Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3~3C~6s4i
AUTOMATIC SYSTE~ E~R A~ALYSIS OF GROUND
i~A'TERIAL SIZE FRACTIO~S
~ he pre~ent invention relatea to measuring in~trument~
and, more particularly, to automatic ~y~tem~ for analy~i~
of ground material-size fraction~ by sedimentation techni-
que.
The i~vention may be used for analysis of the granulo-
me tric composition of ground material~ at concentration
plant~ in ferrous and nonferrou~ metallurgy, in chemical
industry and other indu~tries pro~ucing or uæing dispersed
materisl~.
Known in the art iq an automatic ~y~tem for analy~i~
of the eize ~raction of ~round materiale (USS~ Inventor' 8
Certificate No. 890157, IPC GOI N 15/04, published December
15, 1981) comprising a oedimentation cylinder filled with
liquid, a device for ~ampling and delivery of the ground
material in the ~orm of a ~lurry to the ~edimentation cy-
linder equipped with a ~ample input unit. The sedimentation
cylinder ia communicated with a measuring tube, in ~hich
the liquid level i~ measured by means of a level detector
whose indications are used ~or analysi~ of the granulomet-
ric characteristic of the 601id particle~ in the slurry.
However, mechanical de~tabilizi~g factors: ~hocks, im-
pact~, vibration of the ~edimentation cylinder, which are in-
1306S'-~
-- 2 --
avoidable under condition~ of a production plant, re~ult
in a change in the liquid level in the ~edimentation cylind-
er and mea~uring tube ~nd di~tort the result of the a~aly~i~
of the ground product size.
Known in the art iB an automatic eystem for a~alysis
of ground material size (USSR Inventor's Certificate ~o.
1055998, IPC G01 ~ 15/04, publi6hed No~ember 23, 1983) com-
prising a sedimentation cylinder filled with liquid and com-
municating with a mea~urin~ tube and a correcting tube, in
which the liquid level is converted into an electric signal
by means of elements aensing the liquid level. The sedimen-
tation cylinder iB provided with a samplin~ funnel. l'he li-
quid level sen~ing elements are connected through switches
to a measuring oscillator uith a frequency output. ~he per-
centage of solids in the given ground material Bizes iB de-
termined by the nature of change of the liquid level in the
measuring tube with time by a data processing and display
unit. The prior art system include8 a device for automatic
error correction which eliminates the effect of the destabi-
lizing factors on the analysis by monitoring the change of
the liquid level in the correcting tube and the change in
the tirne of connection of the liquid level sensing elements
to the measurin~ oscillator. However, the automatic error
correction device includes a cortrolled pulEe generator
producing pulses who~e duration varies under the effect of
an analog signal generated by said automatic de~ice. This
results in a low noise immunity of the ~nown ~utomstic sys-
tem and hinders it~ utilization under condition of a produc-
3 ~3C~6S4i
tiOl plant characterized by a high noi~e level.
~ he aPparatu~ which in it~ technical e~sel1ce and thereeult obtained in the closest to the claimed technical eo-
lution~ is an automatic ~ystem for analy~is of ground mate-
rial ~izes (U~S. Patent No. 4,175~426, Int. C1. GOl N 15/04,
publ. November 29, 197~) COmpriBing a device for sampling
and delivery of a ground material in the form of a ~lurry,
a ~edimentstion cylinder filled with liquid whose density
i~ lower than that of` the ground product,~aid cylinder hav-
ing a funnel for introducing the ground material, the narrow
outlet of ~aid funnel being located within 6aid sedimenta-
tion cylinder coaxially therewith; a differential circuit
~or measuring the rrla~s of the ground material, which did
not settle in the ~edimentation cy~inder at any instant of
time of conduction of the ground material ~ize analysi6.
The prior art automatic system include~ a reference cy-
linder communicating with tha sedimentation cylinder. Both
cylinder~ are identical and have attachments for filling
them with a liquid to the same le~el, two pressure sensing
element~ located at the ~ame level in bottom portion of the
cylinder, a di~ferential pres~ure sensor, a data processing
unit whose data input is connected to the output of said
differential pressure sensor while the timer input~ &re con-
nected to timer outputs.
~ he maas percentage of sol.id particles ~ithin the giv-
en sizes i~ determined by the character of a change with
time of the pr~ssure difference on the ~ensing element3 in
the reference and sedimentation cylinders after putting the
- 4 - 13~6S~
~a~ple into the sedimentation cylin~erO ~ov~ever, in the prior
art ~ystem the introduction of the sample into the sedimen-
tation cylinder i3 effected directly from the circulating
slurry stream. It i~ well known that in such a stream the par-
ticles of a different size are segregated, i.e. the stream
has different density along its length. Tnerefore, a ~mall
~ample put into the sedimentation cylinder and localized
in the stream does not reflect the granulometric compo~iti-
on of the slurry and is not representative~ An increase in
the volume of the sample fed into the cylinder is unde3ir-
able because it increase~ the amount of the introduced BO-
lid particles causing their hindered sedimentation (mutual
influence on the settling speed), conglomeration of the par-
ticle~ and a respective inadmissible increase of the analy-
si~ error. The efficiency of the di~ferential circuit is in-
si~nificant~ This is due to the fact that the pressure ~ens-
in~ elements in the sedimentation and reference cylinders
operate in a different way. In the reference cylinder the
sensin6 element is in contact with pure water. In the ~edi-
mentation cylinder the pressure sensing element i8 in contact
with solid particles, therefore, these particles are inevit-
ably stick to the preseure sensing element and cau~e a change
in its ri~idity with reapect to the pressure sen~ing element
in the reference cylinder.
The basic object of the invention is to provide an au-
tomatic system for analy~is of ground material sizes having
such a design and a scheme that would allow one to select
a larger volume of slurry for the analysis, to separate a
required portion of the slurry (sample) from this volume
5 ~3~6S~l
and to conduct an analysis based on a chenge of the time
change of the mas~ of solid particle~, which have not ~ettl-
ed i~ the sedimentation cylinder, at any instant of conduc-
tion of the analy~is, and also on a change of the length
of electric pul~e train~ containing information on the ~iz-
e~ bein~ analyzed to obtain true data on the ~ranulometric
compo ition of the ~round material.
~ his object is attained by providing an automatic 8y8-
tem for analy~is of sizes o~ ground material size fractions
compriPing a ~ampler for sampling and delivery of a ~round
material in the form of a slurr~, a sedimentation cylinder
filled with liquid who~e denPity is lower than that of the
ground material,eaid cylinder havin~ a funnel for faeding
a required portion (do~e) of the ground material, the nar-
row outlet of said funnel being positioned inside ~aid se-
dimentation cylinder coaxially therewith; a differentisl
circuit for mea~urinr the ma~s of the grouna material which
has not settled in the ~edimentation cylinder at any instant
of time of conduction of the ground material aize analysis;
according to the invention, the system has a device for re-
ceiving the slurry, its stirring and do~ed supply into the
sedimentation cylinder, said device being connected to ~aid
sampler and to the widening part of ~aid funnel of the sedi-
mentation cylinder, made in the f`orm of a cylindrical tank
accommodating a pre~sure cup with a propeller mounted on a
shaft, while the bottom part of ~aid cylindrical tank is
made in the form of a truncated cone provided with a -.valve;
an actuator for remo-t~ control of supply of liquid into the
6- 13~65~
the sedimentation cylinder an actuator for remote control
of the sampling and supply of slurry, an actuator for feed-
in~ the s~mple into the sedimentation cylinder, an actuator
for remote control of the remo~al of waste suspended matter
from the sedimentation cylinder, and an actuator for remote
control of slurry stirring connected to the propeller ~haft;
a control device whose control outputs are connected to said
actuators for controlling the supply of liquid into the se-
dimentation cylinder,sampling and delivery of the slurry,
feeding the sample into the sedimentation cylinder,slurry
stirring and removals of the waste suspended matter from
the ~edimentation cylinder; the sedimentation cylinder is
communicated with at lea~t one measuring tube and one cor-
recting tube, which are spaced along the height of said se-
dimentation cylinder; each of said tubes is secured through
its one end to said sedimentation cylinder, while the free
ends of said measuring and correcting tubes are located at
the same level with respect to the upper end face of the
~edimentation cylinder, the end face of the narrow branch
pipe of ~aid funnel being located in a plane perpendicular to
the longitudinal axis of the sedimentation cylinder and e~-
tenda through the lower point of connection of the fixed end
of the correcting tube to the side sur~ace of the sedimenta-
tion cylinder or below thi~ plane; furthermore, the meaeur-
ing tube ie secured below the end face of the narrow branch
pipe of said funnel; the differential circuit for measuring
the mass of the ground material~ includes a measuring and
correctin& liquid level sensing elements connected respec-
tively to the free endg of the measuring and correcting
- 7 - 13~6S~l
tubss; switching circuits; a converter converting the liquid
level into an electric signal connected through said switch-
ing circuits to said mea~urin~ and correctin~ liquid level
sensing element~; an autornatic error correction device whoae
data input is connected to the data output of the converter
converting the liquid level into an electric signal; the out-
put~ of the automatic error correction device are connected
to the control inputs o~ the switching circuits and to the
control inputs of the converter converting the liquid le~el
into an electric signal; a data procesRing and display unit
preoenting information on the percentage of solid particles
in the sizes being analyzed whose data input i9 connected
to the data output of the converter converting the liquid
level into an electric signal; the control inputs of said
unit are connected to the timer outputs of the control de-
vice whose clock-pulse and count-pulse outputs are connect-
ed respectively to the clock-pulse and count-pulse inputs
of said automatic error correction device.
The automatic error correction device may include a
scaler whose input is co~lected to the output of the con-
verter converting the liquid level into an electric signal,
-F; r~
a firRt trigger whose ~ ~ input is connected to the out-
put of the scaler while the output is a first output of the
automatic error correction device, a counting ~lip-flop trig-
ger whose input is connected to the clock input of the cont-
rol device while the direct output is connected to the =
input of the first trigger, a second trigger whose output
is a second output of the automatic error correction de-
~ 8 - 1306S4~
~ r~ f
vice, while the ~ input i5 connected to the inver~e out-
put of the counting trigger, a reversible counter and di-
rect and inverse count ~witching circuits; the signal in-
put~ of the direct and inverse count switching circuits are
interconnected and connected to the counting pulse input
of the control device; the output of the direct count switch-
ing circuit is connected to the adding input of said rever-
sible counter; the output OL the inverse count switching
circuit is connected to the sub~tracting input of the re-
S~Co~
ver~ible counter ~hose output i~ connected to the ~ in-
put of the second trigger, while the control inputs of the
direct and inverse count ~witching circuits are connected
to the outputs of the fir~t and second triggers respective-
ly.
The automatic system for analysis of ground material
size fractions makes it possible to improve the representa-
tiveness of the sample with re~pect to the process flow of
ground material being measured while avoiding a methodical
error in the enaly~i~ caused by hindered sedimentation of
solid particles in the 6ample. For this purpose, a consider-
able amount of slurry is taken from the process flow of ~ro-
und materials and a ~mall sample taken from the selected
slurry is fed into the sedimentation cylinder, said sample
completely preserving all properties of the selected slurry
due to its intensi~e stirring.
~ he e~ficiency of the differential circuit for measur-
ing the mass of the non-settled solid particles in the 8e-
dimentation cylinder at any instant of conducting the ana-
9 130~S~
ly~is is incre~ed due -to complete identity of operation of
the liquid level GenEing elements none of which i5 in con-
tact with the slurry.
In a~ition, the automatic error correction circuit com-
pri~e~ no elements producing analog signals or controlled by
analog signals. This yrovides a high accuracy of the analys-
i~ of the ground material sizes under complex industrial con-
ditions characterized by a high level of electromagnetic
noise.
The invention is further described by way of example
with reference to the accompanying drawings, in which:
Fig. 1 is a block diagram of the sutomatic on-stream
system for analysis of ground material size fractions, accord-
ing to the invention;
Fig. 2 is a functional diagram of the automatic error
correction device, according to the inventioni
Fig~ 3 iB a schematic diagrQm of the converter convert-
ing a liquid level into an electric signal made in the form
of an ~C self-e~cited oscillator with a ~requency output,
accordin~ to tha invention;
Fig. 4 is a block diagram of the control device, ac-
cording to the invention;
Fig. 5 i8 a grsph illustrating a time-dependent change
of the increase in the liquid level in the measuring tube,
according to the invention;
- 10 - ~ 3 ~ 6 SL1~
Figs. 6a-k are time diagrams illustrating the operation of
the measuring and correcting channels of the automatic sy~-
tem in the time ~haring mode, according to the invention.
Figs. 7a-e are time diagrams illustrating the succession
of control signals ~ent to the actuator~.
The automatic syste~ for analysis of ground material
size fraction~ comprises a sampler 1 (Fig. 1) ~or sampling
and delivery of ground materials in the form of a slurry,
a sedimentation cylinder 2 with a funnel 3 filled with li-
quid 4 whose density is lower than that of the ground mate-
rial 5. An e~d face 6 of a narrow branch pipe 7 of the fun-
nel 3 i9 located inside the sedimentation cylinder 2. ~he
funnel 3 is used for feeding a required portion of a ground
material 5 (~ample).
The sedimentation cylinder 2 is communicated with a
mea~uring tube 8 and with a correcting tube 9 spaced along
the height of the ~edimentation cylinder 2. Each tube 8, 9
has one fixable end secured to the sedimentation cylinder 2
while the free ends of the tubes 8, 9 are placed at the
same level with re~pect to the upper end face 10 of the ~e-
dimentation cylinder 2, said end face ~ of the nsrrow branch
pipe 7 of the funnel 3 in this embodiment being arrRnged in
a plane perpendicular to the lon~itudinal axis o~ ~aid ~e-
dimentation cylinder 2 and extends through the lower point
of connection of the fixable end of the correcting tube.9
with the ~ide Burface of the gedimentation cylinder 2.
13~165~1
~ he automatic system alo compri~es a differential cir-
cuit for measuring the mass of the ground material 5, which
have not settled in the sedimentation cylinder 2 at any in-
stant of time of conductin~ the analysis including a measur-
ing li~uid level se~ing element 11 and a correcting liquid
level ~ensin~ element 12 connected to the free ends of the
tubes 8, 9, ~witching circuit 13, 14, and a converter 15
converting the liquid level int~ an electric signal. The
converter 15 is connected to the sen~ing element 11, 12
through switching circuits 13, 14. The outputs of the ~Jitch-
ing circuit~ 13, 14 are connected re~pectively to the measur-
ing and correcting inputs of the converter 15.
The mea6uring tube 8, measuring sensing element 11
and switching circuit 13 form a mea6uring channel.
The correcting tube 9, correctin~ sensin8 element 12
and switching circuit 14 form an error correction channel.
The differential circuit also include~ an automatic
error correction device 16 whose data input is connected
to a data output 17 of the converter 15. The outputs of
the automatic error correction device 16 are connected to
the control inputs 18 and 19 of the switching circuits 14,
13 respectively and to the control inputs 20, 21 of the
converter 15.
The differential circuit also comprise~ a data process-
ing and display unit 22 pre~enting information on the per-
eentage of solid particles in the ~izes being analyzedO The
data i~put of the unit 22 is connected to the data output
17 of the converter 15. The data processing ~r~display
- 12 _ 1306S'~l
unit 22 may be based on any prior art computer, e.g. that
used in U.S. Patent No. 4,175,426.
In addition, the automatic ~ystem includes a device 23
for reception the slurry, its stirring and portio~ed feed
into the sedimelltation cylinder 2. The device 23 is connect-
ed to the sample 1 (Fi~. 1) for sampling and supply of ~ro-
und materials and to the widening part of the fur~lel 3 o~
the sedimentation cylinder 2.
The device 23 is ma~e in the form of a cylindrical
tank 24 accommodatin~ a pressure hou~ing 25 with a propeller
26 mounted on a shaft 27 con~ected to an actuator 28 for re-
mote control of slurry stirri~. The bottom portion 29 of
the tank 24 i~ made in the form of a truncated cone equipp-
ed with a valve 30.
~ urthermore, the automatic ~ystem comprises an actuat-
or 31 for remote control of the supply of liquid into the se-
dimentation cylinder 2 (in Fig. 1 the direction of liquid
is shown by an arrow B), an actuator 32 for remote control
o~ the slurry sampling and delivery (in the fi~ure the slur-
ry i5 fed in the direction shown by the arrow), an actuator
33 for rernote control of the supply of the slurry into the
sedimentation cylinder 2, an actuator 34 for remote control
of the removal o~ the waste suspended matter from the sedimenta-
tion cylinder 2.
The automatic 8y9tem includes a control device 35 whose
control outputs are connected via circuits 36, 37, 38, 39,
40 to the actuators 34, 33, 32, 28 and 31 respecti~ely.
The control inputs of the device 22 are connected to
130654~
- 13 -
the timer outputs 41 of the control device 35, the outputs of
clock and counting pulses of which are connected to the
inputs 42, 43 of clock and counting pulses of the device 16.
The sensing elements 11, 12 include floats 44, 45 connected
to cores 46, and coils 47, 48. The point of connection of
the coils 47, 48 is connected to the common input of the
converter 15. The bottom part of the sedimentation cylinder
2 is equipped with a valve 49.
The actuator 32 is connected to the device 1, the actuator 33
is connected to the valve 30, the actuator 34 is connected to
the valve 49.
The automatic error correction device 16 comprises a scaler
50 (Fig. 2) whose input is connected to the data output 17
(Fig. 1) of, the converter 15, a trigger 51 (Fig. 2) whose
first input is connected to the output of the scaler 50,
while the output is a first output of the automatic error
correction device 16, a counting trigger 52 whose input is a
clock input 42 of the device 16 while the direct output 53 is
connected to the second input of the trigger 51, a trigger 54
whose output is a second output of the device 16, while the
first input is connected to the inverse output 55 of the
counting trigger 52, a reversible counter 56 and direct and
inverse count switching circuits 57 and 58 respectively. The
signal inputs of the switching circuits 57, 58 are
interconnected and serve as a counting input 43 of the
automatic error correction device 16. The output of the
switching circuit 57 is connected to the adding input of
reversible counter 56, while the output of the switching
- 14 - 13(~65'~:~
circuit 58 is co~lected tv the aubtracting input of the re-
ver~ible counter 56~ The output of the reversible counter
5C~C .~
56 is connected to the ~ input of the trigger 54,the
control inputs of the switching circuits 57 and 58 are con-
nected to the outputs of the triggers 51 and 54 respective-
ly. Other embodiment~ of the automatic error correction de-
vice 16 are pos~ible.
The converter 15 converting the liquid level into an
electric signal i8 made in the form of an LC ~elf-excited 08-
cillator and includes tran6i3tor3 59 (Fig. 3), 60; the base
of the transistor 59 is connected to the collector of the
transi~tor 60, while the collector of the tran~i~tor 59
i8 conr.ected to the junction of the coils 47, 48, to which
are connected capacitor~ 61, 62 switched in ~erie~, the se-
cond output of the capacitor 62 being connected to the com-
mon point of the circuit. The common point of the capacitors
61, 62 is connected to the ba~e of the transistor 60. The
converter 15 includes resistors 63, 64 connected in series9
the common point of the resistors 63, 64 bein~ connected to
the base of the transistor 60, while the other outputs of
these resistors are connected re~pectively to the power sup-
plz bus and to the common point of the circuit. ~he emitter
of the transistor 60 is a data output 17 of the converter
15 and is connected via a resistor 65 to the common point
of the circuit.
The collector of the tra~sistor 60 i3 connected to the
power supply bus through a resistor 66.
The converter 15 includes an OR circuit 67 whose in-
- 15 - 13(~6S'~l
put~ are control inputs 2~, 21 of the con~erter 15, while
the output i~ connected to the emltter of the transistor
59.
The switching circuit 14 is made in the form o~ a tra~-
sistor 68, to the base of which i6 connected one end of a
resistor 69 whose second end is connected to the control in-
put 12 of the converter 15. ~he Rwitching circuit 13 is made
in the form o~ a transistor 70, to the base o~ which is con-
nected a resistor 71 whose second output is connected to
the control input 21 of the converter 15. ~he collectors
of the transistors 68, 70 are connected to the outputs of
the coil~ 48, 47 respectively; the emitters of the transist-
ors 68, 70 are connected to the common point of the system.
~ he control device 35 includes 8 reference signal ge-
nerator 72 (Fig. 4), a timer 73 whose input is co~nected to
the output of the referen~*o signal generator 72, the outputs
of the timer 73 being a timer output 41 of the control de-
vice 35.
The control device 35 also includes a counter 74 and
a decoder 75; the input of the counter 74 is connected to
the output of the reference ~ignal generator 72, while the
output of the counter 74 iB connected to the input of the
decoder 75 whose outputs are connected to the cirouits 36,
37, 38, 39s 4. The clock and counting inputs of the refe-
rence signal generator 72 are clock a~d counting outputs
of the control device 35t
The automatic system for analysis of ground material
size fractions operates as follows.
The sampler 1 ~Fig. 1) for sampling and supply of
- 16 1306S~l
ground materials by the con~ands sent by the control device
35 during a ~elected time interval samples and ~tores the
slurry taken from the pr~cees flow A. After a pre~e~ time
interval the ~lurry is fed into the device 23 which effect~
receptio~l~ ætirring an~ small do~e delivery of the s~mple
into the sedimentation cylinder 2. In the device 23 the ~lur-
ry is thorou~hly stirred to provide its unîform density
through the ~ho'e volume. This is obtained by turbulizing
the ~lurry by means of a propeller 26 mounted inside a pres-
sure hou6ing 25. The pre~ure drop formed between the end
faces of the pres6ure housing during the rotation of the
~haft 27 col~lected to the actuator 28 provides intensive
turbulent agitation of the ~lurry. The slurry is stirred
60 that any volume in~ide the de~ice represents the whole
volume of the slurry being analyzed. Then a valve 30 opens
and a small dose of slurry i5 fed through a funnel 3 into
the sedimentation cylinder 2 preliminarily filled with
liquid.
Dependir~ on what is the finest size of the material
being analyzed, the granulometric analysis time is changed,
while the period o~ feedin~ the sample for the analysis
must be not shorter than the time of analysis of the fin-
e~t particles. The control device 35 ~ends command~ for
sampling and preparation of the slurry for analysis and
controls the time of recording the data which are then
stored in a data proces ing and display unit 22.
In order to provide high-accuracy analysis of the sample
size fractions9 the sample must be fed into the ~edimenta-
130654
- 17 -
tion cylinder 2 impulse-like. This means that the time bet-
ween the beginnin~ Pnd elld of delivery of the sarnple intO
the cylinder mu~t be mi~imum so that, as far a~ possible,
settling of the particles in the front and rear parts of
the æample starts ~imultaneously, otherwise a space shift
appear~ between the particles of the same ~ize, which would
distort the result~ of the measurement. The time of open-
ing the valve 3~ must be tenths of one second. In this case
we practically eliminate both the time shift and se~rega-
tion of the particles in the sample being fed. Making of
the bottom portion of the tank 24 in the form of a truncated
cone provides a considersble speed of the sample snd pa~sage
of a required amount of material into the sedimentstion cy-
linder 2 during a short time. Since this speed is practic-
ally the same for all particles, it is taken into account
when c~librating the automatic system for analysis of ground
material size iraction~.
Thus a large volume of slurry is taken from the process
flow and fed into the deYice 23, which very accurately re-
presents the granulometric composition of the ~low. At the
~ame time, the sedimentation cylinder 2 i8 ~upplied with a
small dose of the slurry, which also represents the proces~
flow being measured.
~ he introduction of a ~mall sample of the slurry due
to short-time opening of the val~e 30 eliminates hindered
sedimentation of the particles, i.e. excludes the main me-
thodological error in the analy~
The liquid level in the measuring tube 8 represents
- 18 _ ~306S~l
the ma~ o~ ~olid particles that did not ~ettle in the sedi-
mentation cylinder 2 at any insta~t of time of conduction
of the analysis. A change of the liquid level in the measur-
ing tube 8 presents data on the granulometric composition of
the slurry introduced ~or the analysi6 if rindered sedimen-
tation of particles takes no place. Thi~ condition is ful-
filled by introducing a small amount of slurry into the ae-
dimentation cylinder 2. The liquid level in the correcting
tube 9 is not associated with the amount of solid particles
introduced into the sedimentation cylinder 2. A change of
this level i~ cau~ed by destabilized factors: shocks, im-
pact~, ~ibrations. ~lhiR change is used for correcting the
errors of the analysis of the sizes caused by the destabiliz-
ing factor3. The information on the levels in the tubes 8
and 9 is then converted into elactric signals by means of
the liquid level ~ensing elements 11 and 12 and the convert-
er 15.
The data fed from the converter 15 are proce~sed by
the device 22. ~hi~ proce~sing results in finding the mass
percentage of parti¢le~ o~ given sizes and thi~ is output
dats of the automatic syætem. The obtained results of the
analysis of the ground material sizes are used for controll-
ing the granulometric composition of solid particles in the
proce~ flow.
The solid particles ~ed into the sedimentation cylind-
er 2 occupy the ~pace between the measuring tube 8 and the
correcting tube 9, because the end face 6 of the outlet 7 of
the funnel 3 is located in the plane perpendicular to the
- 19 l3a6s~
longitudinal axis of the ~edimentation cylinder 2 and ex-
tending through the lower point of connection of the fi~-
able end of the correcting tube 9 to the side ~urface o~
the sedimentation cylinder 2. rl~herefore, the liquid levels
in the correcting tube 9 and the upper portion of the sedi-
mentation cylinder 2 are the same (initial level~), while
the liquid level in the measurin~ tube 8 overcome~ the ini-
tial level by an increment hm (Fig. 5). This value is cal-
culated as follow6.
The solid particles introduced into the sedimentation
cylinder 2 exert a pressure on the liquid located above the
inlet of the measuring tube 8, said pressure being expressed
by
Fl V1g(J~ 2) (1)
where F1 i5 the resultant force action on the particles
and equal to the difference between the force of grsvity
and the buoyancy;
S i8 the cross-sectional area of the sedimentation
cylinder 2;
Vl i9 the volume occupied by the solid particles
in the sample introduced into the sedimentation cylinder 2;
g is the free fall acceleration;
P1~2 are the densities of the solid particles and the
liquid respectively.
Under the e~ect of this pressure the liquid level in
the measuring tube 8 rises for a value
1306S~:l
- 2~ -
h = (2)
Having sub~tituted (1) into (2) and replacing
mO
V1 ~ ~ (3)
where mO is the ma~ of introduced solid particles, we
obtain an e~pression form hm
h mO(pl -P2) DmO (4)
where D is the proportionality factor.
~ rom e~preesion (4) it follows that the liquid level
in the measuring tube 8 at ~ny in~tant of time i~ propor-
tional to the mass of solid particles, ~hich ~id not settle
below the level of connection of the mea~uring tube 8 and the
sedimentation cylinder ~
h(t) c D m(t), (5)
where h(t) i~ the increment of the liquid level in the
mea~uring tube 8 at the in~tant t; m(t) is the mass of
particles which did not presettle at any instant of time t
of conduction of the analysi3 (size fraction "~d").
The mass percentage of the 301id particle~ oY the size
fraction "-d" is determined by the formula:
S-d = ~ . 100 (6)
Having substituted in (6) expressions (4) and (5),
we obtain the algorithm of the content of solid particles
of an arbitrary size "-d"
- 21 - 13~6S41
-d h (7)
In
~ he instants of time t of settling the solid partici-
es having a diarneter d are found theoretically by the
Stocks formul~ and are corrected experimentally.
After the sampel has been introduced into the ~edi-
mentation cylinder 2, the liquid level in the measuring
tube 8 (Fig. 1) i~ increa~ed attaining the maximum incre-
ment hm at the instant tm (Fig. 5). The float-type mea-
suring sen~ing element 11 (Fig. 1) convert~ the liquid le-
vel variation into a chan~e of the inductance of a coil 47
connected thr~ugh the switching circuit 13 to the oscilla-
tory circuit of the converter 15 convertin~ the liquid le-
vel into electric signals.
The inforrnation parameter of the converter 15 is the
frequency of electric oscillations. The LC self-excited os-
cillator based on transistors 59 (Fig. 3) and 60 generates
wave trains (radio pulses). The number of oscillatlons (wav-
es) in the train i8 proportional to the increment of the
liquid level in the measuring tube 8 (~ig. 1). ~he wave
trains are applied to the data input of the data processing
and display unit 22 in which the number of waves in the
train is calculated the maximum level hm is recorded (for
example by analyzing the sign of ~teepness of the liquid
level in the measuring tube 8) and the values of the level
at the instant t (Fig. 5) corresponding to the size select-
ed for the analysis; then the mas3 percentage of solid par-
ticles of the given size fraction is calculated by ~ormula
- 22 _ 13Q~i5'~
(7) and thi~ information is pre~ented on a display.
The ~umber of w~ves in the train i~ determined by the
formula
N(t) = F(t)T, (8)
were F(t) i~ the current value of the frequency of oscil-
lation of the ~C self-excited oscillator at the instant t;
T is the duration of the wave train.
From expression (8) it follows that the value N(t),
which is a data parameter, depends not only on the frequency
of oscillations ~(t) but also on the duration T of the wave
train. ~xpression (8) i6 used for automatic corection of the
analy 5i s errors.
In the proce~s of operation the system can be subjected
to the effect of various mechanical and electric destabiliz-
in~ factors. The destabilizin~ mechanical factors result in
a change of the initial liquid level in the measuring tube
8 (Fi~. 1). These factor~ include shock~, impacts and vibra-
tion, which are inavoidable under industrial conditions,and
can cause ~plashing out of liquid from the ~edimentation cy-
linder 2. Since we introduce small do~es to provide free se-
dimentation of the solid particles, the useful chQn~e~ of
the liquid level in the measuring tube 8 are low; as a rule
they are equal to 5-7 mm. The change of the liquid level und-
er the effect of de~tabilizing factors can reach 2-3 mm and
thi~ may cau~e a considerable error when performi~g the mea-
~urements.
The instability of the initial liquid level in the
~edimentation cylinder 2 is also caused by different den-
- 23 ~3()65~
8ity of the ~lurry fed for the analysis. When the ~edimen-
tation cylinder 2 is being prepared ~or operation, it iB fil-
led with liquid to it~ upper end face 10 . The liquid level
in the sedimentation cylinder 2 cannot be higher due to the
overflov~ effected in the direction of the arrow C. ~owever,
the liquid level in the ~edimentation cylinder 2 varie~ with-
in a wide ran~e afte r the sample ha~ been fed into thi~ cy-
linder, because the volume of the splashing out liquid de-
pends on the kinetic energy of the ssmple and this energy
depends on the densit~ of the olurry being analyzed.
~ he electrical de~tabilizing factors include changea
of the parameters of the oscillatory circuit under the ef-
fect of changes in temperature, humidity, ageing of compo-
nents resulting in the frequency fluctuation of the ~C self-
excited oscillator. The effect of the de~tabilizing factor6
on the procese of analy~is is eliminated by an automatic
error correction device 16.
The clock pulse~ Vl (Fig. 6a) are applied to the input
of the counting trigger 52 (Fig. 2) from the direct output
53 of which on the front ed~e of the voltage pulse V2
(Fig.6b) there is transmitted a short command for ~etting
the trigger 51 (Fig. 2) to the 'lone" state. ~he high poten-
tial appearing at the "one" output of the trigger 51 render~
the switching circuit 14 (Fig. 1) conductive and
a correction coil 48 is connected to the oscillatory
circuit of the ~C self-excited o~cillator built around ~ran-
sistors 59, 60. The self-excited oscillator generates a cor-
rective train of oscillations V3 (Fig. 6c) whose duration
- 24 _ 1~06S4~
is in generally vari~ble 2nd includes a rlumber of waves equ-
al to the scale factor of the scaler 50 (~ig~ 2~ ~for ex-
ample, Nl = 10~0 waves). The duration Tl of the correcting
wave train is determined by the formula
N1
Tl fl (9)
where f1 is the ~requency of oscillation of the ~C self-
excited oscillator with a correcting coil 48;
Nl is the selected (fi~ed) number o~ waves in the cor-
recting train (scale factor).
The automatic ~ystem is calibrated with a fixed value
of the liquid level on the ~edimentation cylinder 2. In
this case the correcting channel frequency is equal to f~1
while the duration of the wave train is found from the ex-
pre ssion
Tol = fOl (10)
If the liquid level in the sedimentation cylinder 2
drops do;.~n, the core 46 (Fig. l) of the correcting liquid
level sensîng element 12 enters the coil 48 who~e inductance
increases, while the frequency at the output of the ~C self-
excited oscillator decreases. The duration of the correct-
ing wave train, which, as before, includes N1 waves, increas-
es. In a gelleral ca~e the duration of the correcting wave
train i9 determined by the expre~9ion
where ~ f~ is the variation of the frequency of the LC
- 25 - ~3065~1
self-excited o~cillator with a correcting
coil 48 due to the e~fect of the de~tabiliz-
ing factors.
After Nl wave~ have pas~ed through the scaler 50
(Fig. 2), the latter produce~ an output pul~e re~etting the
trig~er 51 to the "zero" state. The switching circuit 14 i8
rendered nonconductive and the correcting wave train V3
. 6c) is ceaæed.
The time interval (duration) Tl is coded in a binQry
code, stored and then is used during the operation of the
measurin~ channel. ~or this purpose, simultaneously with
switching of the correcting channel, the trigger 51 (Fig.2)
renders the ~witching circuit 57 conductive and the count
pul~e~ are applied to the direct COUl1t input of the revers-
ible counter 56. q`he time interval '~ coded by the numb-
ber N stored in the reversible counter 560
~ = Tl f3 (12)
where f3 is the repeatition ~requency o~ the count pulses.
A regular clock pulse Vl (Fig. 6a) tran3fers the trig-
ger 52 (Fig. 2) to a new state, in which a high potential is
produced at its .inverse output 55. The leading edge of this
voltage pul~e sets the trigger 54 of the measuring channel
to the "one" state (~ig. 6e). In this case the switching cir-
cuit 13 (Fig. 3) of the measuring circuit i8 rendered conduc-
tive and the measuring coil 47 is inserted in the o~cillato-
ry circuit o~ the ~C self-e~cited osciil~tor built around
transistor~ 59, 60. The ~C self-excited oscillator generateR
a measuring wa~e train V5 (Fig. 6k). At the same time,the
- 26 ~ 1306~
~witching circuit 58 (Fig. 2) i8 rendered conductive and
counting pul~e8 are applied to the inver~e count input of
the reversible counter 56. The inverse counting i8 effected
ul1til the previou~l~ recored number lJ i6 read. Since the
readin~ of this number i~ effected by pulse~ of the ~ame
repetition ~requency f3 as during the recording, the dura-
tion o~ reading the number N is equal to Tl /3ee ~12)/.After the proce~ Of reading is over, the counter 56 pro-
duce~ a command ~or reBttin~ the trigger 54 to the ~zero~'
state. (Fig. 6e). Thue, a pulse having a length Tl iB gene-
rated at the "one" output of the trigger 54 ( ~ig. 2 ) . ~his
length is equal to the duration T2 f the mea~uring wave
train (Fig. 6k).
Tl = ~2 (13)
Equation (13) shows that the duration of the mea~uring
wave train under the effect of de6tabilizing factors obey~
the same law as the duration of the correcting Y~ave train.
This provides correction of the measuring error~.
To prove that, a6sume that during the calibration of
the system by ~ome value of the mass of 601id particles fed
into the sedimentation cylinder 2 corresponds to a definite
value of the frequency fo2 f the measuri~g channel. Equa-
tion (13) implies that the number ~02 of waves in the mea-
~uring wave train is gi~en by the expression
No2 = fo2To2 = ~02T01 (14)
Then assume that with a con~tant mass of solid par-
ticle~ in the su~pended matter under the effeet of mecha-
- 27 - 13065'11
nical or electrical destabilizing factors the frequency of
the meaquring cha~lel become~ to be equel to
~2 = fo2 +~ f2 (15)
The number of waves in the measuring wave train is
found as
~2
~ 2 = (fo2 *~f2)Tl fo2 1 fo2 (16)
By ~ubstituting the value ~l (from (11) into (16),
e obtain ~f2
fo2 Tol ( 1 + ~)
f l ( 1 7 )
~1
Because of the fact that the ~ame LC self-excited oq-
cill~tor i9 u~ed and the relative frequency variations are
equal to
2 ~ r~ (18)
02 Ol
from (17) it follows that
~2 = No2 (19)
Thus we have proved that in the claimed automatic ~ystem
the eff~ect of the destabilizing factors had not affected the
reading~ with a constant value of the physical parameter be-
ing measured.
The control devioe 35 (~ig. l) produces a set of com-
mands providing the preparation of the system to operation,
conduction of the analysis and processing of the measure-
- 28 _ 13~65~
ment data~ The reference signal generator 72 (Fig. 4j pro-
duces an initial train of pulses, by means of which a co-
unter 74 and a decoder 75 connected in serie~ produce a set
of commande for controlling the actuators 28 (Fig. 1),31,
32, 33, 34. The timer 73 (Fig. 4) produces time markers for
recording the readings for calculation of the percentage of
the mas~ of solid particles of the sizes being analyzed.
A prPctical embodiment of the invention.
The ~ampling of slurry for the material ~ize analysia
was carried out from a flotation process flow by its multi-
ple crossing by a knife sampler (not shown). By a command
"slurry supply" at the in~tant t1 (Fig. 7a) the slurry is
transported by compressed air through a slurry pipeline
(not shown) to the device 23 (Fig. 1). Simultaneously, at
the instant tl (Fig. 7b) the actuator 28 (Fig. 2) i5 switch-
ed on and the slurry being fed into the device 23 is stirr-
ed during a time interval (t1 t2) (~ig. 7b). The volume of
the ~upplied slurry is equal to about 2 litres.
At the instant t2 (~ig. 7c) the valve 30 (Fig. 1) is
open and the sample is fed into the sedimentation cylinder
2. ~he duration of the input pulse is ~.4 8. The volume of
the sample fed into the sedimentation cylinder 2 is equal
to about 15~ ml. The analysis of the sizes of the taken
sample is effected from the instant t2 to the instant t3.
After the analysis has been done, at the instant t3 (Fig.7c,
d) the valves 49 (~ig. 1) and 30 are opened simulta~eously.
During the interval (t3,t4~ the slurry is drained from the
device 23 and the waste su~pended matter i8 removed from
- 29 ~ V6S4
t~e sedimentatio~ cylinder 2.
At the i~9tant t4 (~ig. 7c, d) both valves 49~
30 are closed, the actuators 28 and ~1 (Fig. 1) are switch-
ed o~ and a liquid i9 fed into the device 23. T~e washing
o:~ this device is carried out during the time interval (t4,
t5) (Fig. 7b). At the in~ta~t t5 both valves 49 (Fig. 1),
30 are opened again a~d the liquid is drained from the de-
vice 23; t~en duri~g the time i~terval (t5, t6) (~ig. 7d)
the device 2~ (Fig. 1) and tne sedimentation cylioder 2 are
wa hed with running water. At the instant t6 (Fig. 7d)
the valve 4g of the sedimentation cylinder 2 is closed while
the valve 30 o~ the device 23 is still open. During the time
interval (t6, t7) (Fig. 7e) the sedimentation cylinder 2 .
(Fig. 1) is filled with liquid. At the instant t7 (Fig.7e)
the supply o~ the liquid is stopped and the valve 30 of the
device 23 i8 closed.
The automatic system is prepared ~or conduction of
a regulator Analysis of the sizes of a ground material.
The claimed automatic system has a higher accuracy
o~ the analysi~ o~ sizes of materials in the process slurry
flow due to the ~ollowing improvementss
(1) higher representatibility o~ the sample sampled
from the proces~ ~low for analysis;
(2) a reduced metnodical error o~ the analysi~ by
providing conditions for free sedimentation of particles
in the sedimentation cylinder;
(3) eliminatio~ of the destabilizing factors o~ me-
chanical and electrioal character on the result of the ana-
_ 30 1306S~
ly~i S .
(4) use o~ an improved differ2ntial system.
Good represe~tatiYene9s of th~ sample is obtaineddue to the use o~ the devic0 23 ~aking it possible to use
for the analy~is o~ the size~ of a considerable volume of
the slurry representi~g the process flow being measured.At
the same time, caref ul stirring of the slurry provides its
uniform density along the height of the device 2~ a~d this
provides representativeness o~ the 3ample being introduced
into th~ sedimentatio~ cylinder 2 as ~ small portion of the
slurry. Thus conditions Yor free settli~g of solid particl-
es are provided.
Tho aocuracy o~ the analysis is increa~ed due to the
~act that the measuring and correcting cha~lnels are identic-
al, with respect to the action of dostabili~ing factors and
efficie~lt ~uppres~ion of the ef~ect of the de~t~bilizing
factors on the process of analysis.
The usa of an LC self~excited oscillator with a fre-
guency output in combination with an error correction de-
vice having no units producing analo~ signals ~ignificantly
improves the noise i~munity of the system a~ a wuole and
makes it suitable for per~orming hi~h-accuracy industrial
analyses of the granulometric composition of ground materials.
