1 The very first longwall supports used to “keep the roof from touching the floor” were simple wooden props. Longwall faces in the UK still used this technology in parts of northern England and Scotland well into the 1970s. I visited a longwall at Bear Park colliery in Northumberland in 1977 that was 1m high, 100m long and fully supported by “Geordie props”. It remains to this day one of the scariest experiences of my life.
2 The first longwall powered roof support was built by Dowty Mining Equipment in 1946. This claim may be disputed by other support manufacturers. The supports were basically four hydraulic jacks linked by a steel framework. There is a photo that shows the first Dowty roof support in front of the latest 6m roof support from Joy. A spectacular comparison.
3 In the 1960s, shearers were hauled through the coal face using a steel rope.
4 In the 1970s, shearers were hauled through the coal face using static chains or “bull chains” as they were commonly known. These chains would “whip” up and down, resulting in many serious and fatal injuries. Thankfully these have been replaced with chainless haulage systems.
5 AFC creep in the “good old days” was controlled by removing an AFC pan plus two supports at one end of the face and reinstalling them at the other end. This process took just a few hours and was very effective.
6 The most popular method of keeping the face straight in the 1980s and 90s was a ball of string.
7 The most popular method of keeping a face straight in the 21st Century is a ball of string (although sadly being phased out by more modern techniques).
8 Some longwalls in Europe in the 70s and 80s were lower in height than the depth of web of modern Australian longwalls today (less than 1m). I worked at Kiveton Park colliery in South Yorkshire (for a very short time) in a seam that was 900mm high. Within that height you had to fit a powered roof support and still be able to travel through the face which was 250m long.
9 In Siberia, it is quite common for longwall faces to be turned through 180 degrees and then mined back in the opposite parallel direction before being salvaged. This is quite a remarkable achievement and takes considerable diligence and attention to detail. Please don’t ask me how.
10 The latest state-of-the-art roof supports being manufactured today can take loads of up to 1750 tonnes before they will yield. To put that into perspective, a Boeing 747-400 weighs 200t empty and 400t fully loaded.
This article first appeared in the June 2012 issue of Australian Longwall magazine.
