Permi - On-Line Porosity Analyse
On-line porosity measurement
The new generation on-line porosity analyzer Permi works as a stand alone gauge or as an analyzer with sophisticated PC software.
Fast and continuous measurement
Unlike other systems Permi measures continuous air flow through the paper web. Measurement frequency can be up to 500 Hz.
Accurate and reliable readings
Due to the fast measurement every porosity reading is an average of several measurements in the machine direction. When it is compared to the laboratory measurement it is clear that there is more variation in the laboratory values. This is the main reason that porosity has not been considered as a good control parameter earlier.
The measurement signal is linearly related to the laboratory methods based on air flow measurement, like Bendtsen and Sheffield. Also time related measurement numbers can be easily calculated e.g. Gurley seconds. This fact means that only one calibration is needed to set up the measurement.
Easy to maintain
Contacting instruments always take dust with the measurement air. Dust plugging is prevented by air filters and automatic self cleaning sequence.
Electronics close to the measuring head
To get an accurate measurement it is important that the total compressing air volume from the web to the measurement position is minimized. This requires that the flow measurement and air filters are as close to the measurement head as possible and the signal is electronically sent to the control box.
Totally new control possibilities
When porosity is constant the process is working well. Changes in raw materials, refining, retention, drainage, wet pressing and surface treatment can easily be seen in the measurement. On the other hand, if porosity is constant paper bulk, strength, formation, opacity, internal bond as well as holdout of coating colour and printing ink are consistent.