ARMOURED FACE CONVEYOR

By Yashwardhan Singh Naruka

In longwall coal mining, the coal cut down by the shearer is transported by the armoured face chain conveyor (AFC), which is laid across the full face width , to the head entry T-junction, where it is transferred to the entry belt conveyor through the mobile stage loader.

The armoured face chain conveyor has large carrying capacity. It is structurally very strong, bendable and low in body height. It serves not only as a guide rail for the shearer, but also as the pivot for support advance.

It transports the coal at a speed in excess of 1 metre/second. However some face conveyors are running at speeds as high as 1.6 m/s. Generally, the power and capacity of AFC are reflected by the motor size, pan width and chain size.

Apart from the AFC's primary function of removing the cut coal from the face, its structure is used for other purposes:

• The edges of the base are used as tracks for the coal cutting machines (shearers) to run on.

• Tracks or chains utilized for haulage of the shearer are mounted on the AFC in most cases.

• Troughs and attachments are mounted on the back plates to carry fixed and trailing cables and hoses.

Major Components of Armored Face Conveyors:

• Drive Head• Various pans ( line pans, ramp pans, connecting pans, and adjusting

pans)• Link chains• Scraper (or flight) bars• Tail end• Double acting ram—used for both the support and conveyor advance. Auxiliary Devices:• Face-side ramp plate• Gob-side spill plate• Cable handling channel• Chain tensioning and conveyor anchorage devices

DRIVE HEADIt consists mainly of:• Drive frames• Drive units• Electric motor• Gearbox• Fluid coupling• Chain sprockets

Pans

There are a numerous pieces of pans in a conveyor. They serve as the supporting structure and moving roadway for the flight bars and the loaded coal. It also acts as the guide rail for the cutting machine.They are of the following types:

• Line or standard pans• Ramp or connecting pans• Adjusting pans• Spilt pans

Chain units

The chain unit consists of the link chain and the flight bars. The chain

unit must be very strong and rigid, and highly wear resistant

because it is subjected to heavy external

loading, both dynamic and static, and to

needs to overcome frictional resistance.

Transfer Methods at Headentry T-junction:

A stage loader or a curved conveyor is used to transfer the coal from AFC to the entry belt conveyor at the head entry T-junction.

From the 2005-2006 Joint Coal Board Survey of Australian Longwall Mines, the following information about AFC's has been calculated.