Rudus Oy crushes 2.5 million metric tons of marine ballast in Inkoo, using a stationary plant from Metso

The work is being undertaken with a stationary plant from Metso with an hourly capacity of 600 metric tons. The plant’s production level was ensured with two new ES screens, new MX series jaw crusher wear liners and GP500S cone crusher, which was delivered last year.

“The marine ballast was crushed at a fast pace, and the plant had to be running whenever necessary. At best, there were four ships at the Port of Inkoo retrieving cargo, which meant that we always needed to have some buffer inventory in hand,” says Kimmo Leppikangas, production and development manager at Rudus Oy.

“This project has lasted for more than two years, and it has presented plenty of challenges. We’ve always received quick expert and maintenance support from Metso when needed. We also have a joint meeting with Metso every month at which we can freely discuss any matters that have arisen.”

Marine ballast and fine fractions

Located right next to the Port of Inkoo, the  plant refines hard and relatively abrasive granite. The blasted rock is transported by truck to a feeder leading to a C125 primary crusher.

The jaw crusher, dating from the 1980s, is still operating reliably. For marine ballast production, the closed side setting is 150 mm. From the jaw crusher, the pre-crushed material is taken to Metso’s second-largest GP series cone crusher, a Nordberg GP500S. The S in the model name stands for secondary, and these GP Secondary cone crushers are known for their extra-large feed opening and steep cavity profile.

The cone crusher, delivered last summer, uses a closed side setting between 60–70 mm and stroke length of 25 mm. The wear liners feature Metso’s Coarse chamber profile. This is the first GP500S secondary cone crusher in Finland with the Metso Metrics remote monitoring system installed. The system wirelessly transmits the key data related to the crushing process.

After the secondary cone crusher, a Metso A132 double-deck screen separates 22–100 mm marine ballast. The screen uses a plate on the upper deck and a rubber mesh on the lower deck.

The weight of the crushed aggregate is an important factor in the production of marine ballast. The bulk density must be sufficient to resist the currents on the seabed.

Fine screening with two ES screens

During the project, 70% of the plant’s entire production has been marine ballast. The remaining 30% is forwarded for fine crushing and screening. Here, two new Metso ES series screens, an ES302 and an ES403 model, handle important tasks with GP550 and GP300 cone crushers.

The double-deck ES302 screen separates 0–4 mm rock dust. Rudus has also tested Metso’s self-cleaning PolyClean screen meshes in this screen. In turn, the three-deck ES403 screen separates key asphalt grades of 0–3 mm, 3–6 mm and 6–12 mm.

“The initial experience of the ES screens installed in Inkoo in January has been positive. The screening process is efficient, and there’s plenty of room for the replacement of the meshes attached at the side,” Kimmo Leppikangas says.

“We’re confident in the functioning of the new screens, because the ES screen has already been used in Espoo to reliably screen more than one and a half million metric tons. And the separate vibrating machinery of the new model makes replacement work easier.” 

MX wear liners break the service life record

The Rudus Inkoo plant also tested the C125 jaw crusher with Metso’s new MX wear liners, made of a metal hybrid material.

“The experience was very positive. We crushed 410,000 metric tons with one pair of MX jaw dies, which is four times the service life of the manganese steel models we regularly use,” says Jan Hammarström, site manager of the Inkoo plant.

“The MX jaw die had the same impact on rock as a regular quarry jaw die. Due to the abrasive rock material, the MX jaw dies were also turned around several times. The MX parts lasted for six months, and wore evenly. Our intention is to test the MX models at the other hard rock quarries operated by Rudus in the future,” Hammarström says.

The service life of the wear liners also has a positive impact on the environment. The MX jaw die’s four times longer service life means approximately 70% less CO₂ emissions in the manufacturing of wear liners per produced metric ton of crushed aggregate.

After the marine ballast project, 90% of production will go to the Baltic countries

The Rudus Inkoo plant is supplying the marine ballast to the international Bova consortium for the Nord Stream 2 gas pipeline project. The Rudus plants in Inkoo and Kotka produce a total of 4.5 million metric tons of marine ballast.

When the project is completed at the end of May, the Inkoo plant will be readjusted for the production of asphalt grades. This will entail fine crushers and a new storage hopper delivered by Metso to balance the production at the secondary stage.

The Rudus Inkoo plant will focus on export; 90% of the grades will be shipped to the Baltic countries. The different standards used in the countries introduce their own challenges.

Asphalt grades at a precision of a millimeter

“We need to produce a lot of intermediate sizes, because there is a one-millimeter difference in the standards used for asphalt grades in Latvia and Estonia, for example,” Kimmo Leppikangas says.

All in all, the product range of the Rudus Inkoo plant is very comprehensive, including three zero-based products, nine cut grades and 32–64 mm track ballast.