WO2013072560A1

WO2013072560A1 - Fiber web machine equipped with fabric heater

Info

Publication number: WO2013072560A1
Application number: PCT/FI2012/051118
Authority: WO
Inventors: Petter Honkalampi; Riku Pihko; Leena Silakoski; Jorma Snellman; Jarmo Virtanen
Original assignee: Metso Paper, Inc.
Priority date: 2011-11-17
Filing date: 2012-11-15
Publication date: 2013-05-23
Also published as: FI124583B; CN204023293U; DE212012000210U1; FI20116150A; AT14236U1

Abstract

The invention relates to a fiber web machine equipped with a fabric heater. The fabric heater includes a frame construction (16), arranged in association with a fabric (13) installed in the fiber web machine and supported with several lead rolls (15), and distribution means (17) for supplying steam towards the fabric (13). The distribution means (17) include a steam distribution surface (19) with one or more openings (20) and a sealing surface (19') surrounding said opening (20). In addition, the fabric heater is arranged in contact with the fabric (13) in such a way that at least the sealing surface (19') is against the fabric (13) in both the cross-machine and machine directions. The frame construction (16) is located in the vicinity of one lead roll (15) in such a way that a deviation is generated in the fabric (13) against the fabric tension. In addition, the fabric heater (16') is arranged on the side of the fabric (13) facing the surface of the web (14) manufactured in the fiber web machine.

Description

FIBER WEB MACHINE EQUIPPED WITH FABRIC HEATER

The invention relates to a fiber web machine equipped with a fabric heater which includes a frame construction, arranged in association with a fabric installed in the fiber web machine and supported with several lead rolls, and distribution means for supplying steam towards the fabric, which distribution means includes a steam distribution surface with one or more openings and a sealing surface surrounding said opening, and the fabric heater being arranged in contact with the fabric in such a way that at least the sealing surface is against the fabric in both the cross-machine and machine directions.

Steam is used for many different purposes in a fiber web machine. In connection with fabrics, such as a press felt supported with lead rolls, steam has two main functions, which are partially overlapping. Steam is used in attempts to condition the fabric and increase the fabric temperature for improving dewatering. Cleaning showers at the driving water temperature are usually included in the conditioning positions, in which case the heating effect of steam remains small. On the other hand, fabric heaters mainly aim to create a uniform moisture profile. For fabric conditioning equipment, it has been proposed to use a fabric-supporting return roll into which steam is supplied. Steam is supplied via the shell holes of the return roll towards the fabric. However, a return roll equipped with a perforated shell is expensive. In addition, part of steam escapes along with the holes as the shell rotates and part of the steam energy is then lost and mist is generated at the same time. In other words, steam spreads to the surrounding air. Sealing of the shell is also challenging when part of the shell holes are open. Fabric conditioners based on cleaning showers and vacuum boxes also exist. It is attempted to locate these, like other fabric conditioning equipment, as soon as possible after the press nip. Thus any increases in the fabric temperature will have time to be eliminated before the fabric enters the press nip again. Fabric heaters are generally so- called profiling steam boxes in which steam is supplied at a high speed via a row of nozzles. Nozzles are expensive and high-speed steam showers generate mist in the environment remaining thus inefficient. Furthermore, a fabric heater must be located far from a press nip and thus the benefit of heat to dewatering remains small. A steam box consists of a frame construction accommodating the nozzles which form the distribution means.

US patent No. 1395219 proposes a manual fabric conditioner which can be used to supply steam towards a fabric. The fabric conditioner includes a steam distribution surface provided with openings for supplying steam.

The object of the invention is to provide a novel fiber web machine equipped with a fabric heater wherein steam can be utilized more efficiently, yet in a simpler way than before. The characteristic features of this invention are that the frame construction is located in the vicinity of one lead roll in such a way that a deflection is generated in the fabric against the fabric tension, and the fabric heater is arranged on the side of the fabric facing the surface of the web produced in the fiber web machine. Thus, firstly, the fabric is sealed against the frame construction and, secondly, steam is uniformly spread over the entire fabric travel. It is also possible to arrange one or more plane or even concave sections at the center of the fabric-deviating steam distribution surface, which section is not in contact with the fabric. In the space defined by such a section, openings can be made or even nozzles can be installed, for supplying steam to the fabric. When dimensioning and designing the fabric heater, attention has been paid to a continuous contact so that wearing of both the fabric and the fabric heater can be kept as low as possible. In addition, the steam pressure itself is surprisingly utilized to- lighten the fabric -and the steam distribution surface. The design and operating principle of the fabric heater differ from prior art in other respects as well. Thus it is possible to use lighter and simpler constructions than before. At the same time, the heat energy contained in steam can be utilized more efficiently than before. In this way, the same heating effect can be provided with a steam amount smaller than before. On the other hand, the heating effect can be increased compared to before and the power control is easy in other respects as well. Steam can be distributed to the fabric more uniformly than before, and the effect of fabric wearing produced by heating is small. Preferably, more steam distribution openings can be arranged than in known steam boxes, which use expensive nozzles located at a distance from the fabric. Increased temperature has also been considered in the fabric design and material.

The invention is described below in detail by making reference to the enclosed drawings which illustrate some of the embodiments of the invention, in which

Figure 1 is a basic diagram of a fabric heater according to the invention,

Figure 2a is an axonometric cross-sectional view of the fabric heater according to the invention,

Figure 2b is a basic diagram of the design of the fabric heater,

Figure 2c shows some of the distribution means of the fabric heater,

Figure 3 shows the positioning of the fabric heater according to the invention in a fiber web machine, Figure 4a shows a second embodiment of the fabric heater according to the invention,

Figure 4b shows the fabric heater of Figure 4a in the machine-direction, Figure 4c shows a third embodiment of the fabric heater according to the invention.

Figure 1 illustrates a part of a fiber web machine according to 5 the invention, equipped with a fabric heater 16'. Generally fiber web machines are paper or board machines. Here the fabric heater is in association with a press felt serving as a fabric. Particularly additional heat provided to the pressing process influences both the process itself and the quality of the end

10 product. Fabric heating contributes, for example, to the transfer of water from the web to the fabric. Thus the dry content after the press increases and the we moisture profile stabilizes. This further improves the productivity and runnability of the fiber web machine. In Figure 1, a press nip

15 10 is formed between the shoe roll 11 and its counter roll 12.

The fabric 13, here a press felt, also travels via the press nip 10 thus supporting the web 14. Usually, in addition to the above-located press felt shown here, a below-located press felt or a transfer belt also travels via the press nip to support

20 the web on the opposite side. The fabric is supported as an endless loop with the lead rolls 15.

Generally, the fabric heater 16' includes a frame construction 16 arranged in association with the fabric 13 installed in the

25 fiber web machine. In addition, the fabric heater 16' includes distribution means 17 for supplying steam towards the fabric 13 (Figure 2a) . The frame construction is supported to the constructions of the fiber web machine and steam is supplied to the distribution means and spread to the fabric. The fabric • 30 heater operates continuously and is in use all the time during the production. The distribution means 17 include a steam distribution surface 19 with one or more openings 20 and a sealing surface 19' surrounding the opening 20. In addition, the fabric heater is arranged in contact with the fabric 13 so

35 that at least the sealing surface 19' is against the fabric 13 in both the cross-machine and machine directions. Firstly, the frame construction is naturally sealed against the fabric without specific edge seals formed from a sealing material as projections. On the other hand, steam is quickly distributed to the fabric without generating mist to the environment. Furthermore, locating the fabric heater in the vicinity of a lead roll facilitates sealing. Thus the distance of the fabric heater along the fabric between the lead roll tangent and the trailing edge tangent of the steam distribution surface is less than 2200, preferably 300 - 1200 mm. This distance is partially influenced by the lead roll diameter. A large lead roll can be located very close to the fabric heater although the distance between the tangents is remarkable. However, the aforementioned distance is selected in such a way that the minimum distance between the lead roll surface and the fabric heater located in the fabric deviating position is at least 15 mm.

As shown in Figure 1, the frame construction 16 is located in the vicinity of one lead roll 15 in such a way that deviation is generated in the fabric 13 against the fabric tension. Generally, the fabric tension T provides a sealing pressure p₁ = T/R, when p_x > p₂ and p₂ is the steam supply pressure and R is the radius of curvature of the surface. In addition, the performance of the fabric heater can be slightly boosted by guiding the boundary layer air away from the fabric surface immediately before the steam supply surface. Preferably the frame construction thus deviates the fabric which then always settles tightly against the fabric heater. If necessary, to support the fabric heater, loading means are arranged which can be used to adjust the pressure effecting the deviation and thus the sealing pressure. Even a slight deviation contributes to sealing. Preferably the deviation is arranged in such a way that the direction of movement of the fabric changes 1 - 15°, more preferably 5 - 10° due to the effect of the fabric heater. It is also noteworthy that the fabric heater is arranged on the side of the fabric 13 facing the surface of the web 14 manufactured in the fiber web machine. Thus the greatest heat effect is applied to the fabric surface from where it is also exerted on the outer surface of the web and improves, for example, the smoothness of the web surface. The effect of 5 heating the surface facing the fabric at a short distance from the press nip is particularly pronounced when using thick fabrics. Then it is possible to utilize precisely this high temperature of the fabric surface contacting the web without losing heat in the thickness direction of the fabric via

10 through-heating. On the other hand, equipment according to prior art mainly heats the backside of the fabric. Then only the backside of the fabric is heated and this heat is easily lost to several lead rolls located on the side of the fabric conditioner, before being transferred through the fabric in the

15 thickness direction.

With its novel operating principle, the structural dimensions of the fabric heater can be reduced. Consequently, the fabric heater can be located as near as possible to the web arrival

20 position or the press nip, by positioning it on the fabric surface at a distance of 0.5 - 8 meters, preferably 1 - 4 meters, prior to the press nip in such a way that the web also contacts the fabric at a distance of 50 - 4000 mm, preferably 200 - 2000 mm, before said press nip. In this way, the benefit

25 achieved by the additional heat generated by steam can be maximized for the pressing process. In other words, heat losses to the environment are avoided and heat can be directed to the preferable side of the fabric. More generally, the fabric heater is preferably located at a distance of less than two

30 lead rolls prior to the press nip included in the fiber web machine.

Figure 2a illustrates the basic design of the frame construction of the fabric heater. Here the frame construction 35 16 is composed of a channel 18 with a sheet metal construction which forms a part of the steam distribution means 17. In other words, earlier expensive nozzles are unnecessary. In addition, the channel forms an equalizing chamber within which steam is uniformly distributed over the entire area of the fabric heater. At the same time, the entire channel is also heated, which improves condensation of steam. Here one wall 18' included in the channel^' 18 is adapted as a steam distribution surface 19, which is arranged in a curved shape. Thus it is possible to generate the fabric tension and deviation without harmful wearing. The surface contacting the fabric can also be replaceable. In this case, the characteristics of the fabric heater can be changed by replacing a part. Similarly, a worn part can be replaced with a new one.

The rest of the distribution means are composed of openings 20 arranged in a subarea of the steam distribution surface 19 for conveying the steam supplied to the channel 18 towards the fabric 13. In Figure 2a, this subarea is defined with a dot- and-dash line and surrounded by a sealing surface 19' according to the invention. Due to the design of the frame construction and the fabric tension, the fabric covers this subarea in the area of the edges, i.e., the sealing surface, 19' as well. Thus the fabric is sealed against the channel and steam misting is avoided. In addition to the novel distribution means, the steam supply is new and surprising. According to the invention, the steam supply pressure is adapted lower than the pressure generated by the fabric tension. Firstly, the steam supply pressure has been reduced compared to before. A significant pressure reduction has enabled a lighter frame construction. Secondly, the steam flow rate has been reduced by using a sufficiently large open surface. In other words, the combined surface area of the openings should be sufficiently large. At the same time, space and time are provided for the steam to condense maximizing thereby the utilization of heat contained in steam. When the supply pressure is lower than the fabric tension, the fabric remains tightly against the surface. In practice, the fabric may rise, off the surface at the openings, which, however, provides more space for the steam to condense. Furthermore, part of the steam distribution surface can be detached from the contact with the fabric. For example, the fabric may lie against the steam distribution surface at least for a half of the travel direction, preferably for a minimum of 2/3 of the travel. At its simplest, the fabric is in contact over the entire deviating area of the steam distribution surface.

The test equipment is made of laser-cut sheet material having a thickness of approximately four millimeters. Hence the material is thin sheet metal. In the embodiment shown, the openings are round holes but other shapes are also possible. Sleeves can also be used. In any case, the holes can be easily made by laser cutting or water cutting. In the embodiment of Figure 2c, the holes 21 are additionally counterbored and the surface contacting the fabric is finally coated with a wear- resistant coating material. The openings 20 are thus preferably arranged in the base material of the wall 18'. The outer dimensions of the fabric heater proposed are 40 - 400 mm, preferably 150 - 300 mm, in the fabric travel direction, which makes it possible to locate it even in confined positions near the press nip. In Figure 1, two alternative locations are marked with X. The fabric heater can be supported at its ends even in a completely fixed manner, in which case the fabric heater can remain in place also during a fabric change. However, supporting is preferably provided with adjustment means with which the alignment and position relative to the fabric can be suitably adjusted. In this case, steam is supplied to the channel with a flexible hose from one end or both ends.

In Figure 2b, the position of the flexible hose is illustrated with a dash line. The figure also shows the design of the steam distribution surface 19. While the basic shape has a large radius of curvature R, the radius of curvature r is smaller at the leading and trailing edges. Thus, despite minor misalignments and slight fabric variations, unnecessary fabric wear is avoided. In addition, the curvature R of the cover may be variable preferably in such a way that the curvature is sharper at the end than at the beginning. In other words, the radius decreases at least in one position or gradually. Then the sealing pressure in the latter part increases, which prevents the steam from escaping along with the travelling fabric.

In practice, the maximum steam supply pressure applied in the fabric heater proposed is 10 kPa. This also ensures the resistance of the sheet metal construction. In addition, holes with a diameter of 20 millimeters in nine rows were used in the test equipment (Figure 2c) . After the fabric heater, the fabric surface temperature measured was 85 - 90°C, which is 20 - 30 °C higher than conventionally. After the press nip, the fabric temperature was 60°C and the web temperature was correspondingly 45°C. At the same time, the dry content was better by several percentages than without a fabric heater and the web surface was also more uniform. It is preferable to bring the steam as close as possible to the press nip. In practice, the fabric heater can be located at a distance of 500 - 8000 mm prior to the press nip.

Figure 3 depicts the positioning of the fabric heater 16' according to the invention in a fiber web machine. Functionally similar parts are referred to with identical reference numbers. Here the fabric cycle also includes fabric conditioners 24 which are located in the horizontal section of the fabric 13, here a press felt, after a drawing roll 25. In other words, the fabric conditioner 24 is located as soon as possible after the press nip 10. Here the fabric conditioner 24 includes cleaning showers 26 which are oriented directly to the fabric 13. Cleaning is followed by drying and moisture adjustment of the fabric 13 using two vacuum boxes 27 located on the same side of the fabric 13. Four lead rolls 15 are located after -the fabric conditioner 24 prior to the press nip 10. A so-called pick-up felt is also equipped with corresponding fabric conditioners.

A second embodiment of the fabric heater 16' is shown in more detail in Figures 4a and 4b. While the operating principle is the same as above, the frame construction and particularly the steam distribution surface 19 have been implemented in a different way. Here the steam distribution surface 19 contacting the fabric 13 and particularly its sealing surface 19' consist of a tubular frame 22 which at the same time defines a large opening 20 for steam. A channel 18 from which steam is conveyed into the frame 22 is also provided on top of the frame. In the embodiment shown, the fabric is lightly sealed against the frame and steam has sufficient space and time to condense whereby it efficiently releases heat to the fabric. In this embodiment, too, separate nozzles are unnecessary, yet possible. In addition, it is preferable to arrange steam supply openings in the tubular construction of the frame directly against the fabric, which reduces the abrading effect when deviating the fabric. These steam supplies are also shown in Figure 4a. The second embodiment is provided with a saveall tray 23 arranged on the side of the fabric 13 opposite to the fabric heater. The purpose of the saveall tray is to collect splashes of water arriving from the back side of the felt. The saveall tray is equipped with a water removal pipe depicted with a dash line in Figure 4a. This fabric heater, too, has a simple and light design and small dimensions. In addition, the steam consumption is low and the utilization of heat contained in steam can be maximized. With a fabric heater, the felt can be precisely heated on the felt side facing the paper surface. Figure 4c depicts a third embodiment of the fabric heater. Here, too, the edges and the center area of the steam supply chamber form an integral construction. Thus part of the openings or nozzles may be located in a recess and the edges may both seal and distribute steam directly against the fabric. The saveall tray can also be a suction box with its cover designed in accordance with the fabric heater. Thus the cover is preferably concave whereas the fabric heater is convex. The fabric heater and the suction box can be arranged movable relative to each other and/or the fabric. In this way, the suction box, for example, is used all the time while the fabric heater is used when necessary. In other words, the suction box can be used to detach or release the felt from the fabric heater during the operation. This at least reduces the friction between the fabric and the fabric heater. The construction is simple and affordable. Furthermore, steam leaks and misting are reduced.

The embodiments proposed share the following characteristics apart from minor exceptions. All fabric heaters are located prior to the press nip and specifically the surface of the fabric facing the web is heated. In addition, the distance between the heater surface contacting the fabric and the roll nearest to the fabric heater can be different at the center compared to the edges. In other words, the sheet metal construction can be provided with a shape that has a spreading effect. In addition, sufficient space is ensured for steam to condense. This can be ensured, for example, by supplying steam from the openings in the fabric heater which have a sufficient surface area. At the same time, pressure increases are avoided and the fabric is kept tightly against the fabric heater. A hole as the shape of the opening is the most convenient shape to make, particularly with counterbored or bent edges. Broached holes provide a larger effective perforated surface without compromising the stiffness of the steam distribution surface. The diameter of the opening ranges from 5 mm to 30 mm, preferably from 10 mm to 20 mm, and the shape of the opening can be - relatively freely selected, using even - an elongated slot. When travelling across the steam distribution surface, the fabric detects the perforated surface for approximately 60 - 200 mm, preferably 100 - 150 mm, in one crosswise position. The perforated area composed of the perforated surface depends on the machine-directional dimension of the fabric heater. Said sufficient perforated area enables a larger amount of steam than before to be conveyed to the fabric without the steam pressure completely raising the fabric off the steam distribution surface. In practice, a high steam supply pressure can be applied, which increases the heating effect. In addition, the width of the perforated surface of the fabric heater is smaller than the felt width, which makes the perforated surface completely sealed when it touches the fabric. The same purpose is supported by the fact that the perforated surface of the fabric heater is shorter in the machine direction than the surface contacting the fabric. Then at least the leading and trailing edges are in contact with the fabric. In addition, a large radius of curvature is used in the curved surface, in which case wearing is reduced. In practice, the curvature R is smaller than 1000 mm, preferably 100 - 900 mm. With a higher curvature than this, the steam escape increases unless the steam pressure is decreased or the pressure of the fabric heater against the fabric tension is increased .

In addition to heating, the fiber web machine according to the invention has been optimized in other respects as well. Additional heat can be best utilized by using a specific type of fabric. The fabric according to the invention is a press felt including a support structure and a backing fabric as well as a crill layer attached at least to the surface facing the web. The basis weight of the fabric according to the invention is suitably low, 1500 g/m² at maximum, preferably 1100 - 1300 g/m², having, however, a sufficient mass to function as a press fabric. The crill layer must be sufficient for its mass and density in order for the fabric to be able to both heat up and absorb water. The maximum dtex values of the crill layer fibers on the surface side, i.e., the web side, are 17 dtex, preferably 6.7 or 11 or 17. A sufficiently smooth crill layer on the side facing the web provides a smooth web surface, while a suitably rough crill layer on the roll side at the same time prevents fabric clogging during the operation. The crill layer on the side facing the web may also consist of two crills with a different degree of fineness. In such a case, the layer nearest to the web may be composed of a slightly rougher crill compared to the crill layer on the side facing the web; for example, 11 dtex / 6.7 dtex / 22 dtex, where the fibers of the surface are indicated first and then those under the surface and finally those of the back side. The fabric heater seals and smooths out both- the felt and the web. If the crill layer facing the web consists of two crills with a different degree of fineness, of which the rougher one is closest to the web, a sufficiently dense felt is achieved in terms of optimal dewatering avoiding, however, the web plucking problem.

PA6 and PA6.6 fibers are conventionally used as the raw material of the crill layer of press felts. Generally, polyamide has good resistance to pressing and good elasticity. Then the fabric is compressed in the press nip and decompressed after the press nip, which creates a pump effect that contributes to the removal of water from the web. Polyamide is also flexible thus equalizing non-uniform loads and enabling the felt squaring without leaving marks in the web. Since polyamide is also resistant to abrasion, the use of a fabric heater that is in continuous contact with the fabric is reasonable .

The fabric heater can be fully utilized by selecting new materials. According to the invention, at least part of the crill layer material of the fabric is PA6.10 or PA12 polyamide fiber or bicomponent fiber or copolyamide fiber. Particularly the layer facing the web or at least the layer closest to the web consists, completely or partially, of the aforementioned special fiber. Then it is possible to use hot steam with as high a temperature as 100 - 130°C, in which case the fabric remains hot (70 - 90°C) all the time.

Conventionally used PA6 and PA6.6 polyamides are advantageous as such in terms of dewatering since they absorb as much as 10% of water in wet conditions. However, a high absorbing capacity together with a fabric heater exposes the fibers to heat, which can damage the fabric. Now it has been invented that part of the fabric fibers are replaced with materials that absorb less water. For example, the water absorbency of the PA6.10 polyamide at 100% moisture is approximately 3%. Correspondingly, the water absorbency of the PA12 polyamide fiber at 100% moisture is approximately 1.5%. Then the penetration of hot steam deep to the fiber texture slows down and the durability of the fabric in hot conditions improves. Nevertheless, the fabric retains the other good properties of polyamide. At the same time, the core and back layers of the fabric heat up less than before and the heat effect is directed particularly to the surface layer and therethrough to the web. As a result, the efficiency of additional heating and the heat effect on the web improve compared to before.

Claims

1. Fiber web machine equipped with a fabric heater which includes a frame construction (16) , arranged in association with a fabric (13) installed in the fiber web machine and supported with several lead rolls (15) , and distribution means (17) for supplying steam towards the fabric (13), said distribution means (17) including a steam distribution surface (19) provided with one or more openings (20) and a sealing surface (19 ') surrounding said opening (20), and the fabric heater (16') being arranged in contact with the fabric (13) in such a way that at least the sealing surface (19') is against the fabric (13) in both the cross-machine and machine directions, characterized in that the frame construction (16) is located in the vicinity of one lead roll (15) in such a way that a deviation is generated in the fabric (13) against the fabric tension, and the fabric heater (16') is arranged on the side of the fabric (13) facing the surface of the web (14) manufactured in the fiber web machine.

2. Fiber web machine according to claim 1, characterized in that the fabric heater (16') is located at a distance of less than two lead rolls (15) prior to the press nip (10) included in the fiber web machine.

3. Fiber web machine according to claim 1 or 2, characterized in that the deviation is arranged in such a way that the direction of movement of the fabric (13) changes 1 - 15°, preferably 5 - 10° due to the effect of the fabric heater (16 ' ) .

4. Fiber web machine according to any of claims 1 - 3, characterized in that the frame construction (16) is composed of a channel (18) having a sheet metal construction, which forms a part of the steam distribution means (17) .

5. Fiber web machine according to claim 4, characterized in that one wall (18') included in the channel (18) is adapted as a steam distribution surface (19), which is arranged in a curved shape.

6. Fiber web machine according to claim 5, characterized in that the openings (20) are arranged in the base material of the wall (18 ' ) .

7. Fiber web machine according to any of claims 1 - 6, characterized in that the steam supply pressure p₂ is arranged lower than the pressure p_x exerted to the steam distribution surface (19) by the fabric tension.

8. Fiber web machine according to any of claims 1 - 7, characterized in that a saveall tray (23) is arranged on the side of the fabric (13) opposite to the fabric heater (16') ·

9. Fiber web machine according to any of claims 1 - 8, characterized in that the fabric (13) has a backing and a crill layer facing the web (14), the maximum dtex value of which is 17, preferably 6.7 or 11 or 17.

10. Fiber web machine according to claim 9, characterized in that at least part of the fiber material of the fabric (13) facing the web (14) is PA6.10 or PA12 or bicomponent or copolyamide fiber.

11. Fiber web machine according to any of claims 1 - 10, characterized in that the fabric heater (16') operates continuously.

12. Fiber web machine according to any of claims 1 - 11, characterized in that the distance of the fabric heater (16') along the fabric (13) between the tangent of the lead roll (15) and the trailing edge tangent of the steam distribution surface (19) is less than 2200 mm, preferably 300 - 1200 mm.

13. Fiber web machine according to claim 12, characterized in that the minimum distance between the surface of the lead roll (15) and the fabric heater (16 ') located in the position deviating the fabric (13) is at least 15 mm.

14. Fiber web machine according to any of claims 1 - 13, characterized in that the fabric heater (16') is arranged at a distance of 500 - 8000 mm, preferably 1000 - 4000 mm, prior to the press nip (10) .

15. Fiber web machine according to any of claims 1 - 14, characterized in that the web (14) is arranged in contact with the fabric (13) at a distance of 50 - 4000 mm, preferably 200 - 2000 mm, prior to the press nip (10) .