Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/0209—Wet presses with extended press nip
  • D21F3/0218—Shoe presses
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G1/00—Calenders; Smoothing apparatus
  • D21G1/006—Calenders; Smoothing apparatus with extended nips

Definitions

• the invention relates to a shoe roll system for dewatering or smoothing a running fibrous web, in particular paper or board web within a machine for producing and / or finishing the fibrous web according to the preamble of claim 1 and a method for monitoring the tightness of a shoe roll according to the preamble of claim 9
• Shoe roll systems are often used in the paper industry as press roll systems. However, they can also be used in the field of smoothing as calender roll systems.
• a shoe roll cooperates with a mating roll and forms a so-called extended nip or also called a broad nip in which the fibrous web is treated under pressure.
• the shoe of the shoe roll has a jacket facing the pressure surface, which is not correspondingly convexly curved to the radius of the shoe roll. Rather, the shoe at this point often has a concave shape that is adapted to the radius of the backing roll. If necessary, press felts, which are also passed through the nip, absorb the moisture released.
• the press cover preferably consists of a flexible and thin plastic material, for example of polyurethane mixtures, and may have reinforcing threads for reinforcement. From the prior art, for example DE 10 2011 079 805, it is known that the interior the roller under a slight overpressure (about ⁇ 0.1 barü) set to improve the concentricity. The coat is literally blown up.
• a disadvantage of the prior art is that damage to the jacket only be recognized when they have a certain size. This leaves the operator of the system very little time to take appropriate countermeasures before it comes to serious damage such as the tearing of the press jacket and any resulting consequential damage such as damage to the pressure shoe.
• a shoe roll system for dewatering or smoothing a running fibrous web, in particular paper or board web within a machine for Fier ein and / or finishing the fibrous web, comprising at least one shoe roll with a circumferential Press jacket, and a pressure-measuring device for determining the internal gas pressure in the shoe roll, and a supply line from a gas supply to a gas inlet into the shoe roll, wherein the supply line has a control device for adjusting the gas flow rate in the shoe roll.
• the shoe roll system has a monitoring device which is adapted to hold the gas pressure by adjusting the gas flow rate by means of the control device at a predetermined target pressure and to send a signal, in particular to shut down the shoe roll system, as soon as the gas flow rate exceeds a predetermined allowable Value range increases.
• the inventors have recognized that already some time before a defect of a press jacket has such a size that it can be recognized by the decrease of the internal gas pressure, there are often already small defects in the jacket, which increase with time. If the defects are small enough, the controller can still maintain the internal gas pressure at the set target value by compensating for the leakage currents that occur by increasing the gas supply. Thus, the measurement of the internal gas pressure in the case will not show any special features. Only when the defect is so great that the control options of the control device are exhausted, the gas pressure will drop. Usually, the time between the measured acute pressure drop and the breakage of the press jacket is only a few seconds and is therefore not large enough to stop the shoe roll and prevent an accident.
• the invention therefore provides a monitoring device which, in addition to the measurement of the internal gas pressure, also provides means for monitoring the gas delivery rate required to maintain this gas internal pressure and which is designed to generate a signal if this gas delivery rate exceeds a predetermined admissible value range.
• a press cover preferably consists of a flexible and thin plastic material, for example of polyurethane blends, and may have reinforcing threads for reinforcement, in particular in the form of woven or laid fabrics.
• the thickness of such press jackets can be between 4mm and 6mm.
• a press cover may have a smooth surface, or a surface which is provided with grooves or blind holes.
• the invention is particularly advantageous because at the points of the grooves or holes of the jacket can already tend to be weakened.
• the shoe roll is pressurized to maintain its roundness during the production process with an internal gas pressure.
• the target pressure is preferably between 0.02 and 0.4 bar above normal pressure, in particular 0.02 to 0.1 bar above normal pressure. Specifically, values between 0.04 and 0.06 bar above normal pressure may be advantageous.
• the preset and desired target pressure is monitored by a pressure measuring device. This is advantageously arranged in the interior of the shoe roll.
• the shoe roll system may be designed as a shoe roll system
• At least one shoe roll for dewatering or smoothing a running fibrous web, in particular paper or board web within a machine for producing and / or finishing the fibrous web, with a fixed axis on which at least one shoe is supported against a flexible, exchangeable press cover acts, wherein the press cover is sealingly fixed in its end regions on front-side rotatable support disks or associated components and can be adjusted with the shoe against a counter-roller,
• the shoe rolling system has a monitoring device capable of shutting off the shoe rolling system as soon as the internal gas pressure in the shoe roll falls below a predetermined allowable value range or the gas delivery amount increases over a predetermined allowable value range.
• the shoe roll system preferably has a lubricant supply, which can usually be switched off, in order to reduce the coefficient of friction between the shoe and the shell inner surface.
• the lubricant increases the risk associated with a leak of the press jacket. If it comes to the escape of the lubricant not only the fibrous web and the manufacturing machine are polluted, it can also come to an explosive and flammable mixture with the ambient air and on an often hot counter roll.
• control device for adjusting the gas flow rate comprises a control valve.
• This value can serve as an indicator of the gas flow rate into the shoe roll and be used by the monitoring device to generate a signal, for example, for shutting down the shoe roll system as soon as the indicator exceeds a predetermined threshold.
• the threshold value may be an absolute value (eg given in l / min) or a relative threshold value.
• a signal can be given if the indicator or the gas flow rate changes by a certain percentage (eg by 2%, 5% or 10%). It is also advantageous if the control device is alternatively or additionally formed by a variable-speed blower on the gas supply.
• the speed of the blower can serve as an indicator of the gas flow.
• a flow measuring device is provided for detecting the gas flow rate.
• the detected gas flow rate can serve directly as an indicator of the gas flow.
• the valve position and a blower speed can increase the accuracy of the monitoring and reduce the risk of 'false alarms'. If e.g. the monitoring device transmits a faulty speed value due to a malfunction, the monitoring device can detect this by means of the redundant value of the valve position in a certain sense, and thus avoid the triggering of an unnecessary signal.
• determining the indicator may be advantageous for determining the indicator to process the determined raw values further.
• measured values such as gas flow rate can be used as a time-averaged quantity. This also reduces the risk of false alarms because punctual erroneous measurements have only a small influence on the indicator. Since it is an objective of the method to give the operator a sufficiently large time saving of several minutes, a time average of the values over a maximum of a few seconds (eg 10 [s], 20 [s] or 30 [s]) is uncritical and can be accepted if it increases the accuracy of the monitoring.
• the monitoring device is suitable for determining a pressure loss per unit of time.
• the monitoring unit advantageously comprises a data processing unit (e.g., a computer) with a memory unit.
• a data processing unit e.g., a computer
• a memory unit is in each case a permissible value or range for the given target pressure
• the indicator can also be determined by the monitoring unit. With stored normal value ranges and the determined indicator, the monitoring unit is thus immediately able to generate a (warning) signal in case of deviations and / or the
• the gas is compressed air.
• This compressed air can be generated, for example, relatively easy with a blower especially for the shoe roll.
• the compressed air can also be removed from the central compressed air supply, which is usually present anyway in the factory halls. Again, no major construction effort is necessary.
• the gas may be an inert gas. In order for an inflammation at the outlet of lubricant and gas can be avoided by a defective press cover from the shoe roll.
• the object is achieved with regard to the method by a method for monitoring the tightness of a shoe roll, in particular in a shoe roll system according to one aspect of the invention, by means of a monitoring device, characterized in that the method comprises the steps:
• a flow measuring device detects the gas flow rate directly, and the value is transmitted to the monitoring unit.
• control device comprises a control valve
• the indicator is determined using the valve position of the control valve.
• the drives of the shoe roll and / or a counter roll are decelerated and / or the lubricant supply is interrupted.
• the predetermined threshold value for the indicator can also depend on one or more process parameters in addition to the internal gas pressure, in particular on the rotational speed of the shoe press roll and / or the press load.
• Figure 1 shows schematically a shoe roll with a counter roll in a shoe roll system according to one aspect of the invention. Since these elements can be assembled from different components, they are simply shown as a box and described below in the variants.
• the system shown in Figure 1 exemplifies a shoe roll 1 with a backing roll 28.
• the shoe roll 1 in Figure 1 has a circumferential jacket 5 (running direction L), which is fixed at its ends to support disks 8.
• the circumferential jacket 5 thus describes at its ends a nearly circular path and has the shell shape A (dashed line).
• an axis 2, on which at least one shoe 3 is supported by means of at least one hydraulic support element 4 and against the mantle 5 in the direction counter-roller 28 extends can be pressed.
• the pressure surface 29 of the shoe 3 is lubricated with a lubricant, usually oil, against which the shoe roll 1 must be sealed.
• the oil is supplied via a lubricant supply 6.
• the pressure surface 29 of the shoe 3 is concave-shaped and the counter-roller 28 adapted.
• a wide nip 30 of at least 30 mm in length is generated in the circumferential direction.
• the different tracks A and B are exaggerated in the figure 1 in order to better illustrate them.
• the difference in height between the low point in the concave pressure surface 29 and the orbit A in the millimeter range or even below moves.
• the resulting increased stresses are not negligible and the more problematic the stiffer the jacket 5 is.
• the jacket is very flexible, it has the disadvantage that it collapses at the unsupported areas. For this reason, the jacket with a gas (for simplicity, often air is used or an inert gas) is placed under a slight internal pressure. He keeps - apart from the pressing area with its concave pressure surface 29 - a round circumference. The gas is passed through the gas inlet 8 in the shoe roll 1.
• a gas for simplicity, often air is used or an inert gas
• a signal line gives the determined pressure value to a Monitoring device 15 on.
• all signal and control lines 14 are shown as dotted lines.
• Further manipulated variables receives the monitoring device 15 from the region of the supply line 16 for the gas from the pressure source 10 to the gas inlet 8.
• this area of the supply line 16 is in this abstract representation in Figure 1, a control device 11 for the gas and a flow measuring device 12 located , From both signals are transferred to the monitoring unit 15.
• the monitoring device is capable of switching off the shoe rolling system, for example by switching off the drives 9 via the shut-off device 20 or stopping the supply to the lubricant supply 6.
• the monitoring device 15 controls the operations that may be in the electronic control of the entire shoe rolling system.
• an external constant pressure source 10 supplies the shoe roll system with gas.
• the internal gas pressure in the shoe roll 1 is measured by an electronic sensor 7.
• a control valve 11 in the influx to the shoe roll is automatically adjusted as a function of the measured pressure so that the pressure in the shoe roll 1 corresponds to a predetermined value.
• the control valve is equipped with a position feedback.
• the shoe roll system is placed in a safe condition for inspection.
• the position of the control valve 11 serves as an indicator of the gas flow rate, which is conveyed into the shoe roll.
• a second variant differs from the first in that the control valve 11 supplies a bypass to the shoe roll 1. Also, this control valve 11 is automatically adjusted depending on the measured pressure so that the pressure in the shoe roll 1 corresponds to a predetermined value. A less open valve means that less compressed air in the bypass, but more compressed air is passed into the shoe roll.
• control valve 11 serves as an indicator of the gas flow rate, which is conveyed into the shoe roll.
• the monitoring device then delivers a signal again and the shoe roll system is transferred to a safe state for checking.
• the internal gas pressure in the shoe roll 1 is via a mechanically directly acting pressure control valve
• a measurement of the amount of air required to maintain the pressure with a flow measuring device 12 is used to detect the air permeability. Increases the required amount of air at a constant internal gas pressure in the shoe roll 1 can be assumed that a leak.
• the shoe roll system is placed in a safe condition for inspection.
• Variant 1 and 2 can be carried out to improve the quality of evaluation with an air quantity measurement as described in variant 3.
• a variable speed fan as the gas supply 10 the amount of air required for the internal gas pressure in the shoe roll 1.
• the internal gas pressure in the shoe roll 1 is measured by an electronic sensor 7.
• the speed of the fan of the gas supply 10 is adjusted so that the desired inner shell pressure results.
• an additional air flow measurement 12 can be provided in the supply line 16 to the shoe roll.
• the monitoring device 15, the unspecified machine control, which includes, for example, the drives 9, as well as the shutdown device 20 are located in a shoe roll system.
• all operating conditions of the shoe rolling system are known and flow into the monitoring of the correlation between valve opening and gas pressure in the shoe roll 1.
• muting of the monitoring or a change in the tolerance values can take place when the line force or change in the machine speed changes, for example during a new paper web introduction process.
• the evaluation of the correlation of pressure values and valve openings is very reliable and avoids misinterpretations.

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• 2018
  • 2018-03-08 DE DE102018105312.6A patent/DE102018105312A1/de not_active Withdrawn
• 2019
  • 2019-02-20 EP EP19707733.2A patent/EP3762540B1/de active Active
  • 2019-02-20 CN CN201980017329.XA patent/CN111819326B/zh active Active
  • 2019-02-20 WO PCT/EP2019/054134 patent/WO2019170410A1/de active Application Filing

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