FI77490B - FOERFARANDE FOER IDENTIFIERING AV YTSKADOR PAO EN STENVALS I ETT PRESSPARTI VID EN PAPPERSMASKIN ELLER LIKNANDE. - Google Patents

Description

1 77490

A method for identifying surface damage to a stone roll of a paper machine or similar press section

The invention relates to a method for identifying surface damage of a design of a paper machine or a similar press part / which design is provided with a pivotable holder, a scraper part extending over the length of the roll / dragging the surface of the roll.

Stone rolls are now used in the press parts of a paper-10 machine, for example. In a modern paper machine, the actual press of the press section can consist, for example, of four rolls arranged relative to each other so that the rolls form three press nips.

Em. of the four rollers, one is made of stone, 15 most commonly of granite. The granite casing of a stone roll is made in one piece by quarrying, machining and finally grinding. Thus, the design becomes an expensive component that is used because of its good properties. Good properties for use are the surface micro-20 structure and electroless.

In use, however, there may be cracks: cracks that, as they progress, damage the roll. At worst, cracks can lead to total breakage of the roll while driving. The consequences of such a roller blast are very serious. In practice, the rock mass of the roll, which can be, for example, about 70 tons, when ejected into the environment, breaks the entire press section and causes a long and expensive production interruption. In addition to material damage, export damage has also led to personal injury.

30 Em. for these reasons, it is very important to detect export damage before the roll finally disintegrates. Current methods can be used to control the shape of the design and the vibration caused by the design to other rolls and to the frame structures of the press section. However, there is no known method in the paper industry for locating roll surface cracks 2,77490 while running.

The object of the invention is to provide a method by means of which the condition of the roll can be monitored while the paper machine is running. This is achieved by a method according to the invention, characterized in that the impacts on the scraper part caused by the surface damage of the design are registered by means of accelerometers arranged in the holder and that the signal from each accelerometer is summed to synchronized roll rotation.

The advantage of the invention is above all its flexibility, since the cracks on the surface of the roll can be precisely located during driving, whereby dangerous roll disintegrations can be eliminated. Another advantage is its simplicity, whereby the implementation of the invention is advantageous. The invention can also be well applied to already existing press parts, since no fundamental changes need to be made to the press part.

The invention will now be explained in more detail by means of the embodiment 20 shown in the accompanying drawing, in which Fig. 1 shows in principle a side view of a press section of a modern paper machine, Fig. 2 shows an arrangement utilizing the invention in axial view. sensor output.

Figure 1 shows in principle the press section of a modern paper machine. Reference numeral 1 denotes the suction roll of the actual press, reference numeral 2 denotes a deflection-compensated roll, reference numeral 3 denotes a stone roll and reference numeral 4 a second deflection-compensated roll. Reference numeral 5 shows a scraper that drags the surface of the design and scrapes the contaminants off the surface of the roll. Web to be dried

II

3 77490 6 runs from left to right in the case of Figure 1.

Em. the structure and operation of the press part is a technique fully known to a person skilled in the art, so that the the issues are not clarified in this context.

Figures 2 and 3 show in principle the diagram shown in Figure 1 by reference numeral 5. In Figures 2 and 3, the corresponding parts are used with reference numerals as in Figure 1.

The scraper 5 consists of a holder 7 and a scraper part 8 attached to it. The holder 7 is mounted on the body of the press part so that it can pivot about its longitudinal axis. The holder 7 and the plant part 8 attached to it extend over the entire length of the design 3 as can be seen from Fig. 3. The holder 7 with its scraper parts 8 is turned so that the scraper part 15 8 drags the surface of the roll 3 as the roll rotates and thus scrapes the surface clean.

In the method according to the invention, the impacts on the plant part 8 caused by the surface damage of the embodiment 3 are registered by means of acceleration sensors 9 20 arranged in the holder. The effect of the impacts on the scraper part 8 is also felt in the holder 7, so that the acceleration sensors can be placed in the holder in a place which is well protected for the operation of the equipment.

In order to locate surface damage to the roll, for example cracks, in the longitudinal direction of the roll, acceleration sensors 9 are placed at a distance from each other over the entire length of the roll 3. The arrangement of the accelerometers in the longitudinal direction of the roll is shown in principle in Figure 3, in which the accelerometers 9 are marked by arrows.

According to the invention, the signal from the acceleration sensors 9 is further summed synchronously to the rotation of the roll 3. In this case, random disturbances do not interfere with the measurement. Em. as a result of the summation, a print according to Fig. 4 is obtained from each sensor 9. From the printout of Fig. 4 35, it can be seen that at points A and B there is a clear disturbance in the sliding of the scraper part 4 77490. The circle shown in Fig. 4 depicts the roll 3, so that the disturbance, i.e. the location of the damaged point on the circumferential surface of the design, can be located. Reference numeral 10 denotes the synchronization point used in signal summation 5. The wavy line 11 in Figure 4 illustrates the shocks to the plant part 8 caused by the surface of the design at the sensor 9. As stated above, there is a clear point of damage at A and B, the rest of the surface of the roll being intact.

The embodiment described above is in no way intended to limit the invention, but the invention can be modified completely freely within the scope of the claims. Thus, it is clear that, for example, the number of acceleration sensors is not limited in any way, but the number of sensors is, of course, selected according to need.

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