joints ever leaking.
At the end of each range connections were make using Cupro Nickel tube. This was about 3/8” diameter and it could be bent by hand as appropriate for connection.
The 1” main were also installed along the coal face using special quick release screwed connections (But they were almost impossible to remove), then at intervals along the face shooting valve connections were installed to allow the shot firer to move down the face shooting the shell.
Most faces had several shells available, sometime longer or shorter, and the shot firers had a box of Slugs. Slugs were bursting disks numbers 1 to may 3 or 4. The lower the number the higher pressure it would fire at. After each shot the shot firers mate would recover the shell, screw off the end, slide in to a slot a new slug, get clear, and the shell would be fired. When a complete coal face needed firing the air pressure would slowly drop in the mains. With this drop the three compressors would kick in automatically and start to top up the mains, but they were not of sufficient capacity to keep the pressure up at 12000, and thus the whole system pressure would slowly fall.
The shot firer would notice that the slug would struggle to fire, so he would drop to a No.2 slug, then No. 3, and so on. He would eventually get down to around 8000 PSI, and at this or maybe a little lower, the shots would no longer burst the coal effectively, then he would have to wait until it built up to a pressure high enough to complete the face.
It was very effective and lasted to my knowledge for maybe some 10 years or more.
|
|
|
Post by smshogun on May 20, 2015 8:44:49 GMT -5
The hydraulic burster was designed to replace Cardox and they were merely a hydraulic ram working in contraction using both tapered ends running against a split, tapered outer sleeve to give around 1-2.5" of expansion, and several variants existed, their downside was they needed a 4" hole to be fitted into, but in coal it was easy drilling as you drilled minimal amounts of holes. They were designed to produce lump coal for steam raising in steam engines as opposed to the much smaller power station coal.
Several types existed:
Pre-pressurised types were loaded with hydraulic pressure underground by pre charging from the chock pump, these were them primed just before use and only used chock tank oil which is obviously water and soluble oil.
Non-pressurised types uses a single hydraulic pipe from the chock tank operating through a single valve.
Both types incorporated a small accumulator to intensify the working pressure and for the pre-pressurised types you opened a valve on the end, this allowed the stored pressure to work through the accumulator and gave you about 30 seconds to get away from it before it had enough pressure to force the coal apart, obviously with the single pipe non pre-pressurised type you just opened the valve.
Several variants existed and they came as short single types or longer multiple types and the single and multiple applied to how many internal rams there were.
|
|
|
Post by andyexplorer on May 20, 2015 15:39:51 GMT -5
A few videos on youtube , this is the best one I think
|
|
|
Post by newdigate on Jul 5, 2018 5:35:10 GMT -5
I served my apprenticeship with the NCB as an electrician. Trained for face work later as strippers were earning twice my wages. That would have been about 1953. First day as a qualified stripper the Cardox shells were introduced. I had all my top coal gone when the borer and shot firer got to my stint. The Cardox shells had a pointy arm on either side so as soon as the det' was fired these arms came out and gripped the sides of the bore hole to stop the shell from shooting out.We left our stints while the shot firer did his job. When I got back to my stint all the bottoms had gone,, the same applied to every stint on the face. All the bottoms had been shot up the waste. They were only used about thee or four times and then the use of Cardox finished.
|
|
Clive
Shotfirer.
Posts: 168
|
Post by Clive on Jul 6, 2018 14:45:18 GMT -5
I don't know how the company stayed in business They were useless. We tried them many times. Rep would come back with a so called better product....just as usless
|
|