Face installation / Salvage

[Wheldale]

Is there a set way of installing a longwall face? Ie are the chocks put in first then the afc etc or was it different from pit to pit? Also, is the shearer put on the afc in one piece or are the cutting drums added later?

When salvaging a face is the shearer and afc removed first?

[John]

Sept 14, 2012 13:42:57 GMT -5 Wheldale said:

Is there a set way of installing a longwall face? Ie are the chocks put in first then the afc etc or was it different from pit to pit? Also, is the shearer put on the afc in one piece or are the cutting drums added later?

When salvaging a face is the shearer and afc removed first?

Varies with conditions, basically yes to most of it.
The first pits I worked down were low advancing faces, so the faces were headed out seam height with an AB15 cutter, drilled and fired and hand loaded onto the AFC, which was "advanced" a pan about every shift. Once broke through to the tailgate, the cutter became the T/G stablehole cutter.
Chocks were then hauled up the face and installed.
Shearer bedframe got onto the face and installed on top of the AFC, plus the shearer came in in four parts, haulage gearbox, motor, interbox and cutting gearbox in one piece, then the drum installed.

I'll go through the process of installing a modern retreat face later.

[spanker]

I think it went like this wheldale but its 20 odd years now since i was mining,cant remember what the machine was called to head out the face but it had a central loading chute and was kept on centre by side rams a bit like the channel tunnel machine,then w bars were set at the back of the machine for say 20 m length these then replaced by wood props and split bars and reused at the back of the ? header differing machines were used i think for varying areas.
The face line when complete was then installed with chocks with special skids made to ease the burden on the direct haulage rope used and was a very scary practice may i say at times.
The pans and chain were then installed but dont forget we needed the power to then couple up the chain again a very scary practice with power on sprag in and slack thrown never liked putting that coupler in
The machines went on in motor,haulage ends ,jibs ,top hats,drums etc.
If i remember salvage was merely a
reverse if it was worthwhile.
Do people remember having to ditch powered supports mid panel when they were nackered,props and bars
What were those couplers called we used when one broke on the face chain ( looked like they had tennon joints and a pin)
What about when the chain broke on the bottom race oh what joy

[John]

OK, how they did it at Angus place, start with new equipment on a new retreat installation.
Pan line being installed, once clear of the T/G working down to M/G, shields are trammed up the face via a modified LHD, placed into position.
We used to have a live and return hydraulic hose laid out along the face line to pressurize the Shields to the roof.
Once enough shields are in place a fitter will be coupling them together and connecting the relay bars to the AFC, another set of fitters will be installing pansides etc as the AFC progresses towards the M/G including running top and bottom chains and coupling those.

Once all shields are in place, pressurized and piped up, and before the M/G drive is installed, the shearer is brought in on a special flat top we had made up, it has a purpose made section that couples to the panline, rack track and flat top. The front section of the flat top is supported with wooden chocks to stop it tipping during the shearer installation.
The shearer is then installed with it's two drums and cabled up, started then driven onto the pan line fully assembled.
The flat top, special pan section etc were then uncoupled and shunted back to the surface via loco.
M/G drive is now ready to be installed, then AFC/Crusher hauled up and coupled to the AFC.

While all this was going on, we the electrical staff were running CCU cables, Signal/lockout/communication cables, installing the face lighting, setting the pantech up, installing AFC, Stage loader and other cables, tidying up as we went along.

Everything was on a tight deadline of around four weeks.

It was planned out to the last nut and bolt with weekly engineers and Management meetings to sort out problems and prevent them happening in the future.

Finally everything is tested ready for the first production run, usually the Monday dayshift after installation is complete.

The AFC's we used usually had hydraulic chain tensioners and a hydraulic motor to operate the AFC slowly for maintenance purposes.
What we did in UK mines was strictly forbidden, no sprags and breaking or joining the chains under load. Strictly a NO, NO!!

If my memory recalls, we had porta packs for breaking the chain and joining it, far safer and no fingers lost or black nails.


If I've missed anything let me know.

I'll go through a face recovery next, that's more detailed, usually as we pulled the equipment off one face it was sent to the new development and installed as soon as it arrived on site.

[John]

Basically it's the reverse of the installation.

During the last week of production from the retreating face, the face crews would complete a shear, then roofbolt and mesh the newly exposed roof before advancing the shields. Main reason was to give extra support and stop the goaf from flushing when the shields were recovered. Also during the shield recovery, wood props and wood chocks were set for safety, we had tons of timber sent down and stacked near the recovery turn where the face was to cease operation.

Once finished, shearer was sent to the surface in one piece on the special flat top via our heavy diesel loco for repairs and full maintenance.

All cables, lights, communications etc recovered and sent to surface for examination and repairs as necessary.

Panline and shields removed and transported to new face line and installed, this went on 24/7 until the new face was ready for production, usually about four weeks more or less depending on any problems that arise.

Then the problems can arise once the shearer starts cutting, usually the goaf hanging up, gets a bit scary when theres a couple of hundred feet of unsupported roof behind the shields. Everyone is wondering what's going to happen when it falls.

I recall one face where we stopped cutting for a while to decide what was to be done. Cut another web, if it doesn't fall after that, the crew were to drill a series of holes in the M/G end of the goaf, and a few popper charges used.... Luckily it came, like I say scary even for seasoned veterans of longwalling...

[John]

The last faces I saw recovered with the NCB during the late 60's were 12's in deep hard, the cutting height was around 62 inches, and 43's in the Piper seam cutting height around 42 inches.
!2's weighted real bad and we had water dripping all along the face and from the roof of the two gates.
The face was backripped and rings set to recover the face.

43's converged very bad, I think most of the chocks were a write off, but the face was still backripped and everything recovered and returned to plant pool.

[welderpaul]

Really interesting posts John et al.
What happened when the roof fell behind the chocks, did it come suddenly or did you get any warning? Was the falls from rock etc dropping from the roof i.e the strata seperating or a sudden closing-up of the space? What sort of length did you have from the back of the chocks to the shearer? Did the roof sometimes fall straight away when the chocks were lowered? Presumably they were lowered from the roof just enough to slide them forward so they still, in a fashion, supported the roof?

Whats the longest a roof has been known to hold up for?

[John]

We had a "massive sandstone" roof, very heavy blocks of sandstone when the roof in the goaf collapses. The fear being that the massive weight of rock falling could cause serious damage to the shields.
Modern chock shields are operated from units called "chock control units" CCU's. A batch of supports are advanced automatically one by one from a safe position, several units from the advancing chock shields. They lower from the roof and automatically advance when they receive the signal from the system.

I've seen the goaf hang up well over 100 feet when a new face has started cutting, like I stated previously, it has stopped production on safety grounds. Our Deputy was very worried at one stage on one face, he phoned the shift Under Manager to come down to examine the goaf hang up... He inturn contacted the Manager, who was already aware from the previous shift Under Manager the safety issue and made interim plans to drill and fire a few poppers to get the goaf to drop.

After a bit of debating on the job, it was decided to lower a few shields from the roof a fraction to help shift the weight back into the goaf and see what happens.

Nothing happened other than the roof started working, a good sign, so the shields were reset, and another web was cut and the face advanced. It worked, the whole lot dropped and we resumed normal production.
Something you never forget looking back into the goaf from the M/G back into a huge void behind the shields!!!
That's the only time I've ever seen so much unsupported roof in a coal mine.

The Deputy took a volunteer back to the "bleeder heading" to examine that road to make sure it was still holding up with all the weight being thrown back from the goaf holding up.

The bleeder heading was to bleed off methane into the returns, between it and the goaf is a barrier pillar about seven yards thick the length of the face.

[John]

This is what was above our heads, the Newnes Plateau, around 1000 feet of solid heavy sandstone.

[John]

Here's Angus Place Colliery surface, you can see the northern parts of the Newnes Plateau in the background.

[John]

Some of the damage caused to Aboriginal art by the longwall below.

[spanker]

John wasn't the firing of shots in the gob an illegal act as was in the mines in the u.k.I know we at times had to fire over chocks as a last resort when they were stuck fast and the panel was being held up due to this.
The gaffers were always pressurizing as well as the men and as a young official i wanted to keep my job and my deputies ticket and have numerous tales to tell of holding up the panels.
Once held up a panel on nights for about 4 days in a row main gate rip too far behind the face, think it would have been around 12m of rip on so panel couldn't advance, overman kept coming and asking whats up, colliery overman bellowing down on tannoys from surface , 1 and a quarter % i said and that's that, very powerful H&S when used correctly.
Every a.m. shift another older deputy would come on and fire the rip. he was no more experienced than me but was happy to do this and there had been no change in the barometer readings or % of gas it was just pressure of gaffers , i would come on nights again and hold up the panel.
The following week i was demoted to the return roads, same money less hassle and no worries ;D

[John]

I didn't know the shotfiring rules in NSW, explosives were rarely used, in fact I can only recall one instance of any shotfiring at either colliery I worked at in NSW. The one instance was to pop a large sandstone rock, and Mick Potter the Manager came in to charge and fire it as none of the Deputy's had any shotfiring experience.

Mick was an ex pat Brit who had his Class 1 from the UK coal industry.
I imagine if the goaf had to be fired to get it to drop, he'd have come in with the district Inspector to supervise it. Hard to say, but I recall if it hadn't dropped at a certain point, that was the plan, drill, load a small charge and fire it.

Like I stated, the worry was if it was left too late, it could have caused a lot of damage and possibly put our lives at risk on the face.

I don't recall any adverse affects taking place, but the longer it held up, the more pressure was being thrown onto the face itself with the "pressure arch". My guess would have been, had we gone another couple of shears with it holding up, and we'd have started to have the shields yielding big time.

Most of the retreat faces I worked on down there, the goaf came in within two to three shifts of production.

[dazbt]

"Cuckoo Shot' .............. boring and firing hanging goafs, illegal but not uncommon worldwide. The William Pit disaster Cumbria 1947, a shot fired into the roof of the goaf resulted in the death of 104 men, a great book written by one this forum's quieter members, 'Amanda Roberts', entitled "104 Men" written in tribute to the memory of the men killed this disaster, well worth a read, I'll find more details of the book IBN etc later.
Longwalls in some Chinese and Indian coal mines that had massive sandstone cover progressed unbelievable distances before effective goaf collapse, in China some faces were forward bored and infused by high pressure water to forward fracture the hard coal, the same system was often used up into the hanging goafs to encourage breakage.

[dazbt]

Sept 16, 2012 13:43:15 GMT -5 dazbt said:

"Cuckoo Shot' .............. boring and firing hanging goafs, illegal but not uncommon worldwide. The William Pit disaster Cumbria 1947, a shot fired into the roof of the goaf resulted in the death of 104 men, a great book written by one this forum's quieter members, 'Amanda Roberts', entitled "104 Men" written in tribute to the memory of the men killed this disaster, well worth a read, I'll find more details of the book IBN etc later.
Longwalls in some Chinese and Indian coal mines that had massive sandstone cover progressed unbelievable distances before effective goaf collapse, in China some faces were forward bored and infused by high pressure water to forward fracture the hard coal, the same system was often used up into the hanging goafs to encourage breakage.

Details of "104 Men" by Amanda Garraway (Roberts)

www.hayloft.eu/104%20men.html

[John]

So the problem is more common than I thought then Daz.

[dazbt]

Sept 16, 2012 14:12:38 GMT -5 John said:

So the problem is more common than I thought then Daz.

Seen plenty of hanging goafs in the UK, (Top Haighmoor seam faces in the Barnsley area were renowned), but the Pathakhera(Pathekera) coal mines of Madhya Pradesh had the most extreme problems that I've ever seen, a massive coarse grained sandstone immediately above the coal seam was 'inflexible', it hung for what seemed an eternity eventualy breaking and shearing, for whatever reason in a perfect line six inches from the coal face, every chock collared instantly, the saving grace was perhaps the fact that the mines weren't very deep. The chocks were released and brought forward by means of firing 'poppers' above them and individually raising each leg by applying pressure using hydraulic intensifiers, with little more than half inch clearance gained in this way the chocks were shuffled forward and the face slowly recovered as shearing recommenced gradually regaining full section extraction. The other benefit was that the extremely hard coal was much relieved by the effect of these massive breaks and production increased ..... almost a reversal of theoretical expectation of forward and downward forces acting on the coal as in normal goaf breakage behaviour. The cycle of goaf standing was repeated, the cutting became more difficult until a sudden easing indicated the imminent break, the goaf fell, the chocks were collared and the cycle restarted ...... a great game!
I realise that we've drifted away from the Topic Title but I thought it ran with the previous comments.
I've worked on dozens of face installations, transfers, withdrawls and machinery overhauls over the years and can honestly say that none of them have ever been exactly the same and very few have ever gone exactly to plan, but as they say, that's another story ....... or set of stories.

[John]

That's probably what the Management at Angus Place were fearing Daz, I wasn't "up" on pressure arches back then and understand now how it affects the workings of longwall faces.
Doesn't matter how heavy duty the shields are, they are just designed for a certain loading to yield at, to control the roof and act like a fulcrum. Once there's a hangup and it breaks on the face edge, they have failed to accomplish what they were designed for.

I doubt very much the heavy duty Joy shields that are rated in excess of 1000 tonnes could stand that sort of weight bearing down on them.

[John]

Here's a very good write up of recovery and installation of a modern longwall, remember this isn't a one all fits all, you will see some of it refers to a colliery on the south coast, near Wollongong.

www.uow.edu.au/eng/longwall/html/changeout.html