FI115982B - Detecting surface damage and/or contamination on nip roll faces in paper handling machines - Google Patents

Abstract

Contamination and/or damage on the surfaces (11,12) forming a roll nip (N) in a paper handling machine such as a calender are detected by vibration monitors. The results are electronically processed based on the point of time of detecting the vibrations to locate the damage. Contamination and/or damage on the surfaces (11,12) forming a roll nip (N) in a paper handling machine such as a calender are detected by vibration monitors. The results are electronically processed based on the point of time of detecting the vibrations to locate the damage (M1,M2) on the faces (11,12) monitored. The vibrations are detected by at least two sets of paired detectors (20,21) with one set mounted on bearing support means and the other set mounted on the mantle of the nip rolls. Preferred Features: The location of any damage is determined by the phase difference of the vibrations arriving at the different detectors. The detectors (20) placed near the roll bearings can also monitor the condition of said bearings. An impulse detector (25) records roll revolutions to help locate said damage around the roll periphery. Electronic processing means to reduce interference from outside sources and average the results to provide locating coordinates are disclosed as are analysis systems and links to display/alarm members.

Description

115982

Method for Detecting Contamination and / or Damage to a Paper Calender Nip or a Surface Passing through the Nipples 5.

The invention relates to a method for detecting fouling and / or damage to the surface of a paper calender nip or through a nip, wherein the method detects and treats vibrations occurring in connection with the calender structures.

The present invention relates to paper calendars, in particular so-called calendars. soft calenders and super calendars using soft-coated rollers that are particularly susceptible to damage.

15

A particularly preferred embodiment of the invention relates to monitoring the condition of soft-coated fish rolls to detect surface damage at a sufficiently early stage and thereby to prevent damage.

It is known in the art that calenders comprise two or more hard and / or soft calender rolls forming a calender nip or nipples through which the paper web to be processed is. led to walk. In particular, • · · '' soft-surface rolls, such as supercalender paper rolls or the like, and so-called.

* Soft roll calender rolls with soft coating, especially polymer coating, are susceptible to damage. Damage is often caused by impurities such as * ..! local "fibrous imprints" which, when passing through the nip, cause a pressure stroke that '' 'loads the soft coating of the calender roll, first causing it to warm up and, over time, permanent deformation of the coating and damage. Similarly, · deformation and damage may also occur in metal calender rolls. 1; 30 on the surfaces and on the surfaces of the tapes passing through the calendering nipples.

115982 With respect to the particular problems underlying this invention, the following is set out. Polymer-coated rolls of known calenders are very resistant to steady loading and wear, but they are very easily damaged if any limited small area warms up to a relatively small extent, e.g., warmer than the environment. Due to the high coefficient of thermal expansion of the polymers and very poor thermal conductivity, even such a small area expands rapidly and continues to heat up to such high temperatures that it can be deformed. If the overcoat is made of so-called. thermosetting resin, it re-melts while losing its original properties. Such a warming reaction 10 as described above may be caused, for example, by a small piece of paper adhering to the roll surface, a bundle of fibers or "stain" which when exposed to the calendering nipple causes greater elasticity of the coating over the local environment.

15 Preventing local contamination, for example by continuous scraping, is neither economical nor generally of best paper quality, as most of the polymer coatings in use are not very abrasion-resistant, and thus preventive cleaning itself may consume more coating than the actual calendering.

: 20 • »· · · · · · · · · · · · If the dirt was detected early enough, eg cleaning ;; : Scraper or other roller cleaning equipment will operate for short periods without · "being damaged by continuous or frequent scraping.

“This would significantly extend the life span of soft-surface calender rolls.

* * * · 'Well-known condition of calender rolls, especially soft-surface rolls'; cross-machine traversing thermometers are used to monitor the coating temperature. In said temperature monitoring application, *. *: Problems in the prior art and in other prior art waste systems arise from the fact that the flexible roller coating, which is monitored by temperature, is generally at least somewhat electrically insulating. Thus, in the partially abrasive contact between the web and the coating, quite high static electricity charges are produced on the surface of the coating and the dry paper web. These voltages tend to discharge along the path of the smallest resistor on the taco. The thermal imaging camera often has to be mounted protruding in its support structure, whereby these static electricity charges just find the thermal imaging camera the easiest way to discharge, thus subjecting the sensitive imaging electronics to quite high voltages and especially protecting them.

10 Although monitoring the temperature of the calender roll surface generally allows for a local rise in temperature due to overload or local internal inhomogeneity of the coating at a sufficiently early stage, it requires the placement of quite heavy, expensive, and bulky equipment near the roll being monitored. In particular, space constraint causes great difficulty in connection with multi-roll processing equipment, in which every device outside the actual web-processing process makes it difficult to maintain and maintain the device.

An object of the invention is to provide a method for calendering; ; The fouling and / or damage to the surface of the rolls forming the nip or nip rolls and / or through the nipples can be effectively and relatively simply controlled using relatively small space.

It is a further object of the invention to provide a method in which actions controlled by a surface passing through a nip can be tracked so fast that there is generally no permanent significant damage to the surface. Before cleaning or similar measures are taken.

It is a further object of the invention to provide a method which, by applying • ♦ '; If necessary, the cleaning of the surface passing through the nip can be targeted to a sufficiently precise area: · J 30 is immersed in the area specifically contaminated, thus saving the cleaning medium and energy. In some cases, the invention allows the purification devices to be reduced in size.

In order to achieve the foregoing and to be apparent objects, the method according to the invention is essentially characterized in that said vibrations are detected by at least one oscillation sensor (s) disposed adjacent to the bearing brackets or associated structures of the calender rolls The vibration is from.

In a preferred embodiment of the invention, at least one accelerometer for measuring the vibration of the calender roll, or a strain gauge for measuring deformations due to the vibration, or the like, is placed on the calender rolls or at least part of their bearing housings and / or roll bodies. The measurement signal of these sensors is monitored and analyzed so that the portion of the measurement signal due to roll rotation and imbalance is "filtered" and the evolution of the portion due to the roll surface geometry is monitored. When the monitored signal reaches a predetermined level or hits a spectral measurement window, the control system will continue to notify it and action can be taken to either replace the roll or eliminate the source of interference.

·; ·; The system of the invention in a way "listens" to the vibrations of the monitored fish blade surfaces and, if necessary, locates the oscillation source so that effective action can be taken quickly to eliminate the cause of the vibrations and / or to prevent further damage.

25 • · · • ·. ···. In the invention, the location of the interference source can also be made by monitoring the rotation of all or a plurality of monitored rolls and measuring the oscillation from where. a suitable place for the glove, eg the body of the machine. By comparing the measured vibration signal, preferably its repetition cycle time, with the measured rotation speeds of the various rollers, the source of the interference can be determined and steps taken to eliminate the interference by either cleaning the roll or replacing the roll prior to damage.

With the monitoring system applying the invention, information databases can be created to determine the most advantageous moment of roll replacement when the severity of the interference leading to 5 roll changes is classified and stored with each roll replacement. In this case, history information can help identify the severity of the disorder and take action at the right time.

The invention can overcome the problems discussed above by abandoning direct measurement of the roll pin surface 10 temperature by indirectly observing local contaminants in the roll and changes in geometry based on the vibrations they cause.

Advantages of the invention in the prior art procedure are as follows: 15 - In the most preferred embodiment of the invention, a soft-surface calender roll, especially a polymer-coated roll, which is contaminated or deformed can be located so that it can be cleaned, e.g. an already damaged roll can be replaced to avoid more i 20 damage or longer production stoppages.

The invention enables the monitoring of calender rolls without

* I

· "" Measuring equipment with a separate bracket structure needs to be built in the frame area, whereby considerable space savings are achieved.

25 - The invention also allows a calender roll or T to cause interference when needed. using relatively simple '· * devices and algorithms to locate the roll region.

The invention can be incorporated into a general calender monitoring system and utilize sensor assemblies already installed in the bearing area for monitoring the condition of the bearing, or alternatively, sensors mounted to implement the invention may also be utilized or observation.

5

The invention is not limited to monitoring interference caused by temperature changes due to the local surface temperature of the calender rolls, but the system of the invention responds at an earlier stage when an impurity is adhered to the roll surface which subsequently causes a local temperature rise.

A further advantage of the invention over the traversing thermal camera is that the system of the invention can be configured to monitor continuously the portion of the roll handling nip across the entire width, locating the interferer even in the axial direction of the roll and in the vertical cross section of the roll.

When the monitoring system of the invention is used in multi-pin fishers, such as a supercalender, all or at least • · '··': rollers particularly susceptible to surface damage, particularly soft-surface rollers, are provided with sensors according to the invention, · a source of unusual vibrations may be * * ;; “Lists the freshly soiled and / or damaged roll so that steps can be taken» · · to remove contaminants or replace the damaged part to avoid further damage and loss of production.

In the following, the invention will be described in detail with reference to certain embodiments of the invention schematically illustrated in the figures of the accompanying drawings, in which details the invention is by no means limited.

Fig. 1 is a simplified block diagram of a control according to the invention system.

7, 115982

Figure 2 is a schematic side view of a 10-nip multi-roll calender as a preferred embodiment of the invention.

First, with reference to Figure 2, a reduced example of a particularly preferred embodiment of the invention will be described.

As shown in Figure 2, the multi-roll calender comprises a body portion 100 on which is mounted a calender roll stack. The calender roll stack forms ten overlapping ka-10 calendering nips Ni-Nio loaded with known loading devices. Calendered paper web W enters the calender from the direction of the arrow Wjn and then exits the last nip Nio direction of the arrow Wout. The calendering paper web W is guided by the guide rollers 17 through the actual calendering nipples Ni-Nio and the change-over nip Nv. The calender has six metal rolls 21, 22, 23, 24, 25, 26 with hard and smooth coating 15 and six rolls 11, 12, 13, 14, 15, 16 with soft polymer coating 10, said hard rolls 20 and soft coating 10 the rollers are disposed alternately in the roll stack, so that two soft rolls 13, 14 are arranged in tandem: the paper web W to be calendered more strongly side of the exchange. With soft »· · *; *; The condition of the rolls 11-16 with the coating 10 is monitored by vibration sensors 41, 42, 43, 44, 45, 46 located in the second bearing housings 18 of said rolls * · · 't *.

* »·

The signals fj (t) ... f6 (t) available from said vibration sensors 41-46 can be used to detect damage to the soft roll surfaces 10 and local adhesion M of the rolls 11-16 before the polymer coating 10 is damaged by the echo; ·, ·. 25 invalid.

> <I I

> ·,;. Referring to Fig. 2, the second bearing rings 18 of the rollers 11-16 (...) (Refer to the vibration signals fj (t) ... f6 (t) 'obtained from the vibration sensors 41-46) via bus 31 to the control system 30-35 applicable to the invention.

t I

ten.

* 30 which embodiment will be described in more detail later with reference to »11598? 8

In FIG. the change nip Nv is formed between two soft-surface rolls 13 and 14. When the rolls 13 and 14 are generally of different diameters, the interference can be localized to either of the rolls 13/14 by following the interruption period 5 Tr. In this case, the vibration transducer 43/44 is required only on the second roll 13/14. This embodiment of the invention may also be generalized such that, for example, in a calender where all rollers are of different diameters, only one vibration sensor 40 and one or more impulse sensors 50 can be used, and the interference can be localized to the newly contaminated roll.

10

Fig. 1 schematically illustrates an embodiment of the system of the invention in which each of the opposing bearing brackets 18 of each of the soft calender rolls 11-16 has pairs of vibration sensors 41a-46a and 41b-46b. References a and b refer to opposite sides of the calender. The representation of Figure 1 differs in this respect from Figure 15 in which the vibration sensors 41-46 are shown to be positioned only in connection with the second bearing brackets 18 of the soft rollers 11-16. Both Fig. 1 and Fig. 2 show an impulse transducer 50 which provides a synchronization signal fr (t) which is utilized in a manner that will be described in more detail later.

The vibration sensor pairs 41a, 41b ... 46a, 46b shown in Figure 2 provide the signals «· ·, ′ · · fai (t) ... fa6 (t) and fbi (t) ... fb6 (t), which is led to unit 30. In addition, to unit 30 ...! deriving from the impulse sensor 50 in connection with the calender roll a signal fr (t), '* which is formed, e.g., by a short voltage pulse from each revolution of the roll, whose period time T represents the peripheral speed of the rolls. The unit 30 may also perform spectral analysis of the signals fa (t) and fb (t), e.g., Fourier ana- 11 known per se; using lysers. In addition to locating the interference, this allows for inferences *; 'Also the quality and severity of the disorder. The signal fr (t) can be used for measurements *. '' For synchronization and for measuring the rotational speed of the rollers in the monitoring system '' of the invention, which will be described in more detail below.

30 •; · The vibration sensors 41-46 are most preferably accelerometers, but piezo-electric or transient-like strain gauge sensors can also be used. These sensors measure, for example, the relatively high-frequency pressure strikes caused by "ridges" M in the calender roll, or the like, on a controlled surface such as a transfer belt or a press felt. These pressure shocks cause mechanical vibrations in the form of longitudinal wave motion, the main energy of which is usually in the sound frequency range. In addition to contaminants, e.g., the local "fibrous web" M, vibrations can be caused by damage to the roll coatings, which occur as local discontinuities or deformations on the roll surfaces, particularly in the susceptible soft coating 11. As shown in FIG. passes through the second nip N2, it causes a distinct signal fi (t) to be transmitted through bus 31 to the system 30-35 described in Figure 1.

The signals fa (t) and fb (t) detected by said sensor pairs are averaged in one to 15, where the phase difference φ of the signals fa (t) and ft (t) is further measured. This phase difference φ is illustrated, for example, by the difference in travel time Δt of the oscillations, which is proportional to (peak. The corresponding travel time difference Δt can be detected by sensor pairs. Based on the above travel time difference Δt, the position of the memory M in the axial direction of the rolls.

V! 20

• I

Based on the signal fr (t) of the pulse encoder 50, it is possible to determine the phase angle ob at which the "memory" M is located from a reference plane defined by the pulse encoder 50, in which the center axis of the roll. Said angular coordinate ab can be determined from the following equation:; 25 _ 360 ° -Tr --f- <1 · * * 1 'where Tr = delay time for detection of vibration by "memory" M and T = period of rotation of the roll • t' '.

I · I

The above assay is based on the fact that the propagation velocity c 115982 10 of the metal portions 11-16 of the rolls is significantly higher than Vk = the peripheral velocity of the rolls, (c »Vk). Thus, the two coordinates of the "memory" M are thus defined, the axial coordinate of the roll and the angular coordinate perpendicular thereto.

5

In the unit 30 of Figure 1, the signals fa (t) and fb (t) are averaged and their phase difference φ is measured. The phase difference φ can also be measured using the correlation technique of the signals fa (t) and fb (t). In addition to measuring the phase difference φ, spectral analysis of the signals fa (t) and fb (t) can be performed in unit 30 and conclusions can be drawn on the quality of the interference. The unit 30 may include a processor (CPU) or a computer controlled by a dedicated computer program 32. The unit 30 provides information I which is fed to a display device 33 that displays appropriate display information and possible alarms to the rigid system supervisor. Further, on the basis of the signal s from said unit 30, the cleaning and reconditioning means 35 of the calender rolls 15 can be controlled such that cleaning operations, e.g., scraping and / or water or steam jets are directed to the contaminated roll 11-16 or even specifically to impurities. less roll surface, cleaning * * »M - consuming media and energy. In addition, unit 30 may be connected, preferably interactively, to other control and monitoring system 34 of the calender to act synergistically therewith.

In the method according to the invention, the measurement signals can be synchronized with the rotational speed of the calender rolls obtained by the signal fr (t) and the impulse sensor ... 25 50. The system according to the invention can operate e.g. provides the trigger point and gives an impulse, the vibration measure- ment described above is started with a constant period of time used. After the measurement period, the next triggering of the sensor 50 is expected and a new measurement period is initiated. A sufficient number of these constant length measurement periods are recovered and the averages of the measurement signals fa (t), fb (t) '·' are calculated. The measurement '' of the measurement signals fa (t) and ft (t) and the synchronization signal fr (t) may also be performed continuously, e.g., for about 1 min. after which Π 115962 program 32 performs synchronized time average calculation.

Pressure shocks resulting from local impurities such as "fiber models" M and the signals fa (t) and fb (t) detected therefrom are generally of relatively high frequency. Since the oscillations caused by, e.g., imbalance of the rollers or the like are at a much lower frequency, they can be filtered by high-pass filters in unit 30 to obstruct the observations of the invention. By utilizing techniques known per se in signal processing, such as bandpass filtering or correlation techniques, the effects of "noise" interfering with the measurements of the invention 10 can be reduced.

Although it has been described above to measure the position coordinates of the impurities M on the roll mantle both axially and circumferentially, the invention can of course be applied so that only one of the coordinates is detected.

15

The invention also encompasses applications in which the coordinates of the oscillator are not determined at all, but only the roll, in particular the soft-surface roll 11-16 and, in Figure 2, specifically the first soft roll, · · 11, where the impurity M is -; 20 operations, eg scraping with equipment 35.

• · i i *. ·: As such, the cleaning and / or condition of the roll surface or similar strip or felt surface can be used as lifting means 35 known per se and / or e.g.

* · 'Nozzle devices such as axially traversing the roll and spraying 25 cleaning media, such as in U.S. Patent 5,603,775.

'1' In a preferred embodiment of the invention outlined in Figure 2, control is provided; * '·' A scraper to specifically clean the roller 11 in Fig. 2 '; On the soft surface 10, impurity M has been detected.

V ί 30 '. ,, * According to the invention, the positioning of the interference source M can also be accomplished by monitoring the rotation of all or a plurality of monitored rolls, usually of different diameters, and measuring the vibration at any suitable point, e.g. then, the interference M can be located on the contaminated roll by comparing the period of recurrence of the measured 5 vibrations with the rotational speeds of the rolls on the Tr transducers 50. Thus, measures can be taken to eliminate the malfunction by either cleaning the soiled roller in question or by replacing the roller in question before further damage occurs. Information units can be collected and created in unit 30 to determine the most economical time to replace the different rolls, e.g., by classifying the severity of the interference and storing in the system 30 the information necessary for each roll replacement. This provides a learning system 30 that can collect historical information to identify the severity of the disorder and take action at just the right time.

When using sensors placed in place of, or in addition to, fixed vibration sensors, the communication from the mobile sensors can be tracked in a manner known per se. Several different solutions are known in the art for transferring the measurement signals fa (t), fb (t) and fT (t) from rotating rollers, which may be applied in the context of the invention. These known solutions include different types of slip rings and radio signal transmission. Sliding rings are possible, but they are often susceptible to interference and typically require a large amount of space on the roller shafts. Commercially available '' * radio equipment for wireless transmission of signals. Known solutions related to said signal transmission are not described in further detail herein, but are exemplified by EP-A1-0075620 and Applicant's FI-92771.

tl * * * * t?

The claims which follow, within the scope of the inventive idea defined by the invention, may vary and deviate from the above * f * · 'by way of example only.

; ; 30

Claims (13)

A method for detecting soiling and / or damage of a surface (10) running through a nip or more nip (Ni-Nio) in a paper calender, in which method 5 oscillations occur in connection with the calender structures (18). ; 100) is detected and processed, characterized in that said oscillations are detected by means of at least one oscillation transducers (40; 41-46; 41a-46a) disposed in conjunction with bearing carriers for the calender rolls (11-16) or , 41b-46b), by which (s) the calender roll (s) (11-16) are located from which oscillation originates and that on the basis of the position coordinates of disturbance sources (M), devices (35) are controlled which clean the surface (10) which is monitored to expose a soiled calender roll, in particular a soft surface roll, to a cleaning operation. 2. A method according to claim 1, characterized in that the rotation of several, most preferably all the rollers monitored is observed in the method and the oscillation is measured at any suitable location as a hoist, for example on the machine body (100), and that at least one oscillator (40) is used. , comparing the period time (Tr) of one of these received oscillation signals with the speed of the rollers being monitored and thus the output source of the interference is determined and measures are taken to remove the interference. :: 20 Method according to claim 1 or 2, characterized in that in connection with bearing carriers (18) for soft-surface (10), most preferably polymer surface-coated rollers (11-16) i. ; calender roll stack (11-16, 21-26) or in conjunction with these connected structures (100), said one or more oscillating sensors (40; 41-46) are provided, by means of which the soft calender roll (11-16) is determined whose soft coating (10). ". is soiled and / or damaged. Method according to any one of claims 1-3, characterized in that the method is applied in a multiple roll calender having alternately hardened (20) metal rollers (21-26) or the corresponding and with soft surface coating. , most preferably, polymer rolls (10) provided with rollers (11-16), which together form a calendering nip (Ni-Nio) and, in connection with the bearing carriers (18) for said soft-surface (10) cage rolls (11-16) vibration sensors (41-46) have been provided from which vibration signals (fi (t) ... f6 (t)) have been supplied to units (30-35) which process the vibrations. Method according to any of claims 1-4, characterized in that the method is applied in such a calender which has one so-called two calender rolls (13,14) formed. exchange nip (Nv), to bead said soft-surface rollers (13,14), which most preferably have different diameters, have a sensor (50) which observes their speed, that a vibration sensor (43/44) is arranged only in connection with one of the said rollers (13,14) and that the disturbance is located to either of said rollers (13,14) by utilizing the period time (Tr) for repeating the disturbance. Method according to any of claims 1-5, characterized in that in the method, oscillations of the body are detected by and / or roller bearings for a roller or rollers forming one or more calendering nip (Ni-Nio) by means of at least one sensor pair 15 and the position of the noise source (11) in the axis direction of said roller is determined on the basis of the phase difference (φ) between the oscillations coming to the different sensors (41-46) in the sensor pair (41a, 41b ... 46a, 46b). ; Method according to claim 6, characterized in that by means of those in conjunction; In addition, with the bearings of the rollers (11-16) being monitored, the sensors (41-46) are monitored and the condition of the calender bearings is monitored. •; .t Method according to any of claims 1-7, characterized in that the position of the source of noise (M) in the peripheral or machine direction of the surface (10) which is monitored is determined by the use of an impulse sensor (50) which registers the rpm. * on the surface (10) being monitored and the timing of an impulse obtained from it in equilibrium. movement with the detection time of the interference (M). Method according to any one of claims 1-8, characterized in that at; The method is separated by an overpass filter and / or a bandpass filter if the signals (fa (t), fb (t)) detected with the oscillation sensors outside the measuring window are due to noise signals due to imbalance of rollers (11-16), tissues and / or bands and 18 11E5G2 on other oscillations. Method according to any of claims 1-9, characterized in that in the process a certain amount of measurement signals are collected in a memory, which are averaged and based on the thus obtained signals, the determination of at least one coordinate of the source of noise on the surface being monitored is carried out. Method according to any of claims 1-10, characterized in that in the method, oscillation signals and a signal (fi (t)) indicating the passage and speed of a reference point on the surface (10) are monitored to a unit (30). or a computer provided with a program (32) which controls the measurement and analyzes the measurement results and that the measurement results are conducted to the said unit (30) or the corresponding til display and / or alarm devices (33). 15 Method according to any of claims 1-11, characterized in that spectral analysis is performed on the signals obtained before the oscillation sensors, on the basis of which conclusions are drawn about the nature of the interference and / or the influence of external noise sources is reduced. • I t • «· '' 20 Method according to any one of claims 1 to 12, characterized in that in said unit (13) such a database is collected and created, by means of which is determined the V, "the most advantageous time for changing the various rollers most conveniently by classification * < * '·: By the severity of the interference and by storing the necessary data in connection with the «II change of each drum in the memory of the system (30).