NO20120721A1 - Tubular body coated with inner wear coating and method of making such coating - Google Patents

Abstract

An elongated channel (1) comprising a sheath (2) and provided with an internal polymer coating (3) constituted by a polymeric material selected from a group consisting of polyurethane and silicone, the inner sheath surface of the elongated channel (1) 5 ( 21) is provided with a primer at least in one end portion (11,12) and the inner casing surface (21) is primer-free in a center portion (13). Also disclosed is a method of coating an elongate channel (1) internally with a polymeric coating (3) comprised of a polymeric material selected from a group consisting of polyurethane and silicone, the method comprising the steps of: a) positioning the channel (1) ) in a jig arranged to be able to rotate the channel (1) about its longitudinal axis (10) and the jig is further arranged to be able to correct deviations in the longitudinal direction of the channel (1); b) applying a primer at least one end portion (11,12) to the inner shell surface of the channel (1) and keeping the middle portion (13) of the channel (1) primer free; C) positioning the polymeric material within the channel (1); and d) rotating the channel (1) about its longitudinal axis (10) until the polymeric material is formed firmly within the channel (1).

Description

TUBULAR BODY COATED WITH INTERNAL WEAR COATING AND METHOD FOR PRODUCING SUCH COATING

This invention relates to an elongated, hollow body where the inner mantle surface is coated with a coating to increase the elongated body's resistance to wear from a fluid flowing through the elongated body. More specifically, the invention relates to a tubular body coated with a polymer material on the inner mantle surface and where the coating exhibits a smooth or closed structure. The invention also relates to a method for coating such an elongated body with such an internal coating.

All channels used for the transport of fluids are affected to a greater or lesser extent by the fluid on surfaces that are in contact with the fluid. For example, water can cause corrosion. Fluid containing particles will cause frictional wear. Maintenance of such channels is in many cases expensive. Transport of the fluid must be interrupted and in many cases the channel or a part of the channel must be replaced due to the wear damage caused. In order to limit the damage and to extend the lifetime of the channels, it is known to apply another material that better resists the influence of the fluid transported in the channels. In the field, it is known to coat the inner casing surface with a Teflon coating to avoid corrosion. It is also known to apply a plastic material by spraying and to glue rubber mats or rubber hoses to the casing surface to avoid mechanical stress such as frictional wear. Such application of a protective coating or material is done manually, which leads to varying quality. The materials are also not good enough for some applications.

Norwegian patent application NO 762309 describes a procedure for coating metal pipes internally with a protective coating. The protective coating can consist of a thermoplastic resin such as, for example, fluorine resin, polyacid resin, polyethylene, polystyrene, acrylic acid resin, polyolefin and polyvinyl chloride. The protective coating can further consist of a curing resin such as, for example, phenolic resin, urea resin, melamine resin, polyester resin and silicone resin. Such curable resins can be injected into the pipes. The tubes are heated to between 220 and 300 °C and rotated so that the resin melts and adheres to the inner casing surface. Air is removed from the inside of the pipe so that the coating is carried out at a pressure lower than the surrounding atmospheric pressure. In order to prevent injected material from being sucked out, patent document NO 762309 relates to an improved method where resin material is fed into the tube shaped like a rod or as a cylinder with a mesh, net or braid shape before air is sucked out and the tube is heated and rotated. In the design examples, the produced coating is between 0.2 and 1.0 mm thick.

Patent document GB 1260961 relates to the coating of internal surfaces of short, cylindrical objects. The coating can consist of a plastic material such as phenol resins, epoxy resins, polyester resins, acrylic and methacrylic resins, urethane, amides, aromatic polyesters, terephthalates, phenoxy resins and polycarbonates. The object is placed inside a spindle which is heated to between 100 and 300 °C. After heating and applying the plastic material which is distributed over the inner surface of the object by means of centrifugation, bubbles are removed by passing a wire back and forth over the surface of the plastic material along the object's axial direction. In one design example, the plastic coating is 0.4 mm thick. In another embodiment, the plastic coating is 0.25 mm and 0.5 mm thick.

Patent document GB 437755 relates to coating the inner surface of a steel pipe with a coating consisting of bitumen. The procedure includes dipping the pipe in a hot bitumen solution so that the pipe is also heated to between 110 and 220 °C, positioning the pipe with remnants of the bitumen solution inside the pipe on a rotation device that turns the pipe slowly around its longitudinal axis, until the bitumen solution has solidified.

Patent document US 4107254 relates to coating the inner surface of a metal pipe with a polyurethane coating. A suitable metal-to-polyurethane binder is applied to the inside of the pipe. Liquid polyurethane is distributed evenly on the inside of the pipe by rotating the pipe. Gas bubbles that may be mixed in the liquid polyurethane mass can be removed by blowing hot air with a temperature of 250 °C ± 10 °C into the pipe for a period of 40 - 50 seconds at the start of rotation. Patent document GB 1596305 also relates to coating the inner surface of a metal pipe with a polyurethane coating. A suitable binder is applied to the inside of the pipe. Liquid polyurethane is supplied to the pipe at a speed which means that air is not mixed into the polyurethane mass. Liquid polyurethane is distributed evenly on the inside of the pipe by rotating the pipe.

Patent document WO 01/02503 relates to coating the inner surface of a metal pipe with an insulating layer. The insulation layer can be made of epoxy or of glass or ceramic material. A suitable binder is first applied to the inside of the pipe. A wear coating can be applied to the insulation layer.

The purpose of the invention is to remedy or to reduce at least one of the disadvantages of known technology, or at least to provide a useful alternative to known technology.

The purpose is achieved by features that are stated in the description below and in subsequent patent claims.

The invention relates to coating elongated channels which form a continuous side wall, such as a pipe, with a coating of thermosetting plastic, polyurethane or silicone on the inner surface of the channel. The coating will protect the channel's inner casing surface against damage and wear. Coating takes place by filling a measured quantity of the desired material into a horizontally oriented channel which rotates about its longitudinal axis at room temperature. Curing takes place during ongoing constant rotation of the channel about the longitudinal axis of the channel. The rotation speed is adapted to the type of material and the channel's cross-sectional dimensions. A coating with an even surface and with the desired thickness can be built up during controlled curing of the material.

In a first aspect, the invention relates to an elongate channel comprising a sheath and provided with an internal polymer coating comprising a polymer material selected from a group consisting of polyurethane and silicone, and where the elongate channel's inner jacket surface is provided with a primer at least in one end part and that the inner mantle surface is primer-free in a middle part. The channel's inner jacket surface can be coated with a thermo-insulating coating between the jacket and the polymer coating. The thermo-insulating coating can consist of a polymer material selected from a group consisting of polyurethane and silicone. The channel's internal polymer coating can be smoothed. The channel can consist of a pipe.

In a second aspect, the invention relates to a method for internally coating an elongated channel with a polymer coating comprising a polymer material selected from a group consisting of polyurethane and silicone, where the method comprises step-o

no a:

a) position the channel in a jig arranged to be able to rotate the channel about its longitudinal axis and the jig is further arranged to be able to correct deviations in the longitudinal direction of the channel; b) applying a primer to the inner casing surface of the channel at least in one end portion and keeping the middle portion of the channel free of primer;

c) positioning the polymeric material within the channel; and

d) rotate the channel about its longitudinal axis until the polymer material is dimensionally stable inside the channel.

The method may further comprise a step e) passing an open flame along it

shape-retaining the internal surface of the polymer material parallel to the longitudinal axis of the channel to smooth the surface after step d). As an alternative, step e) may include guiding an electric heating element along the shape-retaining polymer material's internal surface parallel to the channel's longitudinal axis. The method may further comprise a step bO) of providing the channel with a thermally insulating coating before step c).

In an alternative embodiment, the method can further comprise the steps of: bl) supplying the channel (1) with sealing end plugs after step b);

cl) evacuate air from the interior of the channel (1) after step c); and

dl) equalize the pressure inside the channel (1) after step d).

In the alternative embodiment, the method can further comprise a step

e) passing an open flame along the internal surface of the dimensionally stable polymer material parallel to the longitudinal axis of the channel to smooth the surface after step dl). Step e)

may as an alternative include guiding an electric heating element along the shape-retaining polymer material's internal surface parallel to the channel's longitudinal axis. The method can further comprise a step f) of rotating the channel about its longitudinal axis after step e) to further increase the firmness of the shape-retaining polymer material so that the end plugs can be removed. The method may further comprise a step b2) of providing the channel (1) with a thermo-insulating coating before step c).

The method can be carried out at ambient temperature. The method may further comprise tempering the channel to a temperature between 10 and 50 °C, such as, for example, 25, 30, 35, 40, or 45 °C.

In the following, examples of preferred embodiments are described which are illustrated in the accompanying drawings, where: Fig. 1 schematically shows a cross-sectional view of a channel coated with a wear coating according to the invention; Fig. 2 schematically shows the same as Fig. 1 of a channel coated with a thermo-insulating coating and a wear coating; and

Fig. 3 schematically shows an isometric perspective view of the channel shown in figure 1.

In the figures, the reference number 1 indicates a channel in the form of a pipe. The tube 1 comprises an outer jacket 2. The outer jacket 2 is coated on its inner mantle surface 21 with a polymer coating 3, hereinafter called wear coating 3. The wear coating 3 is formed on its inner surface 31 with a smooth surface.

Figure 2 shows a pipe 1 where the inner casing surface 21 is coated with a thermo-insulating coating 4. The thermo-insulating coating 4 is coated on its inner surface 41 with a wear coating 3. The wear coating 3 is formed on its inner surface 31 with a smooth surface.

The pipe 1 forms a first end part 11, a second end part 12 and a middle part 13 as shown in Figure 3.

A closed channel, exemplified by a pipe 1 which is open at both ends, is placed in a jig (not shown). The pipe 1 rests in each end part 11, 12 on a rotation mechanism of a known type and which is arranged to keep the central axis of the pipe 1 stationary. At least one of the rotation mechanisms is arranged to be able to rotate the tube about its longitudinal axis 10. The jacket 2 of the tube 1 has the same temperature as the ambient temperature. The jig is additionally provided with a righting mechanism. The straightening mechanism can be designed in much the same way as the rotation mechanism and so that one or more wheels or rollers support the pipe 1 at the middle part 13 of the pipe 1, and that one or more wheels or rollers exert pressure against the outer casing surface 22 of the pipe 1. This achieves that any throws or deviations in the longitudinal direction of the pipe 1 are corrected when the pipe 1 is rotated about its longitudinal axis 10.

The pipe 1 is provided at each open end with a sealing first and a second end plug (not shown). The first end plug is provided with a connection to a vacuum pump (not shown). In a first embodiment, the connection is a swivel connection of a known type. Thereby, a negative pressure can be created inside the pipe 1 while the pipe 1 is rotated in the jig. In another embodiment, the connection is provided with a quick coupling to a vacuum pump. Thereby, a negative pressure can be formed inside the tube 1 when the rotation of the tube 1 is stopped for a short while. The connection is further provided with a valve (not shown) to let air into the pipe 1 in order to equalize the pressure between the inside and outside of the pipe 1.

The first and second end plugs are each provided with a removable center plug. The center plug can be removed when the pressure is equalised. The end plug will then form a ring around the pipe 1 jacket 2 and a heating element (not shown) can be introduced into and out of the pipe 1 through the central opening in one of the end plugs.

A primer is applied to the inner jacket surface 21 in a part in each end part 11, 12 of the pipe 1. Suitable primers are known in the field and are not described in more detail. The primer will form a strong bond between the mantle surface 21 and the wear coating 3. Applying the primer in each end part 11, 12, but not over the entire inner mantle surface 21, for example not in the middle part 13, has the advantage that the wear coating 3 can be separated from the jacket 2 by mechanically loosen the wear coating 3 in the end parts 11, 12 and then pull the wear coating 3 out of the tube 1.

After applying primer by brushing, spraying or pouring, a measured amount of polymer material, hereinafter called wear coating material, is filled in liquid form into the pipe 1. The wear coating material can be a mixture of polyurethane and a hardener or an accelerator, as is known in the art the subject. The tube 1 is rotated to distribute the wear coating evenly over the inner casing surface 21. The speed of rotation depends on the diameter of the tube and the properties of the wear coating material. A rotation speed between 1 m/s and 5 m/s peripheral speed has proven beneficial. It has proven to be further advantageous to evacuate the interior of the tube 1 of air by means of a vacuum pump. This has the advantage that the curing process goes faster and that gases and air in the wear coating material more easily reach the surface of the still liquid wear coating material. Pumping out air can be done before the tube 1 is set in rotation or after the tube 1 is set in rotation. The pressure inside the tube 1 can be between 0.9 and 0.001 atmospheric pressure, more advantageously between 0.5 and 0.01 atmospheric pressure, further more advantageously between 0.25 and 0.02 atmospheric pressure, further more advantageously between 0.1 and 0.02 atmospheric pressure.

After a few minutes of rotation, the rotation is stopped and air is admitted into tube 1. It has been found advantageous that the rotation lasts between 2.5 minutes and 15 minutes, more advantageously that the rotation lasts between 5 minutes and 12 minutes, and further advantageously that the rotation lasts between 7.5 minutes and 12 minutes, for example 10 minutes. The center plug is removed in the first and second end plugs. The wear coating material is then dimensionally stable, for example as a gel, but not hardened. The heating element is introduced through the opening in the other end plug and is activated inside the tube 1. The heating element is guided along the surface 31 once parallel to the longitudinal axis 10 of the tube. This has the advantage that gas that forms bubbles in the still sticky wear coating material will burst so that the gas escapes and the bubbles close. The heat from the heating element will also smooth the surface 31. In one embodiment, the tube 1 is at rest while the heat treatment is in progress. In an alternative embodiment, the tube 1 rotates while the heat treatment is in progress. The heating element can consist of an electric heating element. The heating element can be made of a gas burner that emits an open flame. The gas burner can be a propane gas burner.

After completion of the heat treatment, the heating element is removed from the pipe 1. The pipe 1 is rotated further until the wear coating material is dimensionally stable enough for the end plugs to be removed. The pipe 1 is stored until the wear coating material has fully hardened. A wear coating 3 is then formed on the inner mantle surface 21. The wear coating 3 is firmly attached to the pipe's end parts 11, 12. The wear coating 3 exhibits a smooth surface 31 and the wear coating 3 exhibits a uniform thickness. The uniform thickness is achieved by correcting any deviations along the longitudinal axis 10 of the pipe 1 using the jig's straightening mechanism.

In an alternative embodiment, the pipe 1 can first be coated with a thermo-insulating material 4. The procedure is the same as described above, but possibly with a different primer, as is known in the art. The surface 41 of the thermo-insulating coating 4 is not heat treated. It is advantageous that the surface 41 is not completely smooth as this provides better adhesion for the wear coating 3 which is applied to the surface 41. In one embodiment, the wear coating material is distributed over the surface 41 before the thermo-insulating coating 4 is thoroughly cured. This has the advantage that there is good adhesion between the thermo-insulating coating 4 and the wear coating 3. In an alternative embodiment, a primer of a known type is applied to the entire surface 41 when the thermo-insulating coating 4 has fully hardened. The wear coating is distributed over the surface 41 and the process is repeated.

In a further alternative embodiment, an inner coating can be built up in the pipe 1, where the coating comprises further several layers.

The thickness of the thermo-insulating coating 4 and the wear coating 3 is determined by the amount of material that is positioned inside the pipe 1. Rotation speed and curing time are adapted to this. Thus, the thickness of the wear coating 3 can be between 0.5 mm and 50 mm. The thickness can be 10, 15, 20, 25, 30, 35, 40 and 45 mm. The thickness can also exceed 50 mm if the pipe's 1 inner diameter allows it. The thickness of the wear coating is also determined by the desired open cross-sectional area after coating. Correspondingly, the thermo-insulating coating can be between 20 mm and 50 mm thick, for example 25, 30, 35 and 45 mm thick.

Example 1

A riser 1, referred to in the petroleum industry as a riser, is coated on its inner casing surface 21 with polyurethane. The riser's outer jacket 2 can be made of metal, such as, for example, carbon steel or titanium, or of a composite material such as, for example, a fibre-reinforced plastic material as is known in the art. The casing 2 of the riser 1 is designed to be able to withstand external mechanical stresses such as impact, twisting, bending and pressure, and internal stresses in the form of overpressure.

The riser 1 is coated on its inner casing surface 21 with a wear coating 3 which is made of polyurethane. The wear coating 3 is 10 mm thick. The inner surface 31 of the wear coating 3 is heat-treated with an open flame so that the surface 31 forms a smooth, continuous surface. The wear coating 3 resists wear from the liquid flow (not shown) which is led through the riser 1, and wear from particles that are in the liquid flow.

Example 2

A riser 1 is coated on its inner casing surface 21 with a thermo-insulating coating 4. The thermo-insulating coating 4 is made of polyurethane. In an alternative embodiment, the thermo-insulating coating 4 is made of silicone. The thermo-insulating coating 4 is covered by a wear coating 3 which consists of polyurethane as described in example 1.

Example 3

A transport pipe 1 for the transport of petroleum products, such as oil and gas, consists of an outer jacket 2. The outer jacket 2 of the transport pipe 1 can be made of a metal, a thermoplastic, a thermosetting plastic or composite materials such as fibre-reinforced thermosetting plastics or fibre-reinforced thermoplastics. The jacket 2 of the transport pipe 1 is designed to be able to withstand external influences and internal mechanical stresses in the form of an overpressure or underpressure in relation to the surrounding pressure.

The jacket 2 of the transport pipe 1 is coated on its inner jacket surface 21 with a thermo-insulating coating 4. The thermo-insulating coating 4 is made of polyurethane. In an alternative embodiment, the thermo-insulating coating 4 is made of silicone. The thermo-insulating coating 4 is covered on its inner surface 41 by a wear coating 3 which consists of polyurethane as described in example 1.

Claims (15)

1. An elongated channel (1) which comprises a jacket (2) and is provided with an internal polymer coating (3) which comprises a polymer material selected from a group consisting of polyurethane and silicone, characterized in that the inner jacket surface of the elongated channel (1) (21) is provided with a primer at least in one end part (11, 12) and that the inner mantle surface (21) is primer-free in a middle part (13). 2. Channel (1) according to claim 1, where the channel's (1) inner jacket surface (31) is coated with a thermo-insulating coating (4) between the jacket (2) and the polymer coating (3). 3. Channel (1) according to claim 1, where the internal polymer coating (3) of the channel (1) is smoothed. 4. Channel (1) according to claim 1, where the channel (1) consists of a pipe. 5. Method for internally coating an elongated channel (1) with a polymer coating (3) comprising a polymer material selected from a group consisting of polyurethane and silicone, where the method comprises the steps of: a) positioning the channel (1) in a jig arranged to be able to rotate the channel (1) about its longitudinal axis (10) and the jig is further arranged to be able to correct deviations in the longitudinal direction of the channel (1); b) applying a primer to at least one end part (11, 12) of the duct (1) inner casing surface (21) and keeping the duct (1) middle part (13) free of primer; c) positioning the polymer material inside the channel (1); and d) rotate the channel (1) about its longitudinal axis (10) until the polymer material is dimensionally stable inside the channel (1). 6. Method according to claim 5, where the method further comprises the steps of: bl) supplying the channel (1) with sealing end plugs after step b); cl) evacuate air from the interior of the channel (1) after step c); and dl) equalize the pressure inside the channel (1) after step d). 7. Method according to claim 5, where the method further comprises a step e) passing an open flame along the internal surface (31) of the shape-retaining polymer material parallel to the longitudinal axis (10) of the channel (1) in order to smooth the surface (31) after the step d). 8. Method according to claim 5, where the method further comprises a step e) of passing an electric heating element along the shape-retaining polymer material's internal surface (31) parallel to the longitudinal axis (10) of the channel (1) in order to smooth the surface (31) after the step d). 9. Method according to claim 6, where the method further comprises a step e) of passing an open flame along the internal surface (31) of the dimensionally stable polymer material parallel to the longitudinal axis (10) of the channel (1) in order to smooth the surface (31) after the step dl). 10. A method according to claim 6, wherein the method further comprises a step e) of passing an electric heating element along the internal surface (31) of the dimensionally stable polymer material parallel to the longitudinal axis (10) of the channel (1) in order to smooth the surface (31) after the step dl). 11. Method according to any one of claims 9-10, wherein the method further comprises a step f) of rotating the channel (1) about its longitudinal axis (10) after step e) to further increase the firmness of the dimensionally stable polymer material so that the end plugs can be removed. 12. Method according to claim 5, where the method further comprises a step b0) of supplying the channel (1) with a thermo-insulating coating before step c). 13. Method according to claim 6, where the method further comprises a step b2) of supplying the channel (1) with a thermo-insulating coating before step c). 14. Method according to claim 5, wherein the method further comprises tempering the channel (1) to a temperature between 10 and 50 °C. 15. Method according to claim 5, wherein the method further comprises tempering the channel (1) to ambient temperature.