Abstract: A method for treating a moving surface, such as a rotating roller (11) or a moving belt (42), according to which method surface treatment elements (12), such as metallic brushes (12), are pressed against the surface to clean and smooth it. The brushes are cleaned at the edge of the surface. The brushes are connected to an endless chain (16) on which the brushes are moved in a transverse direction by a moving means (17). The apparatus may be mounted in conjunction with a roller or belt or connected to it via a doctor frame (31) or some other supporting structure (47).

Abstract: A procedure for analyzing air content of a liquid, e.g. pulp slurry, wherein the ratio I.sub.att /I.sub.sc between ultrasound attenuation and scattered ultrasound attenuation and/or the logarithm log (I.sub.att /I.sub.sc) is determined. The respective measuring apparatus comprises an ultrasound transmitter (1) and an ultrasound receiver (2) and a scattered ultrasound receiver (3), the latter being disposed to measure members (4) for determining the ratio I.sub.att /I.sub.sc and/or the logarithm log (I.sub.att /I.sub.sc).

Abstract: In a method of measuring the flow velocity of a suspension by ultrasonic echo pulse technique, two or several ultrasonic transducers, located at a distance from each other, are placed on the surface of the pipe conducting a suspension flow. An ultrasonic pulse is transmitted from the transducers through the pipe and an echo of the ultrasonic pulse is received after a time determined by the depth of the suspension. The echo pulses are received, and a low frequency signal contained in such pulses, caused by fibres or other particles in the suspension, is amplitude-detected. A second, or later, echo from the opposite wall of the pipe is utilized if a received echo is masked by the transmitted pulse. The signals derived from the transducers are compared by correlation and the flow velocity of the suspension to be measured is thus determined. The second echo from the opposite wall of the measuring pipe is preferably used.