longwall mining




Cutting Machines - Cable and Hose Handling (Bretby)



Cutting Machines - Cable and Hose Handling (Bretby)

Shearer A shearer has to be supplied with electric power and water and as it is continuously moving, trailing cables and hoses are required. Unlike a continuous miner which is mostly only moving forward with intermittent reversals, a shearer is continuously moving backwards and forwards along the entire face length and in a very congested area. A means of managing and controlling the trailing cables is therefore required, The "Bretby" (named after the location of the research and development section of the British National Coal Board, where the device originated) is a flexible carrier consisting of a series of flat "plates" usually of a plastic material connected in the form of a chain but which only flexes along its length, similar in appearance to tracks on a "caterpillar" driven machine but with a double row of plates. With the aid of pins on the outer edges, this forms a container which is flexible in one direction only (in a vertical plane when installed on the face).


Fixed cables and hoses are run in a services tray attached to the back plate of the AFC from the services supply end of the face (normally the maingate) to mid-face. At this point the shearer trailing cables and hoses, enclosed within the Bretby, are attached to the fixed cables and hoses, with the Bretby then being run in a cable trough attached to the AFC back plate (above the services tray) to both ends of the face as the shearer moves from end to end. The other end of the Bretby is attached to an arm fixed to the goaf side of the shearer of a length to hold the end of the Bretby directly above the cable trough and at a height such that the cable is bent at an acceptable radius when dragged back on itself.

When the shearer is at the tailgate, the trailing cable is fully stretched from mid-face. As the shearer travels to the maingate, the Bretby doubles back on itself to the mid-face position and is then dragged out to full extension again when the shearer is at the maingate. The process is reversed when going back to the tailgate.

Care is needed if the shearer is taken backwards and forwards in one area as the Bretby will be trying to go back on itself several times. There is a height limit to the number of times it is possible to do this, as well as a limit on the radius the cable can be bent to.