'There is a problem that no one has managed to solve for several decades and, perhaps, no one ever will…,' when a customer challenges you this way, you can only do one thing... accept the challenge. What is innovation if not overcoming obstacles that seem impossible to overcome? This is exactly the challenge that FAMUR has faced and overcome recently and gained a brand new patent in this process.
The PL231937B1 patent granted to FAMUR SA in December 2018 is a result of an innovative approach to a problem that underground mines have been facing for a long time. Even the customer who came to our company in Katowice with the matter in question was dubious about the possibility of coming up with a modern and effective solution that would constitute an answer to its needs especially, given that various mining companies as well as machinery and equipment manufacturers have been dealing with this matter for decades. What caused such difficulties?
For various reasons many hard coal mines have had to maintain one or two gateways behind the longwall face (frontage). This is not an easy task. Back in the days, when the daily longwall advancement was relatively small and the workforce was cheap, cribs or wooden chocks filled with stones were placed along gateways. Everyone who visits mining museums is familiar with these solutions, yet they have been applied to this day.
However, even the technically enhanced cribs and chocks with improved supporting capacity require timber to be applied, and erecting them is labour-intensive. These methods are quite ill-adapted to the contemporary conditions of high-yield coal longwalls. Attempting to eliminate unnecessary works, especially the manual ones, and simplifying the processes in coal faces simply makes wooden cribs be anachronistic.
New solutions, introduced later to replace cribs, namely rib-side packs of fast-setting materials, did not eliminate all the difficulties related to building gateways behind longwall faces. It was still necessary to withhold the construction of the next section of rib-side pack, especially the operation of separating (guarding) the area for it, until the roof support was advanced. Neither was the problem solved by introducing the so-called big bags filled with binding material (for example cement-based ones) that served as pillars. In order to make the big bag not move while being filled, it was necessary to guard an adequate area. It meant that the longwall advancement was hindered and its efficiency (production) was decreased.
Thus, regardless of the solutions chosen and the attempts to introduce improvements, the time needed to erect a crib, a chock or a pillar had a negative impact on the efficiency (production) of the entire longwall system. Perhaps the reason why the problem remained unsolved was the fact that there were attempts to automate the manual operations, but no broader look at the problem was taken.
Recently Famur has also faced a challenge related to building gateways behind longwall faces. This Poland's largest manufacturer of mining machinery decided to take it up. The solution to it was found merely a few hours later right in the street– it was a man using a little trolley to transport a big bag filled with scrap that became our inspiration. The bag weighing several hundred kilograms maintained its shape, and one man had enough strength to transport it.
The new patent by FAMUR takes advantage of the opportunities that the present state of the art provides and it constitutes a creative compilation of many existing solutions. The general idea consists in suspending a big bag to a slightly-modified powered roof support, through which the bag maintains its shape when being filled with quick-setting binding material. This process already begins under the powered roof support and does not require any additional support structure (guarding) to be applied. When the filling material begins to harden, it ‘memorizes’ the shape and advancing the powered roof support makes it possible for an even partially-filled bag to stand without supporting. Then all you need to do is to fill up the bag with the binding material.
As the bag is being filled in a safe area under the roof, the duration of this stage depends, in fact, on pump efficiency or, more broadly, on the system that feeds the self-hardening filling.
It should be mentioned that having made small changes, this process may also be used with every type of powered roof supports manufactured by FAMUR SA: caving, backfilling, or top coal caving ones.
And this is how the PL231937B1 patent for FAMUR SA, concerning construction of protective hardened rib-side packs, especially for securing gateways in underground mine excavations was obtained and how the powered roof supports were developed.