salvaging & installation of powered support longwall equipment
TRANSCRIPT
Powered Support
Longwall Technology-
The World Leader of
Underground Mining
Technology
Powered Support Longwall Technology
Powered support Longwall technology is
acclaimed as the safest and most economical
underground coal mining technology prevailing in
almost all the leading coal producing nations in
the world. As a Mass Production Technology it
contributes nearly 50% of the global production of
coal from underground mines.
Longwall Mining – The Fundamentals
• Longwall mining is basically a depillaring operation that entails the extraction of coal from a comparatively larger block of coal named a Longwall panel. The dimensions of a Longwall panel is measured in terms of a few hundred meters to 2-3 km in length and generally from 100 m – 300 m in width.
• The present trend in the world is formation of larger Longwall panels.
Formation of Longwall Panels• A Longwall panel is formed by drivage of two
long-heading galleries driven parallely in coal from main trunk-roadways. The two parallel galleries are ultimately joined with an inter-connecting gallery , called the Face.
• The length of the long-heading galleries determine the length of the panel, whereas the centre to centre distance between these two parallel galleries measures the width of the panel and is termed as Face Length of the panel.
• The long-heading drivage & face connection are generally commenced with Road-header machine.
Different Methods of Working a Longwall Panel
Different methods of working in a LW panel:
• With coal cutting machine and/or blasting in conjunction with individual supports.
• With Shearer Loader in conjunction with individual supports (Closed circuit hydraulic props)
• With Self Advancing Powered Support Longwall Equipment.
Powered Support Longwall (PSLW) Equipment
Powered support longwall equipment is an integrated set of machinery used for fully mechanized extraction of coal from a longwall face. PSLW technology is a non-cyclic technology, which does not involve any blasting operation. The coal loading and coal evacuation does not involve manual drudgery and the persons working at face are predominantly under supported roof.
Components of PSLW Set
• Double Ended Ranging Drum (DERD) Shearer- the cutting machine and also serves the loading machine.
• Armored Face Chain Conveyor (AFC)- installed at face through out the face length for coal evacuation, on which the shearer drums load the coal. Shearer machine is installed on AFC & the collar of AFC is specially fitted with arrangement for shearer movement.
Components of PSLW Set• Stage Loader (STL) : it is also a heavy
duty chain conveyor installed at the main gate on which the AFC discharges the coal carried from the face. STL is comparatively short-between 30-40m in length & is the intermediary between AFC and Gate belt.
• Lump Breaker : it is installed on STL and breaks big lumps of coal to smaller sizes.
Components of PSLW Set• Gate Belt Conveyor : it is the last component
of coal evacuation system within the panel, beyond which starts the trunk evacuation system. Generally it is a 1200 mm wide belt, which is shortened at regular interval ( in case of retreating longwall) as the face retreats. In case of advancing longwall, new conveyor lengths are added.
• Electrical switch Bank : these are a number of electrical switches, installed on movable trolleys & placed in main gate for controlling the operation of all face machineries.
Components of PSLW Set
• Powered Supports : This is the largest component of PSLW set comprising of large number of hydraulically operated self advancing powered support sections needed to cover the entire length of the face. The supports may be chock type, shield type or chock- shield type. Each support section is designed to take a specific load. Supports are generally 4-legged or 2-legged.
Components of PSLW set
• Power Pack Pump : This may be termed as the heart of a PSLW face. The pump generates hydraulic pressure, which is supplied to the powered supports. Hydraulic power is also required at face for several functions like operation of rams for AFC & STL shifting, handling of heavy materials with additional rams etc. Total hydraulic operations are controlled by control valves.
Components of PSLW set
• SIVAD : It ensures the overall control of all operations at the face. It involves the audio system for face communication, pre-warning system before bringing any cutting and evacuation equipment into operation and also the sequential control of operation of AFC, STL and Gate belt. It also ensures liaison between face and surface and other parts of the mine.
AFC with power support
Underground- Plough face
Salvaging & Installation
of Powered Support
Longwall Equipment
Longwall Face Move
In a Longwall mine it is very important to maintain production without interruption, given the high capital involvement. But Longwall production generally stops when one panel has been completed and the equipment is being moved to the next panel for setup. The process of removal of PSLW set from the old panel is termed as Salvaging for reinstallation in a new panel.
Pre-move (Pre-salvage) preparation
• Pre-planning: A well conceived and detailed pre-planning starts as soon as the last Longwall move is completed. It is the key to safe, speedy & economical face move.
• Manpower reorganization: Longwall face move is highly skilled operation and it differs considerably from normal production operation. Hence, reorganization of manpower with detailed code of practice for salvage operation is a must.
Pre-Salvage Operation• Preparation of supplies, tools &
equipment – The most needed supplies during the salvage operation are for roof control. These include wooden slippers, roof bolts, wire-mesh, steel beams/rails etc. Tools for shifting, turning and transporting of heavy materials are also of extreme importance. These tools are to be selected taking into consideration floor condition and safety measures.
Pre-salvage Operation
• Establishment of Transportation route and communication system-The termination point of old panel should preferably be located at the middle of transportation gallery, termed as salvage gallery. The route that leads to the new panel should be verified in terms of entry size, slope & curve and for floor conditions.
• Communication & proper ventilation in case of mid-face collapse due to support withdrawal are important areas of consideration.
Face Move (Salvage Operation)Formation of Salvage Chamber- 7-8m away from the termination point, the preparation for salvage chamber starts. It involves :
Intensive roof bolting throughout the faceLaying of wire mesh up to last cutStopping of support advance at least 1.5-
2m from the termination pointLast cuts from tail entry to head entry
with stoppage of shearer every 6-10m for cleaning of face and proper supporting.
Salvage OperationEquipment Inspection and Repair :-Before the LW face reaches the termination point, a thorough inspection should be made of all equipment and a detailed record should be made. Based on this inspection a maintenance and repair plan must be made. Specially Shearer, AFC & STL gear boxes and sprockets and Hydraulic system of supports.
Sequence of Salvaging
Though the detailed procedure may vary from mine to mine, but in general the sequence of salvaging of a PSLW face with unidirectional movement is as follow :
Gate belt conveyor and its accessories
Moving major power pack to new panel & installing aux. power pack to old panel
Stage Loader , its accessories & Lump Breaker
Sequence of Salvaging
AFC & Shearer in the following sequence: Ram plates, spill plates, chains and flight bars, head drive, cable handler, the shearer, communication and safety system, cables & water lines, AFC pans and tail drive.
Face lighting system
Clearing of the salvage chamber
Powered supports
Sequence of Removal & Transport of Powered Supports
When removing the powered supports, the major considerations are to control the roof and to prevent the caved fragments in the roof and gob from entering into the working area at face. Generally supports are withdrawn from the tail end side towards the head end side where they are loaded for transportation to new panel. The sequence of withdrawal varies with the method adopted.
Sequence of Support WithdrawalSystem of walking supports- In this method last support at tail end is first pulled and then turned towards head end subsequent to which the 2nd last support is also pulled, turned and placed by the side of previous support. These two supports are called walking supports and they act like gob line supports. The 3rd chock is then pulled & removed for transport. Thus with the help of walking supports all subsequent supports are removed and transported to the new face.
Sequence of Support WithdrawalThe second method of support withdrawal is vividly shown in the sketches as enclosed. In this method, last but one support is pulled first and in its place one half by full cog is erected. Then the support is turned, moved to a certain distance and only after that the last support is withdrawn. After the withdrawal of these two supports, cogs are erected as shown in Fig.2. Thus by alternating sequence the supports are withdrawn from the face (as shown in Fig.3 & Fig.4)
Installation of PSLW in New Face
Sequence of Installation : Installation of head entry drive unit, if
shearer enters from the tail entry of the new face, and the AFC pans
Installation of gate belt tail piece (Low height structures)
Installation of STL with its accessories Installation of Power pack pumps
Installation of PSLW set at new face
Installation of powered supports (continued process)
Installation of Electrical switch bank, section switches and transformers.
Installation of Shearer
Installation of the tail entry drive head of AFC
Completion of powered support installation
Face signaling and audio system.
Factors affecting the efficient & economic use of Longwall
technology in Indian coal mines1. Improper Planning leading to wrong place of
application
2. Lack of proper Infrastructure facilities
3. Non-provision of tailor made equipment for specific geo-mining conditions prevailing at the mine
4. Policy failure to develop proper cadre scheme
5. Lack of proper training facilities to generate skill
6. Failure in developing proper indigenous vendors
7. Insufficient study of Rock characteristics and load distribution design, leading to strata control problems
