When Coal Was King
Industry, People and Challenges
Heritage Community Foundation, Year of the Coalminer, Albertasource and Cultural Capital of Canada logos

Home     |      About     |      Contact Us     |      Sponsors     |      Sitemap     |      Search

Mining Techniques

The “Gripper” attaching coal cars to endless rope under rope haulage by means of Smallman’s clips or gripsThe development at the large mines is by means of vertical shafts sunk to the coal seam, while the smaller mines are generally developed either by short slopes in a coulee or by level drifts driven in from the outcrop. The general method of development once the coal seam has been reached is to drive main roadways about eight feet [2.44 m] in width. These main roadways are parallel to the main cleavage planes of the coal and are called "butt entries."

At intervals off these entries other entries at right angles to the main cleavage of the coal are driven and these are called "face entries." Off these face entries again butt entries are driven at intervals, and it is off these butt entries that places from 18 [5.5 m] to 22 feet [6.7 m] are driven, called rooms. A pillar of coal is left between each room, and after the rooms have been driven as far as planned these pillars of coal are removed, starting at the inside end of the room. When the rooms and the pillars have been worked out, the pillars of coal between the butt entries are also worked and the coal in them extracted. The coal underground is loaded into small cars carrying from half a ton [0.45 tonne] to a ton and a half [1.36 tonnes] each, and transported in these cars on narrow gauge tracks to the surface. At the very small wagon mines where the coal is won at only a short distance from the surface the cars are pushed by hand. Where the distance is too great for this, horses are used to haul the coal. Horse haulage however, has its economic limitations and where the distance is too great for economical horse haulage, mechanical haulage is used, generally what is known as "endless rope haulage." This system consists of a long endless rope, driven by an engine underground or on the surface.

Loading out coal from a room, ca. 1951The cars are clamped to this rope, which pulls them out to the shaft bottom where they are unclamped and hoisted to the surface. The empty cars are again clamped to the rope on their return from the surface and pulled in to the workings of the mine. Practically all coal is mined by machines. The machine in general use is the punching machine operated by compressed air. The machine is really a large mechanical pick which breaks into the bottom of the coal for a distance of about five feet [1.3 m] and enables the coal to be shot down and loaded with less explosives and with less breakage than if it be shot out of the solid.

A pit boss testing for methane gas prior to workmen entering the area, Actually, the inspector would have tested for gas before permitting a flash photo such as this to be taken underground; an exploding flash bulb could easily set off a mine explosion. While the Lethbridge field was not considered to be "gassy," gas was present and vigilance was necessary. Adequate ventilation was all-important in coal mines as the incoming air dissipated noxious gases and produced fresh air for the underground work crews.While the mines of the district are not very "gassy," inflammable gas is found in some of them. In these mines the miners use electric lamps, and the mines are kept clear of gas by means of large centrifugal fans situated on the surface. Very large quantities of air are required to properly ventilate the extensive mines in this field, and the cost of maintaining adequate ventilation is considerable. The largest of the fans in the district blows over 200,000 cubic feet [5600 m3] of air per minute through the mine. It will be realized that the power required to drive such a fan is considerable when it is considered that this quantity represents over 9,000 tons [8182 tonnes] of air every 24 hours.

The mines are equipped with up-to-date appliances for properly screening and preparing the coal for the market so as to produce the best possible product. The coal is screened into various market sires varying from lump coal over a four-inch screen [10 cm] to slack through a three-eights [1.0 cm] screen. The larger sizes are transported along slowly-moving belts on the tipple where all impurities are picked out by hand. The smaller sizes are cleaned mechanically by what are known as spiral separators. These machines were first developed in the Pennsylvania anthracite field where they "were used to clean the smaller sizes of anthracite.

They were tried out in this field in 1919 and were found to give equally good results with this coal. The coal to be cleaned goes down spiral chutes which are set on an angle that is adjustable. It is found that owing to difference in the coefficients of friction of coal andiron and rock and iron the coal travels faster down the chute than the rock and, due to centrifugal force, tends to make its way to the outside of the spiral while the rock remains on the inside. In this way a very fine separation of coal and rock is made, giving a very clean product for the market.

By Joseph B. deHart, M. Sc.
The Lethbridge Daily Herald 18 July 2020

bottom spacer