To balance out the natural yellowness of paper, dyes are added to the raw pulp to bring out the blue tones. This is what gives white paper its brilliance – but only when the metering process is exactly right.
Dyeing paper white under difficult conditions
At its factory in Plattling, Germany, Finnish paper manufacturer UPM operates three impressive machines which produce approximately 790,000 tonnes of magazine paper per year. One paper machine is 300 m long and as tall as a three-storey house, and the paper races across the 8 m wide rollers at 60 m/s. First the liquid pulp is pressed into sheets, then the water is extracted until finally the paper is rolled out on large drums. Only at this stage can you tell whether the dyes added at the beginning were metered correctly. This is the first challenge in achieving the right shade of white. The second is that the dyes are so highly concentrated that only 100 ml - 300 ml per hour is required, but the dye must be added continuously. Challenge number three is that the dye containers are 5 m away from the pumps and the point of injection about 20 m away.
- Paper manufacturer UPM in Plattling, Bavaria
- Dyes metered into the raw paper pulp
- Continuous addition of 100 ml - 300 ml per hour
- Solenoid Driven Metering Pump gamma/ L 1601 PVT2
- Flow Meter DulcoFlow® DFMa
Very fine metering with built-in monitoring
Both UPM and the Austrian machine manufacturer are loyal ProMinent customers, won over by the company's high-quality products and excellent on-site support. This time ProMinent once again had the right products to meet the customer's needs. So in 2013 two metering systems were installed, each with four Solenoid Driven Metering Pumps gamma/ L and four Flow Meters DulcoFlow® DFMa. For an even addition of dye, the gamma/ L meters small dye quantities in many small strokes. Its major benefit is the connection to the DulcoFlow® devices, which measure the metered volume via the pump and report it to the central control unit for process monitoring. Both metering systems have built-in redundancy, so only two pumps and flow meters are in use at any one time, with the others ready to step in should a fault occur.
Optimum quality means reliability
- Even, reliable metering
- Process reliability: continuous measurement allows faults to be quickly corrected
- Redundant metering systems prevent system downtime
- Better, consistent paper quality
- Minimal waste reduces costs and increases customer satisfaction