GB1231443A - - Google Patents

Abstract

1,231,443. Photo-electric measurement of moisture content. INDUSTRIAL NUCLEONICS CORP. July 8, 1968 [July 19, 1967], No.32561/68. Heading G1A. Moisture is removed from a travelling web while passing from a first to a second station and the moisture content of the web at the first station is determined by generating signals representative of the mass flow-rate of the web at the first and the second stations, respectively, and of the moisture content at the second station, and using a computer to calculate the moisture content at the first station from these signals. In the described embodiment the web is of paper, produced by the Fourdrinier process as indicated in box 10. The first station C is fitted with a #-ray gauge 47 scanning the web to determine the basis weight (mass per unit area) of the wet web emerging from press 24, before entering a first dryer 26. From this basis weight measurement, the rate of mass flow is determined by multiplication by the width and speed of the web at C, using computer 59, which may be digital, but is preferably analog. A similar gauge 45, at the second station A, where the web emerges from a second dryer 30, measures the basis weight at this station, and a similar computer 53 computes the mass flow at A. A further gauge 49 produces an output representing the actual moisture content of the web at A. (Direct measurement of the moisture content of a very wet web, e.g., at station C, would give inaccurate results). The signals from the computers 59, 53 and gauge 49 are combined in computer 65, preferably analog, according to selected formulae to give an output measure of the moisture content either in lbs water/lbs fibre, or per cent moisture. The gauges 47, 45, 49 may scan the web in synchronism. If the moisture content at A is known to be constant, this moisture factor may be set into computer 65. If differences in speed (or width) between A and C are negligible, one of the gauges measuring speed (or width) may be dispensed with. The output of computer 65 may be in lbs water/lbs basis weight, or other units. The gauges may be located at other "wet" and "dry" positions; e.g., "dry" measurement may be possible after first dryer 26. The signal from computer 59 may be delayed to allow for transport delays. The output of computer 65 may be that recorded or used for controlling headbox consistency, moisture content at the "wet end", etc.