CA2118660A1 - Apparatus for treating a material web - Google Patents
Apparatus for treating a material webInfo
- Publication number
- CA2118660A1 CA2118660A1 CA002118660A CA2118660A CA2118660A1 CA 2118660 A1 CA2118660 A1 CA 2118660A1 CA 002118660 A CA002118660 A CA 002118660A CA 2118660 A CA2118660 A CA 2118660A CA 2118660 A1 CA2118660 A1 CA 2118660A1
- Authority
- CA
- Canada
- Prior art keywords
- layer
- roll
- thickness
- ceramic
- foundation layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F3/00—Press section of machines for making continuous webs of paper
- D21F3/02—Wet presses
- D21F3/0281—Wet presses in combination with a dryer roll
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F3/00—Press section of machines for making continuous webs of paper
- D21F3/02—Wet presses
- D21F3/08—Pressure rolls
Landscapes
- Paper (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
- Laminated Bodies (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to an apparatus for treating a material web, preferably for dewatering a paper web by the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll consisting of a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case having a foundation layer and a thin ceramic surface layer which is applied to the foundation layer and has an improved energy efficiency and at the same time an improved mechanical stability; in such an apparatus it is proposed that the ceramic surface layer has a thickness of less than 1 mm, that the foundation layer consists of ceramic material as thermal insulation and that the foundation layer has a thickness which is greater than the thickness of the ceramic surface layer.
(Figure 1)
The invention relates to an apparatus for treating a material web, preferably for dewatering a paper web by the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll consisting of a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case having a foundation layer and a thin ceramic surface layer which is applied to the foundation layer and has an improved energy efficiency and at the same time an improved mechanical stability; in such an apparatus it is proposed that the ceramic surface layer has a thickness of less than 1 mm, that the foundation layer consists of ceramic material as thermal insulation and that the foundation layer has a thickness which is greater than the thickness of the ceramic surface layer.
(Figure 1)
Description
2~18660 A~varatus for treatina a material web BACKGROUND OF THE INVENTION
1. Field of the Invention The invention relates to an apparatus for treating a material web, preferably for dewatering a paper web in the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll comprising a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case including a foundation layer and a thin ceramic heatable surface layer applied to the foundation layer.
2. Description of the Prior Art In the treatment of a material web, in particular when dewatering a paper web having a high water content, the material web is led through an apparatus comprising at least one pressing gap or nip which is formed by a roll and a counter member arranged opposite the roll. The counter member may be constructed both as a second roll or roller and as a hydraulio shoe. In particular in the dewatering of a paper web, the web still containing a higher proportion of water passes through the pressing gap and the water is mechanically expelled from the paper web between the roll and the counter member. An improvement of the dewatering is achieved in the prior art in that the roll is constructed as heating roll. The objective of the apparatus known in the art is to obtain the greatest possible dewatering of the material web. It has been found disadvantageous here that the still not very strong paper web adheres to the pressing roll and as a result tearing of , , .. . . -21~8660 the paper web may occur. These production disturbances are due in particular to an unsuitable surface constituency of the roll case.
Consequently, from the prior art various working layers for the surface of the pressing rolls are known. For example, from DE-PS 103,677 the use of natural granite as material for the pressing roll is disclosed. This material admittedly has good detachment properties but has the disadvantage that in the event of temperature differences in the granite as arise by heating with steam boxes from the outside said granite is destroyed by thermal stresses.
Therefore, in the course of time various working layers have been developed and have been used as substitute for granite rolls. These solutions known from the prior art comprise as a rule a roll base body of cast iron or steel to which layers are applied which are equivalent to the detachment properties of granite. The detachment properties are based essentially on surface caverns and the mixture of water-repellant and water-attracting components.
For example, filling materials such as granite powder have been worked into plastic coatings. Such a working layer is known from EP-OS 0 337 934.
Furthermore, from DE-OS 3,546,343 a pressing roll is known for an apparatus of the aforementioned type which has a working layer of its cylinder case which is formed from a mixture of metal powder and a powder of inorganic material.
This inorganic material is a ceramic material which can be produced for example by thermal spraying on to the roll body.
In addition, from EP-PS 02 07 921 a pressing roll for a paper machine is made which includes in integrated manner a metal core on which a metallic foundation layer and a 21186~0 ceramic working layer are applied, the foundation layer having a coefficient of expansion which lies between that of the metal core and the surface layer. The ceramic layer has a permeability of 1 to 30%. The ceramic layer has a thickness of 1 to 30 mm. With a layer thickness below 1 mm the detachment behaviour was disturbed. Furthermore, it is known from the prior art, that is EP-OS 0 481 321, to add to the ceramic layer described above mica particles as water-repellant component and impregnations on the basis of synthetic resins.
Finally, it is known in the art to dewater a material web, preferably a paper web, by means of pressing rolls which are heated to very high temperatures. On contact of the wet material web part of the water in the paper surface is suddenly evaporated. The steam forming presses the material web in positive manner away from the pressing roll so that the detachment behaviour otherwise to be considered no longer plays a decisive part. However, it has been found that in particular with metallic surfaces of the pressing rolls with very good thermal conduction properties too much steam is formed and tears the interfibre bonding of a paper web. For this reason it has been found advantageous in this known method as well to provide the metallic surfaces of the pressing rolls with an energy brake, for example a thin ceramic layer. This avoids excessive steam formation. A disadvantage of this known apparatus is however that apart from the roll surface the entire roll and the hydraulic oil of its hydrostatic or hydrodynamic support is heated and said oil loses its lubricating ability at temperatures of more than 150C. It follows necessarily from this that the hydraulic oil must be cooled and this results in a heat loss which reduces the thermal efficiency of the pressing roll for the pulse drying.
211~66Q
Admittedly, the heat loss of the aforementioned pressing roll towards the inside can be limited in that in the roll bore between the roll wall and the bearing elements an insulating layer is arranged, for example a ceramic layer;
however, introduction of this layer is very complicated and involves high constructional expenditure.
Apart from this, in this manner only the heat dissipation into the bore is restricted. It is not possible with this step to avoid the entire metal roll body assuming a high temperature. Since however the coefficient of expansion of ceramic material compared with the metal roll body is almost 50% less, the outer ceramic layer as well as the inner insulating layer is subjected in operation to tensile stresses due to the heating thereof. The ceramic layers can however withstand only small tensile stresses.
Introduction of a thin foundation layer with a coefficient of expansion between that of the ceramic layer and that of the base body and intended to serve as bonding agent did not result in an appreciable solution of the aforementioned problems either. For the thin foundation layers described in EP-PS 02 07 921 and EP-OS O 481 221 expand together with the base body so that the ceramic working layer is again subjected to high tensile stresses.
SUMMARY OF THE INVENTION
The invention therefore has as its object, proceeding from the prior art described above, to provide an apparatus for treating a material web, preferably for dewatering a paper web by the pulse drying method, which avoids the disadvantages of the prior art described above and in particular haR an improved energy efficiency and improved mechanical stability.
::i :,: - . . . . . .
... , ` 211~60 The invention therefore proposes in an apparatus for treating a material web, preferably for dewatering a paper web in the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll comprising a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case including a foundation layer and a thin ceramic heatable surface layer applied to the foundation layer, the improvement wherein the ceramic working layer has a thickness of less than 1 mm, the foundation layer consists of ceramic material as thermal insulation and the foundation layer has a thickness which is greater than the thickness of the ceramic working layer.
An apparatus thus configured has the advantage that the material web to be dewatered adheres to the roll surface to a far lesser extent and at the same time the dewatering of the material web, preferably the paper web, can be improved by a high temperature and a high pressure. It is of particular advantage here that the thin ceramic working layer with external heating has a high temperature at its surface but a low thermal conductivity so that the roll case of metal is heated to a far lesser extent. At the same time, the different expansion of the ceramic working layer and the metallic roll case are adapted to each other by the thicker foundation layer of ceramic material compared with the working layer and consequently no tensile stresses arise in the ceramic working layer.
A simple production of a heating roll for the apparatus according to the invention is achieved in accordance with a further feature thereof in that the thermally in~ulating foundation layer is applied to the roll case by water-stabilized plasma spraying. In the calculation it has been :
r~
21 1~6~0 found particularly advantageous here to apply the foundation layer to the roll case with a thickness of 5 to 30 mm. This avoids tensile stress in the working layer.
According to a further feature of the invention a particularly efficient reduction of the tensile stress in the working layer can be achieved in that the foundation layer has a thickness of 8 to 10 mm, preferably about 9.5 mm. Such a foundation layer can be economically made by using Al203.
It is particularly advantageous for the ceramic working layer to consist of zirconium oxide and have a thickness of 0.5 mm. This ceramic material has particularly suitable thermal conductivity values which permit an optimum temperature effect even with a layer thickness of 0.5 mm.
In a further development of the apparatus according to the invention it is advantageous for pulse drying that the roll case of the heating roll consists of clear chilled casting which in the outer region comprises white iron and in the inner region gray iron. This is a cast iron which due to its particular alloy and casting technique is formed in the outer region as white iron with high hardness between 450 and 600 HV, a high E modulus of about 180,000 N-mm2and a poor thermal conductivity of about 20 W/mK. A roll case formed in this manner has the advantage that it provides a good support effect and thus had good mechanical properties and at the same time acts as a thermal barrier. The thickness of the layer in which the iron forms as white iron can be influenced in accordance with the alloy. It has been found to be particularly advantageous for the white iron to have a layer thickness of 20 to 80 mm. Here, the low coefficient of expansion of the white iron has a "` " ' ' , 2118~60 favourable effect on the thermal stress distribution within the roll case.
In the apparatus according to the invention the heating roll is preferably heated from outside. This achieves a rapid heating of the ceramic working layer and avoids large heat losses. According to a further feature of the invention it has been found advantageous to mix the ceramic working layer with a metal powder so that said working layer is electrically conductive. An apparatus formed with this feature then has the advantage that according to a further feature of the invention the ceramic working layer can be heated by induction of eddy currents in the working layer.
To avoid altering the surface of the ceramic working layer mixed with the metal powder and thus to retain the advantageous low adhesion tendency of the metal web to the working layer, according to a further feature of the invention it is proposed that an electrically conductive layer be located directly beneath the working layer.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in detail hereinafter with reference to an example of embodiment and with the aid of the attached schematic drawings, wherein:
Fig. 1 is a side elevation of an apparatus for treating ! a material web;
Fig. 2 is a front view of the apparatus according to Fig. 1;
Fig. 3 is a front view of a heating roll and ~ . ~
,;:,. .:
:.,.,,; . . ~ : -J,~
~:, ' Fig. 4 is an enlarged frayment of the heating roll corresponding to the circle A indicated in Fig.
i 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An apparatus as apparent from Fig. 1 and indicated by the reference numeral 1 for treating a material web, pre~erably for dewatering a paper web 2 by the pulse drying method, comprises a heating roll 3 and a hydraulic shoe roll 4 which serves as counter member and together with the heating roll 3 forms a pressing gap 5~ The counter roll 4 may also be replaced by a hydraulic shoe.
In usual manner the heating roll 3 is in the form of a tube rotatably mounted about its longitudinal axis. The heating roll 3 may be supported both hydrostatically and hydrodynamically on the continuous stationary shaft 6. The counter roll 4 is a shoe roll and likewise supported hydrostatically or hydrodynamically (14).
In the vicinity of the surface of the heating roll 3 an external heating 8 is provided which for example is in the form of an induction heating which couples electromagnetic energy into the material of the roll case 7 of the heating roll 3 and thus produces a temperature increase, in particular in the working surface.
In Figures 3 and 4 the constructional makeup of the heating roll 3 is illustrated in detail. As can be seen from Fig.
1. Field of the Invention The invention relates to an apparatus for treating a material web, preferably for dewatering a paper web in the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll comprising a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case including a foundation layer and a thin ceramic heatable surface layer applied to the foundation layer.
2. Description of the Prior Art In the treatment of a material web, in particular when dewatering a paper web having a high water content, the material web is led through an apparatus comprising at least one pressing gap or nip which is formed by a roll and a counter member arranged opposite the roll. The counter member may be constructed both as a second roll or roller and as a hydraulio shoe. In particular in the dewatering of a paper web, the web still containing a higher proportion of water passes through the pressing gap and the water is mechanically expelled from the paper web between the roll and the counter member. An improvement of the dewatering is achieved in the prior art in that the roll is constructed as heating roll. The objective of the apparatus known in the art is to obtain the greatest possible dewatering of the material web. It has been found disadvantageous here that the still not very strong paper web adheres to the pressing roll and as a result tearing of , , .. . . -21~8660 the paper web may occur. These production disturbances are due in particular to an unsuitable surface constituency of the roll case.
Consequently, from the prior art various working layers for the surface of the pressing rolls are known. For example, from DE-PS 103,677 the use of natural granite as material for the pressing roll is disclosed. This material admittedly has good detachment properties but has the disadvantage that in the event of temperature differences in the granite as arise by heating with steam boxes from the outside said granite is destroyed by thermal stresses.
Therefore, in the course of time various working layers have been developed and have been used as substitute for granite rolls. These solutions known from the prior art comprise as a rule a roll base body of cast iron or steel to which layers are applied which are equivalent to the detachment properties of granite. The detachment properties are based essentially on surface caverns and the mixture of water-repellant and water-attracting components.
For example, filling materials such as granite powder have been worked into plastic coatings. Such a working layer is known from EP-OS 0 337 934.
Furthermore, from DE-OS 3,546,343 a pressing roll is known for an apparatus of the aforementioned type which has a working layer of its cylinder case which is formed from a mixture of metal powder and a powder of inorganic material.
This inorganic material is a ceramic material which can be produced for example by thermal spraying on to the roll body.
In addition, from EP-PS 02 07 921 a pressing roll for a paper machine is made which includes in integrated manner a metal core on which a metallic foundation layer and a 21186~0 ceramic working layer are applied, the foundation layer having a coefficient of expansion which lies between that of the metal core and the surface layer. The ceramic layer has a permeability of 1 to 30%. The ceramic layer has a thickness of 1 to 30 mm. With a layer thickness below 1 mm the detachment behaviour was disturbed. Furthermore, it is known from the prior art, that is EP-OS 0 481 321, to add to the ceramic layer described above mica particles as water-repellant component and impregnations on the basis of synthetic resins.
Finally, it is known in the art to dewater a material web, preferably a paper web, by means of pressing rolls which are heated to very high temperatures. On contact of the wet material web part of the water in the paper surface is suddenly evaporated. The steam forming presses the material web in positive manner away from the pressing roll so that the detachment behaviour otherwise to be considered no longer plays a decisive part. However, it has been found that in particular with metallic surfaces of the pressing rolls with very good thermal conduction properties too much steam is formed and tears the interfibre bonding of a paper web. For this reason it has been found advantageous in this known method as well to provide the metallic surfaces of the pressing rolls with an energy brake, for example a thin ceramic layer. This avoids excessive steam formation. A disadvantage of this known apparatus is however that apart from the roll surface the entire roll and the hydraulic oil of its hydrostatic or hydrodynamic support is heated and said oil loses its lubricating ability at temperatures of more than 150C. It follows necessarily from this that the hydraulic oil must be cooled and this results in a heat loss which reduces the thermal efficiency of the pressing roll for the pulse drying.
211~66Q
Admittedly, the heat loss of the aforementioned pressing roll towards the inside can be limited in that in the roll bore between the roll wall and the bearing elements an insulating layer is arranged, for example a ceramic layer;
however, introduction of this layer is very complicated and involves high constructional expenditure.
Apart from this, in this manner only the heat dissipation into the bore is restricted. It is not possible with this step to avoid the entire metal roll body assuming a high temperature. Since however the coefficient of expansion of ceramic material compared with the metal roll body is almost 50% less, the outer ceramic layer as well as the inner insulating layer is subjected in operation to tensile stresses due to the heating thereof. The ceramic layers can however withstand only small tensile stresses.
Introduction of a thin foundation layer with a coefficient of expansion between that of the ceramic layer and that of the base body and intended to serve as bonding agent did not result in an appreciable solution of the aforementioned problems either. For the thin foundation layers described in EP-PS 02 07 921 and EP-OS O 481 221 expand together with the base body so that the ceramic working layer is again subjected to high tensile stresses.
SUMMARY OF THE INVENTION
The invention therefore has as its object, proceeding from the prior art described above, to provide an apparatus for treating a material web, preferably for dewatering a paper web by the pulse drying method, which avoids the disadvantages of the prior art described above and in particular haR an improved energy efficiency and improved mechanical stability.
::i :,: - . . . . . .
... , ` 211~60 The invention therefore proposes in an apparatus for treating a material web, preferably for dewatering a paper web in the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll comprising a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case including a foundation layer and a thin ceramic heatable surface layer applied to the foundation layer, the improvement wherein the ceramic working layer has a thickness of less than 1 mm, the foundation layer consists of ceramic material as thermal insulation and the foundation layer has a thickness which is greater than the thickness of the ceramic working layer.
An apparatus thus configured has the advantage that the material web to be dewatered adheres to the roll surface to a far lesser extent and at the same time the dewatering of the material web, preferably the paper web, can be improved by a high temperature and a high pressure. It is of particular advantage here that the thin ceramic working layer with external heating has a high temperature at its surface but a low thermal conductivity so that the roll case of metal is heated to a far lesser extent. At the same time, the different expansion of the ceramic working layer and the metallic roll case are adapted to each other by the thicker foundation layer of ceramic material compared with the working layer and consequently no tensile stresses arise in the ceramic working layer.
A simple production of a heating roll for the apparatus according to the invention is achieved in accordance with a further feature thereof in that the thermally in~ulating foundation layer is applied to the roll case by water-stabilized plasma spraying. In the calculation it has been :
r~
21 1~6~0 found particularly advantageous here to apply the foundation layer to the roll case with a thickness of 5 to 30 mm. This avoids tensile stress in the working layer.
According to a further feature of the invention a particularly efficient reduction of the tensile stress in the working layer can be achieved in that the foundation layer has a thickness of 8 to 10 mm, preferably about 9.5 mm. Such a foundation layer can be economically made by using Al203.
It is particularly advantageous for the ceramic working layer to consist of zirconium oxide and have a thickness of 0.5 mm. This ceramic material has particularly suitable thermal conductivity values which permit an optimum temperature effect even with a layer thickness of 0.5 mm.
In a further development of the apparatus according to the invention it is advantageous for pulse drying that the roll case of the heating roll consists of clear chilled casting which in the outer region comprises white iron and in the inner region gray iron. This is a cast iron which due to its particular alloy and casting technique is formed in the outer region as white iron with high hardness between 450 and 600 HV, a high E modulus of about 180,000 N-mm2and a poor thermal conductivity of about 20 W/mK. A roll case formed in this manner has the advantage that it provides a good support effect and thus had good mechanical properties and at the same time acts as a thermal barrier. The thickness of the layer in which the iron forms as white iron can be influenced in accordance with the alloy. It has been found to be particularly advantageous for the white iron to have a layer thickness of 20 to 80 mm. Here, the low coefficient of expansion of the white iron has a "` " ' ' , 2118~60 favourable effect on the thermal stress distribution within the roll case.
In the apparatus according to the invention the heating roll is preferably heated from outside. This achieves a rapid heating of the ceramic working layer and avoids large heat losses. According to a further feature of the invention it has been found advantageous to mix the ceramic working layer with a metal powder so that said working layer is electrically conductive. An apparatus formed with this feature then has the advantage that according to a further feature of the invention the ceramic working layer can be heated by induction of eddy currents in the working layer.
To avoid altering the surface of the ceramic working layer mixed with the metal powder and thus to retain the advantageous low adhesion tendency of the metal web to the working layer, according to a further feature of the invention it is proposed that an electrically conductive layer be located directly beneath the working layer.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in detail hereinafter with reference to an example of embodiment and with the aid of the attached schematic drawings, wherein:
Fig. 1 is a side elevation of an apparatus for treating ! a material web;
Fig. 2 is a front view of the apparatus according to Fig. 1;
Fig. 3 is a front view of a heating roll and ~ . ~
,;:,. .:
:.,.,,; . . ~ : -J,~
~:, ' Fig. 4 is an enlarged frayment of the heating roll corresponding to the circle A indicated in Fig.
i 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An apparatus as apparent from Fig. 1 and indicated by the reference numeral 1 for treating a material web, pre~erably for dewatering a paper web 2 by the pulse drying method, comprises a heating roll 3 and a hydraulic shoe roll 4 which serves as counter member and together with the heating roll 3 forms a pressing gap 5~ The counter roll 4 may also be replaced by a hydraulic shoe.
In usual manner the heating roll 3 is in the form of a tube rotatably mounted about its longitudinal axis. The heating roll 3 may be supported both hydrostatically and hydrodynamically on the continuous stationary shaft 6. The counter roll 4 is a shoe roll and likewise supported hydrostatically or hydrodynamically (14).
In the vicinity of the surface of the heating roll 3 an external heating 8 is provided which for example is in the form of an induction heating which couples electromagnetic energy into the material of the roll case 7 of the heating roll 3 and thus produces a temperature increase, in particular in the working surface.
In Figures 3 and 4 the constructional makeup of the heating roll 3 is illustrated in detail. As can be seen from Fig.
3, a coating is applied to the roll case 7. This coating consists of an insulating foundation layer 9, a ceramic working layer 10 and an electrically conductive layer 11 which is arranged between the foundation layer 9 and the l......... .. .
.. , ..... ~ - ,; ..
``.. . ~ , . ~ ~. ' .. ~ . ;
. ~ , , .
:-~ . .
.. . ' ; ;, . . .
2~1866() working layer lo and consists of a metal powder. In simple manner the layer 11 makes it possible to heat up the working layer 10 by inducing eddy currents in the layer 11.
In the example of embodiment illustrated the ceramic working layer 10 has a thickness of about 0.5 mm and consists of zirconium oxide. The foundation layer 9 consisting of Al2O3 has a layer thickness of about 9.5 mm and is applied by water-stabilized plasma spraying to the roll case 7. The layer 11 of metal powder arranged between the foundation layer 9 and the working layer 10 has a thickness which is less than the thickness of the working layer 10 and is about 0.4 mm. It is also possible to integrate the layer 11 into the working layer 10.
:~
The roll case 7 of the heating roll 3 consists of clear chilled casting. This is a cast iron which due to a particular alloy and casting technique forms in the outer region 12 as so-called white iron and in the inner region 13 as so-called gray iron. The white iron arranged in the outer region 12 has a high hardness between 450 and 600 HV, a high E modulus of about 180,000 M/mm2 and a poor thermal conductivity of about 20 W/nK. In addition, a roll case of this structure has a high mechanical strength and acts as thermal barrier. The layer thickness of the white iron in the outer region 12 is about 30 mm and the layer thickness of the gray iron disposed in the inner region 13 is about 110 mm so that the diameter of the roll case 7 without the foundation layer 9 and the working layer 10 is about 140 mm and with the foundation layer 9 and the working layer 10 about 150 mm.
Below the expansion average values of the various layers of a roll case 7 with external heating according to the prior i;"~
21~6~
art and according to the invention are compared, all the particulars relating to mean values of the respective layers:
Layer Thick~ess Expansion Prior Art C Invention Coeff. C dl~mm/m) dl(mm/m) Working 0.5 6.5x1 o-6/K 330 2.0 330 .2.0 lay~r Foundation 9.5 6.5x10 ~/K -- -- 276 1.6 layer White 30.0 8.5x1 0-~/K -- -- 207 1.59 iron Gray 110.0 10.5x10-9/K 257 2.7 176 1.64 iron It can be seen that a roll case 7 according to the prior art expands thermally more than the working layer and this results in tensile stresses which oxide ceramic for example can hardly withstand.
In the construction according to the invention the thermal expansion of all the sublayers bearing he working layer 10, i.e. the foundation layer 9 and the regions 12, 13 of the roll case 7, is of the same order of magnitude and moreover less than that of the working layer 10. The working layer 10 is thus under compressive stress during operation and this has a favourable effect on the life of the working layer. Between the foundation layer 9 and the working .:: . : . .
~ - . . ~ ,: . .
,. ~ . -, , , :
.. ~ .: :. ~ .
211~5~0 layer 10 on the one hand and the white iron in the region 12 on the other hand no appreciable relative stresses are present. On a comparison of the energy loss of a heating roll of 1350 mm outer diameter and 150 mm wall thickness of gray iron comprising a 0.5 mm thick layer of zirconium oxide and heated externally to 300 to 400C, it is found that the heat flow with a heating roll 3 constructed according to the invention is reduced from 2Z0 kW/m tube length to about 71 kW/m tube length. As a result, the thermal efficiency of 55% in the prior art is improved to 79% with an apparatus according to the invention and the energy losses are correspondingly reduced.
This also results in the advantage that the cooling means for the hydraulic oil for the hydrostatic or hydrodynamic support can be made substantially smaller and thus more economical.
.. , ..... ~ - ,; ..
``.. . ~ , . ~ ~. ' .. ~ . ;
. ~ , , .
:-~ . .
.. . ' ; ;, . . .
2~1866() working layer lo and consists of a metal powder. In simple manner the layer 11 makes it possible to heat up the working layer 10 by inducing eddy currents in the layer 11.
In the example of embodiment illustrated the ceramic working layer 10 has a thickness of about 0.5 mm and consists of zirconium oxide. The foundation layer 9 consisting of Al2O3 has a layer thickness of about 9.5 mm and is applied by water-stabilized plasma spraying to the roll case 7. The layer 11 of metal powder arranged between the foundation layer 9 and the working layer 10 has a thickness which is less than the thickness of the working layer 10 and is about 0.4 mm. It is also possible to integrate the layer 11 into the working layer 10.
:~
The roll case 7 of the heating roll 3 consists of clear chilled casting. This is a cast iron which due to a particular alloy and casting technique forms in the outer region 12 as so-called white iron and in the inner region 13 as so-called gray iron. The white iron arranged in the outer region 12 has a high hardness between 450 and 600 HV, a high E modulus of about 180,000 M/mm2 and a poor thermal conductivity of about 20 W/nK. In addition, a roll case of this structure has a high mechanical strength and acts as thermal barrier. The layer thickness of the white iron in the outer region 12 is about 30 mm and the layer thickness of the gray iron disposed in the inner region 13 is about 110 mm so that the diameter of the roll case 7 without the foundation layer 9 and the working layer 10 is about 140 mm and with the foundation layer 9 and the working layer 10 about 150 mm.
Below the expansion average values of the various layers of a roll case 7 with external heating according to the prior i;"~
21~6~
art and according to the invention are compared, all the particulars relating to mean values of the respective layers:
Layer Thick~ess Expansion Prior Art C Invention Coeff. C dl~mm/m) dl(mm/m) Working 0.5 6.5x1 o-6/K 330 2.0 330 .2.0 lay~r Foundation 9.5 6.5x10 ~/K -- -- 276 1.6 layer White 30.0 8.5x1 0-~/K -- -- 207 1.59 iron Gray 110.0 10.5x10-9/K 257 2.7 176 1.64 iron It can be seen that a roll case 7 according to the prior art expands thermally more than the working layer and this results in tensile stresses which oxide ceramic for example can hardly withstand.
In the construction according to the invention the thermal expansion of all the sublayers bearing he working layer 10, i.e. the foundation layer 9 and the regions 12, 13 of the roll case 7, is of the same order of magnitude and moreover less than that of the working layer 10. The working layer 10 is thus under compressive stress during operation and this has a favourable effect on the life of the working layer. Between the foundation layer 9 and the working .:: . : . .
~ - . . ~ ,: . .
,. ~ . -, , , :
.. ~ .: :. ~ .
211~5~0 layer 10 on the one hand and the white iron in the region 12 on the other hand no appreciable relative stresses are present. On a comparison of the energy loss of a heating roll of 1350 mm outer diameter and 150 mm wall thickness of gray iron comprising a 0.5 mm thick layer of zirconium oxide and heated externally to 300 to 400C, it is found that the heat flow with a heating roll 3 constructed according to the invention is reduced from 2Z0 kW/m tube length to about 71 kW/m tube length. As a result, the thermal efficiency of 55% in the prior art is improved to 79% with an apparatus according to the invention and the energy losses are correspondingly reduced.
This also results in the advantage that the cooling means for the hydraulic oil for the hydrostatic or hydrodynamic support can be made substantially smaller and thus more economical.
Claims (12)
1. An apparatus for treating a material web, preferably for dewatering a paper web in the pulse drying method, comprising a heating roll and a counter member which together with the heating roll forms a pressing gap, the heating roll comprising a stationary axle, a roll case and at least one bearing element for supporting the roll case on the axle and the roll case including a foundation layer and a thin ceramic heatable surface layer applied to the foundation layer, comprising the following features:
a) the ceramic working layer has a thickness of less than 1 mm;
b) the foundation layer consists of ceramic material as thermal insulation;
c) the foundation layer has a thickness which is greater than the thickness of the ceramic working layer; and d) the roll case consists of a clear chill casting which comprises white iron in the outer region and gray iron in the inner region.
a) the ceramic working layer has a thickness of less than 1 mm;
b) the foundation layer consists of ceramic material as thermal insulation;
c) the foundation layer has a thickness which is greater than the thickness of the ceramic working layer; and d) the roll case consists of a clear chill casting which comprises white iron in the outer region and gray iron in the inner region.
2. An apparatus according to claim 1, wherein the ceramic working layer is applied by metal plasma spraying.
3. An apparatus according to claim 1, wherein the thermally insulating foundation layer is applied by means of water-stabilized plasma spraying to the roll case.
4. An apparatus according to claim 1, wherein the foundation layer has a thickness of 5 to 30 mm.
5. An apparatus according to claim 4, wherein the foundation layer has a thickness of 8 to 10 mm, preferably about 9.5 mm.
6. An apparatus according to claim 1, wherein the foundation layer consists of A2O3.
7. An apparatus according to claim 1, wherein the ceramic working layer consists of zirconium oxide and has a thickness of about 0.5 mm.
8. An apparatus according to claim 1, wherein the white iron in the outer region has a layer thickness of 20 to 80 mm.
9. An apparatus according to claim 1, wherein the heating roll is heated from outside.
10. An apparatus according to claim 1, wherein the ceramic working layer is mixed with a metal powder so that the working layer is electrically conductive.
11. An apparatus according to claim 1, wherein the heating roll is heated by inducing eddy currents in the working layer.
12. An apparatus according to claim 10, wherein an electrically conductive intermediate layer is disposed beneath the ceramic working layer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4307592.4 | 1993-03-10 | ||
| DE4307592A DE4307592A1 (en) | 1993-03-10 | 1993-03-10 | Device for treating a material web |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2118660A1 true CA2118660A1 (en) | 1994-09-11 |
Family
ID=6482443
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002118660A Abandoned CA2118660A1 (en) | 1993-03-10 | 1994-03-09 | Apparatus for treating a material web |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0616073B1 (en) |
| AT (1) | ATE147111T1 (en) |
| CA (1) | CA2118660A1 (en) |
| DE (1) | DE4307592A1 (en) |
| FI (1) | FI941113A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6006442A (en) * | 1996-09-25 | 1999-12-28 | Institute Of Paper Science And Technology, Inc. | Methods for dewatering solid-liquid matrices |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE103677C (en) * | ||||
| FI70273C (en) * | 1985-01-09 | 1986-09-15 | Valmet Oy | SYNTHETIC PRESS RELEASES FOR THE FRAMEWORK OF THE FRAMEWORK |
| DE3662409D1 (en) * | 1985-04-30 | 1989-04-20 | Yamauchi Corp | Press roll for paper machines |
| CH667285A5 (en) * | 1986-02-14 | 1988-09-30 | Sulzer Ag | ROLLER WITH A HARD COVERED SURFACE. |
| FI83895C (en) * | 1988-04-13 | 1991-09-10 | Valmet Paper Machinery Inc | Method and apparatus for press processing a paper web |
| CH674381A5 (en) * | 1988-04-13 | 1990-05-31 | Sulzer Ag | |
| FI85395C (en) * | 1988-11-15 | 1992-04-10 | Valmet Paper Machinery Inc | Arrangement in paper machine |
| FI84506B (en) * | 1990-02-22 | 1991-08-30 | Tampella Oy Ab | PRESSVALS FOER PAPER MASKIN. |
| DE69119690T2 (en) * | 1990-10-08 | 1996-10-02 | Yamauchi Corp | Press roll for paper machines |
-
1993
- 1993-03-10 DE DE4307592A patent/DE4307592A1/en not_active Withdrawn
-
1994
- 1994-02-24 EP EP94102798A patent/EP0616073B1/en not_active Expired - Lifetime
- 1994-02-24 AT AT94102798T patent/ATE147111T1/en not_active IP Right Cessation
- 1994-03-09 FI FI941113A patent/FI941113A/en not_active Application Discontinuation
- 1994-03-09 CA CA002118660A patent/CA2118660A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE4307592A1 (en) | 1994-09-15 |
| FI941113A (en) | 1994-09-11 |
| EP0616073A1 (en) | 1994-09-21 |
| EP0616073B1 (en) | 1997-01-02 |
| FI941113A0 (en) | 1994-03-09 |
| ATE147111T1 (en) | 1997-01-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |