FI103829B - The suction roll - Google Patents

Description

103829

The suction roll

The present invention relates to a suction roll of a paper / board machine having a metal structure. The invention further relates to a method of making a paper / board machine suction roll diaper.

The suction roll is used to remove water from the paper web and to transfer the web to another roll or between different assemblies. In a paper machine, the environment is a web forming section (including a former roll and other wire section suction rolls) or a puris-tin section. Examples of the location of suction rolls in a paper machine environment are illustrated in Figure 1, which will be described in more detail below, with reference numeral I denoting a wire portion, reference numeral II a press portion and reference numeral III a drying portion.

15 The sheath torn on the suction roller rotates mounted on the flange shafts. Inside the diaper may be a single or multiple chamber suction box, the openings of which are limited by sealing strips to the interior surface of the diaper to direct suction to a particular sector of the suction roll. The inside of the roll may also be empty, whereby the suction is applied to the entire circumference of the roll shell. The ends of the roll have connections for connecting the external vacuum 20 to the suction box and / or to the inside of the roll. When the vacuum is connected under the paper web, a vacuum is formed through the wire or felt. The resulting pressure difference removes water from the web to the holes in the jacket or holds the web during transfer. The vacuum in the chambers is defined according to the purpose of the suction roll. Figures 2 and 3 schematically depict some prior art suction roll structures.

In use, the suction roll diaper is subjected to high dynamic loads, mechanical stresses, corrosion, and wear, causing stress corrosion, corrosion fatigue, and thermal fatigue, resulting in various types of casing damage. The diapers of suction rolls typically have about 500,000 suction holes, which in turn causes additional strength problems. For demanding applications, e.g., long nip counter rolls, advanced materials, e.g. powder metallurgy, which are relatively expensive, need to be used.

2 103829

Accordingly, it is an object of the present invention to provide a new type of suction roll in which a material with improved properties, e.g., a material having a higher corrosion fatigue strength or better thermal fatigue resistance, can be used only in those portions of the metal structure jacket. To achieve this object, the suction roll according to the invention is characterized in that the sheath is formed by a composite structure having at least two portions of the sheath in the axial direction made of first and second materials, respectively, of different manufacturing techniques and / or compositions; or at least a portion of the axial length of the mantle at least two layers in which the materials of the first and second layers are metals of different manufacturing techniques and / or compositions.

The method according to the first aspect of the invention is characterized in that the method comprises making at least two axial portions of the roll from first and second material, respectively, which are made of different metals and / or composite materials and assemble the ends together. The welding is done by welding edul-20 0.

The method of the second aspect of the invention is characterized in that the method comprises making at least one axial portion of the first material and forming a structural layer of a second material of different metals in the manufacturing technique and / or composition on the inner and / or outer surface.

The method according to a third aspect of the invention is characterized in that the method comprises making an axial middle portion of the first material and forming a structural layer on the inner and / or outer surface of the second material and end portions of the third material optionally forming a structural layer on the fourth material. the first and second material and the third and fourth material 3 103829, respectively, are metals of different manufacturing techniques and / or compositions, and the suction roll diaper is assembled by attaching an axial center portion to the end portions. Preferably, the second and fourth material forming said structural layers are metal material of the same kind.

5

The tension in the suction roller decreases towards the ends of the roll, whereby, according to the invention, the ends can be made of a first material, which is relatively cheaper, and welded, for example, by electron beam welding to a central part For example, austenitic-ferritic stainless steel, commonly referred to as duplex stainless steel or duplex steel only, may be used as the first material. Such material is produced by conventional methods such as forging, rolling or casting. Another material used in the more demanding subject in the center of the roll is, for example, powder metal. The powder-15 stable is a spherical particulate metal produced by molten metal gas atomization and having a particle diameter of the order of 0.1-0.5 mm. It may be more alloyed than steel grades produced by conventional methods. In the manufacture of powder metal, powder metallurgical methods are used, e.g. injection, extrusion and hot isostatic compression 2 0 (HIP). For example, in the HIP process, the metal body will get its final shape and density under high pressure and temperature while the metal is in a non-molten state, which results in better product properties and more homogeneous than products obtained by melt processes. The material composition of the first and second materials is naturally selected such that their machining and heat treatment properties are sufficiently close to each other. The first and second materials may have the same or different chemical compositions. The better properties of the second material are achieved by non-meltable manufacturing technology.

The roll shell according to the invention may also be formed as a composite structure so as to comprise at least two layers in the thickness direction of the shell, a first material layer and a second material layer. The first layer of material is formed by conventional methods of rolling or forging. The second material layer is formed on the inner or outer surface of the first material layer by powder metallurgical methods. For example, with the HIP method, a powder metal layer can be fabricated on the inner surface of a segment of first material, whereby the segment of first material 5 acts as a mold. The powder metal layer provides the sheath with the desired additional properties at desired locations. The materials of the first and second material layers may have the same or different chemical compositions. The better properties of the second-layer material are achieved by non-meltable manufacturing technology.

10

The roll shell according to the invention may also be formed as a composite structure comprising a central axial portion of a first material having an inner and / or outer surface formed by a second material and end portions of a third material having an inner and / or outer surface 15 optionally formed from a fourth material. the first and second materials, and the third and fourth materials, respectively, being metals of differing manufacturing techniques and / or compositions, the suction roll jacket being assembled by attaching the axial center portion to the end portions, preferably by welding. The second and fourth materials 20 forming said structural layers are preferably of the same metal material.

The invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 schematically shows a press section of a prior art paper machine with associated wire and dryer sections.

Fig. 2 is a schematic diagram of a longitudinal section of a prior art suction roll.

Figure 3 shows a schematic cross-section of another prior art suction roll, 30 5 103829

Figure 4 is a schematic longitudinal sectional view of another embodiment of a suction roll diaper of the invention, Figure 5 is a schematic longitudinal sectional view of another embodiment of the suction roll diaper of the invention, and Figure 6 shows a further development of the embodiment of Figure 5.

Figure 1 shows a press section II of the type with a basic geometry, marketed by the applicant under the trade mark "Sym-Press 10 II" TM, having four successive dewatering press nips Nt, N2, NP, and NP2. NP1 and NP2 are long nipples having a machine length of the long nip zone of the order of 100 ... 300 mm. The machine-directional length of the long nip zone NP1 and NP2 is about (3 ... 10) x the corresponding length of the roll nipples and N2. Of course, the same ratio applies to the pressing times of 15 different nipples. In addition, for wider machines (width> 4.5 m), the center of the press roll is usually a deflection compensated roll 20, which may be heated.

As shown in Figure 1, the paper web W is disengaged in the suction zone 20 11a of the pickup roll 11 from the forming wire 10 of the wire section I passing through the suction roll 60 and applied to the lower roll surface Nv of the first roll nip N1 in addition to the pick-up felt felt 12, a water receiving lower felt 15 guided by the guide rolls 16. The lower roll of the press nip N1 is, for example, a press roll roll 14 with a groove surface 14 'and the press roll nozzle 13 having two successive suction zones 13a and 13b as an upper roll. In the nip N-, dewatering takes place in two directions to the felts 12 and 15 through both surfaces of the web. The press suction roll 13 is provided with a torn jacket and a pickup up felt 12 with a first suction zone 13a and a web W on its outer surface curves to a second roll nipple N2 having a second suction zone 13b at its compression zone preferably employing a higher vacuum. The second roll nipple N2 is formed between the above mentioned press suction roll 13 and the heated deflection compensated central roll 20. In connection with the suction zone 13a of the suction roll 13, there is a steam box 34 near the outer surface of the web W to increase the temperature level of the web before the second roll nip N2 and before the web contacts the heated surface of the hot roll 20. At nip N2, central means 20 may be provided with internal roll means for adjusting and controlling the transverse compression pressure profile of roll nip N2 by the collapse and deflection of the central roll 20 caused by roll nip N2.

After the roll nip N2, the web W follows the 20 smooth surfaces of the center roll to the third press nip having the long nip ΝΡν 10

After the long nip zone NP1, the web W follows the smooth surface of the heated central roll 20 and is assisted by the suction zone 51a of the transfer suction roll 51 to a lower felt 50 having an upper surface for. The upper nip of the long nip NP2 is a suction roll 55 from which the web W is fed to the transfer roll 46 and further to the drying wire 40 of the drying section III.

Fig. 2 is a plan view of a prior art suction 20. The suction roll comprises a roll mantle 111 which is mounted to rotate with shaft pivots 113A and 113B connected via end flanges 112A and 112B to a roll skirt 111. only a portion of the diaphragm 111 perforation 115. The inside of the roll is empty here, but there may also be a suction box 25 within the roll to direct the suction to a particular sector of the roll. At least one of the shaft pins 113B has connections to the interior of the roll to which an external vacuum source (not shown) can be connected. The vacuum source draws air out of the entire interior of the roll or at a sector formed by the suction box (arrow P2), whereby a corresponding amount of air arrow (P.,) flows into the roll 30 through the perforation 115 of the roll jacket. The perforation 115 of the roll shell 111 may consist of bores extending the same diameter through the entire shell 111, or the bores may have been tapered on the outer surface of the shell 111, thereby increasing the surface opening of the shell 115 to the outer surface of the shell 111. The perforation 103829 7 115 of the roll shell 111 is preferably formed in a spiral manner so that the holes are not located in rows parallel to the roll axis. With this arrangement, the emptying of the holes 115 from the water and the subsequent filling of the holes with air can be staggered over time, thereby reducing the noise produced. Holes 115 generally have a diameter 5 of about 2 mm to 5 mm and dents generally have a diameter of about 2 to 15 mm.

Figure 3 shows the current state of the art. The suction box and the seal holder are rigidly attached to each other. The seals 101 are loaded against the diaper 102 by loading hoses 103, thereby causing the seals to be pressed against the diaper 10 at approximately constant pressure, even in the bent position of the suction box. Due to sealing pressure, water lubrication V is necessary to reduce wear on the seals and the inner surface of the roll shell. However, water lubrication cannot be used or water lubrication is uneconomical in those applications of the suction roll where the paper or board web has already been dried (by pressing or drying) to a high solids content (about 35%).

Figures 4-6 illustrate some embodiments of the invention, schematically showing only suction roll diaper blanks without suction holes and without other roll member such as suction boxes, flange shafts, vacuum connections, etc.

20

In an embodiment of the invention according to Fig. 4, the suction roll shell 1 comprises axial end portions 2 between two axial center forming segments 3. These end portions and the central portion are welded to each other at 8. The material of the central portion 3 may be austenitic ferrite can be relatively less expensive duplex steel (i.e., austenitic-ferritic stainless steel produced by forging, rolling, or casting).

In another embodiment of the invention according to Fig. 5, the sheath 1 of the suction roll 30 is made up of end portions 2 and center-forming segments 3 welded at points 8 respectively. In the embodiment of Fig. 5, each axial part 2, 3 is formed in thickness direction by two structural layers 4, 5 and 6, 7, respectively. The layers 4, 6 form e.g. a casting body, the layers 5,7 being powder metal, which is attached to each frame by HIP processing. In the embodiment shown, the structural layers joined by HIP treatment are located on the inner surface of the jacket. The base material 4, 6 may be, for example, 5 duplex steel, the structural layer 5, 7 being, for example, austenitic-ferritic powder metal. Said structural layers 5 and 7 are preferably made of the same material with each other, while the layers constituting the body part 4 and 6 may be of different material e.g. such that the body layer 6 of the middle part 3 is a stronger material than the body layer 4 of the end part 2.

10

Contrary to that shown in Figure 5, the number of thickness layers in the axial segments may be different. For example, the axial end portions 2 may be made entirely of body material and the central part 3 may comprise a cascade structure of body material and powder metal. The structure-15 layer 5, 7 provides mechanical, thermal and chemical strength to the shell structure. It may preferably be thinner than the body but still thick enough to provide the above improvement to the structure.

The suction roll according to the invention is suitable for use in the wire and press sections of a papermaking machine as a suction roll, for example, a suction roll 13 of Figure 1 with two nips N and N2 with a counter roll 14 and a central roll 20 respectively. It is particularly advantageous for the press section to be a back nip roll for a long nip press, for example, a suction roll 55 of Fig. 1 for a long roll nip 56.

The embodiment of Fig. 6 differs from the embodiment of Fig. 5 only in that at the opposite ends of the segments 2 and 3 the structural layers 5 and 7 extend over the end surface of the body part 4 and 6 respectively, whereby welding takes place between end surfaces 9 of the same material.

Naturally, the suction roll of the invention can be used in all other suction roll positions, although the advantage of the invention is best demonstrated in areas where the roll is subjected to high stress.

Claims (14)

9 103829 A paper / board machine suction roll having a metal structure with a perforated sheath (1), characterized in that the sheath (1) is formed by a composite structure having at least two parts (2, 3) in the axial direction of the sheath made respectively from the first and a second material, the first and second materials being metals of a different manufacturing technique and / or composition, and / or at least two layers (4,5; 6,7) in the thickness direction of the diaper at least a portion of the axial length of the diaper, metals of different manufacturing techniques and / or compositions. Suction roll according to Claim 1, characterized in that the diaper (1) consists of axial end portions (2) made of a first material and a central part (3) between the end portions (2) made of a second material, and that said second material is at least superior to that first material selected from the group of: strength, corrosion resistance, fatigue strength, or wear resistance. 20 Suction roll according to Claim 2, characterized in that the diaper (1). the material of the central part (3) is powder metal and the material of the end parts (2) is made of stainless steel. A suction roll according to Claim 1, characterized in that at least one of the axial portions (2,3) of the diaper comprises two layers, the first of which is a suction roll. The material layer (4, 6) forms a thicker body with a thinner structural layer (5, 7) having a different manufacturing technique and / or composition which gives the desired additional structural properties to the inner and / or outer surface. 10 103829 Suction roll according to Claim 4, characterized in that the structural layer (5, 7) is a powder metal attached to the surface of a stainless steel body (4, 6). Suction roll according to one of the preceding claims, characterized in that the roll is a counter roll of a long nip press. A method for manufacturing a suction roll jacket for a paper / board machine, characterized in that at least two axial portions (2, 3) of the roll are produced from first and second material, respectively, of different materials and / or composite metals; by connecting the parts (2, 3) at their ends. Method according to claim 7, characterized in that the parts (2,3) 15 are joined together by welding. Method according to claim 7 or 8, characterized in that the first material part (2) is produced by forging, rolling or casting and the second material part (3) is manufactured by powder metallurgy. 20 A method for manufacturing a paper / board machine suction roll diaper, characterized in that at least one axial portion (3) of the first material (6) is formed and a structural layer (7) is formed on the inner and / or outer surface of the second material. different metals of 2. composition. Method according to Claim 10, characterized in that the part (3) is made by forging, rolling or casting the first material and a structural layer (7) is formed on its inner and / or outer surface by powder metallurgy. 11 103829 Method according to Claim 11, characterized in that the structural layer (7) is formed on the inner surface of the first material (6) by hot isostatic compression. 13. A method for manufacturing a paper / board machine suction roll, characterized in that the method comprises making an axial middle portion (3) of the first material (6) and forming a structural layer (7) on the inner and / or outer surface of the second material and 4) optionally forming a structural layer (5) on the inner and / or outer surface of the first fourth material, the first (6) and the second (7) and the third (4) and fourth (5) materials respectively being of manufacturing technique and / or composition various metals, assemble the suction roll sheath by attaching the axial center portion (3) to the end portions (2), after which the sheath is perforated. Method according to Claim 13, characterized in that the second and the fourth material constituting the layer (7) and the optional structural layer (5) are of the same metal material. «12 103829