Longwall 6 Leg Roof Support Circa. 1965, Support capacity 300 tons
Manufacturer- Gullick – UK
Longwall Roof Support Chock and Armoured Face Conveyor Pan
Support capacity 1000 tons, Circa. 2010.
Manufacturer – Joy USA/Australia
Following the introduction of mechanized the mining in the 1940’s mining machinery developments followed with continuous miners and shuttle cars replacing coal cutting and coal loading machines in the 1950’s.
As the depth of cover overlying the Bulli Seam increased roof conditions deteriorated and production from the Continuous miner units decreased. This led mine operators to look for and alternate mining system and the retreat longwall system of mining was chosen.
The Timeline above provides a snapshot of the first steps taken by a number of mines in Illawarra to harness the potential of the longwall system to successfully mine the Bulli Seam.
A review of these first installations reveals that the roof supports supplied in the early equipment packages were manufactured in the UK, and were found to be both structurally weak and completely inadequate, and did not have the capacity and structural strength required to support and control the sandstone roof overlaying the Bulli Seam. This led to damage of the roof supports, roof falls on the face and damage to other equipment in the package in the immediate coal face area.
The above issues were addressed and progressively solved over time by the persistent efforts and tolerance of the mineworkers, mine engineers and longwall equipment manufacturers from the UK and later on Germany.
Other issues that had to be addressed and resolved included airborne dust control, the operation of the face shearing machine, and control of gas make on the face and in the goaf, adjustments to the working hours of the longwall and longwall development panels and mineworkers.
The mines listed above in the Timeline table pioneered the introduction and use of the Longwall Retreat System in this country at great expense, time and effort with a great deal of ”watching on” by other mine operators.
As time went on more bigger and better longwall installations followed, and one of some interest and success was the Miniwall (short face length) unit installed in 1990 at the Brimstone No1 Colliery in the Burragorang Valley, supplied by a Chinese manufacturer.
The longwall system is now widely accepted as the preferred system of mining with each major item of the equipment package linked to a sophisticated system of automation and control with on line access at the mine site and beyond.
Production from underground mines using the Longwall Retreat system of mining are capable of achieving an annual production of + 3 million tons per annum.
A Timeline – Longwall Faces
Coalcliff 1 Westphalia Germany -Coal Plough, 2 Leg Roof Supports, Armoured Face Conveyor (AFC)
Equipment removed & returned to Westphalia. Support density 80/115 tons/metre of face(tmf).
Coalcliff 2 Gullick 6x50ton/ leg roof supports, AFC, Powered Shearer. Support density 250 (tmf).Ranging Drum Coal Face Shearing machine installed.
All: Ranging Drum Shearers were supplied as part of all LW packages from this time onwards
Kemira Gullick 6x50ton/leg roof supports, balance of LW Package similar Coalcliff 2
South Bulli Ditto equipment package
Kemira and South Bulli Coal Industry Tribunal (CIT) permits 24 hr continuous operation of LW faces
Research modelling of roof support behaviour (ACIRL). Overseas study visits.
Kemira Roof Support legs modified from single to double acting. As supplied legs hydraulic raised, lowered by sandstone roof above.
Appin LW package installed Dowty E type six leg roof supports 600 ton yield and setting load
Appin Additional Roof Supports added at centre of face
Coal Industry Tribunal (CIT) grants permission for 24 hours per day production on all mining units 5 days per week.
South Bulli New LW Equipment package. Gullick Dobson 7 leg supports 500 ton yield & setting load 193(tfm)
South Bulli Longwall installed in the No2 Balgownie Seam
Kemira Longwall operations ceased.
South Bulli Additional face supports added & support density increased to 323(tmf)
South Bulli Japanese Taiheyo LW Package Purchased. First appearance of the Chock/Shield roof support with a non- flexible floor base
South Bulli Nine LW panels completed
Appin Westphalia LW package installed & included 4 leg Chock Shield roof supports.
Westcliff LW package purchased & included Gullick Dobson 4 leg Chock Shields of 900 tons support capacity
Corrimal Face width of 1984 installation increased from 50 to 100 metres. New Shearer installed.