3D paved the way for new filter screens
The old filter screens were worn out, but replacing them proved to be harder than expected. FVB’s 3D scanning was the key to solving the problem and they were installed by the end of November.
When the water and sewage company Nodra in Norrköping, Sweden, had to replace filter screens, it faced unexpected challenges. Working closely with FVB, a solution was found that improved both the filtering process and the working environment.
Nodra filters about 45 million litres of wastewater every day at the Slottshagen treatment plant. The first filtering step traps dry solids in wastewater using filter screens.
“We get around four tonnes of dry solids a week that should not be in wastewater at all. Mobile phones, tampons, cotton swabs and all sorts of other stuff are trapped by the filter screen,” says Roger Allen, Project Manager at Nodra, before continuing:
“The old filter screens were worn out and needed replacing. Our supplier had also informed us they were no longer able to service the screens, which made replacing them a matter of urgency.”
Roger Allen, Project Manager, Nodra
Difficult replacement
There are three parallel filter screens at the plant, each of which is five metres long, one metre wide and weigh around three tonnes. The screens – which are mechanical – act as a moving flight of steps over which the water passes, leaving the dry solids behind thanks to the filter screen. The dry solids are then sent to Händelö CHP to be incinerated for district heating and electricity.
But replacing the old screens turned out to be more difficult than Nodra had expected. That's because they were located in a small room and without an overhead crane. The new screens and screw wash presses were also bigger and longer.
“Initially, our job was to design the filter screens and related machinery in the same place as the old ones, but we realised very early on that replacing the old filter screens would be a problem, and Nodra needed more help than first expected,” says David Lindén Elofsson, FVB’s Project Manager.
Visualising through 3D
“The limited space caused a complex problem and we tried out various ideas on how to manage the replacement. One of the methods we used was 3D scanning of the room and new designs in a 3D tool, enabling us to give the customer a clear visualisation of our proposed design, illustrating the changes,” says Lindén Elofsson.
He also points out that the 3D tool made it possible to check installation issues and available space, which prevented delays and extra costs from overtime work.
Roger Allen believes that FVB’s skills with the 3D scanner were key to success in the project.
“Using 3D, we could see the various alternatives quickly and easily. And that saved time,” he concludes.
David Lindén Elofsson, FVB’s Project Manager.
Untraditional solution
The solution was installing a liftable hatch in the roof to be able to lift out the old machinery and drop in the new ones. This was an unconventional solution but worked well in practice. The last machine will be in place in November.
Apart from the roof hatch, Nodra inserted a complete steel structure into the building with a traverse crane able to cover the entire floor area.
“This was important to be able to remove and install the filter screen and for major maintenance work. Parts of the filter screen will need to be replaced about every three years, which will require the traverse crane. The room has also been extended to make maintenance work easier, improving the working environment as well,” says Lindén Elofsson.
Collaboration with FVB worked very well according to Roger Allen.
“There is no standard solution for solving problems within our plants, which calls for exceptional skill and know-how. Two things that FVB have. David was responsive and came back to us with various proposals for ways of how to solve our problem, and now we have a facility that is better suited to the activity and for the people who work there,” concludes Allen.
