Nordkalk’s mine located in Parainen has long traditions in limestone mining. Marble-like limestone has been mined locally since the 17th century and the company has been incorporated since 1898. Every year, the total amount of mined material is around 2 million tonnes of which ends up in lime productions in the region of 1.3 million tonnes. The remaining 700,000 tonnes of so-called gangue, which is used amongst other things in road production. Half of lime produced is delivered directly to a local cement production factory and the other half is used as raw material for food and metal industries.
The limestone’s journey begins in Parainen with an open-cast quarry and continues to the coarse crushing plant situated a 100 metres underground. From the crushing plant, two conveyors transfer the aggregate through a primary screen to the sorting plant which is above ground. It then moves along four lines where it is sorted by size. On the sorting lines, any raw material which is not suitable for production is separated optically, whereas the screened material is analysed further to check the composition to allow for a quality end product.
– We deal with aggregates that have their own challenges with regards to the conveyors and the sorting plant. In addition, the environment is very humid which adds a strain to the steel structures. The lifespan of the lines is only around 10-15 years. The lines are replaced alternatively in order to equalise the investment costs explains Nordkalk’s Maintenance Manager Sami Lindström.
The latest investment in Parainen was the so-called fifth line. The fifth line is the one that sorts coarse rock and it was near the end of its lifespan. For example, spare parts for the equipment were difficult to source making it hard to operate and maintain the line.
Oucons, a member of the Comatec Group, was selected as the main designer of the line during a call for tender in September 2018. Installation began in November 2019, and commissioning was completed at the turn of November and December.
– Placing new equipment and the necessary parts of the structure in the existing environment is always a challenge. Space can be tight and parts are lifted to the installation site via a separate hatch. Issues cannot be avoided completely but overall everything went smoothly without any big problems, thanks to successful planning and are local main contractor. The final phase was perfecting the optical sorter to distinguish between the stone grades, now the line is operating at full capacity, Lindström explains.
Oucons has a long experience with the design of material handling systems, conveyors and associated steel structures.
– As the site’s plant designer, we were responsible for situating of the main equipment, the design of the supporting structures and maintenance levels. When designing for challenging environments the strength of the structure, installability and available space must be taken into account, says Timo Viljanen, the Business Manager at Oucons.
The plant design begins with a pre-design phase, during which data is collected, sketches drawn for the supports and other arrangements, and the structures were given dimensions. During the design phase, the details of the structures are finalised. Then the production and installation schematics for the site’s main contractor.
Whilst planning the new line a 3D scan and photographs were utilised instead of the traditional tape measure and sketchbook.
– Modern design programs and practices are a prerequisite for a successful plant design. For example, Nordkalk’s new sorting line had to be installed in a confined space, which required a very precise design. The 3D model allows the structures to be designed at the correct size, which speeds up the actual installation process. The lines used for processing aggregate are under a heavy strain. We were able to utilise our knowledge in material handling to design the funnel structure at the end of the line along with the dimensions and vibration analysis of the support structures Viljanen adds.
Nordkalk was responsible for the tendering and the selection of the equipments suppliers. For design purposes, Oucons received information such as location, size and opening direction of the service hatches from the equipment vendors. Good results were achieved through smooth cooperation between different suppliers.
– Compared to the previous sorting line, this new ones seems to have improved in functionality. Especially for maintenance purposes, large maintenance levels increases the ergonomics and safety at work. The next investment is likely to take place in a few years time and our goal is to unify our equipment to match the new line. At the moment, the equipment is from a variety of ages and suppliers which adds an extra challenge for sourcing of spare parts, says the Proactive Maintenance Designer Johan Pelto from Nordkalk.
Also Oucons is pleased with the result.
– Thanks to good cooperation, we received comprehensive base information from the equipment suppliers, and were able to examine the lines and structures before the actual design work began. This is the first time we have worked with Nordkalk’s plant in Parainen, and it was important to study the plant carefully. Sometimes it’s good to use existing solutions but other times it’s good to make new recommendations for fixing or supporting structures, says Viljanen.
3D scanning was used to design the sorting plant for Nordkalk. During the scanning, the camera equipment captures the desired area in relation to a specified reference point.
– As a result of the scan, we received a comprehensive 3D model of the area in RCS-format as well as illustrative panoramic photos. The 3D model was introduced into the design environment and was used for inspecting collisions and fitting structures to the existing environment, states Timo Viljanen from Oucons.
3D scanning brings reliability to the design and it speeds up both the design and installation phase.
– Without the scanned data, it would have been necessary to carry out a time-consuming on-site measurement using traditional methods including tape measures and sketchbooks. Automatic measurements also help reduce the likelihood of measurement errors. The sorting line equipment and the structures we had planned fitted together perfectly, which significantly sped up and made the installation easier, stated Viljanen.
TEXT Marianne Valta PHOTOS Nordkalk Oy Ab