METHOD FOR MEASURING THE PROPERTIES OF A COMPOSITION CONSISTING OF A LIQUID AND SOLID PARTICLES AND APPARATUS USED IN THE METHOD

Abstract: A method for measuring the properties, especially dry matter content of a composition consisting of a liquid and solid particles. According to the method, the composition is supplied (E, 3, 9, 45) with electromagnetic radiation, whose wavelength is selected to be smaller than the smallest dimension of particles contained in a composition to be measured. The size of a zone to be radiated is maintained substantially constant and the composition and the zone to be radiated are set in motion relative to each other. A measuring means (6, 12, 9, D) is used to measure the intensity of radiation reflecting or scattering back from an electromagnetically radiated zone. The variations of intensity, caused by particles (P) travelling into, within and out of a zone to be radiated, is used to identify the configurations of particles and to produce, on the basis of these configurations, signals which represent the particles. These are processed into a message proportional to the properties, especially dry matter content of a composition.

Description: Method for measuring the properties of a composition consisting of a liquid and solid particles and appa¬ ratus used in the method. The present invention relates to a method as defined in the preamble of claim 1 for measuring the proper¬ ties of a composition consisting of a liquid and solid particles and to an apparatus used in the method. In particular, but not exclusively, the invention re¬ lates to a measuring method of the properties, especial¬ ly the dry- matter content of cellulose pulp. The most important measurement at the wet end of a paper-making machine is the measurement of dry matter content and quantity of the pulp. The material quantities can be readily measured from a finished product but the wet end optimal control requires a method and apparatus capable of measuring reliably the dry matter content of mass suspension. Presently available are mechanical (FI 33814 and SE 343683) and optical (FI application 824185) methods and mechanisms, based on the measurement of the shear¬ ing force of a composition or the light scattered from a pulp. All these mechanisms are characterized by be¬ ing non-linear and by the fact that they must be adjusted on the basis of laboratory samples. Another drawback in mechanical measuring methods are the measuring in¬ accuracies caused by the flow rate of a composition. A drawback in the optical composition measuring methods is that the properties of a composition, such as white¬ ness, chamicals, additives and variations in particle size distribution, lead to inaccuracies in the measure¬ ment. The above disturbance factors affect the outcome whenever any of them obtains a new value. In other words, the presently available mechanisms, are capable of producing a signal suitable for a control oper¬ ation and dependent on the dry-matter content when the dry-matter content is the only variable that changes. Variations in flow rate, composition whiteness, chem¬ icals and additives are disturbing factors and lead to inaccuracy and adjustment requirements in the pre¬ sent measuring methods. An object of this invention is to introduce a method for measuring the properties of a composition consist¬ ing of a liquid and solid particles in a manner that the method is capable of measuring the properties, es- peacially the dry-matter content of a composition di¬ rectly from the composition without allowing the other properties of a composition to affect the measuring results. In order to achieve this object, a method of the invent¬ ion is essentially characterized in that - the electromagnetic radiation led into a composition is given a wavelength that is smaller than the small¬ est dimension of the particles in a composition to be measured, - an intensity function is formed as a result of the movement of an individual particle arriving in and passing by any given zone exposed to radiation and - the intensity function is processed for finding out time relationships that are proportional to the thus appearing properties of a particle. The theoretical basis of the above-described method, particularly when a composition to be measured is cel¬ lulose pulp, can. be derived as follows: Fibres in a mass suspension build a three-dimensional network on rather low consistencies. The network ac¬ cumulates in. so-called floes when consistency exceeds the value of one percent. It is natural that the pulp should be as free of floes as possible when it comes onto the wire of a paper-making machine. There are studies available indicating that, such floes are pro¬ duced on consistencies over one percent in a few milli¬ seconds when the mass is not turbulent. In other words, cellulose pulp or mass must be in continuous motion. Fig. 1 is a schematical view of cellulose pulp with cellulose fibres in random order. Thus, cellulose mass or pulp consists of disorderly bundles of fibres, in* which the fibre lengths are usually in the order of 100...1000 microns, sometimes more- than that. The mass further contains short flour, whose length is less than 100 microns, as well as additives (clay etc.) with part¬ icle size less than 10 microns. In theory, it is con¬ ceivable that, as shown in fig. 2, the fibres are evenly distributed over the entire mass volume. The pattern shown in fig. 2 can be argued by pointing out that the fibres are Poisson-distributed with a certain parameter representing a relative distance h. Supposing further that the fibres have a great length X- and the fibres have a certai mean diameter d, it is possible to de¬ rive the dependance between mass consistency C and para¬ meter h. It can be seen from fig. 2 that the volume can also be divided e.g. in hexagonal elements, whose longitudinal axis coincides with the longitudinal axes of evenly distributed fibres. The mass consistency can be described by equation C = π^/V (1) where C = consistency q/JL IΓL, = mass of the fibres V = volume containing the fibres on the other hand m_ - j - σ ^ τ " ^ where _ - fibre density (close to one) V_F •= fibre volume On the basis of the above ,- equations (1) and (2) lead to C =/ F /V (3) Calculating from fig. 2 that τ r ■ -ϊ- -t (4) - V - /T 2 -ι/2 ( 5 Inclusion of (4) and (5) in equation (3) leads to C = P F- ~ 2<i /Th 2 . t /2) and after cancellation C = 'e.d /(2yTh -- 6 - 1 or C = constant term • ( _ \ / ) ~~ in which a constant term - *ø c../2y_r * Equation 6 indicates that an absolute measurement of consistency is possible,provided it is possible to measure the mean fibre diameter d -and the distance h between fibres, i.e. C=f(d,h). Following now is a description of the theoretical basis for the fact that such quantities d and h can indeed be measured from a fibre suspension. Supposing that e.g. an electromagnetic radiation is led into a mass or pulp to cover a circle whose diameter is D. Within this zone is located a d-diameter fibre, as shown in fig. 3. As the fibre, travels across the ra¬ diated zone in the direction of. a positive x-axis, the shaded portion, thereof, will be. visible- The surface area I of this- portion as an-jX-rfunc ion of the position when the fibre is within the radiated zone will be 2 I Q =r • (r 2 -sin τ 2 cos Ύ 2 ~ (γ χ - sin τ χ cosv.)) (7) where . and Ϋ ~ are the central angles defined in the figure I = 0 / when x < 0 or x > D+d x = 0, when the leading edge of a fibre touches a radiated zone r = D/2 cos 2 = 1-x/r, when C<zz<p , when d<x D+d, +d If the mass is radiated over a zone having diameter D, I will represent the intensity of reflected light as an x-function of the position of a- fibre. In digital image processing, configurations are identified by finding the sharpest-changing points in the variation of image intensity. In order to study its variations, signal I Q must be derived and the result for the first (I..) and the sec¬ ond (I 2 ) derivative as a function of x with the desig¬ nations and conditions of equation (7) will be: dI Q I χ - -3S- - 2r.(sinγ 2 - sin^ ) < 8 > dl χ I 2 = αx = 2 ' ( co : r 2 " < ~ o^ ) (9 ) Fig. 4 shows the describers of a. function I Q , I_. and I- when the diameter of a radiated zone is 180 microns and the mean fibre diameter d is 30 microns. The figure shows, an interesting characteristic of the second derivative of f nction I Q : I- has singularities at points x. = Q r , D and D+d. These singularities can be derived from equation (9) by including the variables as a function of x. Further, as a function of time, the mass travels across the examined zone at a velocity v. Since fibres are randomly positioned in the mass, the x-directed velo¬ city obtains an average value v V k = 2v/τr (10) which is the average of a fibre's velocity in direction x with the position of fibres varying arbitrarily re¬ lative to the x-axis. Intensity I Q obtains a corresponding statistical coeffic¬ ient 2/ * T , since the angle between fibres and z-axis varies randomly with respect to the plane of fig. 3. When a suspension travels at velocity v, equations (7) , (8) and (9) obtain a new form since electronics offer a possibility of deriving time functions with respect to time. The result will be voltage functions u Q , xi. and u , u. = K (t) ( 11) dx where = 0 Q * P Q • NA_, * NAg * R g • G 0 Q = output emitted by a light source p . = effective reflection factor of a fibre NA_, = emitter aperture NA S = receiver aperture R- = receiver sensitivity G = electronics gain T_. and T- = derivation time constants When noted that —dx = v, the following is observed: If dt a sample is obtained from voltages u Q and u 2 when u. = 0, the last term of equation (13) can be eliminated and the ratio u 2 /u Q °*^ samples is proportional to the square of flow ra,te. At this point where r = D/2 z = D/d In addition to derivation time constants 1 and 2 the velocity signal obtains as a scaling factor the radius r of a radiated zone and as a disturbance term, in accord¬ ance with equations (14) and (15), a term resulting from the variations of fibre diameters. For the determination of dry matter content, according to the above formulae (formula 6) , it is necessary to have information about the magnitude of d and h. Fig. 4 indicates that the interval between successive oppo¬ site-sign singularities (o, d) of u 2 is T. - d/v and the repetition interval of signals is T- = h/v. The situation is outlined in fig. 5. If a flip-flop in the electronic component of the apparatus is control¬ led to be on during time T.. (time between singul¬ arities o - d) and off during time T- - T- (includes singularities D and D+d) , a pulse sequence of fig. 6 will be obtained. Filtration of the pulse sequence and its complement gives the voltages τ ι u d ■ • u (16) T 2 s - T 2 T l u h T. . s (17) Equation (16) can also be described as d/v u d = h/v (16a) where u = flip-flop operating voltage. 5 When the filtered u, is squared and scaled by dividing bv voltaσe Vre, the result will be a signal ucs pro- portional to consistency C of equation (6) : - - u _ us . ,d,2 u cs ~ -vre vre ( h } ( 13 ) where V = scaling voltage for electronic circuit of fig. 12. It can be noted that equation (18) provides a voltage equal or at least proportional to the consistency, said voltage being in principle independent of flow rate, colour and additives. The above argument is based on the following hypotheses: 1. By means of automatic control of electronics gain factor, u n can be made constant 2. amplitude of electronics noise can be kept to such a level that the peaks of u ? are distinguished with a sufficient probability 3. the mass flow rate is within suitable limits, at too low a rate, u_ goes to zero and at too high a rate, the electronics passband runs out; passband must be restricted for limiting the noise to a suf¬ ficiently low level (item 2) * 4. additives do not reflect light the same way as fibres, i.e. fibres must be distinguishable from background. Thus, the above describes how the dry matter content of a composition can be measured according to the charac¬ terizing section of claim 1. According to the method, it is hence possible to measure the dry matter content of a composition directly from the composition, whereby the measurement disturbing factors can be more readily controlled. A condition for this operation is that the particles, to be measured are to such a degree distinguishable from the. background that the noise in a signal derived from a signal pro¬ duced by said particles and due to a detector and elec¬ tronics does not override said utility signal. Other fea¬ tures characteristic of the method as well as the appa¬ ratus are set forth in the other annexed claims. As for the advantages gained thereby, reference is made to the above section explaining the theoretical basis of the invention. Alternative embodiments of an apparatus of the invention are schematically illustrated in figs. 7-11 and one pre¬ ferred diagram for the electronics component of said apparatus is shown in figs. 12 and 13. The apparatus will now be described in more detail with reference made to those figures. In the embodiment of fig. 7, the optical components of an apparatus are fitted inside a protective tube 1 and the end of this protective tube is provided with a win¬ dow 2, whereby the optical components in said protect¬ ive tube are in contact with a composition to be mea¬ sured for measuring the dry matter content of particles P contained in the composition. Inside the protective tube is fitted a radiation source E_ the radiation emitted thereby being directed through a collimating lens 3 to an optical fibre 4, at whose end is a fiber- optical lens 5 for directing the radiation by way of window 2 into a composition to. be measured for creat¬ ing a zone to be radiated. The radiation reflected back from the radiated zone through window 2 is collect¬ ed by means of a condenser lens 6 on a detector D., where¬ after the radiation arriving in* detector is preamplified at 7 and the amplified message is conveyed from protect- ive tube 1 by way of an adapter 8 along a cable 9 into the electronics', section 10 of the apparatus,which then supplies a consistency signal 11. Fig. 8 is otherwise, similar to fig. 7 but a radiation source E and a collimating lens 3 as well as a detector D are mounted in connection with the apparatus' elec¬ tronics section, the electronics section and protective tube 1 being only connected by a bipolar fibre cable instead of a multicore cable shown in fig. 7. Thus, the radiation issuing from a condenser lens 6 is de¬ livered along an optical fibre 12 to the apparatus' electronics section 10. This embodiment serves to re¬ duce the need for cables as compared to the embodiment of fig. 7. Fig. 9 illustrates an embodiment of the apparatus which employs a surface 16 that reflects at 14 and is perme¬ able at 13 to radiation. The radiation emitted from a radiation source E is di¬ rected through a lens 15 to a permeable surface 13, whereafter the light of a radiation source is further collected * by means of a lens 17 on an optical fibre 18, at whose end the radiation is further directed by means of a lens 19 into a composition to be measured for pro¬ ducing a zone to be radiated. The radiation reflected back from a radiated zone finds its way in reverse order to a reflective surface 14 and further by way of a lens 20 to a detector D. A system corresponding to that shown in fig. 9 can also be embodied fiberoptically, as shown schematically in fig. 10. Thus, in this case, a reflective and perme¬ able surface 13 is directly used in conveying a radiat¬ ion transmitted by optical fibres, without using any lens systems. A radiation directed from a radiation source Ξ to an optical fibre 21 is reflected by way of a surface 14 to an optical fibre 18, whose end is fitted with a fiberoptical lens for allowing the radiation into a composition to be measured for producing a zone to be radiated. A radiation reflected back from this radiated zone is directed by way of optieal fibre 18 -through the reflective surface to a detector D along an optical fibre 22. Fig. 11 shows an optical arrangement for the apparatus, designed by using laser technology. Inside a protect¬ ive tube 1 is fitted a He-Ne laser device 23, from which a laser beam is directed through a focusing lens 24 and a window 2- into a eomposition. Inside protective tube 1, the frame of window 2 is provided with one or a plu¬ rality of detectors D, connected to the apparatus* electronics section 10. In fig. 11, preamplifiers for the electronics section are fitted inside protective tube 1 in an element 25. The rest of the electronics are disposed outside the optical arrangement. In view of the invention, the most essential part of the electronic. circuit section 10 of an apparatus used in the method is shown in block diagrams in figs. 12 and 13. Its operation proceeds as follows: A control voltage Vre is used to stabilize the rad- iation from a radiation source E by utilizing a feed¬ back from a photodiode S and a resistance R_. The ra- diation source can also be non-stabilized. The rad¬ iation output must be over 2 mW. From the radiation source, radiation is directed by way of the optical arrangements shown in figs. 7-11 into a composition to be examined. A zone to be radiated ful- f ils the scale condition stated in th theoretical basis of the i vention ! considering the size of partic¬ les contained in a composition to be examined. Referring to fig. 12 , the radiation that has reached detector D is converted into current and in a load resistance R^ into voltage . This voltage signal is amplified by a preamplifier A- and its direct voltage cαπponent is elitriinat- ed by means of a filter -F Q . The preamplifier sensitivity must exceed 5 kV/W. The lower limit frequency of filter F Q is circa 1 G-Q Hz . The maximum gain of amplifiers - - and - _ must exceed 60 000 for a sufficient level of signal u Q . The gain of amplifier A- 1 is controlled by means of an integrating level adjustment amplifier A AGC having a time con¬ stant of circa 1 s , in a manner that the mean peak value of pulses u Q or u 2 does not exceed a reference voltage V . (circa 7 V) . Peak values are measured by means of peak value detectors u Q and u - • Detector u Q measures the positive peak value of u_ and u 2 measures the peak-to-peak . value of u 2 - Detector u , measures the values of u.. the same way as u 2 measures the values of u- . The value of a tracking time constant is circa 400 iis and the holding time constant circa 80 ms . Since the signal must be subjected to derivation , its noise band¬ width must be optimized for maintaining, a sufficiently good signal-to-noise ratio . The signal-to-noise ratio remains sufficient when the passband of the filter F, is adjust¬ ed as a function of mass flow rate . Approximate data of flow rate is obtained from voltage, L. for controlling the band of filter F. . Voltage u v is produced by means of computational circuits . -20 and A^ of fig. 13 as well as by means of a. suπming ampli ¬ fier A 22 ( circuit F c I in fig . 12 ) as a weighted sum of the ratios of voltages upu_, up .i an up___,. The weight- ing factor K.,ι Λ θ of ratio up.i,/up Λ θ is circa 0.53 and the weighting factory of ratio u 0 2/ u αι *^ s ci ^ ca 0.72. Thus, when using value 10 V for voltage V . the scale of volt¬ age u will be 1V for rate 1 m/s. A suitable bandwidth is selected by means of comparators A--,, _ 4 , 2 c and A 26 controlled by voltage u as well as by means of relays R Q , R. , R 2 and R_ by eonnecting the one of filters B Q , B_. , B 2 , B-, or B. , which is most suitable for a particular rate range in question, between amplifiers A.. . and 12 - The voltage division provided by ~ ~ resistances Rv Λ O, Rv .1 , Rv2-,, Rv3 ' . and Rv4. determines the rates at which the change of bandwidth occurs. Suitable filters are Bessel-type filters, of tenth order. Delays are approximately 21, 10, 6.8, 4.7 and 3.5 micro¬ seconds when change-over speeds are circa 0.6, 1.4, 2.75 and 4.25 m/s. The diameter of an illuminated zone is then 50 microns and derivation time constants T.. and T_ are 10-20 microseconds. With the above time constants, derivation units D 1 and D 2 produce voltages u 1 and u 2 from voltage u Q . A positive threshold voltage required by a comparator C 2+ is obtained as a weighted sum of voltages u 2 and u. from a summing circuit A, g , ion which the weighting factors are roughly as follows: K-2 circa 0.37 and Kv circa 0.25. The con- stant V is circa 0.41 V. A negative threshold voltage is produced by an inverter I. Comparator C 2+ sets a flip-flop 1 when u 2 exceeds the positive threshold volt¬ age, which happens at the final end of fig. 4. The next overrun of threshold voltage on comparator C sets a flip-flop FF 2 - This is followed by going below a negative threshold volt- age and that is detected by comparator C~_ , which re¬ sets flip-flops FF 1 and FF 2 - Comparators C Q and C. prevent by way of NOR-gates the setting of flip-flop FF 2 as a result of noise and dis- turbancies. Comparator C Q compares, the gain adjustment voltage u AGC with a reference value V rd (circa 10 V) and prevents the operation of flip-flop FF_, in case the signal is too low. Comparator C. prevents the re¬ setting of flip-flop FF 2 as a result of noise. The output waveform of flip-flop FF 2 is as shown in fig. 6 and, by means of a filter F 21 having a buffer amplifier, it is processed into the voltage u, of equat¬ ion 16. The upper limit frequency of filter F 21 is below 1 Hz. A comDutational circuit A, g produces a voltage u by squaring voltage u,, scaled by voltage V . The thus obtained voltage u can be processed with prior known methods to form a desired consistency message. In case a microprocessor is used, the consistency cal¬ culation can be effected by measuring the on-times of signals 1 and 2 by means of a timer circuit or a counter, which is either inside, the microprocessors, included in a peripheral circuit or is an external circuit. The aver¬ ages and a desired digital message are calculated from the obtained times T.. and 2 by way of a program. Times 1 and T 2 can also be determined by way of a program after recording in the memory of a micropro¬ cessor a sufficiently long sequence of samples of sig¬ nal u Q with a resolution of below 10 us. The obtained message can be transformed by means of a digital-analog converter into an analogous standard signal in a desired scale or it can be output by way of the digital interface of a microprocessor onto a control system. The method and its theoretical, basis are described above so that the diameter of a zone to be radiated exceeds the smallest dimension of particles. As an alternative, it is also possible to have such scaling that the diameter of a zone to be radiated is less than the smallest dimension of particles. In this case, the form of an intensity function changes to some degree, as a skilled person can readily appreciate, but the characteristics of the second derivative (sin¬ gularities) of an intensity function are still dis¬ cernible.

Claims: Claims 1. A method for measuring the * properties, especially the dry matter content of a composition consisting of a liquid and solid particles, said method comprising - leading electromagnetic radiation into the composit¬ ion, - maintaining the. size of a zone to be radiated sub¬ stantially constant, - setting the composition and the zone to be radiated in motion relative to each other, - measuring with a measuring means the intensity of radiation reflecting or scattering back from an electromagnetically radiated zone, the signals there¬ from being processed into messages proportional to the properties, especially the dry matter content of a composition, c h a r a c t e r i z e d in that - the electromagnetic radiation led into a composition is given a wavelength that is smaller than the small¬ est dimension of the particles in a composition to be measured, - an intensity function is formed as a result of the movement ' of an individual particle arriving in and passing by any given zone exposed to radiation and - the intensity function is processed for finding out time relationships that are proportional to the thus appearing properties of a particle. 2. A method as set forth in claim 1, c h a r a c t e r i z e d in that an elliptical or circular area is used as a zone to be* radiated. 3. A method as set forth in claim 1 and 2 , c h a r a c t e r i z e d in that the greatest diameter of a zone to be radiated is selected to be smaller than the great¬ est dimension of particles to be measured from the com¬ position but greater than the smallest dimension of par¬ ticles to be measured in the composition. 4. A method as. set forth in claims 1-3,. c h a r a c ¬ t e r i z e d in that the composition is set in motion and the zone to. be radiated is. kept, stationary. 5. A method as. set forth in claims 1 -4 , c h a r a c ¬ t e r i z e d in that - a time-dependent counter-function (u Q ) of a function (I Q * = f (D, y_,, f 2 ) corresponding to the surface area of particle figures in a zone to be radiated is de¬ rived two times relative to time for discovering the singularities of the second derivative of counter- function (u Q ) , - an apparatus' electronics circuit is used to measure analogically and/or digitally, as individual particles travel past a zone to be radiated, a time interval (T 1 ) between two successive, opposite-sign singular¬ ities, which corresponds to the diameter of partic¬ les, and a repetition interval (T 2 ) such as the inter¬ val between the above pairs of singularities, which corresponds to a distance between successive particles as they travel past a zone to be radiated, - an apparatus' electronics circuit is used to produce an electric message u Co = f(T_I., T___) , which is porport- ional to * * the consistency of a composition and whose 2 general configuration is u = V " (T_./T 2 ) / wherein V is a reference voltage. 6. An apparatus for carrying out the method of claims 1-5, said apparatus comprising: - a radiation source (Ξ) - means (3, 4, 5, 2; 3, 9, 4, 5/ 2; 15, 13, 17, 18, 19; 21, 14, 18; 24) for leading the radiation of said radiation source (E) into a composition to be measured for producing a zone to be radiated, - a detector (D) , - means (2, 6; 2, 6, 12, 9; 19, 18, 17, 13, 20; 18, 13, 21) for directing the radiation reflecting or scattering back from a radiated zone onto said de¬ tector (D) and - a block (10) comprising of. electronic circuits, which is connected to detector (D), c h a r a c t e r i z e d in that - said electronic circuits block (10) comprises means (D-,,- D-, FF 1 , FF-) for processing a time-dependent elect¬ ric counter-function of the intensity of reflecting or back-scattering radiation for producing signals (T 1 , ~ ~) representing the configuration of particles contained in the composition and means (A 1g ) for pro¬ ducing a message (u ) proportional to the properties, especially the dry matter content of the composition. 7. An apparatus as set forth in claim 6, c h a r a c ¬ t e r i z e d in that said electronics component (10) comprises - an amplifying and filtering unit (A Q , F Q , A...., F.. , 12 ) , - two successive derivation units (D 1 , D-) , - two flip-flops (FF., FF-) > - a threshold voltage producting unit (A, g ) - comparators (c 2+ . C 2 _ for contro ---l in< 3 ' flip-flops (FF 1 , FF 2 ) according to the variations in voltages arriving by way of derivation units (D.., D 2 ) and - a means (F 21 . A- t g) for producing a message, which is formed on the basis of the output of flip-flop (FF 2 ) and which represents the dry matter content. 8. An apparatus as set forth in claim 6, c h a r a c ¬ t e r i z e d in that,in order to optimize the signal- to-noise ratio, the passband of a filter (F..) be¬ tween amplifier units (A. 1 and - 2 ) is adapted to be selected by means of a. selector circuit (Fc.i,), whose input variables- comprise voltages (u . , u . , u_ 2 ) > pro¬ portional to voltages (u Q u 1 , u 2 ) acting upstream of derivation units, between and/or downstream of derivat¬ ion units, and whose output comprises a voltage (u ) , which is produced on the basis of voltages (u Q , u . and u 2 ) preferably as a weighted sum thereof and on the basis of which a comparator circuit ( 23 , A 24 , - e/ 26 ) is operated to switch on the passband (B Q , B- , B 2 , B 3 or B 4 ) of filter (F 1 ) .

Inventors: KARAILA ILKKA, KARAILA, ILKKA
Applicants: VALMET OY
Application year: 1987
Main classification: G01N15
IPC codes: D21F1, G01N15, G01N21, G01N33