A gigantic dust cloud rises over the rocky Oksala area in Palokka, Jyväskylä, central Finland. It is -25 °C, and the crushing chain of RKJ Rahikainen (RKJ) is crushing stone as usual. Actually, it is crushing better than before, now that the old screen is no longer the bottleneck in the production process.
Jukka Rahikainen, one of the owners of the crushing contractor company, steps down from the excavator cabin and comes to talk.
“This is a family business. I’ve been involved in crushing with my brother and father since 2007.” Pre-2007, Rahikainen’s father, Reijo, had worked in earth construction, digging ditches in forests, for example.
“They opened a rocky area near our home in Petäjävesi, and we thought that we could start processing it further. Our operations have expanded a bit since then,” says Rahikainen, grinning.
It can be said that they have indeed expanded their operations quite a bit. The company already has two crushing chains, one in Palokka and the other one in Leustu, Korpilahti. The goal is to produce one million tonnes per year with the two chains. They are currently producing up to 700,000 tonnes per year. The new Nordtrack S2.11 double-deck screen purchased to work at RKJ customer Perälä’s quarry in Palokka contributes to achieving this goal.
“We were looking for a screen that would have enough capacity to screen the material so that we wouldn’t have to slow down the crushing process. Metso contacted us and asked us if we were interested in trying this kind of solution,” Rahikainen reminisces.
The new screen has been in use for six months now. The upper deck of the screen has a 10-mm mesh, and a 2.5-mm mesh is used on the lower deck. When making road-sanding gravel with the previous screen, the capacity was 200 tonnes per hour. Now, it is easy to produce 250 tonnes of clean output if the material is dry.
All kinds of grades are produced by RKJ at Perälä’s quarry: road-sanding gravel, capillary break gravel and aggregates from 0–16mm to up to 0–90mm. According to Rahikainen, it is possible to produce 300–400 tonnes of 0–31mm aggregates per hour. When making larger aggregates, only the feed bank and the feeder might slow down the process.
At Perälä quarry, RKJ is using a chain with Metso Outotec’s LT130E jaw crusher and a tertiary crusher, which is their own creation: a MX4 cone crusher installed on a LT300 track. A Nordtrack S2.11 screen was added to the chain at the same time with the jaw. It keeps the MX4 cone as full as possible, which enables the crushed stones to have the best possible shape.
“The shape is important when producing 8–16mm grades for the construction business. Stones should look like a Rubik’s cube: if there are too many long edges, the stone falls into pieces easily,” Rahikainen explains.
“It has worked well. I don’t know if we really had a bottleneck, but the machine has certainly enhanced our operation. We’ve been able to increase the capacity considerably. Simplicity and pure power. They are the key,” he says.
Rahikainen also praises the ease of maintenance of the screen. Greasing points have been centralised well and there’s more room around the oil check point, so things have developed a lot. It is easy to change meshes and prepare the machine for transportation.
“When you fold the conveyors, the screen becomes so compact that there’s no need to have an extra car driving in front when transporting the machine,” he notes.
Metso Outotec’s maintenance service is also much appreciated.
“The whole package is really comprehensive, quick and of high quality. We’ve always got help when we’ve needed it, although we haven’t always called them during business hours,” Rahikainen laughs.
