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Longwall Mining 

 

Summary

This review explores the longwall methods of mining. Links to longwall equipment and selection, consultants, suppliers, software, publications, and videos are also given.

INTRODUCTION

Longwall mining is a highly productive underground coal mining method where a long wall of coal is mined in a single slice, typically of thickness 0.6 m to 1.0 m.

Hundreds of articles and informative web pages can be found on longwall mining methods. The best way to start will be to go through the Longwall Methods section of the online course Underground Mining Methods and Equipment. I especially liked the publication Longwall Mining in Seams of Medium Thickness, by Myszkowski and Paschedag, which gives a very detailed insight on the longwall mining method covering subjects such as utilization, equipment, technical aspects, hazards, and economy.

Wikipedia also gives a good insight on the Longwall Mining method. I would also advise you to take a look into the links mentioned in Longwall Mining Methods on LinksMine. Chapter 20.1 Longwall Mining of the SME Mining Engineering Handbook is also very informative. The Video section below contains videos on longwall mining methods and can serve as a source for a quick insight into this method.

A typical longwall mining layout

A typical longwall mining layout. Source: http://rajikorba.blogspot.ca/2011/06/long-wall-technology-in-coal-mines.html

LONGWALL EQUIPMENT AND SELECTION

CAT, Joy Mining Machinery, and Kopex Group are among the major suppliers of longwall mining equipment. In general, the following equipment are required in a longwall mine.

1. Shearers or Plow Systems:

a. Longwall Shearers
Three types of shearers have been used in mines around the world: Double Ended Ranging Drum (DERS), Single Ended Ranging Drum (SERS) and Single Ended Fixed Drum (SEFS). The most common among these is DERS used to extract coal seams from 1.8 m to 3.0 m, though a thickness up to 6.0 m has been achieved. SERS is not so common and is preferred for seam thicknesses of around 1.5 m. SEFS is used for thinner seams (1.3 m), but it has to compete with the plow system which is more productive than shearers for thinner coal seams.
A shearer in Bochum (Deutsches Bergbau-Museum
A shearer in Bochum (Deutsches Bergbau-Museum)
b. Plow System: Two types of plow system are used in a longwall mine - Base Plate Plow and Gliding Plow.
A gliding plow
A gliding plow

The selection of shearer or plow system depends primarily upon the average coal seam height. The table below can be considered as a general guideline:

The following publications describe the selection criteria for either of the above two excavators:

The technical applicability in selection of mining equipment for longwall is best described in the paper by Myszkowski and Paschedag and is mentioned below:

2. Powered Support Systems:

Three types of support systems are usually used in longwall mining and are described below:

Roof Type Roof Nature Support Types
Weak Immediate Roof Caves Immediately Two leg shields
Medium Roof Relatively thin and overhangs slightly Four leg shields or Chock Shields
Strong Roof Massive intermediate roof that overhangs considerably into the gob Four leg shields or Chock Shields

Four-leg chock shield
Two-leg chock shield

3. Armoured Face Conveyors (AFC):

Four types of armoured face conveyors are used: Single Centre (SCS), Double Centre (DCCS), Double Outboard (DOCS) and Triple Chain Strand (TCS). DCCS provides larger cross section, more flexibility, less chain wear and easier maintenance in comparison to DOCS. DCCS and SCS are most common, though SCS is getting more acceptances because of recent increase in chain strength and its reduced cost over other types. AFC width ranging from 0.75 m to 1.3 m are available in the market.

4. Longwall Facebolter:

This is an AFC mounted hydraulically propelled roofbolting machine platform specifically designed for longwall face bolting during salvage or installation, or during severe adverse geological conditions.

5. Other Equipment:

Roof Support Carriers to carry hydraulic supports, Roadheaders for development of gate roads (main gate and tail gate) and other ventilation, roof support equipments of gate roads, Power Drive System, exploratory and blast hole drilling for gate roads and conveyor belts used to transport coal from AFC.

Roof support carrier
Roof support carrier. Source: CAT

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