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Edit Comment Close Premium member Presentation Transcript LONGWALL MINING : LONGWALL MINING Venkat COAL - Background : COAL - Background COAL : COAL Most abundant fossil fuel Major fuel used for electricity generation world wide Safe and secure fossil fuel Cost effective WORLD ELECTRICITY GENERATION(% By Fuel-2005) : WORLD ELECTRICITY GENERATION(% By Fuel-2005) (Source: BP Statistical Review of World Energy 2005) WORLD SCENARIO : WORLD SCENARIO As the International Energy Agency has commented: “World reserves of coal are enormous and compared with oil and natural gas, widely dispersed... The world’s proven reserve base represents about 200 years of production at current rates... Proven coal reserves have increased by over 50% in the past 22 years. The correlation of strong growth of proven coal reserves with robust production growth suggests that additions to proven coal reserves will continue to occur in those regions with strong, competitive coal industries.” INDIAN SCENARIO : INDIAN SCENARIO Coal accounts for 63% of Country’s energy needs. Coal based thermal power generation capacity presently stands at 61,476MW and a capacity addition of around 60,000 MW has been targeted in next 7 years. Total annual hard coal production in India is about 373.79 million tonnes (2004-05) out of which nearly 80% is from Opencast Mines. SCCL share is 10%. INDIAN SCENARIO : INDIAN SCENARIO Coal Demand & Production (in Million Tonnes) (Source: Coal Summit 2005) Proved coal reserves at end 2005 : Proved coal reserves at end 2005 RESERVES - India : RESERVES - India (Source: GSI Report, January 2005) As on January 2005 in Billion Tonnes RESERVES - SCCL : RESERVES - SCCL As on January 2006 in Million Tonnes LONGWALL – World & India : LONGWALL – World & India Longwall in India : First mechanized powered support longwall caving face was introduced in August 1978 at Moonidih, CIL. First Longwall face introduced in GDK.7 Incline in September 1983 in SCCL. There is no much improvement taken place in India in respect of Longwall technology due to various reasons. Longwall in India Longwall in India : Serious efforts not made perhaps due to availability of alternate technologies. Upgrading not made when most of the world improved in 90s. Spares management was poor. Coal India do not need due to opencast and flat gradients. Use of indigenous spares of low quality is increased, which deteriorated the condition of faces. Longwall in India Reasons for less concentration on Longwalls in India Australian Coal Industry : Australian Coal Industry World’s largest exporter of coal 230 mt worth Au$ 16 b (Rs. 53,000 crs) in 2004. Most of the 74 bt reserves in NSW and QLD 378 mt in 2004, 82 mt from underground. 24 longwalls produced 73 mt in 2004 and plans to produce 96 mt in 2006. 148 wagons per rake 2 km length, 8,500 t. Australian Coal Industry : Australian Coal Industry Less than 25,000 employees. Each mine has 120 to 200 permanent and 100 contractors’ men. Productivity: OMY is 15,000 t. OMH 5t for UG, 10t for OC Longwall Geometry - World : Longwall Geometry - World LONGWALL - METHOD : LONGWALL - METHOD Slide 18: Direction of retreat FACE Bottom Gate TOP Gate LONGWALL GENERAL LAYOUT Dip direction Longwall mining method includes drivage of two long roadways in coal and joining them at the end by a perpendicular drivage forming a face. Different Longwall Methods : Different Longwall Methods 1. Longwall Advancing Method 2. Longwall Retreating Method Modern Longwall Plans in Australia : Modern Longwall Plans in Australia Modern Longwall Plans in Australia : Modern Longwall Plans in Australia Gateroad Plans in Australia : Gateroad Plans in Australia Advantages of Longwall Method : Advantages of Longwall Method High Recovery. Lower Operating Costs. Easier to Supervise. Easier to Train Miners. Works Under Weak Roof. Clean Coarse Product. Simple Ventilation. Disadvantages of Longwall Method : Disadvantages of Longwall Method Small Problems = Big Production Losses. Dust Control Difficult. Overloading Conveyor System. Retreat Longwall Mining Advantages Over Advance Longwall Mining : Retreat Longwall Mining Advantages Over Advance Longwall Mining Reserves are “Proven” on Development Gateroads in the “Solid” Gateroad Development is Separate Water Easier to Control Recovering Equipment Easier Easier Ventilation Retreat Longwall Mining Disadvantages Over Advance Longwall Mining : Retreat Longwall Mining Disadvantages Over Advance Longwall Mining Delay in getting production for the preparation of first panel. MAIN GATE WITH SWITCH TRAIN : MAIN GATE WITH SWITCH TRAIN C H O C K S LONGWALL METHOD : LONGWALL METHOD Retreat per day –5 meters/day Production –3000 Tonnes/day Thickness of 2.0 m to 3.5 m POWERED ROOF SUPPORT AT LONGWALL FACE : POWERED ROOF SUPPORT AT LONGWALL FACE LONGWALL - EQUIPMENT : LONGWALL - EQUIPMENT Equipment for Longwall Mining : Equipment for Longwall Mining Powered Face Supports Shearer Armored Face Conveyor Conveyor System Electricals & Communication Slide 32: CHOCK SHIELD SUPPORT Powered Roof Supports (Two legged) : Powered Roof Supports (Two legged) POWERED ROOF SUPPORT AT LONGWALL FACE : POWERED ROOF SUPPORT AT LONGWALL FACE Capacity -4x450 T to 4x800 T Thickness of -2.0 m to 3.5 m Weight -12 T to 20T Weight -1.5m Powered Face Supports : Powered Face Supports Armored Face Conveyor : Armored Face Conveyor Armored Face Conveyor : Armored Face Conveyor Slide 38: Armored Face Conveyor Armoured Face Conveyor (1 pan set) : Armoured Face Conveyor (1 pan set) Shearer working at Longwall Face : Shearer working at Longwall Face SHEARER WORKING AT LONGWALL FACE : SHEARER WORKING AT LONGWALL FACE Capacity -2x375 Kw Thickness of 2.0 m to 4.5 m Web -0.63/0.85 Drum Dia -1.6 to 1.83m Length -10m Shearer : Shearer Shearer - Front Half : Shearer - Front Half Shearer - Rear Half : Shearer - Rear Half Shearer Drum : Shearer Drum Cutter Bits with Spray : Cutter Bits with Spray Conveyor Belts : Conveyor Belts LONGWALL – STRATA CONTROL : LONGWALL – STRATA CONTROL Slide 49: STRATA CONTROL PLAN OF A LONGWALL PANEL Slide 50: Strata monitoring of in a Longwall Panel Gate Road ways studies. Face monitoring. Goaf monitoring. Slide 51: Gate Road ways studies – Convergence indicators Load cells Tell tales Stress capsules Strata monitoring The maximum convergence depends on the following factors : The maximum convergence depends on the following factors Caving properties of the strong bed causing weightings, indicated by the Caving Index Number ‘I’ of the strong bed. Thickness of cavable beds forming the immediate roof in between strong bed and the coal seam in terms of height of extraction. Resistance offered by the support system. Convergence and Roof Degradation at Longwall Weightings (GDK.10A) : Convergence and Roof Degradation at Longwall Weightings (GDK.10A) Slide 54: Face monitoring– Leg Pressures Leg Closures Face Convergence Strata monitoring Rated Support Resistance : Rated Support Resistance The Rated Support Resistance should take into account the following deficiencies during the actual operation. Leakage in leg circuit Setting load deficiencies Miscellaneous (deviation from normal span, premature bleeding of leg circuits, etc.) Slide 56: Goaf monitoring – Remote convergence indicator Multi Point Borehole Extensometer (MPBEx) Strata monitoring Longwall Caving Diagram : Main Overburden Longwall Caving Diagram Hc Hs F Dc Cl Ro A Gob Coal Floor Immediate Roof Shield Support T Longwall Caving : Cut after cut, shear after shear the AFC & subsequently Chock shield supports will be advanced and the immediate roof rock above caves in. Longwall Caving Slide 59: As the retreat further proceeds substantial area of main roof rock forms a plate & caves in by imposing load on supports, known as main weighting. Main Fall Slide 60: Periodic Fall LONGWALL – ORGANISATION : LONGWALL – ORGANISATION Slide 62: Organisation Chart Slide 63: MANPOWER Pre shift EE/AE 1 Mech. Charge Hand 1 Overman 1 Mining Sirdar 1 Shearer F+3 AFC & BSL F+5 Power pack & Chocks F+3 Switch train & U/Frame Shifting F+7 GBC F+4 Miscellaneous 9 ------------- 40 General Shift Overman 1 Mining Sirdar 1 Gate Road Support 6 Face Supporting (Bamboo bolting & Fore polling etc.) 8 Face Cleaning 10 Slush Tanks cleaning along M.G. 6 Material transport 6 -------- 38 Slide 64: MANPOWER Production Shift 1. Under Manager 1 2. Engineer 1 3. Overman 1 4. Mining Sirdar 1 5. Shearer Operator 2 6. Multi Job Workmen 9 7. Face fitters 3 8. Face Electricians 1 9. Outbye belt Fitters 1 10. Outbye Electricians 1 11. Helpers 6 12. Conveyor Operators 6 13. Misc/cleaning 4 ------------- 37 LONGWALL – FACE TRANSFER : LONGWALL – FACE TRANSFER MESHING : MESHING Wire meshing is laid in roof from 12 to 15m behind the face stop line with individual roof bolts for 5 to 8m and later on along with W-straps/Channel for balance portion at 1m interval. Maximum height will be extracted for the last 8m from face stop line, sothat enough clearance is there for PRS passing underneath the line supports. After stoppage of the face, meshing and bolting is done to the face also. DISMANTLING : DISMANTLING All the equipment in the face are dismantled except chocks and loaded on to the GMT (Gyro Machine Trolley) and transported to surface of new face. Shearer is dismantled into two parts for easy transport. AFC pansets were dismantled in such a way that 5 pansets together forms a unit for loading onto GMT. Similarly BSL, Belt sections are dismantled and loaded on GMT. CHOCKS TRANSPORT : CHOCKS TRANSPORT PRS turning is done generally from dip to raise and 2 buttress supports are used as goaf edge supports at dip most point of the face. PRS are being marched with self hydraulic power upto loading station and shifted on to GMT for further transport to surface or to new face. SCCL – A Review : SCCL – A Review Slide 70: Strut Pit, Yellandu Singareni : Singareni Presently operating 47 Underground and 11 Opencast mines. Godavari Valley Coalfields spread out over 350 Kms. Slide 72: LOCATION Slide 73: The Godavari Valley Coalfield LOCATION Mile stones - Technology : 1975: Opencast mining 1979: Side Discharge Loaders 1981: Load Haul Dumpers and Road Headers 1983: Longwall mining 1986: Walking Dragline 1989: French Blasting Gallery method 1994: In-pit crushing and conveying 2004: Phasing out manual Coal filler launched. Mile stones - Technology Technology-Wise production- 2005-06 : Technology-Wise production- 2005-06 Opencast :23.42 mt (64.8%) Underground :12.71 mt (35.2%) Manual mining :7.12 mt Longwall :0.85 mt Intermediate mech. :4.74 mt (LHD, SDL, BG & RH) PROJECTIONS : PROJECTIONS General Organisation of SCCL : General Organisation of SCCL General Organisation of Areas : General Organisation of Areas General Organisation in the Mines : General Organisation in the Mines Organisation of statutory personnel : Organisation of statutory personnel STATUS OF LONGWALLS AT SCCL : STATUS OF LONGWALLS AT SCCL INTRODUCTION : INTRODUCTION The first Longwall was commissioned in SCCL at GDK.7 Incline, RG-II in September, 1983. Till now 10 sets of Longwall were purchased by SCCL. Mainly the equipment was purchased from UK and China. Till now 70 Longwall panels have been completed in SCCL and presently 4 Longwall units are in operation in 4 Underground mines. Slide 83: EXISTING LONGWALL MINES OF SCCL 2006-07 LONGWALL PRODUCTION TREND-SCCL : LONGWALL PRODUCTION TREND-SCCL INTRODUCTION OF LW SETS : INTRODUCTION OF LW SETS GDK.7 INCLINE : GDK.7 INCLINE Longwall equipment introduced in no.3 seam bottom section in September 1983. After completion of two panels, due to non availability of the property the equipment was shifted to adjacent GDK.9 Incline. Main Problem - Strength of coal is high for Shearer cutting & sand stone bands running across the panel. GDK.7 INCLINE : GDK.7 INCLINE Borehole Section showing 3 seam Top & Bot Section. GDK.7 INCLINE : GDK.7 INCLINE Two panels have worked with 4x360T supports in No.3 seam bottom section with a face lengths of 110m and 96m. The production achieved is 0.8LT with an average production of 1900T/day. VK.7 INCLINE : VK.7 INCLINE Longwall equipment with 4x360T Conventional supports was introduced in Top seam in 1985. With 4x360T supports, 8 panels of 120m face length and 7 panels of 60m face length have been worked successfully. Second set (4x450T IFS) shifted from GDK.11A Inc in 1994 & is presently in operation. Experience in – varied face lengths, up hill transport, crossing the developed gallery, working in between goaves, fault running across the panel. Main Problems – Underrated capacity of supports, Cavity formation. VK.7 INCLINE : Borehole Section showing Top seam (Middle Section) VK.7 INCLINE Depth Thickness Strata Description VK.7 INCLINE : VK.7 INCLINE 8 panels of 120m face length have completed With 4x360T supports by producing around 3.6MT and daily production varied from 400 to 1800T. 7 panels of 60m face length have completed With 4x450T supports by producing around 1.6MT and daily production varied from 1000 to 1300T. GDK.11A INCLINE : GDK.11A INCLINE Two longwall sets were introduced with 4x450T/4x430T supports during 1991, followed by 3rd Longwall unit with 4x450T supports during 1992. First time longwall was introduced in No.1 Seam of Ramagundam. Main Problems – Underrated capacity of supports, Oblique fault running across the panel, high water seepage, improper geo-technical investigations. GDK.11A INCLINE : Borehole Section showing No.1 seam (Bottom Section) GDK.11A INCLINE GDK.11A INCLINE : GDK.11A INCLINE Longwall unit –I : 2 panels worked producing around 0.5MT of coal. Longwall unit – II : 4 panels worked producing around 1.3MT of coal. Longwall unit – III : 3 panels worked producing around 0.96MT of coal. While working with Longwall unit-II & III, experienced more strata problems and cavity formations, due to underrated capacity of supports. PADMAVATHIKHANI : PADMAVATHIKHANI First time Chinese longwall was introduced in PVK in 1995 in Queen Seam (Top seam). 2 sets were introduced, One in 1995 and the other in 1996 with 4x760T supports. 11 panels have been completed by producing around 5 MT. Experience in – varied face lengths, negotiation of fault, deviation of gate roadways. Main Problems – Non-availability of Spares. PADMAVATHIKHANI : Borehole Section showing Top seam (Middle Section) PADMAVATHIKHANI JK-5 INCLINE : JK-5 INCLINE Longwall with 4x450T supports (IFS) was commissioned in June 1990. Longwall panels were extracted in both, Top and bottom sections of Queen (Top) seam after allowing for goaf settlement. 2 panels in Queen seam bottom section and 8 panels in Queen seam Top section have been completed by producing around 2.7MT of coal. Experience in – varied face lengths, negotiation of fault, in between goaves, steep gradient (1 in 3.6). Main Problems – Geological disturbances, Cavity formation, underrated capacity of supports. JK-5 INCLINE : Borehole Section showing Top seamTop & Bottom section JK-5 INCLINE GDK.9/9E INCLINE : GDK.9/9E INCLINE Longwall equipment (4x360T) introduced in no.3 seam bottom section in 1986 which was shifted from GDK.7 Incline. New Longwall set with 4x800T capacity was introduced in No.1 seam in 1996. Main Problem – underrated capacity of supports for 3 seam, Cavity formation, Insufficient geological data, slow progress in development of panels, more water seepage, spares mgmt. GDK.9/9E INCLINE : GDK.9/9E INCLINE Borehole Section showing 1 seam GDK.10A INCLINE : GDK.10A INCLINE Longwall equipment (4x800T IFS) was introduced in no.1 seam in 1994. GDK.10A longwall produced daily, weekly and monthly record output in India. In the year 1997-98, the mine produced 8.67LT. GDK 10A produced 5.40 LT of coal against the target of 5.38 LT in the year 2005-06. Main Problem –more water seepage, non-availability of good quality spares, Cavity formation. GDK.10A INCLINE : Borehole Section showing 1 seam GDK.10A INCLINE FUTURE LONGWALLS AT SCCL : FUTURE LONGWALLS AT SCCL FUTURE LONGWALL PROJECTS : FUTURE LONGWALL PROJECTS Adriyala Shaft Project – Extension of GDK.10A dip side Jallaram Shaft Project – Extension of GDK.9 Inc Dip side Peddampet Shaft Project - Extension of GDK.11A Inc Dip side Kakatiya Longwall Project, Bhupalpally - Steeply inclined, New mine. Shanthikhani Longwall Project, Bellampalli - Extenstion of existing mine STATUS OF APPROVAL OF LW PROJECTS : STATUS OF APPROVAL OF LW PROJECTS ADRIYALA SHAFT PROJECT : ADRIYALA SHAFT PROJECT 1. Location : Ramagundam coal belt Ramagundam Area 2. Geological Block : RG SB-II & RG SB-III Geological Reserves : 109.59 Mt Extractable Reserves (Apr.) : 43.38 Mt 5. Area (in Sq.Km) : 3.40 Capacity (MTPA) : 2.14 Life of the Mine : 31 years Face length : 150m Panel length : 700 - 1300 m Depth range : 294 – 644m Gradient : 1 in 6.0 to 1 in 7.8 : ADRIYALA SHAFT PROJECT : Details of seams: ADRIYALA SHAFT PROJECT SHANTIKHANI LONGWALL PROJECT : SHANTIKHANI LONGWALL PROJECT Location : Dorli - Bellampalli coal belt Bellampalli Area 2. Geological Block : Shantikhani Extn Block Geological Reserves : 8.87 Mt Extractable Reserves (Apr.) : 17.78 Mt 5. Area (in Sq. Km) : 6.81 Capacity (MTPA) : 1.17 Life of the Mine : 23 Years Face length : 150m Panel length : 450 - 2000 m Depth range : 309 – 596m Gradient : 1 in 3.5 to 1 in 5 SHANTIKHANI LONGWALL PROJECT : Details of seams (Phase-I) SHANTIKHANI LONGWALL PROJECT KAKATIYA LONGWALL PROJECT : Location : Mulug coal belt Bhoopalpalli Area 2. Geological Block : Gollapalli block & Peddapur block Geological Reserves : 67.45 Mt (Phase-I)+ 60.06 Mt (Phase-II) Extractable Reserves (Apr.) : 40.02 Mt (Phase-I)+ 35.99 Mt (Phase-II) 5. Area (in Sq. Km) : 9.71 Capacity (MTPA) : 2.16 Life of the Mine : 24 + 22 Years Face length : 250m Panel length : 1200 - 2900 m Depth range : 35 – 412m Gradient : 1 in 2.8 to 1 in 3.3 KAKATIYA LONGWALL PROJECT KAKATIYA LONGWALL PROJECT : Details of seams (Phase-I) KAKATIYA LONGWALL PROJECT JALLARAM SHAFT PROJECT : JALLARAM SHAFT PROJECT Location : Ramagundam coal belt Ramagundam Area 2. Geological Block : RG SB-II Geological Reserves : 206 Mt Extractable Reserves (Apr.) : 79 Mt 5. Area (in Sq.Km) : 7.29 Capacity (MTPA) : 2.28 Life of the Mine : 53 years Face length : 200m Panel length : 500 - 1800 m Depth range : 123 – 579m Gradient : 1 in 5 to 1 in 8 JALLARAM SHAFT PROJECT : Details of seams JALLARAM SHAFT PROJECT PEDDAMPETA SHAFT PROJECT : Location : Ramagundam coal belt Ramagundam Area 2. Geological Block : GDK-6B Integrated Mine Block Geological Reserves : 112.62 Mt Extractable Reserves (Apr.) : 41.40 Mt 5. Area (in Sq.Km) : 7.25 Capacity (MTPA) : 1.46 Life of the Mine : 32 Years Face length : 150m Panel length : 470 - 1200 m Depth range : 118 – 443m Gradient : 1 in 6 to 1 in 10 PEDDAMPETA SHAFT PROJECT PEDDAMPETA SHAFT PROJECT : Details of seams PEDDAMPETA SHAFT PROJECT Slide 116: Variants of Longwall Mining (NEW CONCEPTS) Slide 117: Punch Longwall - Developing longwall panels directly off high walls of OC Slide 118: Field site operations Punch Longwall Slide 119: Advantages Step change in cost and productivity More production capacity High productivity & low cost Longer term and higher % of reserves extraction Easy logistics – near surface High gate road development rates feasible Higher and faster returns on investment Total investment ~ $100 million – compared with > $300 millions UG Punch Longwall Slide 120: Longwall Top Coal Caving (LTCC) Slide 121: Longwall Top Coal Caving (LTCC) Supports used Slide 122: Advantages of LTCC Longwall Top Coal Caving (LTCC) Increased resource recovery in thick seams (> 75%) Lower face working height (better face control) Improved spontaneous combustion control More efficient capital utilisation/ financial performance Reduced operating costs Improved production consistency Less gate road development requirements Some dust and gas issues LONGWALL – INDIAN PERFORMANCE : LONGWALL – INDIAN PERFORMANCE Slide 124: INDIAN LONGWALL PAST EXPERIENCE: Introduction of advanced technology system in Indian coal mining industry marked a major step with the installation of first mechanized Longwall Powered support face at Moonidih in August 1978. In between 1978 to 1985, a major number of first generation Longwall faces started through out India in various mines of CIL such as Moonidih, Jhanjra, Seetalpur, Dhemomain and Pathakhera Colliery and in SCCL at GDK-7 & VK-7 Incline. Slide 125: PAST EXPERIENCE: Churcha Longwall face failed due to dynamic loading. Jhanjra with shallow depth Longwall working face ran into acute spares problem. Kottadih face failed after successful completion of two Longwall panels due to dynamic loading and underrated capacity of supports. GDK.11A failed due to underrated capacity of supports. INDIAN LONGWALL Slide 126: PAST EXPERIENCE: Longwall technology was introduced in Seven mines of SCCL. Their performance has been: GDK-10A, JK-5 and VK-7 Incline gave consistently good results, and The other four mines GDK-7, GDK-9, GDK-11A and PVK suffered mainly due to non availability of sufficient geological data. LONGWALL- SCCL Slide 127: MAIN REASON : Insufficient geo-technical investigations resulted in surprises by encountering major geological disturbances while working the longwalls. Thus effecting the performance of Longwalls to the maximum extent. INDIAN LONGWALL Slide 128: PRESENT & FUTURE : With the likely reduction of contribution from Open cast and the more or less stagnant production from Underground by Conventional methods, it is time that an impetus is given to boost Long wall Technology to able to meet the future energy needs of the country. On the positive side, coal companies have now gained sufficient experiences right from senior executive level to front line workforce to be able to plan, execute and work longwall faces. What are required are proper geo-technical investigations for effective layout of longwall panels. INDIAN LONGWALL Slide 129: REASONS FOR POOR PERFORMANCE OF LONGWALL >Large expansion in opencast mining in the past two decades provided cheaper and safe method for bulk coal production and as a result long wall had to take back seat. > Clear strategies were not pursued for its sustenance as there was mixed results from long wall in the early years of its introduction. Slide 130: > Long walls were introduced mostly in the blocks left over by working Bord and pillar method. Clean and extensive blocks have not been identified. Even the smaller blocks, which were identified, were of inferior grade coal. > Long wall had to co exist with the conventional mining in most of the mines, which caused management problems. > There were some deficiencies in the imported spares management and the supplies were not reaching in time. REASONS FOR POOR PERFORMANCE OF LONGWALL Slide 131: > Coal companies were sensitive to the failures of a few long wall faces and were not prepared to risk huge investments. > Development could not keep pace with the extraction of Long wall panels, slow progress in dip has delayed the formation of Long wall panels and affected the performance. REASONS FOR POOR PERFORMANCE OF LONGWALL Slide 132: Longwall should be promoted as a technology mission. A high level thrust group could be constitute at national level to promote, coordinate and interact different aspects related to Longwall technology. FUTURE REQUIREMENTS Slide 133: Huge investments incurred on different operations for extraction of coal from greater depths in future can be attained by imposing a special cess on present OC production or from other sources. R&D efforts are to be doubled. Efforts are required by the policy makers to transform ideas into actions. FUTURE REQUIREMENTS Slide 134: FUTURE REQUIREMENTS Foreign participation is required for extraction of thin seams and steeply inclined seams. The manufacturing companies of India such as MAMC and Jessop are to be reconstructed/ re-organized. More number of longwall blocks are to be identified to assure the market for manufacturers. Slide 135: THANK YOU You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.