SE1951117A1 - Electronic scale for continuous digester feeder - Google Patents

Abstract

An electronic scale arrangement (100) is configured to be mounted on a continuous digester feeder (1; 1) for measuring the position of a rotor in a housing of the continuous digester feeder (1; 1) and comprises a magnetic position sensor (160) and a magnet (170), wherein the magnetic position sensor (160) is configured to sense the position of the magnet (170), and wherein the position of the magnet (170) indicates the position in an axial direction of the rotor relative to the housing of the continuous digester feeder (1 1)

Description

ELECTRONIC SCALE FOR CONTINUOUS DIGESTER FEEDER TECHNICAL FIELD The present invention generally relates to continuous digester feeders, and more particularly to rotor adjustment in such continuous digester feeders.

BACKGROUND Continuous digester feeders are part of the conventional feeding line in theKraft process for papermaking. The high pressure (HP) feeder, or transferdevice, is used to transfer steamed wood chips in a liquid (typically whiteliquor) at low pressure to the top of the continuous digester, at high pressure.A typical HP feeder has a rotor mounted in a housing for rotation with respectto inlet and outlet ports and having a plurality of through going pockets, eachhaving opposite end openings which function as both inlets and outletsdepending upon the angular position of the rotor. A high pressure pump isoperatively connected to one of the ports to provide the flow of liquid underhigh pressure through the port. The low pressure (LP) feeder is used to movechips from the inlet of the process into the steaming vessel, where the airpressure is about twice the pressure at the inlet and has a similar construction with a rotor inside a housing for rotation with respect to inlet and outlet ports.

Fig 1a is a schematic illustration of a typical high pressure (HP) feeder 1according to prior art and Fig. 1b is a schematic illustration of a cross-sectionof a typical HP feeder 1 according to prior art, showing the rotor 10 inside thehousing 20. Fig. 1c and 1d are corresponding illustrations of a low pressure(LP) feeder 1' according to prior art. To get the correct change of pressure inthe HP feeder, as well as in the LP feeder, it is important to have a tight fitbetween the rotor and the housing. The tight fit however causes a loss ofmaterial due to friction between the metal rotor and the metal housing. Tocompensate this loss of material of the tapered rotor it is necessary to move the rotor further into the housing, typically by approximately 0.5 mm once or lO twice a week. This is done by rotating the adjustment wheel/ hand wheel 30shown in Figs. 1a and b, where the rotating movement of the hand wheel istransferred into a linear movement of the rotor inside the housing, so that therotor moves in an aXial direction, i.e. in a direction along the rotational aXis ofthe rotor and housing. Eventually the material loss is so large thatreconditioning of the rotor is necessary. The reconditioning will restore thefeeder to an almost brand-new state and the price is much lower than theprice for buying a new feeder. It can take up to 10 years before reconditioning is required.

The continuous digester feeder is an invention that can be traced back to thelate 19th century. Small changes in e.g. material and service method havebeen done during the years, but the method to measure the wear and the wearrate on the rotor is the same now as it was back in the mid- 1900s. The methoduses a mechanical scale /steel scale to indicate the axial position of the rotorrelative to the housing and gives a crude indication how much wear time isleft on the rotor before reconditioning is needed. This is a very simple solutionthat is seen as old-fashioned and which causes some inaccuracy in themeasurement. The operator must count the number of hand wheel spokemovements to determine approXimate rotor displacement. It is very difficult todetermine accurate rotor displacement from the scale and the result is proneto judgement error. The solution is also dependent on the operator havinggood knowledge of the machine. It is not possible to see the start value, thelast point of operation, or how much wear time is left until the nextrecondition. There is no history of previous values available and therefore theoperator must make sure to document and keep track of when and how muchthe hand wheel has been moved in order to calculate an approximation of howmuch time it is left until reconditioning is needed. Furthermore, it is oftenpossible to remove the steel scale and put it back again. If this is done theoperator is “blind” and must begin all over again with the adjustment in orderto find a new starting position, and then all previous history is useless. An active, regular adjustment of the rotor is important for the overall lifetime of lO the feeder but if the operator adjusts the Wheel too much and too often the feeders are Worn faster.

Therefore, there is a need in the art to improve rotor adjustment in continuous digester feeders.

SUMMARY It is an object to provide an electronic scale arrangement Which improves andfacilitates measurement of the position of a rotor in a continuous digester feeder.

This and other objects are met by embodiments of the proposed technology.

According to a first aspect, there is provided an electronic scale arrangementconf1gured to be mounted on a continuous digester feeder for measuring theposition of a rotor in a housing of the continuous digester feeder. Theelectronic scale arrangement comprises a magnetic position sensor and amagnet, Where the magnetic position sensor is conf1gured to sense the positionof the magnet, and Where the position of the magnet indicates the position inan axial direction of the rotor relative to the housing of the continuous digester feeder.

According to a second aspect, there is provided a method for measuring theposition of a rotor in a housing of a continuous digester feeder. The methodcomprises a step of providing an electronic scale arrangement on thecontinuous digester feeder, the electronic scale arrangement comprising amagnetic position sensor and a magnet, and a step of sensing the position ofthe magnet With the magnetic position sensor, Where the position of themagnet indicates the position in an axial direction of the rotor relative to the housing of the continuous digester feeder. lO According to a third aspect, there is provided a method for estimating Wearand/ or lifetime of a rotor in a continuous digester feeder. The methodcomprises measuring the position of the rotor in the housing of the continuousdigester feeder according to the above method, sending the measured rotorpositions to a computer and estimating Wear and/ or lifetime of the rotor based on the measured rotor positions.

Some advantages of the proposed technology are: - A more exact measurement of the rotor position is obtained - Manual operator errors are reduced - Rotor adjustment is facilitated - Possibility for automatic calculation of an approXimate lifetime - Possibility for visual information of e.g. the position of the rotor and remaining lifetime estimation Other advantages Will be appreciated When reading the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, together With further objects and advantages thereof, may bestbe understood by making reference to the following description taken together With the accompanying draWings, in Which: Fig. 1a is a schematic illustration of a typical high pressure feeder according to prior art; Fig. lb is a schematic illustration of a cross-section of a typical high pressure feeder according to prior art; Fig. 1c is a schematic illustration of a typical low pressure feeder according to prior art; lO Fig. 1d is a schematic illustration of a cross-section of a typical low pressure feeder according to prior art; Fig. 2 is a schematic illustration of a cross-section of a high pressure feederprovided With an electronic scale arrangement for measuring the position of arotor in a housing of the high pressure feeder according to an embodiment of the present disclosure; Figs. Ba and Bb are schematic illustrations of an electronic scale arrangementfor measuring the position of a rotor in a housing of a continuous digester feeder according to an embodiment of the present disclosure; Fig. 4 is a more detailed illustrations of an electronic scale arrangement formeasuring the position of a rotor in a housing of a continuous digester feeder according to an embodiment of the present disclosure; Fig. 5 is a schematic floW diagram of a method for measuring the position of arotor in a housing of a continuous digester feeder according to an embodiment of the present disclosure; Fig. 6 is a schematic floW diagram of a method for estimating Wear and/ orlifetime of a rotor in a continuous digester feeder according to an embodiment of the present disclosure.

DETAILED DESCRIPTION The present invention generally relates to continuous digester feeders, and more particularly to rotor adjustment in such continuous digester feeders.

Throughout the draWings, the same reference designations are used for similar or corresponding elements. lO As mentioned in the background section, a mechanical scale is used in currentcontinuous digester feeders to indicate the rotor position relative to thehousing and thereby estimate how much Wear time is left on the rotor beforereconditioning is needed. The mechanical scale may be e.g. a steel scale orruler attached to the housing of the feeder. On this scale / ruler, the operatorcan read how far the rotor has been moved into the housing. A sleeve may beconnected to the hand Wheel such that When the Wheel rotates the sleevemoves inWards during adjustment. The position of the sleeve is indicated onthe scale by e.g. a pointer and is used to determine the current Wear of the rotor. The steel scale is adjusted in its attachment during reconditioning.

As also indicated in the background section, there are a number of problemsWith the prior art solution and therefore there is a need in the art to improve rotor adjustment in continuous digester feeders.

These problems are solved by the present invention, Where an electronic scalereplaces the mechanical scale on the continuous digester feeders indicatingthe position of the rotor relative to the housing. The rotor position adjustmentdetermines the relative linear travel in the axial direction into the housing andthe amount of life left on the rotor before reconditioning is required. The ideais to provide a more exact measurement of the rotor position and an automaticcalculation of an approXimate lifetime, together With visual information of theactual position, maximum position so far and remaining lifetime estimation.The invention comprises both mechanical and electronic/ software part solutions that Work together.

Fig. 2 is a schematic illustration of a cross-section of a high pressure feeder 1according to an embodiment of the present disclosure. As can be seen fromthe figure, the solution can be applied to a usual prior art HP feeder, oralternatively to a prior art LP feeder. A sensor installation/ electronic scalearrangement 100 is arranged on the hand Wheel 30 of the feeder 1 and measures the rotor position in the housing, the measured information is sent to a computer 200 with communication cards for data processing andcalculation of e. g. the wear of the rotor and its remaining lifetime etc., and thedata is stored in a memory so that the history can be followed. The data canin an embodiment be sent from the sensor installation 100 to the computer200 via a sensor cable 300, where e.g. Synchronous Serial Interface (SSI)communication can be used in an embodiment. For easy control of the sensorinstallation and visualization of data the computer can be provided with e.g.a touch screen in an embodiment. The information can in an embodiment besent from the computer 200 to an external electrical cabinet (not shown) atthe paper mill via cable Work 400, using e. g. Ethernet RJ 45 for communicationwith the mill network, or perhaps via e.g. an Open Platform Communications (OPC) link to external systems.

Figs. 3a and 3b are schematic illustrations of an electronic scale arrangement100 mounted on the hand wheel of a continuous digester feeder according toan embodiment of the present disclosure. The mechanical part of the solutioncomprises a base plate 110 that is mounted on the feeder 1 ; 1”. The base plate110 can be made of e.g. steel or similar material in an embodiment. When thehand wheel 30 is turned an arm or rod 150 is pushed along a sliding rail by aflange 130 mounted on the hand wheel 30, where the flange 130 can e.g. beplaced on the inside of the hand wheel 30 in an embodiment. A magneticsensor (not visible in the figure) senses the position of a magnet (not visible inthe figure) which is mounted on the rod 150 and moves together with the rod150. Fig. 3b illustrates the situation when the hand wheel has been turned sothat the rotor has been pushed further inside the housing of the feeder thanin Fig. 3a, and it can be seen in Fig. 3b that the rod has been pushed towardsthe left in the figure.

Fig. 4 is a more detailed illustrations of an electronic scale arranged on thehand wheel of a continuous digester feeder according to an embodiment of thepresent disclosure. A base plate 110 is arranged on the feeder 1; 1', and in a particular embodiment a cover/ housing 120 can be arranged on the base plate 110 to protect the electronic scale from e.g. dirt and continuous digesterWashing. A flange 130 is arranged on the hand Wheel of the feeder, the flangepressing/pushing on a rod 150 Which is springy/elastic in an embodiment.The flange 130 and the rod 150 are used together to translate a rotatingmovement into a linear movement. For this purpose, the rod 150 can in anembodiment be provided With a rolling Wheel at its end, such that the flange130 presses/pushes on the rolling Wheel. A sleeve 140 can in an embodimentbe connected to the flange and the hand Wheel, such that When the handWheel rotates the sleeve 140 moves inWards during adjustment, as describedabove. A magnet 170 is arranged on the rod 150 and a magnetic position sensor 160 senses the position of the magnet 170.

Fig. 5 is a schematic floW diagram of a method for measuring the position of arotor in a housing of a continuous digester feeder according to an embodimentof the present disclosure. The method comprises a step S10 of providing anelectronic scale arrangement on the continuous digester feeder, Where theelectronic scale arrangement comprises a magnetic position sensor and amagnet, and a step S20 of sensing the position of the magnet With themagnetic position sensor, Where the position of the magnet indicates theposition in an axial direction of the rotor relative to the housing of the continuous digester feeder.

Fig. 6 is a schematic floW diagram of a method for estimating Wear and/ orlifetime of a rotor in a continuous digester feeder according to an embodimentof the present disclosure. The method comprises a step S100 of measuring theposition of the rotor in the housing of the continuous digester feeder accordingto the above method, a step S200 of sending the measured rotor position to acomputer, and a step S300 of estimating Wear and/ or lifetime of the rotor based on the measured rotor position.

With the currently presented solution the operator still needs to turn the Wheel by hand but all information regarding the Wear and the lifetime of the rotor is lO provided automatically. This solution is more reliable and accurate, reducingthe impact of human error. It would also be possible to connect the electronicscale to e. g. a robot which handles the turning of the hand wheel, making the solution completely automatic.

This solution can be provided as “stand alone” and may in the future bedeveloped further, maybe to a system for e.g. recording, analyzing, onlinesupport and other services. A system like this could give direct feedback onhow reconditioned feeders perform, and knowledge on how to improve processes and methods in the future.

Some benefits with the presented solution are: 0 Precision measurement to capture position0 Precise digital reading of rotor position with accuracy within +/ -0.01mm on-site0 Easy operation, activated by hand wheel0 Wear trend- Build knowledge regarding wear trend- Easier to predict the lifetime, less unplanned shutdowns0 Accurate indication of the rotor position movement can lead to a longerlifetime0 Optional remote connection år DCS - Drives Control System (operatorcontrol visibility)0 Development potential - Expandable system; other signal inputs can bedeveloped and combined, e.g.:- Vibration signal- Drive power0 Can be adapted to all continuous digester feeders at the reconditionstage0 Accurate adjustments 81, elimination of judgement error 0 Improved visibility of feeder (rotor) status and wear progress. lO 0 Programmable alarm limit settings 0 Easy backlash zero reset 0 Absolute value measurement of position (no calibration needed if poweris disrupted) 0 Adjustments (linear displacements) can be trended over time 0 Rotor position signal can be used for Interlocking (a type of adjustmentat startup) or included as a start permissive 0 Potential for future “industrial internet connection to cloud baseddashboard services” 0 10-15 years lifetime The embodiments described above are merely given as examples, and it shouldbe understood that the proposed technology is not limited thereto. It Will beunderstood by those skilled in the art that various modifications,combinations and changes may be made to the embodiments Withoutdeparting from the present scope as defined by the appended claims. Inparticular, different part solutions in the different embodiments can be combined in other configurations, Where technically possible.

Claims (6)

1. An electronic scale arrangement (100) configured to be mounted on acontinuous digester feeder (1; 1') for measuring the position of a rotor in ahousing of the continuous digester feeder (1; 1'), the electronic scalearrangement (100) comprising a magnetic position sensor (160) and a magnet(170), Wherein the magnetic position sensor (160) is configured to sense theposition of the magnet (170), and Wherein the position of the magnet (170)indicates the position in an axial direction of the rotor relative to the housing of the continuous digester feeder (1; 1').

2. The electronic scale arrangement (100) according to claim 1, furthercomprising means for translating a rotational movement of a hand Wheel (30)into a linear movement of the magnet (170), Wherein the hand Wheel (30) isconfigured to move the rotor in an axial direction inside the housing of the continuous digester feeder (1; 1') When the hand Wheel (30) is rotated.

3. The electronic scale arrangement (100) according to claim 2, Whereinthe means for translating a rotational movement of the hand Wheel (30) into alinear movement of the magnet (170) comprises a rod (150) attached to themagnet (170) and a flange (130) mounted on the hand Wheel (30) Where therod (150) is arranged to be pushed in an axial direction by the flange (130), sothat the rod (150) and the magnet (170) are movable together in the axial direction in relation to the housing of the continuous digester feeder (1; 1').

4. The electronic scale arrangement (100) according to any of the previousclaims, Wherein the electronic scale arrangement (100) is configured toelectronically send measurements of the position of the rotor relative to thehousing of the continuous digester feeder (1; 1') to a computer (200) for data processing and calculations.

5. A method for measuring the position of a rotor in a housing of a continuous digester feeder (1; 1'), the method comprising: lO 12 providing (S10) an electronic scale arrangement (100) on the continuousdigester feeder (1; 1'), the electronic scale arrangement (100) comprising amagnetic position sensor (160) and a magnet (170); sensing (S20) the position of the magnet (170) With the magneticposition sensor (160), Where the position of the magnet (170) indicates theposition in an axial direction of the rotor relative to the housing of the continuous digester feeder (1; 1').

6. A method for estimating Wear and/ or lifetime of a rotor in a continuousdigester feeder (1; 1'), the method comprising: measuring (S100) the position of the rotor in the housing of thecontinuous digester feeder (1; 1') according to the method of claim 5; sending (S200) the measured rotor positions to a computer (200) ; estimating (S300) Wear and/ or lifetime of the rotor based on the measured rotor positions.