US 3322276 A
Description (OCR text may contain errors)
United States Patent Ofifice 3,322,276 Patented May 30, 1967 3,322,276 INTERFACE CONTRQL SYSTEM FOR HYDROSEPARATURS John R. Riede, White Bear Lake, and John L. Hill, North St. Paul, Minn, assignors to Ramsey Engineering Company, St. Paul, Minn., a corporation of Minnesota Filed Apr. 14, 1964, Ser. No. 359,591 8 Claims. (Cl. 209-158) This invention relates generally to liquid level control, and pertains more particularly to a system for maintaining the position of the interface in a hydroseparator.
Although hydroseparators are sometimes referred to by other names such as elutriators or deslimers, it can be explained that such apparatus is employed in the processing of ferrous ores for the recovery of a mineral from the rock in which it is found. The hydroseparation method or process involves a preliminary grinding of the ore into a finely divided state in a rod or ball mill in the course of which it is mixed with a quantity of Water to form a slurry which is commonly called pulp. The pulp is introduced at the center of a large circular tank from which point it flows radially toward the perimeter where the water and much of the rock overflows as waste or tails. The heavier concentrate settles to the bottom from where it is collected. One means of collection is to utilize an underfiow pump which pumps the rather thick mixture or slurry of rich ore. What is called auxiliary wash water is added to the tank in order to enhance the separation of the heavier ore particles from the lighter rock.
In typical operation, a relatively distinct interface between the descending ore and the suspended rock particles will develop. The position or level of this siliciamagnetite interface will vary in height within the tank depending upon the amount and character of pulp being fed into the hydroseparator. The present invention provides an automatic control of the interface position or level by first adjusting the amount of auxiliary wash water. If this adjustment proves to be inadequate then the under-flow rate is changed so as to return the interface position to its desired level. After the interface position has been rte-established, then the underflow rate is restored to its original value.
Accordingly, one object of the present invention is to provide a hydroseparator interface control system that will control the interface position or level automatically, thereby to improve the elliciency of the separation and to increase the amount of ore which can be processed through a hydroseparator of a given size. More specifically, it is an aim of the invention to first adjust the amount of auxiliary wash water that is being added to the hydroseparator to be sufiicient to lift the rock particles into the waste stream without carrying the valuable ore particles therewith and under conditions where the limits of the wash water would be exceeded for the accomplishment of this purpose, to temporarily transfer the control to a more effective but less desirable control function, namely the speed of the underflow pump, until the more normal operating conditions can be re established. The re-establishment of a preselected underflow pump speed upon the return of normal conditions is automatically accomplished by the teachings of this invention.
These and other objects and advantages of our invention will more fully appear from the following description, made in connection with the accompanying drawing, wherein like reference characters refer to the same or similar parts throughout the several views and in which:
The single figure constituting the drawing is a schematic diagram of one form that the interface control system can assume, the electrical circuitry being shown in conjunction with a conventional hydroseparator.
Referring now in detail to the drawing, a typical hydroseparator has been denoted by the reference numeral 10. As already indicated, such apparatus is sometimes referred to by other names. The hydroseparator 10 includes a circular bowl or tank 12. A pulp supply inlet conduit 14 introduces the finely ground ore suspended in a water slurry into the tank 12, the pulp arriving from an undepicted source in the direction of the arrow 16. It will be understood that the amount of mineral ore in the pulp will vary quite widely and it is the function of the hydroseparator to produce a desired percentage of ore in the underilow by removal of virtually all of the free silica and low grade middlings particles while maintaining the necessary high metallurgical recovery. Ac cordingly, the hydroseparator 10 further includes a wash water supply inlet conduit 18 having a plurality of nozzles 20 located within the interior of the tank 12. Thus, the auxiliary wash water is introduced into the tank 12 in the direction of the arrows 22. The water is obtained from a suitable supply and enters the conduit 18 in the direction of the arrow 26. Most of the water carrying the unwanted silica overflows the tank 12 and is collected in a gutter 2'7 and carried to a waste disposal area. Further included as a part of the hydroseparator 10 is an outlet conduit 28 at the lower end of the conical bottom of the tank 12. Contained in the conduit 28 is a pump 30 which withdraws the underfiow from the hydroseparator, dis charging the underfiow in the direction of the arrow 32.
The silica-magnetite interface, the desired position or level of which is to be maintained, has: been indicated at 34. In order to sense the height of the actual interface as it shifts relative to the desired level 34, a pancake-type coil '36 is utilized. As the interface position or level rises, the magnetic permeability of the material surrounding the coil increases, and as it falls, the permeability is decreased. These changes are evidenced by a variation in inductance. In order to sense the changes in inductance, an interface detector 38 is employed. This interface detector 38 includes an electrical bridge, an amplifier and a pair of relays, one relay having normally open contacts 40 and the other having normally open contacts 42. The contacts 40 will close when the bridge is unbalanced in one direction due to the position of the interface becoming too low with respect to the desired lever 34 and the contact 42 will close when the bridge is unbalanced in the opposite direction by the interface level becoming too high with respect to the level 34. In the region of the selected or desired value for the interface position which has been designated by the numeral 34, neither set of contacts 40, 42 will be operated.
In order to operate the wash water control valve 24, a reversible electric motor 44 is employed, this motor having field windings 46, 48 for effecting its reversal. A shaft 49 extends downwardly from the motor and is connected to the valve stem 5t? on the valve 24 through the agency of a splined coupling 51. The coupling 51 is designed so that the valve stem St) can move vertically to obtain the operation of the valve 24.
Carried on the valve stem is a disc 52 that is integral therewith. Consequently, when the valve stem 55) is rotated to open or close the valve 24, any resulting vertical movement thereof will be imparted to the disc 52. In this way, the disc moves longitudinally in the direction of the double arrow 54.
A first electrical limit switch unit 56 and a second limit switch unit 58 are located so as to be actuated by the disc 52. The switch unit 56 comprises a movable contact 60 that is pivotally mounted at one end and which carries a lug or button 62 that is engageable by the disc 52 when the disc has moved sufficiently upwardly. As will become clearer as the description progresses, it will then be understood that the lug or button 62 is engaged at one maximum position of the valve 24, this being its fully open position. Cooperable with the movable contact 60 is a fixed contact 64, the contact 60 being normally engaged with said contact 64. Another fixed contact 66 is spaced above the normal or unactuated position of the contact 60 by an amount that insures its closing by the coasting movement of the motor 44 when its energizing circuit is opened at contact 64. The construction of the second limit switch 'unit 58 is identical to that of the switch unit 56. Accordingly, the unit 58 includes a movable contact 68 having a lug or button 74) thereon, the movable contact 68 being normally engaged with a fixed contact 72 when in one position and when in a second position engageable with a fixed contact 74.
Next to be described is the pump motor 76. This motor 76 has a shaft 78 that is mechanically coupled to the pump 50. The motor also has a field winding 80. In order to control the speed of the motor 76, a rheostat 82 is incorporated into the circuitry, the rheostat 82 conventionally having a resistance 84 and a wiper arm 86.
In order to adjust the speed of the pump motor 76, a speed adjust motor 88 is employed. This motor 558 has associated therewith a pair of windings 9t), 92 so that its direction can be reversed. Extending from the motor 88 is a shaft 94 having a pulley 96 at its free end. An endless belt or wire 98 is entrained about the pulley 86 and also about an idler pulley 16th. The wiper arm 86 is mounted on the belt so :as to be movable in opposite directions, as indicated by the double arrow 162.
At this time, attention is directed to a first potenti ometer 104 having a resistance 166 and a wiper arm 108. For convenience of explanation, the wiper arm 1% is also carried by the belt 98, since it is under the supervisory control of the motor 88 for a purpose presently to be made manifest. Hence, the wiper arm 168 moves upwardly and downwardly in the direction of the arrow 110 in the same fashion as does the wiper arm 86 which motion has been previously referred to as being indicated by the arrow 102. A second potentiometer 112 is employed, this potentiometer including a resistance 114 and a wiper arm 116. Unlike the wiper arm 1%, the wiper arm 116 is manually adjustable and is left in its adjusted or set position for the purpose of determining the nominal speed of the pump motor '76 as will hereinafter be described.
What will be referred to as an off-nominal detector 113, which is sensitive to voltage differences existing between the movable contacts on potentiometers 194 and 112, is employed for operating a relay 120. The relay 120 has four sets of contacts, two sets of these contacts being normally open and designated by the reference numerals 122, 124 and the other two sets being normally closed and indicated by the reference numerals 126, 123.
The operation of the interface control system will now be described. For the sake of discussion, it will be assumed that the interface position or level has fallen somewhat from the desired level indicated by the numeral 34, thereby indicating a low condition of the interface that should be corrected. Hence, the coil 36 supplies an appropriate signal to the interface detector which results in the low contacts 40 being closed. Inasmuch as the contacts 126 belong-ing to the relay 126 are normally closed, a circuit is completed through the contacts 40, the contacts 126, the movable contact 60, the contact 64, the field winding 46 and the armature of the motor 44. Hence, the motor 44 is connected to what will be regarded as a 115 volt power supply.
Since the interface has fallen with respect to the level 34, the valve 24 must be opened wider so as to add more auxiliary wash water via the conduit 18. It is the function of the motor 44 to do this and the energization thereof via the winding 46 causes the shaft 49 to rotate in a direction to in turn rotate the valve stem 50 to open the valve 24 to a greater degree than the valve was open prior to the closing of the contacts 40.
If the interface level is returned to its proper height, as indicated at 34, then the contacts 40 will be opened before the lug or button 62 on the limit switch 56 is engaged. If this occurs, then all the correction has been made that is required. On the other hand, if the interface has not been returned to its proper position or level, 34 then continued opening of the valve 24 will cause the disc 52 to be moved sufficiently upwardly so as to cause engagement with the lug or button 62. This action results in the separation of the contact 60 from the contact 64 but at the same time causing engagement of the contact 641 with the contact 66.
Engagement of the contact 60 with the contact 66 immediately produces an energization of the pump speed adjust motor 88 through its Winding 92. This circuit can readily be traced through the contacts 41 the contacts 126, the contacts 60 and 66, the winding 92 and the armature of the motor 88. It will be appreciated that actuation of the contact 66 through the medium of the disc 52 takes place at one maximum or extreme position of the valve 24. In this way, every opportunity is given the valve 24 to correct the situation prior to changing the speed of the pump 30. However, with the motor 88 operating, the shaft 94 causes the pulley 96 to move the wiper arm 86 in a direction to cause more resistance to be added by the rheostat 82 to the circuit including the motor '76. Thus, the motor 76 slows down the pump 39 so that less underflow is removed via the conduit 28. Of course, when the contact 66 was separated from the contact 64, the circuit to the valve motor 44 was interrupted and this motor stops further actuation of the valve 24 which has at this point reached its fully opened position.
It will be recalled that the wiper arm 108 of the potentiometer 10 i is also actuated by the speed adjustor motor 88. Consequently, when the motor 88 has run for a sufficient time, a voltage differential will be established between the two potentiometers 104 and 112. In other words, an originally balanced condition existed between the potentiometers 104, 112 but this balance has been upset by movement of the wiper arm 108. When the wiper arm 1% has been moved to the extent necessary to cause a voltage differential to be impressed across the off nominal detector 118, the detector causes the relay 129 to be energized with the consequence that the contacts 122, 124 are closed and the contacts 126, 12-8 are opened. In practice approximately a two percent change is all that will be needed to effect the operation of the relay due to the sensing action taking place by the detector 118.
Up to this time, the motor 88, has been energized through the contacts 6%, 66. With the operation of the relay 120, however, closure of the contacts 122 causes the motor 238 to be energized through the contacts 40, the contacts 122, the field winding 92 and the armature of the motor 88. It will be perceived that operation of the relay 126 which closes the contacts 122 opens the contacts 126; hence, the circuit is interrupted with respect to the previously-established electrical path through the contacts 60, 66. It should be further noted that the circuit from contact 42 to the field 43 of motor 44 is also interrupted at this time by the opening of contacts 128. At any rate, the motor 86 continues to rotate and its rotation will progressively reduce the speed of the pump motor '76 and the pump 31 also.
Depending upon how low the interface has fallen with respect to the desired level 34 thereof, the correction will continue until the removal of the underfiow has been reduced sufiiciently so as to raise the interface to the desired position 34. The detector 38 senses the height of the interface through the coil 36 and causes the com tacts 40 to open when the proper position 34 of the interface has been reached.
Even though the interface has been returned to its proper level 34, the off nominal detector continues to sense a voltage differential between the potentiometers 104 and 112. This is by reason of the fact that the speed adjust motor 88 has moved the wiper arm Hi3 from its normal or null balance position. Hence, the relay 12G remains energized or picked up with the consequence that the contacts 122, 124 remain closed and the contacts 126, 128 remain open.
With the contacts 48 open, though, there is no path for energizing either the valve motor 44 or the speed adjust motor 88. Consequently, the actual interface, due to the fact that the pump motor 76 is now running at a reduced speed, will continue to rise. This happening, quite obviously, will be influenced by the type of pulp being fed through the conduit 14. Assuming, though, that the interface rises to such a height that the contacts 42 are closed, then an electrical path can be traced through these contacts 4-2, the now closed contacts 124 (still closed because of the off nominal detector 118 is sensing a voltage differential between the potentiometers 14114, 112), the field winding 90 and the armature of the motor 88. It will be noted that instead of the field winding 92 being energized, the field winding 9% is energized which causes the motor 88 to operate in a reverse direction, thereby causing the belt 98 to move the wiper arm 1% in a direction toward its null or balanced position. Continued movement in this direction, this being an increased direction as far as the pump 39 is concerned, will cause the motor 76 to speed up and increase the rate of underflow. If these same assumed conditions continue then the difference in voltage between the potenticmeters 104 and 112 will decrease sufiiciently and the of? nominal detector 118 will reilect this rebalancing with respect to the relay 120. The relay 120 will then become de-energized and the contacts 122 and 124 will open and the contacts 126 and 128 will close.
When the interface level has been lowered sufficiently, then the high contacts 42 will open and the entire system will be returned to a passive state but ready for any subsequent change that might require correction. It is important to note that the pump (it) has been returned to the speed at which it was operating prior to the sequence just described. This is an important feature of the invention, for the pump speed can be initially set through the agency of the potentiometer 112, more specifically its wiper arm 116, and after the interface has been returned to its proper level 34-, then the pump 30 will return to its nominal or preselected speed.
Owing to the detailed description presented with respect to the operation that occurs when the interface becomes too low with respect to its desired level 34, it is thought that the operation that takes place when the interface initially becomes too high with respect to said level 34 will be equally comprehensible without further explanation. All that occurs is that the disc 52 moves downwardly as the valve 24 is moved toward a closed position. When the maximum position, usually a complete closing of the valve 24, is reached, then the limit switch 58 is actuated by virtue of the engagement of the disc 52 with the lug or button ill. The inverse of the preceding operation then transpires.
It will, of course, be understood that various changes may be made in the form, details arrangements and proportions of the parts without departing from the scope of our invention as set forth in the appended claims.
What is claimed:
1. A control system for maintaining a desired interface level in hydroseparators comprising:
(a) means for detecting the interface level in a hydroseparator;
(b) means responsive to said detecting means for increasing the rate of flow of wash Water to said hydroseparator when the interface has fallen below said desired level and decreasing the rate of flow of wash water to said hydroseparator when the interface has risen above said desired level between predetermined upper and lower limits, respectively, and
(c) means controlled by said increasing and decreasing means for decreasing the rate of underflow from said hydroseparator when said upper limit is reached and increasing said underflow when said lower limit is reached.
2. A control system for maintaining a desired interface level in hydroseparators comprising:
(a) means for detecting the interface level in a hydroseparator;
(b) means responsive to said detecting means for increasing the rate of flow of wash water to said hydroseparator when the interface has fallen below said desired level and decreasing the rate of flow of wash water to said hydroseparator when the interface has risen above said desired level between predetermined upper and lower limits, respectively;
(c) means for removing underflow from said hydroseparator at a substantially uniform rate, and
(d) means controlled by said increasing and decreasing means for decreasing said uniform rate when said upper limit is reached and for increasing said uniform rate when said lower limit is reached.
3. A control system for maintaining a desired interface level in hydroseparators comprising:
(a) means for detecting the interface level separator;
(b) means responsive to said detecting means for increasing the rate of how of wash water to said hydroseparator when the interface has fallen below said desired level and increasing the rate of flow of wash water to said hydroseparator when the interface has risen above said desired level between predetermined upper and lower limits, respectively;
(c) means for removing underflow from said hydroseparator at a substantially uniform rate, and
(d) means for changing said substantially uniform rate to a different rate after either of said limits is reached and for returning to said uniform rate after said increasing and descreasing means has re-established the desired interface level.
4. A control system for maintaining a desired interface level in hydroseparators comprising:
(a) means for detecting when the interface level in a hydroseparator has become too low or too high with respect to said desired level;
(b) means responsive to said detecting means for increasing the rate of flow of wash water to said hydroseparator to a predetermined value. when said interface level has become too low with respect to said desired level and for decreasing the rate of flow of Wash water to a predetermined value when said interface level has become too high with respect to said desired level;
(c) means for normally removing underflow from said hydroseparator at a substantially uniform rate until either of said predetermined values has been reached;
(d) means for decreasing the rate of said underflow when said first-mentioned predetermined value has been reached and for increasing the rate of said underflow when said second-mentioned predetermined value has been reached, and
(e) means for r e-establishing said substantially uniform rate after said interface level has been returned to its desired level between said low and high levels.
5. A system for controlling between low and high levels the position of the interface in a hydroseparator to realize a desired interface level, the system comprising:
(a) means for initiating an increase in the rate of flow of wash water to said hydroseparator when said low interface level below said desired level has been reached and for initiating a decrease in the rate of flow of wash water when said high interface level above said desired level has been reached;
in a hydro- (b) means for normally removing underfiow from said hydroseparator at a given flow rate;
(c) means for stopping said increase in flow rate of wash water when a predetermined maximum has been reached (but continuing at said maximum rate) and for stopping said decrease in flow rate of wash water when a predetermined minimum has been reached (but then continuing at said minimum rate);
(d) means for normally removing underflow from said hydroseparator at a selected rate;
(e) means for decreasing said selected rate when said maximum rate of wash water flow has been reached and for increasing said selected rate when said minimum rate has been reached, and
(f means for first returning said underflow to its selected rate prior to changing said wash water from either its said maximum or minimum rate as the case may be.
6. A control system for maintaining a desired interface level in hydroseparators comprising:
(a) means for detecting the interface level in a hydroseparator;
(b) a valve for increasing the rate of flow of wash water to said hydroseparator when the interface has fallen below said desired level and decreasing the flow of wash water to said hydroseparator when the interface has risen above said desired level;
(c) a motor for positioning said valve between predetermined positions which provide maximum and minimum wash water flow rates;
(d) means controlled by said detecting means for causing said motor to operate said valve toward an open position when said interface level is below said desired level and to operate said valve toward a closed position when said interface level is above said desired level;
(e) means for normally removing underfiow from said hydroseparator at a given rate, and
(f) means for decreasing said given rate of underflow when said valve has moved to its maximum wash water flow rate position and for increasing said given rate when said valve has been moved to its minimum wash water flow rate position.
7. An interface control system in accordance with claim 6 including:
(a) means for returning to said given underfiow rate after said desired interface level has been re-established.
8. A control system for maintaining a level hydroseparators comprising:
(a) means for closing a first set of normally open contacts when the interface has become too low with respect to said desired level and for closing a second set of normally open contacts when the interface has become too high with respect to said desired level;
desired interface (b) a valve for increasing the rate of flow of wash water to said hydroseparator when the interface has fallen below said desired level and decreasing the fiow of wash water to said hydroseparator when the interface has risen above said desired level;
(c) a motor for positioning said valve between predetermined positions which provides maximum and minimum wash water flow rates;
(d) a first limit switch unit in circuit with said first contacts actuated by said motor when said valve has reached the predetermined position corresponding to maximum flow;
(e) a second limit switch unit in circuit with said second contacts actuated by said motor when said valve has reached the predetermined position corresponding to minimum flow;
(f) a pump for removing underflow from said hydroseparator;
(g) a motor for driving said pump;
(h) means for decreasing the speed of said pump motor when said first limit switch unit is actuated and for increasing the speed of said pump motor when said second limit switch unit is actuated;
(i) a first potentiometer adjusted by said speed decreasing and increasing means for providing an electrical signal variable in accordance with the amount said speed means has decreased or increased the speed of said pump motor;
(j) a second potentiometer adjusted manually to provide an electrical signal corresponding in value to the desired speed of said pump motor, and
(1:) means for sensing any differences between said electrical signals including two sets of normally open contacts one of which sets shunts said first switch unit when closed and the other of which sets shunts said second switch unit when closed,
(1) said one set of contacts being in circuit with said first set of contacts and said other set of contacts being in circuit with said second set of contacts whereby said speed decreasing and increasing means is returned to a normal position and said first potentiometer is returned to a position of electrical balance with respect to said second potentiometer after whichever first or second sets of contacts that are closed have opened and upon subsequent closure of the other first or second set of contacts as the case may be.
References Cited UNITED STATES PATENTS 2,723,754 11/1955 Darby 209-5 X 2,811,257 10/1957 Hisle 209500 3,268,592 9/1965 Smith 209-158 FRANK W. LUTTER, Primary Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,322,276 May 30, 196.
John R, Riede et a1 0 at error appears in the above numbered pat- It is hereby certified th 7 id Letters Patent should read as ent requiring correction and that the sa corrected below.
Column 2, line 44, for "lever" read level column 3 line Zff after "belt" insert 98 column 4, line 6, for "level," read level line 7 for "34" read 34 line 35, for "adjustor" read adjust column 5, line 18, strike out "of"; column 6, line 31 for "increasing" read decreasing line 40, for "descreasing" read decreasing column 7, line 50, after "level" insert in a Signed and sealed this 2nd day of January 1968 n (SEAL) Attest:
EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.
Attesting Officer A