US2302326A - Automatic consistency control - Google Patents

Description

Nov. 17, 1942. R. D. KEHOE arm.

AUTOMATIC CONSISTENCY CONTROL Filed Nov. 28, 1940 4 Sheets-Sheet l Nov. 17, 1942. R. D. KEHOE ETAL AUTOMATIC CONSISTENCY CONTROL Filed Nov. 28, 1940 4 Sheets-Sheet 2 New. 17, 1942. KEHOE ETAL Z,3Q2,3Zfi

AUTOMATIC GONSISTENCY CONTROL Filed Nov. 28, 1940 4 Sheets-Sheet 3 INVENTORS /P/c/-/4/?0 0. Kay/05 BY Cu/PT Wf/L 4 Sheets-Sheet 4 Nov. 17, 1942. R. D. KEHOE ETAL AUTOMATIC CONSISTENCY CONTROL Filed Nov. 28, 1940 Patented Nov. 17, 1942- 2.302.326 AUTOMATIC CONSISTENCY CONTROL Richard D. Kehoe, Hadlyme, Conn., and Curt Well, New York, N. Y., assignors to Paper and Industrial Appliances, Inc., New York, N. Y., a corporation of New York Application November 28, 1940, Serial No. 367,530

4 Claims.

This invention relates to apparatus for controlling the stock consistency of a pulp such as is used forpaper making, or of rag stock used in the manufacture of dry felts, or of free sulphite stocks.

Variations in stock consistency cause trouble whenever and wherever they occur. It is impossible to attempt manual control of consistency because no operator can judge stock consistency accurately. Manual control, aided by consistency testing is also impractical, because no operator.

can make consistency tests with sufilcient-speed and accuracy and adjust the amount of diluting water quickly enough to prevent consistency variations. Many devices, based on various principles, have been used to control diluting water automatically in an' attempt to prevent irregularities in operation that result from consistency variations.

The operation of this invention is based on the following principle:

Stock flowing through a trough or channel assumes a natural slope. The angle of slope depends on the consistency of the stock. The

higher the consistency the steeper the slope. A

slope is formed because a certain amount of energy is needed to move the stock through the trough to overcome internal and wall friction.

'This energy is expressed in the form of a pressure head. The potential head energy is converted into velocity energy and as the stock moves alon less energy is required. The velocity is accelerated and as the stock quantity'remains the same, and the velocity is increased, it follows that the cross-section of the stock must decrease to allow the same amount of stock to pass through the cross-section in the time unit. As the width of the trough remains the same the height 'of the stock must decrease, thus forming a slope.

This phenomenonthe difierence in head pressure between two spaced points in a trough-is used to actuate a valve, controlling the admission of diluting water to the stock. Inasmuch as the pressure is taken at two points in the same trough,

it follows that variation in the static head, caused by reasons other than consistency changes, is the and result from the changing resistance which the stock solids offer to the beater roll, andfrom the flow disturbances caused by coarse lumps or aggregations of solids or the like.

It is one of the objects of this invention to establish suitable stock flow conditions as a basis for the proper functioning of the viscosity control device. Another object is to improve and simplify the construction of the control device.

To obtain some of these objects, a special viscosity control station or tank is provided and disposed at a point past the beater and made independent of the disturbing influences thereof and of pumps. This control station is designed to provide an undisturbed, even, and constantvolume stock flow as a basis for the viscosity in- 'dications and responses from which the impulses same at the two points and will not affect the with the demand of the fluctuations. That is to for viscosity control are to be derived. Since the function of the control station is to supply to the stock more or less water, the stock acted upon in the control station must have at least a maximum viscosity and a minimum dilution ultimately required of it.

Features relating to the control station comprise the arrangement of a flow passage or channel for stock whose viscosity is to be regulated at a favorable point in the stock flow path. The flow through this passage or channel is kept substantially free from undue fluctuations or disturbances by the provision of a specially arranged feed and outlet means.

This control station is designed with an inlet or feed section so arranged that unregulated or undiluted stock excessively fed thereto beyond the amount that can have its viscosity regulated overflows and is returned to a point in the flowpath ahead of the control station. This acts somewhat as a safety valve and excess flow absorber so that to the viscosity-controlling section of the station there is admitted a substantially constant volume of stock into the flow passage for viscosity regulation. The slope of the liquid level between inlet and outlet 01 the control station is the basis for the operation of the viscosity control. A controllable discharge opening at the outlet section of the control channel permits the withdrawal of the quantity of stock of regulated dilution needed for the current production.

Other features have to do with the construction of the viscosity control device per se, and with the manner of its mounting in the control station.

The mechanical design of the control of this invention consists of two pressure pipes submerged in the stock at two spaced points supplied with compressed air. The back pressure in the two pipes varies according to the angle of the slope of the stock. This diflerence in pressure actuates an impulse amplifying instrument and controller, which in turn operates the motor of the diluting water valve. The instrument is designed so that the air pressure regulates the diluting water valve to keep the differential back 'pressure in the two pressure pipes the same. In

other words, the angle of the stock slope is kept the same by admitting the proper amount of diluting water as the consistency changes.

Other features include a flushing water connection for the bubble pipes, and for vertical ad- .justability of the bubble pipes relative to one another.

In one embodiment the flow passage that is part of the control station is established in a tank by way of a longitudinally extending vertically disposed round-the-end-fiow baiile so that inlet and outlet are disposed substantially at the same end of the tank, the bubble pipes of the control device straddling the baffle.

In a more specific case the bubble pipes are incorporated directly in the battle wall in such a way as to oifer no obstruction to the stock flow and to avoid flow disturbance.

In an embodiment comprising the application to the treating of paper pulp, the control station or box is disposed at a point in the fiowpath, which lies between the beater engine and the refiner, or more specifically between the stuff chest following the heater and the refiner or Jordan. This is by way of example, since the control station can be disposed at other suitable points in the fiowsheet. However, this embodimerit may be modified by placing the control station at other points of the flow-path, for instance, more nearly ahead of the screen that feeds'the paper machine, so long as it is independent of disturbing influences normally present in the stock flow-path.

Another feature of this invention resides in the use of a controller operated by the differential pressure derived from the bubble pipes, which controller operates a diaphragm type of motor operated valve-for supplying more or less diluting water to the stock. This invention also proposes to use a pneumatic recorder that records or registers onone disc or tape: (1) the consistency of the stock in the viscosity control station, and (2) the consistency of the stock at some point in the flow-path prior thereto. It is common to have such discs marked not only by days, for say, six days at a time, but by hours of each day. Thus, a supervisor can, from an inspection of such a recorder disc, observe the record of action of the viscosity control station but also compare the performance of that station with performance of a prior station in the flow-path. If the performance of the viscosity station is indicated as having become uneven at some time, and at the same time, uneven operation is shown of the prior station, then the inspector is thus informed that the trouble was at a station ahead of the viscosity control instead of in the control itself.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description. In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts. as the art will permit. In the accompanying drawings there has been illustrated the best embodiment of the invention known to me, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention is not to-be limited thereto.

The novel features considered characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its. organization and its method ofv operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings in which:

Figure 1 shows a longitudinal sectional view of the viscosity or consistency control tank.

Fig. 2 is a perspective view thereof with parts broken away.

Fig. 3 is a vertical transverse sectional view thereof with a diagrammatic showing of the mechanisms associated with the control tank.

Fig. 4 is a plan view of the tank.

Fig. 5 is an elevational view of the bubble-pipe assembly shown in its position in the midfeather of the control tank.

Fig. 6 is a side view of the apparatus of Fig. 5.

Fig. 7 is a sectional plan view taken along the line 1-1 in Fig. 5.

Fig. 8 is a somewhat diagrammatic view of a recorder chart or disc but with actual operating graphs shown thereon.

Taking up for description first, the viscosity or consistency control station and its details, ll indicates the control basin or tank that provides a flow-through channel or trough, and has a vertical, longitudinally-extending partial partition or midfeather l2 that leaves a free round-the-end passage l3 at one end but at the other end there are provided three adjustable height dams I 4, i5 and 16 extending between the midfeather and the tank walls i1, i8 and I9 respectively. 20 indicates the other wall of the tank which may be rounded or bevelled. These dams form a feed inlet compartment 2| and an overflow compartment 22. A stock inlet pipe 23 communicates with inlet compartment 2| and a stock outflow pipe 24 communicates with overflow compartment 22. 25 indicates an outlet for the regulated and diluted stock, outflow from which is controlled by suitable valve mechanism indicated generally by 26. Each of the adjustable height dams is preferably formed of removable boards or sections 21 that slide vertically in appropriate aligned grooves 28 and 29 respectively on the midfeather and the tank wall.

A water inlet pipe or conduit 30 has a perforated and enlarged terminus section 3! disposed in the stock flow-path just after the stock spills or cascades over the dam H from the inlet compartment 2|. This pipe 30 has a valve 32 between its terminus 3| and a source of diluting water. The valve is controlled, in my preferred embodiment, by a diaphragm motor mechanism 33 that is air operated. Disposed adjacent to the midfeather l2 on the high stock-slope side of the mid-feather is a high head bubble pipe 34 and on the other side of the midfeather, a

4 2,802,826 lower head bubble pipe 35, each having a free outlet or nipple 36 from which air bubbles are emitted into the stock 31. The bubble pipes must be spaced from oneanotherin the direction of stock flow. Thus these pipes may straddle the midfeather I2, although my preferred disposition of these pipes is to embed them out of stock flow obstructing position within the contour of the midfeather I2 in a recess 38 therein into which fits a boxlike construction or casing 39. A certain amount of vertical slidable adjustment is provided between the bubble pipe outlets or nipples 38 and the air outlet slots 40 in the casing 33, since the bubble pipes 34 and 35 are adjustably mounted as by means of a clamping member 43* and bolts 4Il upon a common frame or base construction 40.

High head bubble pipe 34 is connected to a bent or flexible pipe 4I that provides a conduit that passes upwardly to connect with a U-shaped casing 42, then outwardly through valve 43 into a pressure leveling casing or throttling device 44, out from the bottom thereof by pipe 4| leading into a manifold pipe 45 associated with which is a pressure gauge 48. Manifold pipe 45 passes into a knob-operated pressure-reducing valve 4'! which in turn is connected with a source of airpressure through pipe 48. Lower head bubble pipe 35 similarly is connected to a bent or fiexible pipe 49 that provides a conduit that passes upwardly to connect with the U-shaped casing 42, then outwardly through valve 50' into a pressure leveling casing or throttling device 50, then out from the bottom thereof by pipe 49' leading into the manifold pipe 45, through the pressure 'reducing valve 41 to air-supply pipe 48. The 'U-shaped casing 42 is connected at its top with a water pipe that has a valve 52 controlling it. It will be noted that the throttling or resistance devices 44 and 50, as well as the reduction valve 41 and the U-shaped casing 42 are also mounted upon the common frame 40, making this control device inclusive of the bubble pipes, the throttling devices and the reduction valve, a substantially self-contained unit.

Referring to Fig. 3, from pressure leveling casing 44 there extends a branchpipe 53 from the high head pressure line that leads to and is connected with a control or regulator instrument 54. Similarly, from the pressure leveling casing 50 there extends a branch pipe 55 from the lower head pressure line that leads also to the control instrument 54. Also connected to the control instrument 54 is an air-pressure line 55, the air in which is controlled by the regulator instrument 54 and then passes through pipe 51 to the diaphragm motor valve operating mechanism 33. The control instrument 54 is of the type obtainable in the open market and operates when differential pressure passes a danger point. That is, when the high head back pressure from bubble pipe 34 is dangerously higher than the pressure in the lower head back pressure from bubble pipe 35, the regulator instrument permits air pressure from line 55 to pass to and operate the motor controlled valve 32 that provides diluting water. For example, the trade name of a-satisfactory instrument of this type is Stabilog made by TheFoxboro Company, of Foxboro, Mass.

Such an instrument has a recording or registering attachment including a recording chart 50 that usually has a capacity for a. one day record, and the record is divided into hours and minutes. In my preferred embodiment, I use an'instrurefiner or Jordan.

and 82. One stylus makes a graph 53 on the chart 60 that is a record of the consistency of the regulated stock leaving the control station or tank II, while the other stylus makes a graph 34 on the same chart 80 (and usually more or less concentric therewith) that is a record of the consistency of the unregulated or undiluted stock entering the viscosity control station II.

The viscosity or consistency control station II andits associated parts is located in a place in a paper-making fiow-path where it is substantially free from pulsations or other variations. In one preferred form, it is located between the stuil chest and the refiner. That is, in the complete flow-sheet, there would first come the beating engine, then the stuff-chest, from which the stock is usually pumped to the control station II'. Following the control station is the Excess unregulated and undiluted stock spills from the entrance end of the control station and flows back to the stufl chest, whereas regulated and diluted stock flows from the control station to the refiner, although any excess of this can also be recycled back to the stufl chest along with the excess unregulated stock that is going back there. In another arrangement, the control station II and its associated parts, are located between the refiner or Jordan station and the screen that is ahead of the paper machine.

In the operation of the control station II and its associated parts, stock enters the tank II of the tank II.

through the inlet pipe 23 upfiowing into the inlet compartment 2I. The liquid level in this compartment is controlled by the adjusted height of the top plank or weir of dam I4 over which the stock spills or cascades into the control area The top plank or weir of dam I5 is so adjusted that any unregulated and undiluted stock in inlet compartment 2| that is in excess of that desired to enter the main control area of the tank I I, is spilled or cascaded over the dam I5 into overflow compartment 22 from whence it is conducted by outlet pipe 24 back to the stuff-chest or other point ahead of the control station. Stock that has spilled over dam I4 flowsin a U-shaped path around the midfeather I2 through space I3 and ultimately to dam I6 over which the stock spills or cascades into overflow compartment 22. Thus excess regulated and diluted stock mixes with the excess unregulated and undiluted stock in the overflow ment that has two recording pens or styluses BI '15 compartment 22- and passes in admixture therewith out through pipe 24 to the stufl chest. Regulated and diluted stock is drawnofl from the control station through take-ofl opening 25 thatis controlled by valve 26. This regulated stock then goes to a refining station or to whatever the subsequent treatment of it is to be.

Stock in spilling over dam I4 encounters the perforated section 3| of the water diluting pipe 30 where and by which the stock is diluted as required, due to the control thereoi initiated by the difierential back pressure set up inthe bubble pipes 34 (higher pressure) and 35 (lower pressure). The diflerence in back pressuresset up in the air-emitting bubble pipes is due to the slope of the fluid level assumed by the stock as it flows from the feed end at dam I4 to the outlet end at dam I6. This slope in level is to be seen in Figs. 1 and 3.

The bubble pipe assembly operates as follows: Air under pressure comes into pipe 48 and is controlled by reducing control valve 41 to a pressure as indicated on gauge 46. Air pressure then flows from the manifold 45 through pipe 4| upwardly through casing 44 in which there is a known or usual pressure leveling apparatus. From this casing, the air-pressure passes through valve 43, casing 42 and downwardly through coiled pipe 4i into the bubble pipe 34, from which air is emitted through elbow and nipple 35 into the high level stock, From manifold 45, air pressure also flows through horizontal pipe 49' through casing 50, that is equivalent to casing 44, through valve 50 to and through U-shaped casing 42, down coiled pipe 49 into bubble pipe 35, from which air is emitted through elbow and nipple 36 into the lower level stock. The same degree of air pressure is thus supplied to both bubble pipes 34 and 35, but since pipe 34 has a higher back pressure in it, than pipe 35, the pressure pipes 53 leading from casing 44 and 55 leading from casing 50 have difierential pressures in them. This differential pressure between the pipes causes the instrument 54 to act when their relative difference becoms too great, or passes a. danger factor, whereupon the instrument permits air pressure to flow through line 51 tothe diluting water valve control 33. This valve remains open until the relative differential pressures between pipes 53 and 55 decrease to withinthe allowance permitted, whereupon the diluting water valve is operated to reduce the volume-of diluting water being added, or-perhaps is completely closed. Thus undue fluctuations in relative back pressure differential exerted on the bubble- pipes 34 and 35 due to change in the slope of the fluid level of the stock flowing in the control station, brings about more or less diluting water to be added to the stock through the water pipe 3|.

The horizontal zone of emission of air by the nipples 36 of the bubble pipes permit of adjustment relatively. That is, they can be in the same horizontal plane as shown in Fig. 7, or one can be adjusted to be higher than the other, as some peculiar or unusual stock conditions might require. The coils in the pipes 4| and 49 allow for vertical adjustment of the bubble pipes without interfering with the air-lines connected to them. This can be accomplished by having the nipples 36 pass through a plate that is fastened to the nipple and arranged to slide vertically in grooved flanges ll provided on the inner faces of the casing sides 39, whereby there is established a face-to-face relationship between the plate Ill and the inner face .01 a respective side wall portion of the casing 39.

Occasionally the bubble pipes 34 and 35 may, become clogged or encrusted, so a water flushing arrangement has been provided for them which is operable by shutting of! valves 43 and followed by turning on valve 52 which permits water from the pipe-line 5| to flow downwardly through the casing 42 .and then downwardly through pipes 41 and 49 to and through bubble pipes 34 and 35 respectively, to flush from them any accumulations therein.

A control tank that has proven satisfactoryrfili had as inside measurements an overall length of 6' 2%", a width of 27 /4", and a depth of 36". The inlet and overflow compartments were about 13" square, while the midfeather was 4' 0" long.

Among the advantages realizable from the practice of this invention are: Manually initiated changes of consistency can be easily made by turning the knob on the control or regulator instrument 54 which changes the relative position of the valve opening, admitting more or less water to the stock stream and reducing or increasing consistency. As the measuring system is not required to do any of the mechanical work of controlling the valve, light parts can be used in the control, eliminating inertia. Hunting of the valve is eliminated as it responds instantly to the slightest change in consistency. The recording of consistency before and after regulation, on a twenty-four hour ormore chart, is a distinct advantage, especially for checking irregularities in stock consistency during preparation or handling from heaters to stufl chest, for if the consistency of the stock in the chest is beyond the range of the control, it shows on the chart and the reason for the unsatisfactory operation can be investigated. This control apparatus has proved that it can maintain consistency within plus or minus {a of 1% provided the stock is delivered to the control station at consistencies between 2 and 7%.

We claim:

1. A control station for regulating the consistency of a supply of fluid stock by way of regulating the dilution thereof, comprising a throughflow channel construction for a substantially constant flow volume of said stock, which channel construction comprises a container having a vertical round-the-end flow baflle wall to establish a horizontal turn of flow, a feed inlet at one end of said channel, overflow means associated with said inlet for disposing of a quantity of stock of unregulated consistency excessively fed to the feed inlet, overflow outlet means at the other end section of said channel for the discharge of stock of regulated dilution, said feed inlet and said overflow outlet means thus being disposed at the same end of the container, a controllable outlet opening ahead of said outlet means for the discharge of stock of regulated dilution, and a dilution control device for the unregulated stock comprising a pair of air pressure bubble pipes operable in the flowing stock in said channel and said bubble pipes being eifective in oppositely directed respective flow portions of the channel,

2. A control station according to claim 1, with the addition of a feed inlet chamber having an overflow for unregulated stock into the flow channel andan overflow for excess volume of said unregulated stock, and an outlet chamber to receive the overflow of stock of regulated dilution, and also adapted to receive the overflow of said excess volume.

3. A control station according to claim 1, in which the bubble pipes are disposed at said baflle wa 4. A control station according to claim 1, in which the bubble pipes are at least partially concealed in the thickness of said baille wall.

RICHARD D. KEHOE. CURT WEIL,

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