FR2508069A1 - METHOD AND DEVICE FOR ADJUSTING THE VACUUM FOR DEHYDRATION OF A PAPER SHEET - Google Patents

Abstract

THIS DEVICE FOR ADJUSTING THE VACUUM IS INTENDED FOR A SYSTEM OF SUCTION BOXES OF A PAPER MACHINE, WHICH INCLUDES SEVERAL SUCTION BOXES 21 TO 25 ARRANGED IN SERIES AND CONNECTED BY A MANIFOLD 27. DEVICES FOR ADJUSTING THE VACUUM ARE CONNECTED TO A NUMBER PREDETERMINED SUCTION BOXES FOR ADJUSTING AND PRODUCING DESIRED VACUUM CONDITIONS IN SUCTION BOXES. THE SHEET IS PASSED ON THE SUCTION BOXES TO DEHYDRATE IT. A VACUUM PUMP 35 TRANSMITS A VACUUM TO THE SUCTION BOXES AND DEHYDRATES THE SHEET THAT PASSES ON THESE LAST. MEANS 40, 38 RELATED TO AT LEAST THE LAST SUCTION BOX 25 AND THE VACUUM PUMP 35 AND SENSITIVE TO A MODIFICATION OF THE VACUUM LEVEL OR TO THE AIRFLOW REQUEST OF THE LAST SUCTION BOX 25 THEREFORE ADJUST THE SPEED OF THE VACUUM PUMP 35 TO OBTAIN THE VACUUM DESIRED AT LEAST IN THE LAST VACUUM BOX.

Description

There are many well known dehydration processes which are

  currently in use in industry

  of paper making A device commonly used

  is a Fourdrinier paper machine that uses a system

  teme of flat suction boxes comprising a series of flat suction boxes arranged in series and connected by a collector At least the last box is usually called a dry box In the known device, vacuum adjustment members are connected to each of the boxes of the series to maintain the desired vacuum conditions there In this interconnected device, it is generally necessary to achieve a maximum vacuum level in the manifold due to the pressure drop that occurs in the vacuum adjustment device assigned to the last box (es) who

  normally work with the highest vacuum The requirement

  sity of establishing a maximum vacuum level implies a high demand for energy, even when this vacuum level is not

  necessary for the purposes of dehydration in the ins-

  tallation Consequently, a device capable of reducing energy consumption in a paper machine would

extremely desirable.

  There are several basic types of vacuum pumps that are used to perform the vacuum installation the

  more efficient for different types of machine application

  Paper nes such as the one discussed above Three basic types of vacuum pumps used in the paper industry are the liquid ring pump, the displacement pump

  positive and the centrifugal enhancer sometimes called sou-

  flante Each type has its advantages and disadvantages compared to the others and the choice of vacuum pump is based

  on the various parameters of the Natural installation-

  It is desirable to be able to use screw pumps.

  of any of the types mentioned above in a conventional manner as part of a paper machine

  such as a Fourdrinier paper machine In addition, such a

  use in combination with particular parts of the machine such as the vacuum box system for

  form a vacuum adjustment device allowing eco-friendly

  nomies of important energy so that it constitutes

  a more efficient and inexpensive device is another

  fectionment. We have already recently achieved price savings of

  comes back by making devices that reduce the

  vacuum pump power care These developments are fully explained in the patent applications filed with

  E U A under No 100 617 on 6 December 1979 and 100 814 dec-

asked on December 6, 1979.

  In view of the above, it is among the main

  main aims of the invention to provide a new vacuum adjustment device for a paper machine, in particular for

  the flat vacuum box system of a Four- machine

  An object of the invention is to use a variable speed drive on one of the various well-known vacuum pumps, such as a centrifugal enhancer or a liquid ring vacuum pump, to adjust the vacuum level. where the

  air demand from the last suction box, or dry box

  che, of a Fourdrinier paper machine This device is

  advantageous in that a significant reduction in the

  energy care of the vacuum pump used to dehydrate

  a sheet in the flat vacuum box system of a

  do paper machine We get spectacular results

  on machines that produce nuances or multi-grade

  multiple, o the specifications of the air flow required of the pumps

  vacuum weights vary when we have to dehydrate different qualities

verses of papers.

  An object of the invention is to provide a new means

  vacuum adjustment to dehydrate a sheet in the system

  teme of suction boxes of an ana- type paper machine

  logues to those described in the aforementioned requests.

  The invention resides in the suppression of the apparatus for

  vacuum setting on the last dry box (es) of a series of vacuum boxes connected by a collector in the vacuum box system The vacuum adjustment device of the last dry box is replaced by a variable speed drive mechanism for the vacuum pump Par

  therefore, instead of using a speed adjuster

  of on the last box to adjust its vacuum to a desired value, the running speed of the vacuum pump is adjusted to meet the needs of this box The result is a reduction in the maximum vacuum level requested from the collector

  due to the elimination of pressure drop in the ap-

  same setting for the last vacuum container (s) which normally work under the highest vacuum. By reducing the vacuum level in the collector from 381 mm Hg for example to 304.8 mm Hg, which is the typical vacuum for the

  last vacuum box we reduce the power of drive

  19% when using a centrifugal enhancer and

  10% when using a liquid ring vacuum pump.

  Energy saving can be much higher in many cases because the figures given are based on

  the use of a perfect vacuum pumping device-

  adapted in which the air flows required for vacuum boxes do not vary For example, if the air requirements in vacuum boxes vary by 3 cpo, which is not unusual, the vacuum pump can be slowed down

  with a liquid ring of 30% while maintaining its level of vi-

  of This reduces the drive power of the vacuum pump

  about 50 Sa compared to a vacuum pump

  constant size 30% reduction in air flow in

  the case of an economical variable speed centrifugal enhancer

  again 14%, bringing the total savings to about 33% Unlike what happens in a pump

  vacuum with liquid ring or positive displacement, in an ex-

  the maximum vacuum is affected by the speed It

  it is therefore not possible to reduce its speed as much as

  of a liquid ring pump while maintaining a given vacuum level In both cases, using a

  liquid ring or a centrifugal enhancer,

significant energy savings.

  It is also significant that an adjustment of the speed of a vacuum pump for controlling the moisture content in a part of a vacuum adjustment device for dehydrating felts constitutes an ideal means of saving energy. This observation also applies to the vacuum box system of the paper machine. The modification of the device can consist in the use

  an additional suction box placed in the dry area

  che, and used to take advantage of the excess air volume

  re of a vacuum pump, according to a principle analogous to the extension

  management of the dehydration passage time of the felt which has

  has been disclosed in the patent applications indicated above.

  In summary, the subject of the invention is a device

  vacuum adjustment system for the vacuum box system

  paper machine This device includes several

  suction boxes arranged in series, and connected by a collar

  reader Vacuum adjustment means are connected to a name

  predetermined bre of boxes to regulate and generate the desired vacuum conditions therein Means are provided for passing a sheet to be dehydrated over the

  crates Vacuum generating means transmit the

  de to the crates and dehydrate the sheet that passes over these

  adjustment means connected at least to the last

  re crate and vacuum pump and sensitive to modification

  tion of the vacuum level or the air flow demand of the last suction box accordingly regulate the speed of the vacuum pump to obtain the desired vacuum at least on

the last box.

  The characteristics and advantages of the invention ap-

  will appear during the description which follows On

  attached drawings, given only by way of example, Fig 1 is a schematic view of the vacuum adjustment device incorporated in the flat box part of the paper machine; and

  Fig 2 is a block diagram of the com- ponents

  command of the vacuum adjustment device according to the invention.

  The 20-fold flat vacuum box system

  paper machine such as a Fourdrinier machine is illus-

  shown in schematic form in Fig 1 As shown

  qué by the arrow, the sheet passes on the upper face

  flat suction boxes 20 moving from the left

  che to the right and from the wet end of the machine to its dry end in the dehydration process In

  the embodiment shown, there are five boxes as-

  pirantes plates 21, 22 j 23, 24 and 25 The last box 25

  is a dry box located at the end of the cash register system

  its suction from the machine The device is shown seen from the front so that the sheet to be dehydrated passes successively, from left to right, on the boxes 21, 22, 23, 24 and 25 Each of the boxes has, in its upper surface, suitable openings for access to the

  sheet and liquid suction from the latter The li-

  which passes from the body 21 to a hollow collector 27 by a conduit 26 The collector 27 is a hollow conduit which is perpendicular to the conduit 26 leaving the body 21 A

  analog conduit 28 leads from the body 22 to the collector 27.

  A similar parallel duct 29 connects the body 23 to the neck

  reader 27; another conduit 30 runs from the body 24 to the neck

  reader 27 and a conduit 31 connects the body 25 to the collector

  27 The conduits 26, 28, 29, 30 and 31 have ends that are not

  open shanks that open into a hy-joint pit

  hydraulics 45 The open end of each duct is placed

  created below the free surface 47 of the liquid in the pit

  of hydraulic seal 45 in order to maintain the vacuum in

the installation.

  The end of the manifold 27, located at the dry end of the machine is connected to a conduit 32 The conduit 32 enters a separator 33 to ensure the conventional separation between the liquid and the air in the installation of

  vacuum The air then passes, via a duct 34, to a vacuum pump.

  of conventional or to a conventional centrifugal enhancer 35, which

  evacuates the air through an outlet 36 in the usual way.

  The separated liquid passes from the separator 33 to the hydraulic seal pit 45 through a conduit 49 The separated liquid which has been collected in the conduits 26, 28, 29, 30 and 31 also accumulates in the hydraulic seal pit 45, exiting through the open lower end of each of

these conduits.

  A conventional variable speed motor 37

  is connected to the vacuum pump 35 to regulate the speed of this

  the vacuum pump in response to a signal emitted by a control panel 38 of conventional nature The control panel 38 is connected to the variable speed motor 37 by an electrical connection 39 and it is also connected by a line 40 for collecting the vacuum , electric or pneumatic, at the last

  suction box 25 of the system 20 A class sensor mechanism

  suitable sic 43 is in communication with the interior of the duct 31 to detect the vacuum conditions prevailing in this duct 31 and adjust the variable speed motor and the vacuum pump accordingly via the table

control.

  Appropriate vacuum adjustment devices 41 may

  9 be used on vacuum boxes other than the

last dry box 25.

  In operation, when the sheet passes over the suction boxes and the conditions of this sheet

  dehydrate vary, the vacuum demand in duct 31 re-

  linked to the dry box 25 is detected by the sensor 43 The electrical panel 38 then reacts to this request for vacuum and adjusts the variable speed motor accordingly, which regulates the speed of the vacuum pump Instead of using a

  vacuum adjustment device in the last box for

  maintain the desired vacuum, the speed of the vacuum pump is adjusted to meet the needs of this box This reduces the

  maximum vacuum level requested from the collector 27 thanks to Ites-

  elimination of pressure drop in the control unit

  for the last vacuum box 25, which works normal-

  the highest vacuum Reducing the level of

  vacuum in the collector 27 reduces the driving power

  necessary for the centrifugal exhaustor or for a pump

  eg liquid ring type vacuum This translates into energy savings in the use of the installation.

  The electrical panel 38 works as follows:

  , described in relation to Fig 2 The vacuum level in the vacuum detection line 40 is transformed into a signal

  low level electric by a pressure gauge transducer

  usual signal 42 This low level signal is amplified by a signal conditioning amplifier 44, which may also possibly have a nonlinear gain characteristic In this way, the air flow characteristics

  nonlinear pump or enhancer can be ef-

  fectively made linear This makes it possible to achieve stable control over a range of values of the air flow wider than that which would be possible without

non-linear gain.

  The amplified signal is transmitted to a communication circuit.

  proportional control 46 of classic type Adjustment of the

  adjustment point of this control circuit allows

  set the vacuum level The output signal from this proportional control circuit 46 is used as the speed control signal transmitted in the form

  analog by a line 39 to the variable speed motor 37.

  In addition to adjusting the pump motor speed under normal conditions, the controls must protect the pump and the motor from abnormal conditions.

  circuit 48 which is composed of limit and gate detectors

  your digital logic, ensures an appropriate and safe stop in these circumstances These circuits also control the

  switching on the control device The digital signals

  The risks emitted by the circuits are transmitted directly to the control inputs provided on the drive motor.

variable speed motor 37.

  The organs necessary to carry out all the par-

  parts of the apparatus described above are found in the

  trade For example, an acceptable device as a trans-

  pressure driver 42 is the DP 15 model manufactured by Vali-

  dyne Engineering Corporation of Northridge, California, 91324 (E U A) The CD 15 model from the same company would work well as an electronic amplifier 44

  signal conditioning system The control circuit pro-

  portional 46 could be satisfactorily constituted

  health, for example, by model AP 2162-3106 from Action Instruments Co, Inc of San Diego, California 92133

  (E.U A) An example of apparatus acceptable for the

  limit switches and switching devices for com-

  Mande 48 is the model AP 1020-3007 from the same firm Action Instruments Co, Inc.

  Other standard components can also be used.

  to form the device according to the invention By

  example, a vacuum pump or a centrifugal exhaustor

  qué by the firm Offman Air and Filtration System of Syracuse, New York, E U A, would be acceptable In addition, the Firm

  Nash Engineering Company of-Norwalk Connecticut (E U A) four-

  nit also acceptable vacuum pump equipment A

  example of an acceptable variable speed drive motor

  ble for the device is the one known as

  variable frequency motor generation and manufactured by

  Parametrics firm of Oranges Connecticut (E U A).

Claims (10)

R E V E N D I C A T I O N S   1 vacuum adjustment device for the flat suction box system of a paper machine comprising several suction boxes (21 to 25) arranged in series and connected by a collector (27); vacuum adjustment means connected to a predetermined number of suction boxes to adjust and produce the desired vacuum conditions in   these cases; means for passing a sheet   dehydrate it on the crates; means (35) forming a vacuum pump intended to transmit the vacuum to the boxes and to dehydrate the sheet passing over them, this device being   characterized in that it comprises: adjustment means,   linked at least to the last suction box (25) and to the   vacuum pump and sensitive to a change in the level of vi-   from or from the air flow request in the last suction box, to adjust the speed of the vacuum pump correspondingly and obtain the desired vacuum level at least   in the last suction box (25).   2 Device according to claim 1, character-   laughed in that the adjustment means comprise a motor with   variable speed (37) for driving the vacuum pump.   3 Device according to claim 1, character-   laughed in that only the last box (25) is connected to the adjustment means connected to the vacuum pump so as to adjust   the speed of the vacuum pump correspondingly.   4 Device according to claim 1, character-   risé in that the vacuum pump is a liquid ring pump.   Device according to claim 1, character-   risé in that the vacuum pump is a centrifugal enhancer.   6 Device according to claim 1, character-   laughed in that the last suction box (25) is the case   dries out of a Fourdrinier paper machine.   7 Device according to claim 2, character-   laughed in that the adjustment means comprise a transducer   relative pressure sensor (42) sensitive to the vacuum level and   transforming it into a low level electrical signal, an am-   signal conditioner (44) for amplifying the low level electrical signal, a proportional control circuit (46) for receiving the amplified electrical signal and having adjustment point adjustment means for maintaining the adjustment of the or-   vacuum calf, the proportional control circuit (46) is   both connected to the variable speed drive motor (37)   in such a way that the output signal from the com-   proportional control controls the drive motor to   variable speed intended to drive the vacuum pump.   8 Method for adjusting the vacuum conditions prevailing in the flat suction box system of a paper machine which comprises several suction boxes arranged in series and connected by a collector, vacuum adjustment means connected to a predetermined number of suction boxes to adjust and produce the desired vacuum conditions in the suction boxes; means for passing a sheet to be dehydrated over the suction boxes and means   forming a vacuum pump to transmit the vacuum to the crates as-   pirantes and dehydrate the sheet which passes over these boxes, this process being characterized in that the speed of the vacuum pump is adjusted by using adjustment means connected at least to the last suction box and to the vacuum pump, which respond to a change in vacuum level or   air flow request applied to the last vacuumed box   rante so as to obtain the desired vacuum level at least on the last vacuum box.   9 Method according to claim 8, characterized   in that the adjusting means comprise a screw motor   variable size (37) for entrainment of the vacuum pump.   Method according to claim 8, character-   dried in that only the last suction box (25) is re-   linked to the adjustment means connected to the vacuum pump, to   adjust the speed of the vacuum pump accordingly.   11 Method according to claim 8, characterized   in that the vacuum pump (35) is a liquid ring pump.   il 12 Method according to claim 9, characterized   in that the vacuum pump (35) is a centrifugal enhancer.   13 Method according to claim 8, characterized in that the last suction box is the dry box (25) of a Fourdrinier paper machine. 14 Method according to claim 9, characterized in that the adjustment means comprise a pressure transducer sensitive to the vacuum level and converting it into   a low level electrical signal, a power amplifier   signal summation used to amplify the electrical signal   low level gauge, a proportional control circuit intended to receive the amplified electrical signal and equipped with adjustment means making it possible to fix the vacuum level to be maintained, the proportional control circuit being connected to the variable speed drive motor of such   so that the output signal from the control circuit   proportional control acts on the variable speed motor   vacuum pump drive.