WO2005047595A1

WO2005047595A1 - A method for changing roll plates of a roll body

Info

Publication number: WO2005047595A1
Application number: PCT/SE2004/001614
Authority: WO
Inventors: Björn JANSSON
Original assignee: Metso Paper Inc.
Priority date: 2003-11-13
Filing date: 2004-11-08
Publication date: 2005-05-26
Also published as: SE0302993D0; SE0302993L; SE526150C2

Abstract

A method for changing at least a portion of a roll plate of a roll body comprising sectional roll plates, the mantle section of the roll body comprising frame rings (6), where the method comprises mounting a new roll plate (5), comprising the steps of: Attaching a clamping device, comprising two clamping device units (8, 9; 3.8, 3.9) and clamping means, to the new roll plate (5, 3.5) by attaching respective clamping device unit (8, 9; 3.8, 3.9) to either side of the transverse joint (10, 3.10); Lifting the new roll plate (5, 3.5) onto the roll body; Connecting the clamping device units (8, 9; 3.8, 3.9); Controlling the clamping means, until the new roll plate (5, 3.5) is abutting around the mantle section; Marking the frame rings (4, 6, 3.6) for positioning of backing bars (14); Lifting off the new roll plate (5, 3.5); Attaching the backing bars (14) to the frame rings (4, 6, 3.6) along the marks made on the frame rings (4, 6, 3.6); Lifting the new roll plate (5, 3.5) onto the roll body and connecting the clamping device units (8, 9; 3.8, 3.9); Centring the transverse joint (10, 3.10) to the backing bars (14); Attaching one of the short sides of the new roll plate (5, 3.5); Adjusting the gap of the transverse joint (10, 3.10); and Welding the transverse joint (10, 3.10).

Description

A METHOD FOR CHANGING ROLL PLATES OF A ROLL BODY

Technical Field The present invention relates to a method for changing at least a portion of a roll plate of a roll body comprising sectional roll plates, the mantle section of the roll body comprising frame rings arranged along the longitudinal axis of the roll body, against which the roll plates abut. The method comprises dismounting an old roll plate and mounting a new roll plate.

Background of the Invention Upon producing cellulose-based products, a roll press is frequently pre- sent for removing water from the cellulose-based pulp. The pulp is passed through at least one press roll comprised in the roll press, preferably having a perforated mantle surface, whereby the mantle surface is permeable to water pressed out from the pulp, and is pressed against the press roll, whereby water is pressed out from the pulp. One example of such a roll press for removing water from pulp is disclosed in SE 505 539, e.g.. SE 509 81 1 discloses an edge ring for a press roll, extending around the edge side of each roll end, where the edge ring is diametrically divided into at least two sections, and in radial section forms a hook in its radially outer portion, where the hook in turn, together with the roll end forms a clamping bond. SE 519 753 describes a sealing of a press roll in a roll press having two co-operating press roils for removing the water from material suspensions. SE 512 904 discloses a scraper device for roll presses, comprising a removing unit for each press roll, which abuts the mantle surface of each press roll. The removing unit comprises scraping sections having scraping blades in- eluded in a module system. The sections are supported by a coarse shredder bin mounted above the press nip, which together with the scraping sections forms a rigid structure in the longitud inal direction of the press rolls. The above mentioned roll presses have in common that they usually have a mantle surface comprising several roll plates mounted along the longitudinal di- rection of the press roll, which abut each other edge to edge and abut around the mantle section of the press roll. Preferably, these roll plates are perforated in order to be permeable to water pressed out from the passing cellulose-based pulp. Naturally, during operation, these roll plates are subjected to wear and must be changed because they become damaged. However, a problem arises if a roll plate, which is to be replaced by a new roll plate, is centrally positioned on the press roll. In this case, according to conventional methods, the peripheral roll plate or roll plates must be removed from the press roll before the damaged roll plate can be removed. The problem is more complex the more central the damaged roll plate is positioned on the press roll, which involves a removal of more undamaged roll plates in order to enable the removal of the damaged roll plate. This involves longer shutdowns of the roll press and consequently of the plant, and results in great dropping off in production and is thus expensive. Further, a problem of prior art methods is that these comprise an uncontrolled grip of the roll plate around the roll body, or the loss of such.

The Object of the Invention The object of the present invention is to provide a method for changing roll plates of a roll body, for example a press roll for removing water from cellulose- based pulp, which method solves the above mentioned problems by enabling an efficient and easy change of roll plates at a prescribed shrink grip.

Summary of the Invention The solution of the present invention to the above mentioned problem is to provide a method providing a radical increase in efficiency and simplification of the change of roll plates of a roll body by a method of the kind defined in the preamble of claim 1 , comprising the special measures that the dismounting of the old roll plate comprises the steps of: • Separating the old roll plate along the circumference of the roll body at both longitudinal sides of the old roll plate; • Splitting the old roll plate substantially along the longitudinal axis of the roll body; and • Removing the old roll plate; and that the mounting of the new roll plate comprises the steps of: • Attaching a clamping device, comprising two clamping device units and clamping means, to the new roll plate by attaching respective clamping device unit at respective short side of the new roll plate, on either side of the transverse joint extending along the short sides of the new roll plate; • Lifting the new roll plate onto the roll body; • Connecting the clamping device units by means of the clamping means; • Controlling the clamping means, causing the clamping device units to move closer to each other, until the new roll plate is abutting around the mantle section; • Marking the frame rings along one of the short sides of the new roll plate for positioning of backing bars; • Lifting off the new roll plate; • Attaching the backing bars to the frame rings along the marks made on the frame rings; • Lifting the new roll plate onto the roll body and connecting the clamping device units by means of the clamping means; • Rotating the transverse joint so that it is centred to the backing bars; • Attaching one of the short sides of the new roll plate to the frame rings; • Adjusting the gap of the transverse joint by means of the clamping means to a suitable width of gap; • Welding the transverse joint; and • Disconnecting and removing the clamping device units. According to an advantageous embodiment of the method according to the present invention, the separation of the old roll plate at both longitudinal sides of the old roll plate is effected by cutting-off in a lathe, and preferably the separation is effected at the round joints of the old roll plate. According to a further advantageous embodiment of the method according to the present invention, the dismounting of the old roll plate comprises the further steps of: • Arranging a strap around the circumference of the old roll plate to secure the old roll plate before splitting; and • Adjustment turning at the round joints to provide a suitable diameter of the frame rings adjacent to the round joints and a suitable width of the uncovered surface, to which the new roll plate (5, 3.5) is to be attached. According to another advantageous embodiment of the method according to the present invention, when mounting the new roll plate, respective clamping device unit is attached by its rear edge side and front edge side at the short sides, and preferably the transverse joint is positioned in a twelve o'clock position during the mounting of the new roll plate. According to still another advantageous embodiment of the method according to the present invention, when mounting the new roll plate, the marking of the frame rings is done where the joints of the frame rings of the mantle section are positioned. According to yet another advantageous embodiment of the method according to the present invention, the mounting of the new roll plate comprises the step of: • Attaching a hold, in the form of a flat bar, behind one of the clamping device units to facilitate the handling of the new roll plate during mounting. Further, according to an advantageous embodiment of the method according to the present invention, in all said steps of the mounting of the new roll plate the attachment is effected by welding. According to a further advantageous embodiment of the method according to the present invention, the mounting of the new roll plate, after adjusting the gap of the transverse joint and prior to welding the transverse joint, comprises the steps of: • Disconnecting the clamping device units and laying down the unattached short side of the new roll plate; • Heating the new roll plate; and • Lifting up the unattached short side of the new roll plate, and connecting the clamping device units. Preferably, prior to removal of the clamping device, the new roll plate is cooled down. According to another advantageous embodiment of the method according to the present invention, the mounting of the new roll plate is finished with the steps of: • Turning the welding seam of the round joints, welding the round joints, and removing the weld reinforcement. The method according to the present invention is especially suitable to be performed on perforated roll plates and a roll body in the form of a press roll, especially intended for removal of water from pulp, preferably cellulose-based pulp. Brief Description of the Drawings The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which: Fig. 1 is a schematic perspective view of a portion of a conventional press roll, Fig. 2 is a schematic sectional view of a portion of a conventional press roll having a new roll plate mounted by a method according to the present invention, the roll plate being perforated and having a clamping device mounted, Fig. 3 is a schematic partial top view of the new roll plate of Fig. 2 having a clamping device mounted, and Fig. 4 is a schematic flow diagram of an embodiment of the method according to the present invention.

Detailed Description of a Preferred Embodiment Fig. 1 shows a portion of a conventional press roll having several roll plates 1 , which are perforated. Each roll plate 1 abuts against the mantle section of the press roll, and its short sides meet in a transverse joint 2. Both longitudinal sides of the roll plate 1 are bordered by a round joint 3. The mantle section com- prises frame rings 4 arranged regularly spaced along the longitudinal axis of the press roll, against which the roll plates 1 abut, and thus provide a support for each roll plate 1. Fig. 2 shows a cross section of a portion of a conventional press roll having a new roll plate 5 mounted by the method according to the present invention, which abuts the frame rings 6. Several flat bars 7 are arranged inside the frame rings 6 and form, together with, inter alia, the frame rings 6, the mantle sections of the press roll. A clamping device is attached to the roll plate 5 according to the method of the present invention. The clamping device comprises a first clamping device unit 8 and a second clamping device unit 9. To the second clamping device unit 9 clamping means are pivotally attached in the form of three coupling screws 11. In the first clamping device unit 8 there is a complementary recess to each coupling screw 11 , into which respective coupling screw 11 rests. Each coupling screw 11 is provided with a nut 12 and a lock nut 13. The first and second clamp- ing device units 8, 9 are attached to the new roll plate 5 about 12 mm from respective short side of the new roll plate 5. Along the short sides of the new roll plate 5 and between the first and second clamping device units 8, 9, a transverse joint 10 extends along the longitudinal axis of the press roll. At this transverse joint 10 the short sides of the new roll plate 5 are welded together. According to the method of the present invention, prior to welding, the transverse joint 10 is positioned in such a way that the transverse joint 10 is positioned straight above backing bars 14 previously welded. According to the method of the present invention, these backing bars 14 have been welded near the weld joints 15 of the frame rings 6. The backing bars 14 act as a support in the transverse joint 10 during welding. The backing bars 14 are arranged between the frame rings 6 at their outer periphery along a line extending along the longitudinal axis of the press roll. Each backing bar 14 consists of a piece of iron, e.g.. Without these backing bars 14 the weld would harmfully melt the new roll plate 5 at the transverse joint 10. According to the method of the present invention a hold 16 in the form of a flat bar is attached to the new roll plate 5 behind the first clamping device unit 8 in order to prevent the tack welds at the frame rings 6 and at the new roll plate 5 from being subjected to too strong forces during later handling of the new roll plate 5, and thus run the risk of breaking off the new roll plate 5 during handling. Fig. 3 shows a portion of the new roll plate 3.5 shown in Fig. 2, having a clamping device arranged, which is shown from the top. Here are several frame rings 3.6 visible in the transverse joint 3.10, arranged regularly spaced along the longitudinal axis of the press roll. Fig. 4 shows an embodiment of the method according to the present invention in the form of a schematic flow diagram, where the roll plate is perforated and the roll body is a press roll. The numbered steps of the flow diagram comprise:

4.1. Dismounting the old roll plate • Placing the press roll in a lathe, preferably a capstan lathe. • Checking the press roll so it is not radially warping more than 0.05 mm. This check is suitably carried out by means of a so called dial test indicator, i.e. a measuring device measuring warping, which is applied to a previously turned surface in the periphery of the press roll. • If necessary, adjusting the warping of the press roll by means of grip holders, i.e. the means of attachment of the lathe, at the jaw chuck of the lathe. The lathe is of conventional type and is controlled in a conventional manner. • Cutting-off the old roll plate along its longitudinal sides along the circumference of the press roll, at the line of holes closest to the round joint of both longitudinal sides of the old roll plate.

• Splitting the old roll plate along the longitudinal axis of the press roll by means of an angle grinder having a cutting wheel. A groove or a cut is pro- vided in the centre of the old roll plate, e.g. about 100 mm long, which groove extends along the longitudinal axis of the press roll. Since there are shrinkage tensions in a perforated roll plate, e.g., the old roll plate must be secured with a strap abutting the old roll plate around the circumference of press roll. The strap is placed around the old roll plate across the groove and is tightened. After this, the old roll plate is prepared for splitting. Preferably, the splitting is effected through careful cutting in the groove of the old roll plate, since there is a risk of cutting too deep and by mistake cause cuts in the mantle section inside the old roll plate.

• adjustment turning at the round joints, preferably to a width of the uncov- ered surface, to which the new roll plate will be applied, of 340 mm, equably distributed on the present, e.g. 100 mm thick, frame rings. In order to achieve a suitable diameter on these frame rings, the lathe tool is applied to the present frame rings at preferably 4 mm. Said width of 340 mm preferably applies to a width of the roll plate of 338 mm. Preferably, the transverse joint of the new roll plate is positioned where the joints of the frame rings of the mantle section are positioned, i.e. about 15 mm from the longitudinal side of a flat bar of the mantel section.

• Marking the press roll at a spot indicating the existing transverse joint.

• Rotating the press roll in such a way that the mark is positioned in a twelve o'clock position, i.e. that the mark is turned upwards, so that the correct position for the coming welding of the transverse joint is provided before the press roll is lifted off. • Lifting off the press roll and positioning it in rubber-faced sheet metal cradles or wooden cradles, e.g., preferably these cradles having the same radius as the mantle surface of the press roll.

4.2. Attaching a clamping device to the new roll plate • Attaching a clamping device to the new roll plate by welding respective clamping device unit to either side of the transverse joint, this being done before the new roll plate is placed onto the press roll, about 12 mm from respective short side of the new roll plate. The attachment is effected by conventional TIG welding at the rare edge side of respective clamping device unit in every other undrilled region. The roll plate is drilled according to a certain pattern and the undrilled regions are located where the frame rings are provided as a support. Also at the front edge side at the short sides of the clamping device units, a minor point welding is provided to secure each clamping device unit. Preferably, the auxiliary material has the same quality as the roll plates.

4.3. Marking for backing bars of the transverse joint • Lifting the new roll plate having a clamping device arranged onto the press roll, the coupling screws being positioned across the transverse joint and the nuts are tightened, for example with manual power. Rotating the trans- verse joint to said mark on the press roll, and further tightening of the nuts of the coupling screws, while the roll plate surface is gently knocked with a wooden club, e.g., in order to provide vibrations making the new roll plate to find its right position. • Tightening said nuts until the new roll plate is abutting around the mantle section, the welding gap between the short sides of the new roll plate forming the weld joint of the transverse joint being preferably about 6-8 mm. In this position it becomes apparent if the transverse joint presents perpendicular alignment. • Marking the frame rings with a marking tool along one of the short sides of the roll plate. • Loosening the nuts and lifting off the new roll plate, the new roll plate being lifted off to make room for attaching the backing bars by welding. 4.4. Welding the backing bars to the mantle section • Welding the backing bars by TIG welding along the marks on the frame rings in the periphery of the mantle section. Welding is done only between the frame rings, and any weld crests preferably being removed by file. Pref- erably, the material of the backing bars is the same as the material of the roll plates.

4.5. Attaching the new roll plate to the mantle section • Lifting the new roll plate having a claming device arranged onto the press roll and positioning the coupling screws across the transverse joint. • Tightening the coupling screws, e.g. by manual power. • Rotating the transverse joint to the correct position, i.e. where the trans- ^• verse joint is centred to the backing bars. • Attaching one of the short sides of the new roll plate by TIG welding, preferably the short side without coupling screws in order to enable the use of the coupling screws as handles when laying down and lifting up the new roll plate, tack welding being done in all frame rings. Preferably, the width of the tack welds is not greater than 2 mm at the base of the tack weld. • Welding a hold, in the form of a flat bar having a length preferably longer than the width of the roll plate, to the new roll plate. Preferably, the welding is done in the old round joints to avoid damaging the other present roll plates.

4.6. Adjusting the gap of the transverse joint • Tightening the coupling screws in the same way as in 4.3. Measuring the gap between the short sides of the new roll plate. Preferably, the gap of the transverse joint is 2.5 mm when the new roll plate is heated. • Setting a distance between the lock nuts and respective clamping device unit so that the correct gap is provided when the new roll plate is heated. If the gap measures 7 mm, e.g., a distance between the lock nut and respective clamping device unit is set to 4.5 mm.

4.7. Heating and welding the new roll plate • Disconnecting the clamping device units and laying down the unattached short side of the new roll plate, i.e. the short side with the coupling screws, towards the floor and into a sheet metal cradle with a U-shaped cross section, preferably of a stainless material. • Heating the new roll plate by means of a LP-gas heater, e.g., preferably with large sweeping movements. Preferably the roll plate is heated during about 10-15 minutes until it obtains a lightly brown shade in the surface layer. At that time the temperature is 250-300°C. Preferably, the sides of the roll plate is heated in a larger extent in order to provide an even roll plate. • Lifting up the unattached short side of the new roll plate and connecting the clamping device units. Checking that the correct gap is provided and ad- justing the gap if necessary. • MIG welding the transverse joint in a conventional manner, except of just under the coupling screws. During welding, checking the length of the new roll plate by inspecting the "hanging down" of the new roll plate in relation to the remaining roll plates. When the roll plate is heated it becomes larger in diameter, which is shown by the "hanging" of roll plate on the underside of the press roll. • Supportive heating if necessary. • Disconnecting the clamping device units and grinding down the start point of welding and the end point of welding, i.e. the regions under the coupling screws. • Supplementary welding. • Cooling down the new roll plate. • Removing the clamping device and the hold from the new roll plate. • Grinding down the weld reinforcement and tack welds of the transverse joint with caution.

4.8. Welding and turning the round joints • Placing the press roll in a lathe. • Checking the press roll so it is not radially warping more than preferably 0.05 mm by means of a dial test indicator positioned in the periphery of the press roll. If necessary, adjusting the warping of the press roll by means of the grip holders at the backside of the lathe. • Turning the weld joint of the round joints. • Welding the round joints with a conventional MIG weld. Turning the weld reinforcement, i.e. the abundance of welding material, and adjustment grinding.

Claims

1. A method for changing at least a portion of a roll plate of a roll body comprising sectional roll plates, the mantle section of the roll body comprising frame rings (4, 6, 3.6) arranged along the longitudinal axis of the roll body, against which the roll plates abut, the method comprising dismounting an old roll plate and mounting a new roll plate (5, 3.5), wherein the dismounting of the old roll plate comprises the steps of: • Separating the old roll plate along the circumference of the roll body at both longitudinal sides of the old roll plate; • Splitting the old roll plate substantially along the longitudinal axis of the roll body; and • Removing the old roll plate; and the mounting of the new roll plate (5, 3.5) comprises the steps of: • Attaching a clamping device, comprising two clamping device units (8, 9; 3.8, 3.9) and clamping means, to the new roll plate (5, 3.5) by attaching respective clamping device unit (8, 9; 3.8, 3.9) at respective short side of the new roll plate (5, 3.5), on either side of the transverse joint (10, 3.10) extending along the short sides of the new roll plate (5, 3.5); • Lifting the new roll plate (5, 3.5) onto the roll body; • Connecting the clamping device units (8, 9; 3.8, 3.9) by means of the clamping means; • Controlling the clamping means, causing the clamping device units (8, 9; 3.8, 3.9) to move closer to each other, until the new roll plate (5, 3.5) is abutting around the mantle section; • Marking the frame rings (4, 6, 3.6) along one of the short sides of the new roll plate (5, 3.5) for positioning of backing bars (14); • Lifting off the new roll plate (5, 3.5); • Attaching the backing bars (14) to the frame rings (4, 6, 3.6) along the marks made on the frame rings (4, 6, 3.6); • Lifting the new roll plate (5, 3.5) onto the roll body and connecting the clamping device units (8, 9; 3.8, 3.9) by means of the clamping means; • Rotating the transverse joint (10, 3.10) so that it is centred to the backing bars (14); • Attaching one of the short sides of the new roll plate (5, 3.5) to the frame rings (4, 6, 3.6); • Adjusting the gap of the transverse joint (10, 3.10) by means of the clamping means to a suitable width of gap; • Welding the transverse joint (10, 3.10); and • Disconnecting and removing the clamping device units (8, 9; 3.8, 3.9).

2. A method according to claim 1, characterized in that the dismounting of the old roll plate comprises the further step of: • Arranging a strap around the circumference of the old roll plate to secure the old roll plate before splitting.

3. A method according to claim 1 or 2, characterized in that the separation of the old roll plate at both longitudinal sides of the old roll plate is effected by cutting-off in a lathe.

4. A method according to any of the preceding claims, characterized in that the separation of the old roll plate at both longitudinal sides of the old roll plate is effected at the round joints (3) of the old roll plate.

5. A method according to claim 4, characterized in that the dismounting of the old roll plate comprises the step of: • Adjustment turning at the round joints (3) to provide a suitable diameter of the frame rings adjacent to the round joints and a suitable width of the un- covered surface, to which the new roll plate (5, 3.5) is to be attached.

6. A method according to any of the preceding claims, characterized in that the transverse joint (10, 3.10) is positioned in a twelve o'clock position during the mounting of the new roll plate (5, 3.5).

7. A method according to any of the preceding claims, characterized in that, when mounting the new roll plate (5, 3.5), respective clamping device unit (8, 9; 3.8, 3.9) is attached by its rear edge side and front edge side at the short sides.

8. A method according to any of the preceding claims, characterized in that, when mounting the new roll plate (5, 3.5), the marking of the frame rings (4, 6, 3.6) is done where the joints (15) of the frame rings (4, 6, 3.5) of the mantle section are positioned.

9. A method according to any of the preceding claims, characterized in that the mounting of the new roll plate comprises the step of: • Attaching a hold (16) in the form of a flat bar behind one of the clamping de- vice units (8, 9; 3.8, 3.9) to facilitate the handling of the new roll plate (5, 3.5) during mounting.

10. A method according to any of the preceding claims, characterized in that, in all said steps of the mounting of the new roll plate (5, 3.5) the attachment is effected by welding.

11. A method according to any of the preceding claims, characterized in that the mounting of the new roll plate (5, 3.5), after adjusting the gap of the transverse joint (10, 3.10) and prior to welding the transverse joint (10, 3.10), comprises the steps of: • Disconnecting the clamping device units (8, 9; 3.8, 3.9) and laying down the unattached short side of the new roll plate (5, 5.3); • Heating the new roll plate (5, 5.3); and • Lifting up the unattached short side of the new roll plate (5, 5.3), and connecting the clamping device units (8, 9; 3.8, 3.9).

12. A method according to claim 11 , characterized in that, prior to removal of the clamping device, the new roll plate (5, 3.5) is cooled down.

13. A method according to any of the preceding claims, characterized in that the mounting of the new roll plate (5, 3.5) comprises the step of: • Removing weld reinforcement and tack welds of the transverse joint (10, 3.10) after the removal of the claming device.

14. A method according to any of the preceding claims, characterized in that the mounting of the new roll plate (5, 3.5) is finished with the steps of: • Turning the welding seam of the round joints (3), welding the round joints (3), and removing the weld reinforcement.

15. A method according to any of the preceding claims, characterized in that the method is performed on a perforated roll plate and a roll body in the form of a press roll, especially intended for removal of water from pulp.