Reliability is very important in paper machine lines. Hydraulics is used through the machine to control heavy weight components. Proportional valves have been used for decays in hydraulics. They however need high precision mechanics to achieve required accuracy. The proportional valves can be replaced by digital hydraulics. Digital hydraulics uses sophisticated control system and robustic on/off valves to create better reliability.


IN EFFIMA program the digital hydraulic technology was developed to be compatible with a paper machine environment. The project was started with technology suitable for laboratory. With a pilot machine the principle of the digital hydraulics was proved to be working and outperforming proportional valve controls. Better reliability was the main interest of the technology, but some other advantages was also discovered. Energy savings was noticed to be huge in certain applications. In loading cylinders it was up to 98 percents. Also savings in more simple hydraulic pipings and power units was achieved.


The principle of the digital hydraulics was developed in Tampere University of Technology. In the program Valmet’s task was to develop digital hydraulic controls for paper machines. 

In the beginning there were no commercial components which were designed for digital hydraulics. First target was the control system. We had to find an industrial platform which was cheap enough and capable of running Simulink code. Smaller and faster on/off valves had to be developed, and the valve driver electronics (booster) was not existing.


In the program all missing technologies were developed. A lot of co-operation was done with hydraulic and control system companies. A solution for digital hydraulic product was developed to suit for all paper machine applications. Valmet has protected the solutions in paper machines, but the control system and valves are commercial and can be used in other industry.

Based on the concept Valmet has delivered several digital hydraulic controls all over the world. In some projects it has been an asset to receive a project. Especially in modernisation business which is at the moment very important area, digital system has many advantages. It is easy to test fully in assembly shop and downtime at paper mill will be very short in start-up. The technology has also made it possible to use new functions which were not possible with traditional controls.


Juhani Toppari, Valmet Technologies Oy


Tampere University of Technology 
Aalto University 
Åbo Akademi


Author missing

Juhani Toppari


Valmet Technologies Oy