Note: Descriptions are shown in the official language in which they were submitted.
Background of the Invention
This invention relates generally to apparatus for monitoring the
operation of cyclones of the type adapted to carry out centrifugal separating
operations.
Cyclones such as are employed for effecting centrifugal separation
operations on a variety of feed materials, such as pulps and slurries, are
customarily made with a cylindrical body section having a tangentially dis-
posed feed inlet and a lower conical shaped body section terminating in an
apex having an underflow orifice. The overflow is discharged through a
centrally located pipe or vortex finder. In normal operations swirling move-
ment is imparted to the body of material within the cyclone, whereby separat-
ing forces cause heavier components of the feed to be separated and discharged
through the underflow orifice, with an overflow being continuously discharged
through the vortex finder. ~ormally the underflow is discharged as a spray
having a hollow conical shaped pattern or configuration. Various abnonnal
operating conditions serve to prevent the discharge of the underflow in the
normal pattern. For example, oversized rocks or lumps in the feed material
may choke or partially choke the underflow discharge orifice, thus interfering
with the development of the usual conical sp-ray pattern. Also under certain
conditions, such as improper loading, material is discharged from the under-
flow orifice as a solid stream or rope. In the various industries where such
separating cyclones are employed it is important to detect the malfunctioning
of a cyclone, and to disconnect it from the system, without interfering with
the operation of other cyclones which may be incorporated in the system.
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In some instances one or more cyclones are connected to a
closed circuit milling system, such as a ball or other
grinding mill circuit operating on ore solids to produce a
pulp or slurry oE suitable concentration. In such a system
abnormal operation that is visually noted may enable the
operator to correct operation of the milling system and thus
restore proper loading of the cyclones.
U.S. Patent 3,114,510 granted December 17,1963,
discloses means making use of conductive probes in the form
of insulated rods extending into the underflow spray pat-
tern of a cyclone, and connected to circuitry which provides
a signal response in the event there is a substantial change
in the spray pattern. The illpUt to the circuitry in that
instance employs three insulated conductors, one being
connected to the metal body of the cyclone and the other two
to the probes. The tip ends of the probes, which are unin-
sulated, are disposed adjacent the inner and outer peripheries
of the hollow conical shaped spray. A substantial change
in the resistivity between one probe and the metal body of
~0 the cyclone indicates a change in the spray pattern such
that the spray is no longer enveloping the tip end of that
probe. Likewise, a change in the resistance between the tip
end of the other probe and the body of the cyclone indicates
a chnage in that boundary of the pattern with which that
2~ particular probe is associated. As disclosed in said patent,
the associated circuitry serves to gen~rate aresponse signal
which may be used to control the feed to a grinding mill
which is employed to reduce the particle size of the feed
solids, and thus adjust the loading of the cyclone. Also
~0 the patent shows use of a generated signal for adjusting
11~'76;~()
valve means for controlling the rate of discharge oE underflow material.
Summary of the Invention
The invention provides an apparatus for monitoring the operation of
. a hydrocyclone from which a conical spray of heavier underflow material is
continuously discharging, sensing means responsive to abnormal operation of
the cyclone which interrupts the normal conical spray pattern of the discharg-
ing material, said means comprising an assembly having a probe extending into
the spray pattern, a sensing circuit controlled by the sensing means, the
circuit including a path that is electrically conductive when the underfl.ow
is discharged in a normal spray pattern and which is substantially reduced in
`~ conductivity when the underflow discharge pattern is interrupted or becomes
abnormal, and electrical circuitry connected to said path, said circuitry
comprising switching means serving cyclically to momentarily apply a predeter-
mined voltage across the conductive path established by the probe, a com-
parator for generating a signal, the inputs of the comparator being connected
to the output of the switching means and also to a source of reference volt-
age whereby the voltage across the conductive path of the probe is sequential-
ly applied to the comparator by the switching means, the comparator serving
.- to apply an output pulse when the voltage applied from the switching means
is less than the reference voltage, time delay means connected to receive
each output pulse from the comparator and to deliver an output pulse after a
predetermined time delay, an indicator adapted to be energized to indicate
faulty operation of the cyclone, and means for energizing the indicator when
the voltage on the probe is such that it causes the delay means to deliver
an output pulse.
The apparatus can be used for monitoring the operation of one or
more cyclones whereby an operator, who may be at a remote station3 is immediate-ly apprised of abnormal operation. The monitoring means is applicable to a
number of cyclones connected to receive feed from common manifol.ding. The
arrangement is preferably such that a single circuitry can be used to moni.tor
a plurality of such cyclones, and one or more cyclones may be disabled, whil.e
permitting the other cyclones to continue operation with monitoring. Prefer-
.4_
1~7 E;~
ably the monitoring means avoids an alarm when the abnormal condition is
relatively of short duration, as for example, for only a few seconds.
The apparatus can be used to monitor various equipment other than
cyclones which are used in the handling of pulps or slurries.
The monitoring arrangement preferably uses circuitry which is
immune to spurious signals which might otherwise be induced by nearby
electrical equipment, such as pump motors, mill motors and the like.
The invention also provides an apparatus for monitoring the oper-
ation of a hydrocyclone, a sensing assembly comprising a probe having a
member disposed within the conical spray pattern and forming an impact sur-
face area that is impacted by the discharging spray, a bar having one end of
the same attached to said member, means for supporting the bar whereby the
bar together with said member may tilt between a first position in which the
impact member is within the spray pattern to a second position in which the
angularity of the bar relative to the horizontal is increased, said means
serving to yieldably urge the bar toward said first position, an electrical
switching means operated by changes in the angularity of said bar for opening
or closing an electrical path, and electrical indicating circuitry connected
to said path.
In general the present invention is employed in connection with
equipment such as one or more cyclones of the type adapted to receive a pulp
or slurry feed to effect centrifugal separation, with discharge of an overflow
and an underflow, the underflow for normal operation being a spray having a
hollow conical configuration. In one embodiment an electrically conducting
probe is disposed adjacent the underflow discharge orifice of an associated
cyclone in such a position that it is within the spray pattern and whereby
the discharging underflow material establishes a conductive path to the probe.
Electrical circuitry is connected to the probe for producing a visual or
audible alarm in response to an increase in the electrical resistivity of the
path beyond a predetermined value. The apparatus can be installed in con-
junction with a plurality of cyclones receiving feed from common manifolding.
Each such cyclone is provided with a probe, and the probes are connected to a
.~
common circuitry. In the event of abnormal operation of one of the cyclones
of the group with energizing of the alarm means, means is provided whereby
its probe can be effectively disabled, without interrupting continued oper-
ation of the other cyclones and their continued monitoring. The apparatus
preferably incorporates de]ay means whereby the alarm means is not energized
if the abnormal condition persists for only a short time. In another
embodiment the sensing means consists of a paddle like probe disposed within
the spray pattern and serving to control the operation of the electrical
switch. The circuitry in that instance is connected to the switch contacts.
-5a~
,J
~1~76;~
~dditional objects and features of the invention
will appear from the following description in which the
preferred embodiment has been set forth in detail in con-
junction with the accompanying drawing.
Brief Deseription of the Drawing
Figure 1 is a side elevational view illustrating
a probe assembly mounted upon a eyclone.
Figure 2 is a schematie view having a single probe
eonneeted to eleetronie eircuitry.
Figure 3 is an enlarged side elevational view of
the lower portion of the probe assembly.
Figure 4 is a plan view of the probe assembly.
Figure 5 is a schematic diagram showing a plurality
of eyelones forming a eluster fed from a eommon manifold.
Figure 6 is a block diagram of suitable circuitry.
Figure 7 is a side elevation showing another embodi-
ment of the sensing means or probe assembly.
Figure 8 is like Figure 7 but shows the paddle-
like probe in a different operating position.
Description of the Preferred
Embodiments
The cyclone illustrated in Figure 1 is of conven-
tional construetion, consisting of a body 10 having an
upper cylindrical part lOa, a conieal shaped part lOb and
- 25 a lower apex part lOc. The eonical part lOb may be made ina plurality of sections that are bolted together as
illustrated. The upper body part receives feed material
through tangentially connected pipe 11. The overflow pipe 12
~7~0
connects with the inner vortex finder 13, which extends
axially within the body. The lower apex part lOc has an ori-
fice through which the underflow discharges.swirling move-
ment of the material within the body creates centrifugal
forces which cause separation of heavier components, whereby
the heavier components are discharged in an underflow from
the apex orifice, while the remaining material ls discharged
as an overflow through the pipe 12. By way of example,
the feed pumped to the cyclone through pipe 11 may be
a pulp or slurry such as is produced by the grinding of
metallurgical ores. Also in some instances, as in the paper
pulp industry, the slurry may be a pulp containing cellulose
fiber together with contaminating solid particles which are
to be separated. The separating action may simply produce
an underflow concentrate, or it may result in classification
of solids having different separating characteristics. When
operated as a classifier heavier components of the ore
solids are discharged in the underflow~ and lighter solids
are discharged in the overflow.Generally such cyclones are
operated in vertical position, although in some instances
they are inclined or may be operated horizontally. Irres-
pective of the type of pulp or slurry being handled, and
whether operation is for simple separation or classification,
the underflow discharge of a normally operating cyclone is
a hollow conical spray. Such a spray is indicated schematically
at 14 in Figure 1. Abnormal operation of the cyclone causes
the discharging underflow to depart from its conical pat-
tern, and in such instances the discharge may be broken or
erratic, or it may be a solid stream as indicated at 15
in Figure 1, in which event the condition is termed roping.
IL1~76;~0
For the purpose of monitoring operation of the
cyclone to detect abnormal operatlon, a probe assembly 16
such as is shown in Figures 1, 3 and 4 can be employed. The
assembly includes an electrically conductive probe 18
which may be in the form of a metal bar made of suitable
metal, metal alloy or other conducting material capable of
resisting erosion. The probe is secured to a suitable mount-
ing means 19 which in turn is suitably attached to the cyclone.
In practice the bar may have a width of the order of 3/4
to 1-1/4 inch and a thickness of about 1/4 to 3/8 inches.
As shown in Figure 1 the probe bar 18 is in a plane extend-
ing substantially parallel to the direction of movement
of the spray particles, and the free end of the probe extends
well within the spray pattern. When so positioned the spray
continually wets the upper edge and the side surfaces of the
probe. secause of small amounts of chemical that are always
present in industrial pulps and slurries, they are elec-
trically conductive, and when the spray underflow discharge
assumes its normal pattern, there is relatively constant
electrical conductivity between the probes and the grounded
metal body of the cyclone. In a typical instance, where
the slurry being acted upon consists of a slurry of ore
solids, the resistance between the probe 18 and the cyclone
body may be of the order of 25 to 50 kilohms. However, under
abnormal operation of the cyclone the resistance may be
many times this value.
The probe assembly 16 as shown includes a mount-
ing plate 20 tha-t may be attached by bolts to mating flanges
between sections of the conical part lOb. A tu~e or pipe
21 of insulating material has its upper end fixed to the
1~'76;2~
plate 20. A metal extension pipe 22 has its upper end fixed
to the lower end of pipe 21 and its lower end carries a plate
23. The bar 18 is secured to plate 23 as by bolts 24. The
bar 18 is provided with a slot 25 through which the bolts
24 pass to permit the position of bar 18 to be adjusted.
The bar 18 is inclined downwardly as for example at an angle
of 45 to the axis of the cyclone.
In conjunction with the probe assembly 16 an
electronic circuitry is provided which generates a signal
for the operation of a visual and/or audible alarm when
the resistance of the path between the probe and the cyclone
body increases beyond a predetermined value. In Figure 2
the electronic circuitry is indicated generally at 26, and
is shown being connected to a visual and/or sound alarm
device 27. Assuming that the electronic circuitry 26
has proper sensitivity and can be adjusted to provide a
response signal for operation of alarm 27,when the resistance
of the path between the probe 18 and the body of the cyclone
increases beyond a predetermined value (e.g., more than twice
normal resistance), then such an arrangement can be used to
indicate abnormal operation of the cyclone. Under abr.ormal
conditions the spray pattern no longer forms a path be-
tween the probes of sufficient electrical conductivity to
avoid a signal response. As previously mentioned, such ab-
normal operation may be caused by lumps or fragments which
partially or completely choke the underflow discharge orifice.
Also it may be caused by improper loading of the cyclone, or
by abnormal changes in the density of the feed.
Figure 5 illustrates the probes incorporated with
a plurality of cyclones all having their inflow pipes con-
ll1~76;;~0
nected to common manifolding. The cyclones 10 are each pro-
vided with a probe assembly 16, and the probe 18 of each
assembly is connected by a lead to the circuitry shown in
Figure 6.
Figure 6 shows the lines leading from probes 18
being connected by jacks 29 and switches 31a to the inputs
36 of the analog swit~h 37. Switches 31a enable indi-
vidual cyclones to be isolated from the alarm circuitry if
desired. When a switch is closed the corresponding lead
to analog switeh 37 is connected to a voltage source through
resistor 32, thus effectively shorting out that particular
probe. The analog switch in this instanee comprises a
multiplexor which receives address signals on lines 38
from a counter 39. In the embodiment illustrated, counter
39 is an 8-bit binary eounter which receives clock pulses
from a clock oscillator 41. The clock oscillator is of known
design for producing generally rectangular pulses of suit-
able width and rate, e.g., 250 nanosecond pulses at a rate
of 400 KHz.
The output of analog switch 37 is connected to one
- input of a voltage comparator 42. A reference voltage VREF
is applied to a second input of the comparator from a suitable
source. In the preferred embodiment, thereference source
is adjustable to accommodate different operating conditions,
as by use of the potentiometer 42c. The output line from
switch 37 connects to the comparator through the voltage
divider 42a and the output line from the comparator is
shown connected to a voltage source through resistor 4~b.
The output of comparator 42 is connected to one
input 43 of a coincidence gate 44 and to the input of a
-- 10 --
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delay circuit 46. The delay circuit comprises a timing
circuit of known design Eor delivering an output pulse a
predetermined time after receipt of an input pulse. A
delay on the order of 3 seconds has been found to provide a
satisfactory discrimination against temporary disturbances
due to factors such as splashing of the slurry, momentary
blockage of the cylone orifice or electrical noise. The
output of the delay circuit is connected to a second input
47 of gate 44.
Sampling pulses derived from the clock pulses are
applied to a third input 48 of gate 44 by an inverter 49 and
an AND gate 50. As illustrated, the input of the inverter
is connected to the least significant bit output of counter
39, and the output of the inverter is connected to one input
ofAND gate 50. Gate 50 receives a second input from clock
oscillator 41 and delivers the sampling pulses to input 48
of gate 44. The sampling pulses occur at one-half of the
clock rate and toward the center of the scan of each probe.
The output of gate 44 is connected to the data
input of a fault memory 51. In the preferred embodiment
memory comprises a plurality of addressable latches which
receive address signals from counter 39 via address inputs
; 52. Being addressed by the same signals as the multiple~or
of analog switch 37, the latches are addressed in sychroni-
zation with the scanning of probes 18. Reset signals can be
applied to the memory on a line 53 from one or more suitable
sources, not shown, for the purpose of clearing the latches.
The outputs 54 of the fault memory are connected
to the inputs of NAND gates 56, one such gate being provided
for each of the latches. Each gate also receives a second
- 11
i~76~0
input from a flasher 57. In the preferred embodiment, the
flasher comprises a conventional bistable oscillator operat-
ing at a suitable frequency such as lHæ. The output signals
from NAND gates 56 control the operation of indicator lamps
58 which provide alarm means.
Connecting jacks 59 are shown in the leads from
the fault memory 51. Preferably shorting switches 31b are
provided for shorting out a particular lead to ground.
Preferably switches 31a and 31b are interconnected, as by
mechanical means, for conjoint operation. The lamps 58
together with the shorting switches preferably are incorporated
in a unit that is remote from the cyclones. Also the entire
circuitry of Figure 6 may be at a remote station.
Operation of the circuit of Figure 6 is as
follows. The signals from probes 18 are scanned successively
by analog switch 37 in accordance with the address signals
from counter 39. When operative disconnection occurs between
a probe 18 and lead 36 the voltage developed across resistor
42 falls to zero. Each successive probe signal is compared
with the reference signal VREF. In the event that a probe
signal drops below the level of the reference signal in
response to a decrease in the underflow discharge, comparator
42 delivers an output pulse to gate 44 and to delay network
46. Three seconds later, the delay network delivers a
second pulse to gate 44. Upon conjoint receipt of pulses
from the comparator, delay network and gate 50, the gate 44
delivers an output pulse to fault memory 51. This signal is
stored in the memory latch selected by the address signals
then present on lines 52. Since the memory is addressed in
synchronization with the analog switch, the signal is stored
- 12 -
111~620
in the latch corresponding to the probe which detected the
decrease in the underflow discharge. The presence of a
signal in one of the latches enables the corresponding N~ND
gate 56 to pass the signal from flasher 57, and the lamp
58 connected to the enabled gate flashes and the flashing of
the corresponding lamp 58 indicates which probe is sensing
the decreased slurry flow. The flashing rate may be one
flash per second. The corresponding shorting switches
3la and 3lb may then be closed to permit servicing of a
malfunctioning cyclone or its replacement, without inter-
fering with monitoring of the remaining cyclones.
The manner in which the probe is mounted avoids
possible short circuiting and false operation due to
splashing of the discharging material. This is because
the insulating pipe 21 is well above the zone near the
apex end of the cylone where splashing is apt to occur.
The probe assembly shown in Figures 1, 3 - 5
is desirable for many operating conditions, including
instances where the cyclone is inclined or disposed hori-
zontally. However, in some instances it may be desirable
to use the paddle like probe shown in Figures 7 and 8,
particularly when the cyclone is operated in a ~ertical
position. The probe assembly in this instance consists
of a mounting plate 62, similar to the plate 20 of
Figure 1, which is secured to the upper end of a flat flexible
strip 63 that is made of insulating material. The lower
end of the strip 63 is secured to member 64, which in turn
is secured to a plate 66 that is adjustably secured by
bolts 67 to the bar 68. One end of this bar carries a
counterweight 69 on which the switch 70 is mounted. ~he
- 13 ~
~11'76ZO
other end is secured to plate 71, which serves to mount
a spray impact member 72, preferably made of wear resistant
refractory material such as carborundum. Member 72 may
for example have a width of the order of 3 inches, and a
length in the direction of the bar 66 of the order of 4-1/2
inches.
The switch 70 mounted upon the counterweight 69
may be of the mercury type which is operated by tilting.
When the cyclone is not in operation strip 63 is vertical
and the impact member 72 is disposed at an angle to the
horizontal, as for example about 45. However, the impact
member is positioned within the normal pattern of the dis-
charging underflow spray when the cyclone is in operation.
Figure 8 illustrates the cyclone in operation, at
which time the discharging spray impacts member 72 and
deflects this member in the manner illustrated, with flexing
of the strip 63. The resulting tilting of the switch
70 causes the switch contacts to be closed. The switch is
connected to the circuitry of Figure 6 in substantially the
same manner as the probe previously described. Assuming that
several cyclones having assemblies as shown in Figures 7
and 8 are incorporated in the system, the lead 76 from
each of the switches 70 is connected to the analog switch
37 through a jack 29, and the other side of the switch is
grounded. When each switch 70 has its contacts closed due
to its tilted position, with the impact member 72 being
substantially in the position shown in Figure 8, the alarm
devices of Figure 6 are not energized. However, if one of
the cyclones ceases to operate in a normal manner, thus
interrupting discharge of underflow in the normal spray
tr~clernafk
- 14 -
1~1'7~ZV
pattern, the impact member 72 is permitted to move to a
position comparable to that shown in Figure 6 whereby
the switch 70 is positioned to open its contacts, thus
causing an alarm response as previously described to
indicate the particular cyclone which is malfunctioning.
