WO2019088913A1

WO2019088913A1 - Method for coating an inner surface of a pipe and the pipe having the coating

Info

Publication number: WO2019088913A1
Application number: PCT/SG2017/050547
Authority: WO
Inventors: Masuda SHO; Siew Peng CHIA
Original assignee: AGC Asia Pacific Pte Ltd
Current assignee: AGC Asia Pacific Pte Ltd
Priority date: 2017-10-31
Filing date: 2017-10-31
Publication date: 2019-05-09
Anticipated expiration: 2020-04-30
Also published as: CN110191791B; KR102339490B1; TW201923276A; CN110191791A; KR20200074051A; TWI727215B

Abstract

There is provided a method for coating an inner surface of a pipe and the pipe having the coating. The method may comprise pressing a lining material spirally against an inner surface of a pipe over a length of the pipe and heating the pressed lining material to attach the lining material as a coating on the inner surface of the pipe. The lining material may be an elongate strip. The method may comprise overlapping a portion of edges of the elongate strip as the lining material is pressed spirally against the inner surface of the pipe over the length of the pipe.

Description

METHOD FOR COATING AN INNER SURFACE OF A PIPE AND THE PIPE

HAVING THE COATING FIELD OF THE INVENTION

The present invention relates to a method for coating an inner surface of a pipe and the pipe having the coating on the inner surface of the pipe.

BACKGROUND

The inner surfaces of various types of conventional pipes used in the industry (such as water pipes, gas pipes, heat-transfer tube etc.) are required to be resistant to corrosion and resistant to chemical reactions between the pipe and a fluid flowing therein. This can be achieved by coating the inner surface of such pipes with a resin layer such as a fluororesin layer.

Coating or lining with fluororesin is often applied particularly in chemical, pharmaceutical and semiconductors plants where exposure to highly corrosive chemicals is possible.

The fluororesin material may be in a form of pulverized powder whereby it either comprises the resin itself or as a compound mixed with additives like coloring agent, an acid scavenger or filler. A method of coating the fluororesin material to an inner surface of a pipe can be done by applying electrostatic powder coating on the inner surface of the pipe using an electrostatic powder spraying gun, followed by heating the pipe to melt the powder to form the coating layer. However, this method can only produce a pipe with only one layer of film at one time. If several layers of film are required, several separate coatings have to be carried out to achieve the targeted film thickness. This slows down the pipe manufacturing time. Furthermore, back ionization is a problem in this method as excess accumulation of charge may prevent further deposition of electrostatic powder on the surface of the pipe with existing coating.

Another method is the Roto-lining method, which involves introducing granular fluororesin material on the inner surface of a substrate and heating the pipe such that the granular fluororesin material is melted and allowed to flow uniformly via well controlled rotation and heating processes, it is inherently difficult to control the exact flow of the molten granular fluororesin material because the flow depends not only on the rotation of the substrate, but also on factors such as the evenness of the heating, the interactions between fluororesin material and the substrate. Generally, Roto-lining method is applied for lining or coating that is thicker than 1mm, and is not suitable for thinner lining or coating of less than 1 mm.

In both of the abovementioned methods, achieving an inner coating of uniform thickness without the occurrence of lining defects is difficult as it is difficult to control the spraying of the electrostatic powder spraying gun and the flow of molten granular fluororesin material.

In response to the abovementioned problems/difficulties, various technological developments have been made. For example, coating of fluororesin powder on a metal flat plate prior to bending and welding has been used to obtain a tubular pipe with inner surface coating. However, there is a negative impact due to the use of the welding technique. The parts, which are subjected to welding, experience a temperature higher than the thermal decomposition temperature of the fiuororesin lining material. A touch up is necessary to the affected parts where the fiuororesin lining material has decomposed due to the elevated temperature. In addition, the decomposition of fiuororesin results in the release of harmful gas which poses a risk to the human body.

Another method as described in Japanese Patent Application Number JP1992- 352689 involves lining the inner surface of a tank with a single sheet of fiuororesin film without any overlap of the fiuororesin film. The terminal edges of the fiuororesin film are adjacent to each other such that the edges form a butt joint. A sealing film is subsequently placed above the butt joint to cover it. The butt joint is sealed using techniques which involve the application of heat and pressure on the sealing film (for example, heat sealing or weiding).However, this process requires additional heating and melting of the sealing film. These additional steps make it difficult to control the uniformity of the thickness of the coating and reduce the efficiency of the process of coating the inner surface of a tank.

Japanese Patent No. 3954120, on the other hand, describes a method involving the drawing of a tubular lining hydrocarbon based material into a metal tube and pressing the tubular lining to the inner surface of the tube by compressed air supplied into the lining material. This method is applicable to hydrocarbon resins such as polyethylene and polypropylene but may not be suitable for other resins such as fiuororesin, which have higher yield point strength. Unlike hydrocarbon resins, fiuororesins need a higher pressure before they deform plastically. Consequently, if this method is applied to the coating of fiuororesin, a considerable pressure will be required in the process, which might affect the efficiency of the process or result in safety risk. sufymARY

In accordance with an aspect of an example of the present disclosure, there is provided a method for coating an inner surface of a pipe. The method may comprise pressing a lining material spirally against an inner surface of a pipe over a length of the pipe. Heat may be applied to the pressed lining material so as to form a layer of coating to the inner surface of the pipe.

In accordance with another aspect of an example of the present disclosure, there is provided a pipe having a coating on an inner surface of the pipe coated by the method. The coating has a lining material spirally attached on an inner surface of the pipe over a length of the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be better understood and readily apparent to one skilled in the art from the following written description, by way of example only and in conjunction with the drawings, in which:

FIG. 1 is a perspective view of a pipe having a lining material spirally coated on its inner surface;

FIG. 2 is a top view of the pipe and a pressure roller located on an outer surface of the pipe of FIG. 1 ; FIG. 3 is a see-through view of the pipe spirally coated with the lining material of FIG. 1 ;

FIG. 4 is a see-through view of the pipe spirally coated with overlapping portions of the lining material of FIG. 1 ; FIG. 5A is a first example of a cross-sectional view of the lining material of FIG. 4 along line A-A in FIG. 4;

FIG. 5B is a second example of a cross-sectional view of the lining material of FIG. 4 along line A-A in FIG. 4;

FIG. 5C is a third example of a cross-sectional view of the lining material of FIG. 4 along line A-A in FIG. 4;

FIG. 5D is an example of the lining material comprising 5 layers and a portion for overlapping;

FIG. 5E is another example of the lining material comprising 5 layers and a portion for overlapping; FIG. 5F is an example of the lining material comprising 1 layer and a portion for overlapping;

FIG. 5G is an example of the lining material comprising 4 layers and a portion for overlapping;

FIG. 6 illustrates an example of how a multi-layer lining material is fed to pressure rollers to spirally coat the inner surface of a pipe.

FIG. 7 is a front view of a lining material dispenser and guide rolls for feeding the lining material to the inner surface of the pipe of FIG. 1.

FIG. 8A is the front view of an example illustrating a lining material dispenser and guide rolls for feeding the lining material to the inner surface of the pipe of FIG. 1. FIG. 8B is the top view of an example illustrating a lining material dispenser and guide rolls for feeding the lining material to the inner surface of the pipe of FIG. 1.FIG. 9 is a perspective view of a pipe illustrating an example of how the position of pressure rollers can be fixed at the pipe.

These figures are not drawn to scale and are intended merely for illustrative purposes.

DETAILED DESCRIPTION

The present disclosure relates to a method for coating an inner surface of a pipe. This method comprises:

a) pressing a lining material spirally against an inner surface of a pipe over a length of the pipe; and

b) heating the pressed lining material so as to attach the lining material as a coating on the inner surface of the pipe. The lining materia! may be an elongate strip and the method may further comprise overlapping a portion of edges of the elongate strip as the lining material is pressed spirally against the inner surface of the pipe over the length of the pipe.

A pipe having a coating on an inner surface of the pipe coated by the method has a coating, which is a lining material spirally attached on an inner surface of the pipe over a length of the pipe.

FIG. 1 illustrates an example of how the method may be performed. In FIG. 1 , there is shown a pipe 100 being coated with a lining material 104. The lining material 104 is in a form of an elongate strip. The lining material is spirally coated on an inner surface of the pipe 100 such that a portion of edges of the elongate strip overlap one another over the length of the pipe 100. The lining material 04 is dispensed from a dispenser 105 located inside the pipe 100 and fed between a pressure roller 103 located on the inner surface of the pipe 100 and the pipe 100. The pressure roller 103 presses the lining material 104 against the inner surface of the pipe and a pressure roller 102 presses an outer surface of the pipe that is opposite to the inner surface of the pipe 100.

In the present example, the shape of the pipe 100 is substantially tubular or cylindrical in shape and has a hollow core suitable for conveying objects, such as fluids, in the pipe. The cross-section of the pipe 100 is of a ring shape that is substantially circular. However, it is appreciated that other shapes of the pipe 100 suitable for coating the inner surface with the lining material 104 are also possible. For instance, the pipe 100 may have a substantially quadrilateral or polygonal cross- section. For such non-tubular shapes, the corners of the inner surfaces of the pipe 100 may be rounded to facilitate coating via the curved or rounded surfaces of the pressure roller 103. The pressure roller 103 may be configured mechanically to reach the corners of the non-tubular pipe 100 and orientate to an inclination as required to coat the inner surface of the pipe 100 spirally. In this case, the other pressure roller 102 may be configured to work with the pressure roller 103 to apply pressure.

In the present example, the pipe 100 is made of metal, for instance, aluminum or copper. However, it is appreciated that the pipe may be made of different types of material, including metal, plastic or composite material, depending on the fluid or object which is intended to be conveyed through the pipe.

The lining material 104 may comprise an adhesive surface to adhere to the inner surface of the pipe 100, or the lining material 104 may be made of an adhesive material that can adhere to the inner surface of the pipe 100. In the case that the lining material 104 is made of an adhesive material, it may be that the adhesive property of the lining material 104 is activated upon heating the lining material 104 to a certain temperature. An adhesive material comprising a carboxyl functional group is an example of a material with adhesive property that is suitable to be used as either the lining material 104 or the adhesive surface on the lining material 104.

In the present example, the lining material 104 is a fluororesin film. Examples of fluoropolymers that can be used to form the fluororesin film include ethylene tetrafluoroethylene (ETFE) and perfluoroalkoxy alkanes (PFA). The f!uorocopolymers as described in patent publication, US7112640B2, are also examples of suitable polymers which can be used to form the fluororesin film. In other configurations, the lining material 104 may consist of more than one layer of the fluororesin film. The layer of fluororesin film that is in direct contact with the inner surface of the pipe 100 may be configured to be an adhesive surface with adhesive property for adhering to the inner surface of the pipe 100. A fluororesin film comprising a carboxyl functional group is an example of a material with adhesive property that is suitable to be used as the lining material 104 that is in direct contact with the inner surface of the pipe 100.

In the present example, two pressure rollers 102 and 103 are provided and they move in tandem. Having two pressure rollers 102 and 103 provides counteracting forces that exert clasping or gripping pressure on an area or portion of the inner surface of the pipe 100 to be coated. However, it is possible in another configuration that just the pressure roller 103 is provided but in this case, the pipe 100 has to be held to prevent movement of the pipe 100 due to the pressure roller 103 pressing the lining material 104 against the inner surface of the pipe 100.

The pressure rollers 102 and 103 are each substantially cylindrical in shape. Each of the pressure rollers 102 and 103 is rotatable about a rotational axis. It is possible in another configuration that just the pressure roller 103 is rotatable and the pressure roller 102 does not rotate.

There are several methods for performing the spiral coating of the lining material on the inner surface of the pipe. In the present example, a starting end of the lining material 104 is initially clamped between the pressure roller 103 and the inner surface of the pipe 100. The other pressure roller 102 moves in tandem with the pressure roller 103 to provide a counteracting force that exerts clasping or gripping pressure on the area or portion of the inner surface of the pipe 100 to be coated. During the coating process, rotation of the pressure roller 103 pulls the lining material 104 fed from the dispenser 105 and presses the lining material 104 over the inner surface of the pipe 100. The dispenser 105 comprises a roll of lining material 104 and has to be reloaded with a new roll of lining material 104 when it runs out.

It is appreciated that performing spiral coating of the lining material on the inner surface of the pipe as described herein has an advantage in terms of better control over the thickness of the coating layer and reduction in the occurrence of lining defects. Unlike the conventional Roto-lining method, the thickness of the lining material 104 is not restricted to 1mm or more in the present example.

One example to spirally coat the inner surface of the pipe 100 is to keep the pressure roller 103 stationary and continuously rotate the pipe 100 and move the pipe 100 in a direction along the length of the pipe 100 as the lining material 104 is being pressed by the pressure roller 103. The pressure roller 103 would rotate and pull the lining material 104 fed from the dispenser 105 as the pipe 100 is rotated and moved. Alternatively, in another example, the pressure roller 103 may be continuously rotated around the circumference of the inner surface of the pipe 100 and moved in a direction along the length of the pipe 100 while the lining material 104 is being pressed and the pipe 100 remains stationary. The pressure roller 103 would rotate and pull the lining material 104 fed from the dispenser 105 as the pressure roller 103 is moved. In yet another example, the pressure roller 103 may continuously rotate around the circumference of the inner surface of the pipe 100 without moving the pressure roller 103 in the direction along the length of the pipe 100 while the lining material 104 is being pressed and the pipe 100 is moved in a direction along the length of the pipe 100 without rotating the pipe 100. In a further example, the pressure roller 103 may be moved in a direction along the length of the pipe 100 without rotating the pressure roller 103 around the circumference of the inner surface of the pipe 100 while the lining material 104 is being pressed and the pipe 100 is rotated without moving the pipe 100 in the direction along the length of the pipe 100. In all of these examples, the other pressure roller 102, if present, would move in tandem with the pressure roller 103.

The pressure roller 103 can be rotated and roiled over the inner surface of the pipe 100 or alternatively, the pressure roller 103 can be rotated by moving the pipe 100 instead while the pressure roller 103 remains stationary. To coat the inner surface of the pipe 100 spirally, the pressure rollers 102 and 103 are disposed at an inclined angle with respect to a longitudinal axis along a lengthwise direction of the pipe. Details on the angle of inclination of the pressure rollers 102 and 103 relative to the longitudinal axis along the lengthwise direction of the pipe would be provided later.

In the present example, the pressed lining material 104 is attached as a coating to the inner surface of the pipe 100 by heating as the lining material 104 is of the type that adheres to the pipe 100 upon application of heat. Heat applied to the pressed lining material 104 reduces the viscosity of the pressed lining material 104 and makes it sufficiently adhesive to attach to the inner surface of the pipe 100.

It should be noted that the heating of the lining material 104 should not completely melt either the pressed lining material 104 or the pipe 100. Otherwise, there may be undesirable variation in the thickness of the coating of lining material 104 throughout the inner surface of the pipe 100. Applying heat to the pressed lining material 104 for short time duration, for example, less than one minute, which is applicable to the present example, helps to prevent complete melting of the pressed lining material 104. Furthermore, in the present example, the pressed lining material 104 is heated to a temperature between 80°C lower than melting point of the lining material 104 to 10^CC higher than the melting point of the lining material 104. This is a desirable range of temperature to soften the lining material 104 to an extent that the lining material 104 can adhere to the inner surface of the pipe 100 and/or adhere to another lining material already present on the inner surface of the pipe 100 in the case where overlapping of lining material is implemented. In addition, since the melting point of the lining material 104 is of a temperature much lower than the temperatures used in welding processes (which involve the melting of metals), the abovementioned range of temperatures would not melt the pipe 100 or decompose the lining material 104. Hence, unlike some conventional techniques to coat an inner surface of a pipe that involve metal welding, the method described herein has an advantage that the lining material 104 would not be heated to metal welding temperature that would decompose the lining material 104.

The heating of the lining material 104 can be carried out at the same time as the lining material 104 is pressed by heating up the pressure roller 103 and/or pressure roller 102. Alternatively, in the case that the pipe 100 is made of a thermally conductive material such as metal, the pipe 100 may be heated instead to cause the lining material 104 to be adhered to the inner surface of the pipe 100. In another configuration, both the pressure roller 103 and/or pressure roller 102 and the pipe 100 may be heated. In yet another configuration, the lining material 104 may be pressed and adhered to the inner surface of the pipe 100 before heating is carried out on the lining material 104 to secure its adhesion to the inner surface of the pipe 100.

The pressure roller 103 may be coated or manufactured with a non-stick material to prevent the pressed lining material 104 that is heated from attaching to the pressure roller 103. Examples of such non-stick materials include fluoropolymers such as polytetrafluoroethylene (PTFE) and the like. The application of heat to the lining material 104 may be accomplished through, for example, induction heating of the pressure roller 102 and/or 103, and/or the pipe 100. In the present example, a portion of the edges of the lining material 104 is overlapped to form an overlapped portion 106 as the lining material 104 is pressed spirally against the inner surface of the pipe 100 over the length of the pipe 100. The lining material 104 may be overlapped such that the thickness of the overlapped portion 106 of the lining material 104 is 20% to 100% more than the thickness of a non-overlapping portion of the lining material 104. More information on how the overlapped portion 106 can achieve such thickness would be discussed later. The thickness of the lining material in the pipe 100 may be between 100 pm to 500 μηη depending on the extent of overlapping that is to be implemented. This thickness may be achieved by having more than one layers of the lining material 104. Such thickness range of the lining material 104 is suitable for metal pipes used to convey metal corrosive fluids in the industry. It is noted that such overlapping of the lining material 104 is optional and may be provided depending on circumstances. For instance, in the case that the coating of the pressed lining material 104 on the inner surface of the pipe 100 is intended to prevent direct contact between the contents in the pipe 100 and the inner surface of the pipe 100, the coating of the lining material 104 should cover the entire inner surface of the pipe 100 and not leave any gaps exposing the inner surface of the pipe 100. The overlapping portion 106 helps to ensure that there is no exposed inner surface of the pipe 100, which is not covered by the lining material 104. This advantageously reduces the occurrence of lining defects and provides for a more secure attachment of the lining material 104 to the inner surface of the pipe 100.

FIG. 2 shows a top view of the pressure roller 102 of FIG. 1 disposed at an inclined angle, a, with respect to a longitudinal axis 107 along the length of the pipe 100. More specifically, an axis 204 that is orthogonal to an axis of rotation of the pressure roller 102 is at the inclined angle, a, with respect to a longitudinal axis 107 along the length of the pipe 100. The pressure roller 103 of FIG. 1 is disposed within the pipe 100 in the same manner and at the same inclined angle, a, as the pressure roller 102.

FIG. 3 further illustrates how the inclined angle, a, described with reference to FIG. 2 can be derived. FIG. 3 shows the pipe 100 of FIG. 1 displaced vertically and coated with some of the lining material 104. FIG. 3 is deliberately drawn to be see-through in order to reveal the lining material 104 coated in the inner surface of the pipe 100. Diameter108 of the pipe 100 is marked out in FIG. 3. For illustration purposes, an unrolled portion 302 of the lining material 104 is shown in FIG. 3. The unrolled portion 302 has a right angled triangle shape with a base being the circumference 109 of the pipe 100. Hence, the base has a dimension, which is equivalent to the circumference 109. The base of the unrolled portion 302 is longer than the height of the unrolled portion 302. In the example of FIG. 1 , there is present an overlapping portion 106 of the lining material 104. A shortest distance110 from a point at which the base and the height of the unrolled portion 302 intersect with the hypotenuse of the unrolled portion 302 is defined as a width of the non-overlapping portion of the lining material 104 in FIG. 1. In other words, the width of the portion of the lining material 104 that is non-overlapping on the inner surface of the pipe 100 is 110. The inclined angle, a, described with reference to FIG. 2 can be derived from equation 1 as shown below.

w

a⁼ ^D In Equation 1 , D refers to the diameter 108 of the pipe 100, πΌ refers to the circumference 109 of the pipe 100, and W refers to the width 1 10 of the non- overlapping portion of the lining material 104 in F!G. 1.

FIG. 4 further illustrates features in earlier figures and is deliberately drawn to be see-through in order to reveal the lining material 104 in FIG. 1 coated in the inner surface of the pipe 100 in FIG. 1. The pipe 100 is displaced horizontally in FIG. 4. FIG. 4 also illustrates more clearly the widih1 1Q of the non-overlapping portion 1 12 of the lining material 104 that is described with reference to FIG. 3. FIG. 4 also shows a width 1 11 of the lining material 104 which includes width of the overlapped portion 106 that is present in FIG. 1 and the width 110 of the non-overlapping portion 1 12.

The width1 10 of the non-overlapping portion 1 12 of lining material 204 can be derived from Equation 2 as shown below.

In Equation 2, W refers to the width 1 10 of the non-overlapping portion 1 12 of the lining material 104, W₀ refers to the width 11 1 of the lining material 104 including the width of the overlapped portion 108 and the width 110 of the non-overlapping portion 1 12, and a refers to the percentage of overlapping of the lining material 104.

FIG. 4 also shows how the pressure roller 102 of FIG. 1 is disposed at the inclined angle, . With reference to FIG. 2 and FIG. 4, the inclined angle, a, is formed between the axis 204 that is orthogonal to the axis of rotation 202 of the pressure roller 102 and the longitudinal axis 107 along the length of the pipe 100.

FIG. 5A shows an example of a cross-sectional view 500 of the lining material 104 along line A~A in FIG. 4 in a top half of FIG. 5A and shows a perspective view 509 of an example of part of the lining material 104 in a bottom half of FIG. 5A. The lining material 104 in the example of FIG. 5A has 3 layers, specifically, a top layer 502, a middle layer 504 and a bottom layer 506. Each layer may be a layer of fluororesin film. The bottom layer 506 is adhered to the inner surface of the pipe 100. FIG. 5A shows the width 1 10 of the non-overlapping portion 112 of the lining material 104 that is described with reference to FIG. 4. FIG. 5A also shows the width 1 11 of the lining material 104 which includes the width of the overlapped portion 108 that is described with reference to FIG. 4. The thickness of the non-overlapping portion 1 12 and the thickness of the overlapped portion 106 can be varied. In FIG. 5A, the non- overlapping portion 112 consists of 3 layers constituting the lining material 104 whereas the overlapped portion 106 consists of 4 layers forming the lining material 104. The overlapped portion 106 has an additional layer compared to the non- overlapping portion 1 12 that is formed by an extension (or extended portion) of the top layer 502 in the example of FIG. 5A. It is appreciated that any one or more of the layers can be extended to form part of the overlapped portion 106 in other configurations to increase the thickness of the overlapped portion 106. In this case, the thickness of the overlapped portion 106 is about one third or 33% more than the thickness of the non-overlapping portion 112. In another configuration of a lining material with 6 layers, where the overlapped portion 108 consists of 12 layers, and the thickness of the non-overlapping portion 1 12 is 6 layers, the overlapping total thickness of the overlapped portion 106 is 100% more than the thickness of the non- overlapping portion 1 12.

FIG. 5B shows another example of a cross-sectional view 510 of the lining material 104 along line A-A in FIG. 4 in a top half of FIG. 5B and shows a perspective view 519 of an example of part of the lining material 104 in a bottom half of FIG. 5B. The lining material 104 in the example of FIG. 5B has 2 layers, specifically, a top layer 512 and a bottom layer 514. Each layer may be a layer of fluororesin film. The bottom layer 514 is adhered to the inner surface of the pipe 100. FIG. 5B shows the width 1 10 of the non-overlapping portion 1 12 of the lining material 104 that is described with reference to FIG. 4. FIG. 5B also shows the width 11 1 of the lining material 104 which includes the width of the overlapped portion 106 that is described with reference to FIG. 4. In FIG. 5B, the non-overlapping portion 112 consists of 2 layers constituting the lining material 104 whereas the overlapped portion 106 consists of 3 layers of the lining material 104. The overlapped portion 106 has an additional layer compared to the non-overlapping portion 1 12 that is formed by an extension (or extended portion) of the bottom layer 514 in the example of FIG. 5B. It is appreciated that any one or more of the layers can be extended to form part of the overlapped portion 106 in other configurations to increase the thickness of the overlapped portion 106. In this case, the thickness of the overlapped portion 106 is about half or 50% more than the thickness of the non-overlapping portion 112. In another configuration of a lining material with 4 layers, where the overlapped portion 106 consists of 7 layers and the thickness of the non-overlapping portion 1 12 is 4 layers, the overlapping total thickness of the overlapped portion 106 is 75% more than the thickness of the non-overlapping portion 112.

FIG. 5C shows another example of a cross-sectional view 520 of the lining material 104 along line A-A in FIG. 4 in a top half of FIG. 5C and shows a perspective view 529 of an example of part of the lining material 104 in a bottom half of FIG. 5C. The lining material 104 in the example of FIG. 5C has 2 layers, specifically, a top layer 522 and a bottom layer 524. Each layer may be a layer of fluororesin film. The bottom layer 524 is adhered to the inner surface of the pipe 100. FIG. 5C shows the width 1 10 of the non-overlapping portion 1 12 of the lining material 104 that is described with reference to FIG. 4. FIG. 5C also shows the width 1 1 1 of the lining material 104 which includes the width of the overlapped portion 106 that is described with reference to FIG. 4. In FIG. 5C, the non-overlapping portion 1 12 consists of 2 layers constituting the lining material 104 whereas the overlapped portion 106 consists of 3 layer of the lining material 104. The overlapped portion 106 has an additional layer compared to the non-overlapping portion 112 that is formed by an extension (or extended portion) of the top layer 522 in the example of FIG. 5C. It is appreciated that any one or more of the layers can be extended to form part of the overlapped portion 106 in other configurations to increase the thickness of the overlapped portion 106. In this case, the thickness of the overlapped portion 106 is about half or 50% more than the thickness of the non-overlapping portion 1 12. In another configuration of a lining material with just 1 layer, where the overlapped portion 106 consists of 2 layers and the thickness of the non-overlapping portion 112 consists of just 1 layer, the overlapping total thickness of the overlapped portion 106 is 100% more than the thickness of the non-overlapping portion 1 12.

FIG. 5D shows a perspective view of an example of part of the lining material 104 of FIG. 4. The lining material 104 of FIG. 5D has 5 layers and one of the 5 layers 532 is extended so as to form part of the overlapped portion 106 and the other four of the 5 layers 534 are not extended. Each layer may be a layer of fluororesin film. In the case that the lining material 104 of FIG. 5D is used, the overlapped portion 106 will have 6 layers forming the lining material 104 and the non-overlapping portion 1 12 will have 5 layers. Hence, the overlapping total thickness of the overlapped portion 106 will be 20% more than the thickness of the non-overlapping portion 112.

FIG. 5E shows a perspective view of an example of part of the lining material 104 of FIG. 4. The lining material 104 of FIG. 5E has 5 layers and three of the 5 layers 542 are extended so as to form part of the overlapped portion 108 and the other two of the 5 layers 544 are not extended. Each layer may be a layer of fluororesin film. In the case that the lining material 104 of FIG. 5E is used, the overiapped portion 108 will have 8 layers forming the lining material 104 and the non-overlapping portion 112 will have 5 layers. Hence, the overlapping total thickness of the overlapped portion 108 will be 80% more than the thickness of the non-overlapping portion 112.

In view of FIG. 5A to FIG. 5E, the thickness of the overlapped portion 108 and the thickness of the non-overlapping portion 1 12 can be said to be governed by the following Equation 3.

E

0 = - X 100 In equation 3, O is the percentage of the overlapping total thickness of the overlapped portion 106 that is more than the thickness of the non-overlapping portion 1 12. E is the number of layer(s) extended to form part of the overlapped portion 06 and L is the total number of layers forming the lining material 104. Each layer may be a layer of fluororesin film or may be other suitable layer of material.

FIG. 5F is an example showing that the overlapping total thickness of the overlapped portion 106 can be less than the thickness of the non-overlapping portion 1 12.

Specifically, FIG. 5F shows an example of a cross-sectional view 550 of the lining material 104 along line A-A in FIG. 4. The lining material 104 in the example of FIG. 5F has 1 layer. This layer may be a layer of fluororesin film. This layer 104 is adhered to the inner surface of the pipe 100. In the present example, the lining material 104 has two opposing edge portions. Each edge portion is tapered so as to form a triangular cross-section with one pointed end being the terminating end of the lining material 104. FIG. 5F shows the width 1 10 of the non-overlapping portion 1 12 of the lining material 104 that is described with reference to FIG. 4. FIG. 5F also shows the width 11 1 of the lining material 104 which includes the width of the overiapped portion 106 that is described with reference to FIG. 4. The thickness of the non-overlapping portion 1 12 and the thickness of the overiapped portion 108 can be varied by adjusting distance between adjacent layers of the lining material 104 to be adhered to the inner surface of the pipe 100. In FIG. 5F, notably, the non- overlapping portion 1 12 consists of 1 layers constituting the lining material 104 whereas the overlapped portion 106 consists of less than 1 layer of the lining material 104. In this case, the thickness of the overlapped portion 106 is less than the thickness of the non-overlapping portion 1 12.

FIG. 5G is an example showing that there can be overlapping of the lining material 104 at the edge portions but the overlapped portion 108 is still the same thickness as the non-overlapping portion 1 12.

Specifically, FIG. 5G shows an example of a cross-sectional view 560 of the lining material 104 along line A-A in FIG. 4 in a top half of FIG. 5G and shows a perspective view 569 of an example of part of the lining material 104 in a bottom half of FIG. 5A. The lining material 104 in the example of FIG. 5A has 4 layers, specifically, a top layer 562, two middle layers 564 and 566, as well as a bottom layer 568. Each layer may be a layer of fluororesin film. The bottom layer 568 is adhered to the inner surface of the pipe 100. The 4 layers are arranged in a staggered manner such that two opposing stepped edge portions are formed in the lining material 104. FIG. 5G shows the width 1 10 of the non-overlapping portion 1 12 of the lining material 104 that is described with reference to FIG. 4. FIG. 5G also shows the width 1 1 1 of the lining material 104 which includes the width of the overlapped portion 106 that is described with reference to FIG. 4. The thickness of the non-overlapping portion 1 12 and the thickness of the overlapped portion 106 can be varied by adjusting distance between adjacent layers of the lining material 104 to be adhered to the inner surface of the pipe 100. In the example of FIG. 5G, the opposing stepped edge portions of the lining material 104 are arranged to correspond or flush with one another such that the non-overlapping portion 1 12 consists of 4 layers constituting the lining material 104 and the overlapped portion 106 also consists of 4 layers forming the lining material 104. In this case, the thickness of the overlapped portion 106 is the same as the thickness of the non- overlapping portion 1 12.

FIG. 6 shows an example of an apparatus and a method of dispensing two or more layers of fluororesin film to form the lining material 104 described with reference to earlier figures. In FIG. 6, a first dispenser 121 dispenses a layer of fluororesin film

123 and a second dispenser 122 dispenses a layer of fluororesin film 124. Although fluororesin film is described, it is appreciated that films made of other suitable material may also be used to form the lining material 104. Downstream of the first and second dispensers 121 and 122, there are guide rolls 125 to guide the layers of fluororesin films 123 and 124 to a pair of guide rolls 126. More dispensers and guide rolls may be added to the set up of FIG. 6 accordingly to form the lining material 104 with more than two layers. The pair of guide rolls 126 places the fluororesin films 123 and 124 in contact with each other. After passing through guide rolls 126, the fluororesin films 123 and 124 form a multilayer film 127 that would constitute the lining material 104. In the present example, the individual fluororesin films 123 and

124 in the multilayer film 127 are not permanently attached to each other but are stacked adjacent to each other.

Further downstream of the pair of guide rolls 126, there is a plurality of guide rolls 128. The guide rolls 128 are used to guide the multilayer film 127 such that the multilayer film 127 is placed between two pressure rollers 129 and 130. The multilayer film 127 is then fed between the pressure roller 103 of FIG. 1 and the inner surface of the pipe 100 shown in FIG. 1 for coating the inner surface of the pipe 100 with the multilayer film 127. When heat is applied to the multilayer film 127 during the process to spirally coat the lining material 104 to the inner surface of the pipe 100, the layers of the multilayer film 127 will adhere to one another and one of the layers facing the inner surface of the pipe 100 will adhere to the inner surface of the pipe 100.

The setup of FIG. 6 may be used to achieve a thickness of the overlapped portion 106 as described with reference to earlier figures that ranges from more than 0 % to 100 % compared to the thickness of the non-overlapping portion 1 12 as described with reference to earlier figures. However, the setup has to be adjusted such that the one or more layers being dispensed would be placed in contact with each other in a manner that would provide an extended portion required to form part of the overlapped portion 106. If the layers all start out with the same width, trimming of excess edges of the layers on one side would be necessary so that only one side of the layers has the extended portion required to form the part of the overlapped portion 106.

FIG. 7 shows an example of a setup used to guide the multilayer film 127 of FIG. 8 from the pressure rollers 129 and 130 of FIG. 6 to a guide roll 131 before being fed such that the multilayer film 127 is placed between the pressure roller 103 of FIG. 1 and the inner surface of the pipe 100 of FIG. 1. FIG. 7 is a view looking into the pipe 100 from one end such that the circumference of the pipe 100 (in this case, circular) can be seen. Preferably, the guide roll 131 comprises an adjustable joint (such as an adjustable universal joint or ball joint) that is configured to enable adjustment of an angle at which the multilayer film 127 is fed between the pressure roller 103 and the inner surface of the pipe 100. In the present example, the angle at which the multilayer film 127 is fed between the pressure roller 103 and the inner surface of the pipe 100 is the same as the inclined angle, a, described with reference to FIG. 2 to 4.

FIG. 8A shows an example of a cross-sectional side view of the setup of FIG. 8. The pipe 100 is in a cutaway view to reveal rollers within the pipe. The reference numerals of the same elements appearing in FIG. 6 are re-used in FIG. 8A. The setup of FIG. 8A guides films 123 and 124 dispensed from two respective dispensers 121 and 122 to a position between a pair of guide rolls 126 to form a multilayer film 127. The dispensers 121 and 122 are mounted to a mounting block 805 that is attachable to a fixed location, which can be a wail. The dispenser 122 resides above the dispenser 121. The multilayer film 127 formed between the pair of guide rolls 126 is further fed to a cone roller 802. The cone roller 802 is an additional feature not shown in the setup of FIG. 6. The setup of FIG. 8A also does not have the guide rolls 128 present in FIG. 6. The cone roller 802 diverts the multilayer film 127 at appropriate angle towards a position between a pair of guide rollers 129 and 130. Thereafter, the multilayer film 127 is further guided to between a pressure roller 103 and an inner surface of a pipe 100 to be spirally coated on the inner surface of the pipe 100. A pressure roller 102 operating in conjunction with the pressure roller 103 to press the multilayer film 127 on the inner surface of the pipe 100 is located on an outer surface of the pipe 100 opposite to the inner surface of the pipe 100. The dispensers 121 and 122 are fixed to supporting structures 803 so that unnecessary movement that would affect dispensing is avoided.

FIG. 8B illustrates a top view of the setup of FIG. 8A arranged such that the dispenser 122 and the pressure roller 102 are visible. The pipe 100 is deliberately made to be see-through to reveal the roller 129 and the multilayer film 127 located within the pipe. The rotational axis 202 of the pressure roller 102, the axis 204 orthogonal to the rotational axis 202 of the pressure roller 102, and the longitudinal axis 107 along the length of the pipe 100 are drawn in FSG. 8B for illustration purposes. It is appreciated that the rotational axis 202 of the pressure roller 102 is parallel to the rotational axis of the pressure roller 103 as these two pressure rollers

102 and 103 as working in conjunction to provide spiral coating of the lining material 104.

With reference to FIG. 8A and FIG. 8B, the cone roller 802 is mounted to a shaft such that the cone roller 802 is rotatabie about a longitudinal axis of a shaft 804. The shaft 804 has two opposing ends mounted respectively to a pair of elongate support 808 extending from the mounting block 805. The cone roller 802 is positioned so as to divert the multilayer film 127 to between the pressure roller 103 and the inner surface of the pipe 100 at an appropriate angle. In the present example, the appropriate angle at which the multilayer film 127 is fed between the pressure roller

103 and the inner surface of the pipe 100 is the same as the inclined angle, a, described with reference to FIG. 2 to 4. FIG. 9 illustrates a perspective view of the pipe 100 of FIG. 1 and further illustrates how the position of the pressure rollers 102 and 103 of FIG. 1 can be fixed inside the pipe 100. A support apparatus 900 is shown in FIG. 9. The support apparatus 900 comprises the pressure roller 103, a roller support 905, an extendable shaft 904, a roller support 906, another roller 907, a guide roll support 903, guide rolls 129 and 130, and a support shaft 902. The pressure roller 103 to be located within the pipe 100 is fastened to one end of the roller support 905. Specifically, the pressure roller 103 is rotatably mounted to the support 905 such that the pressure roller 103 can be rotated. Another end of the support 905 is attached to one end of the extendable shaft 904. Another end of the extendable shaft 904 is attached to the roller 907 through the roller support 906. The pressure roller 103 and the roller 907 are at opposing ends of the support apparatus 900 and are both arranged to exert pressure on the inner surface of the pipe 100. The extendable shaft 904 is capable of being mechanically adjusted such that length of the support apparatus 900 from a point in which the pressure roller 103 exerts pressure on the inner surface of the pipe 100 and presses on the lining material 104 to a point in which the opposing roller 907 contacts either the lining material 104 coated over the inner surface of the pipe 100 or the inner surface of the pipe 100 fits the diameter of the pipe 100. The pressure roller 102 is mounted outside the pipe 100 in a manner so that it will contact the outer surface of the pipe 100 above the inner surface of the pipe 100 coated by the pressure roller 103, and move in tandem with the pressure roller 103.

The extendable shaft 904 may comprise biasing mechanisms such as springs to exert on the pressure roller 103 and the roller 907, which are at opposite ends of each other. The pressure roller 103 and the roller 907 in turn exerts pressure on the lining material 104 on the inner surface of the pipe 100 or the inner surface of the pipe 100.

The guide roll support 903 extends orthogonally from a position at the extendable shaft 904 that is midway of the support apparatus 900. The pressure rollers 129 and 130 are fastened to the guide roll support 903. The support shaft 902 extends from an end opposite to the direction in which the guide roll support 903 extends orthogonally from the position at the extendable shaft 904. The length of the support shaft 902 is adjustable.

The support shaft 902 may extend for a length longer than the length of the pipe 100 to a fixed position external or outside the pipe 100 so as to fix the position of the support apparatus 900. The support apparatus 900 has to be fixed in position in the case where the pipe 100 is moved and the pressure roller 103 is to stay stationary during spiral coating.

In another configuration in which the pipe 100 remains in the same position and the pressure roller 103 is to move across the pipe 100, the support shaft 902 may be attached to an actuator (not shown in FIG. 9) for rolling the support apparatus 900 to different positions to be coated within the pipe 100.

In another example, where the pressure roller 103 may be rotated around the circumference of the inner surface of the pipe 100, the extendable shaft 902 may be attached to a rotation actuator that is capable of rotating the support apparatus 900, which in turn rotates the pressure roller 103 along the circumference of the pipe 100.

The support 905 and/or the extendable shaft 904 may be configured as heating devices for heating the pressure roller 103, which in turn heats the lining material 104. Alternatively, the pressure roller 102 may be the one that is heated instead, in another configuration, it is possible that both the pressure rollers 102 and 103 are heated together through heating devices,

The dispensing and/or the guiding and feeding of the lining material 104 may be performed entirely within the pipe 100 in a manner such that the lining material 104 would not come into contact with components or elements of the setup other than the guide rolls guiding and feeding the lining material 104 to the location between the pressure roller 103 and the inner surface of the pipe 100. In other configurations, it could be that the dispensers (e.g. 121 and 122) are located outside the pipe 100 and the guide rolls as described herein are inside the pipe 100. It is also possible that some of the guide rolls are outside and some of the guide rolls are inside the pipe 100. The configuration depends on how the guide rolls are deployed to guide the lining material 104 to the location between the pressure roller 103 and the inner surface of the pipe 100.

In the specification and claims, unless the context clearly indicates otherwise, the term "comprising" has the non-exclusive meaning of the word, in the sense of "including at least" rather than the exclusive meaning in the sense of "consisting only of. The same applies with corresponding grammatical changes to other forms of the word such as "comprise", "comprises" and so on.

While the invention has been described in the present disclosure in connection with a number of embodiments and implementations, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of the invention are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.

Claims

A method for coating an inner surface of a pipe, the method comprising: a) pressing a lining material spirally against an inner surface of a pipe over a length of the pipe; and

b) heating the pressed lining material to attach the lining material as a coating on the inner surface of the pipe.

The method as claimed in claim 1 , wherein the lining material is an elongate strip and the method comprising:

overlapping a portion of edges of the elongate strip as the lining material is pressed spirally against the inner surface of the pipe over the length of the pipe.

The method as claimed in claim 2, the method comprising:

overlapping total thickness of an overlapped portion of the lining material is 20% to 100% more than a thickness of a non-overlapping portion of the lining material.

The method as claimed in any one of claims 1 to 3, wherein the lining material comprises one or more layer of fluororesin film.

The method as claimed in any one of claims 1 to 4, wherein the lining material is an adhesive material comprising carboxyl functional group.

The method as claimed in any one of claims 1 to 5, wherein thickness of the lining material is between 100 pm to 500 pm.

The method as claimed in any one of claims 1 to 6, wherein the pressed lining material is heated to a temperature between 60°C lower than melting point of the lining material to 10°C higher than the melting point of the lining material.

The method as claimed in any one of claims 1 to 7, wherein the pressing of the lining material is done using at least two pressure rollers, wherein one of the pressure rollers presses the lining material against the inner surface of the pipe and another pressure roller presses an outer surface of the pipe that is opposite to the inner surface of the pipe.

The method as claimed in claim 8, wherein heating of the pressed lining material is done by heating at least one of the pressure rollers.

The method as claimed in claim 8 or 9, wherein an axis orthogonal to an axis of rotation of each of the pressure rollers is at an inclined angle with respect to a longitudinal axis along the length of the pipe.

The method as claimed in claim 10, wherein the inclined angle is provided by using a cone roller to divert the lining material being dispensed at the inclined angle towards the pressure roller pressing the lining material against the inner surface of the pipe.

The method as claimed in any one of claims 8 to 11 , wherein the pressure roller pressing the lining materia! against the inner surface of the pipe is connected to a first end of a support apparatus within the pipe and a second end of the support apparatus opposite to the first end of the support apparatus comprises a roller for contacting either the lining material coated over the inner surface of the pipe or the inner surface of the pipe.

The method as claimed in any one of claims 1 to 12, the method comprising: rotating the pipe and moving the pipe in a direction along the length of the pipe as the lining material is being pressed.

A pipe having a coating on an inner surface of the pipe coated by the method as claimed in any one of claims 1 to 13, the coating being a lining material spirally attached on an inner surface of the pipe over a length of the pipe.

The pipe as claimed in claim 14, wherein the lining material is an elongate strip and a portion of edges of the elongate strip overlap one another over the length of the pipe.

The pipe as claimed in claim 15. wherein total thickness of an overlapped portion of the lining material is 20% to 100% more than a thickness of a non- overlapping portion of the lining material.