A Pipe

Abstract

A pipe 1 suitable for conveying a material from one opening of the pipe to another opening, the pipe having an inner surface 3 and an outer surface 4, in which at least a portion or the whole of the i

Description

This invention relates to a pipe for conveying a fluid from one place to another. Pipes are used in a huge range of industrial and commercial applications. In this application the term pipe is used to refer to an elongate hollow cylinder, typically but not exclusively having a circular cross section which is intended for use in conveying a fluid from one place to another. A pipe typically has a length many times greater than the diameter- of the order of tens or hundreds or more times greater, with lengths of pipes often being supplied in a form where smaller lengths can be cut off on site to suit the distance that fluid is to be carried by the pipe. For small diameter pipes of below 1cm the distances are typically of a few cm to a few metres. Larger diameter pipes may be used to form networks that are many kms or even hundreds of kilometres in length, connecting cities or even countries. Pipes can be used to convey any fluid that will flow, typically liquids and gases, but also small solids such as powdered material. Pipes are typically circular in crosssection as this makes them simple install as there is no “right way up” that would alter the performance of the pipe if fitted incorrectly. A fluid will enter a pipe at one opening, flow along the pipe and exit through another opening. The openings are conventionally the ends of the pipes but may be ports located part way along a pipe. The openings may be retained by suitable connectors to allow them to form a part of a fluid tight flow path from a source to an output. The choice of material of the pipe is critical to the performance of the pipe. The inner wall of the pipe must not react with the material being conveyed and the pipe must be strong enough to cope with any pressure inside the pipe and to prevent accidental damage. The wall thickness also plays an important role. Other properties include a resistance to extreme temperatures, both hot and cold. The applicants have appreciated that it is desirable to enhance the performance properties of the inside of a pipe in certain applications. A surface that is resistant to wear when transporting granular materials, or that has a low coefficient of friction reducing the chances of a blockage may be desirable. Other desirable benefits include a reduced need for cleaning allowing increased service intervals, fewer blockages etc., a reduced requirement for algal growth inhibitors which reduces the need to flush with harsh chemicals, an increased corrosion resistance giving increased service intervals, and a laminar flow at the pipe surface which creates better flow conditions for embedded sensing, reduced energy required to pump / less velocity drop per pipe length, reduced noise / vibration from pumping fluids. It is known to apply coatings to the inside of pipes to improve their properties. An example is the application of a film of low friction material such as PTFE to help the flow of fluid. There are however questions over the robustness of such coatings which may make this unsuitable for some applications. Fluoropolymer coated metals can’t be easily recycled, end up in landfill, and bits of the fluoropolymer may seep into ground water. These coatings also thermally degrade at high temperatures limiting the use of such coated pipes to carry high temperature fluids. According to the invention there is provided a pipe suitable for conveying a material from one opening of the pipe to another opening, the pipe having an inner surface and an outer surface, in which at least a portion or the whole of the inner surface of the pipe is provided with a digitally defined pattern of texture features. By digitally defined pattern of texture features we mean that the texture comprises a repeating pattern of discrete texture features whose geometry is determined by digital data stored in a memory that may is machine readable by an apparatus that applies the pattern by steering a laser beam emitted by a laser ablation device. The digitally defined pattern of texture features may comprise closed boundary concavities dimples or that comprise open ended concavities. Examples of the former are dimples, triangles, and regular and irregular polygons. Example of the later are linear or non-linear groove. They may form regular patterns of lines such as chevrons or cross hatches with each line in the pattern either continues or a linear arrangement of closed boundary concavities. A mixture of grooves and dimples may be produced. Each texture feature may have a width between 5 micrometers and lOOmicrometres with an area coverage of the pipe inner surface from 10-90%. The digitally defined pattern of surface features may be applied to the surface using laser ablation in a process known as laser surface texturing. The digitally defined pattern of surface texture features may provide the pipe with a biocidal function. The digitally defined pattern of surface texture features may provide the pipe with anti-fouling property. The digitally defined pattern of surface texture features may provide the pipe with non-stick properties by decreasing the surface energy of the pipe surface compared with an untextured equivalent surface. The digitally defined pattern of surface texture features may provide the pipe with resistance to corrosion by decreasing water contact angle compared with an untextured equivalent surface. The digitally defined pattern of surface texture features may provide the pipe with a reduced resistance to the flow of liquid through the pipe by reducing the contact area between the liquid and the pipes surface. This may be beneficial in that the improved flow resulting from the surface texture reduces energy consumption associated with pumping the liquid. The improved flow resulting from the surface texture may also help reduce noise or vibration caused by the flowing liquid. The texture may provide other benefits. For instance, where the surface texture improves mixing at the intersection between two pipes, or may result in a more laminar flow across an in-pipe sensor The textured surface may be easier to clean than the equivalent non-textured surface. The pipe may have an inner surface that comprises a metal or metal alloy. The metal pipe may comprise a seamless drawn metal tube. Alternatively, the pipe may be an extruded pipe. The pipe may comprise a metal pipe. The metal may be copper, brass or steel although this is not an exhaustive list of the metals that could be used. The pipe may be a polymer material. Examples of some common pipe materials that may be used in accordance with the invention include but are not to be limited to ABS (Acrylonitrile Butadiene Styrene), HDPE (High-Density Polyethylene), PE (polyethylene), PEX (cross-linked polyethylene) and PP (polypropylene). The pipe may be suitable for delivery of liquid fuel including but not limited to gasoline, diesel, biodiesel, ethanol, or hydrogen, or may be suitable for use for delivery of food or drink products In one specific arrangement the pipe may comprise a connecting line for use in conveying the supply of cutting fluid within a CNC machine tool. The pipe maybe suitable for use in carrying coolant for the purpose of cooling equipment or machinery such as but not limited to motors, battery modules, nuclear reactors, laser systems etc. According to a second aspect the invention comprises a method of manufacture of a pipe suitable for conveying a material from one opening of the pipe to another opening, the pipe having an inner surface and an outer surface, the method comprising: providing a stock material, processing the stock material to form an intermediate pipe defining the inner and outer surfaces, and forming a digitally defined pattern of texture features on the inner surface of the intermediate pipe using a process of laser texturing to form a pipe according to the first aspect. The step of processing the stock material may comprise extruding the material. The processing may comprise cold drawing the material. Alternatively, the intermediate pipe may be formed from strip stock by a process of seam welding. Any other conventional pipe forming process may be used to form the intermediate pipe. Preferably the intermediate pipe prior to the step of applying the texture may be relatively smooth. There will now be described by way of example only several embodiments of the present invention with reference to and as illustrated in the accompanying drawings of which: Figure 1 show an exemplary section of pipe in accordance with the present invention; Figure 2 shows a texture that is applied to the inside of the pipe of figure 1. Figure 3 is an overview of a suitable apparatus that may be used to provide the texture pattern to an internal surface of a pipe; Figure 4 is a detailed block diagram showing the functional features of the exemplary treatment head of the apparatus, Figure 5 is a flowchart of the steps of a method of use of the apparatus to apply the texture pattern; Figure 6 is representation of a digital pattern that can be applied to a stainless steel surface of a pipe to provide an antibacterial or anti-microbial environment with the dimensions of the induvial features marked in nanometres; Figure 7 shows a surface having the pattern of Figure 6 applied in (a) in plan and (b) as a 3D contour plot; Figure 8 is an illustration of a set of ground and textured surfaces in which the texture comprises circular outline concave dimples arranged in a regular pattern that have different diameters and the same pitch between adjacent dimples that enhance the laminar flow of fluid over the surface compared with a polished surface; Figure 9 is a set of images showing the contact angle results for polished and laser irradiated 316L stainless steel pipe surface samples to provide different levels of surface wettability; and Figure 10 is a set of images similar to those of Figure 9 showing the contact angle results for a textured pipe surface with different hatch. Figure 1 and Figure show a pipe 1 that is suitable for conveying a material from one opening of the pipe to another opening. The pipe 1 shown has a constant cylindrical cross section although the invention is not limited to cylindrical pipes. The pipe therefore can be an elongate hollow cylinder. As shown the pipe is formed from a single material to form a solid wall 2 defining an inner surface 3 and an outer surface 4 by a process of extrusion such that the wall comprises a homogeneous matrix of thermoplastic material. The pipe in this example is free from any coating on the inner wall and in the context of this description is called an intermediate pipe. Rather than a coating, the inner surface 3 of the intermediate pipe is provided with a digitally defined pattern of texture features which are applied by laser ablation. Figure 3 shows an apparatus for use in texturing the inside of an intermediate pipe to form a pipe in accordance with the first aspect of the present invention. The apparatus has three main functional parts. The first is a treatment head that is located inside of a pipe in use as shown in Figure 3. This connects to a laser which is located outside of the pipe, and to a controller 30 that is also located outside of the pipe. The controller is shown separate from the laser but the two can be combined to form one device. An alternative is shown in Figure 4 where the fibre is omitted and the light from the laser passes through free space to the input port of the texture head whilst steered by a network of mirrors 41,42. This may be suitable for the texturing of pipes in highly controlled environment such as cell on a factory production line. The use of fibre is preferred however as it eliminates the need to precisely control the path of the light. The treatment head is connected to the laser through a fibre, which in this example is a hollow core optical fibre. The laser is an ultrashort pulse laser that generates pulses below 500 nanoseconds in duration. The controller is connected to the laser and sends timing signals that control when the laser emits light and when it does not, thereby controlling the timing and duration of the pulses emitted from the laser. These light pulses are coupled into the fibre and carried to the texture head. The treatment head is shown in more detail in Figure 4. The treatment head 10 comprises a set of optical elements that can be moved relative to the base. As shown, there is a single optical element 11 comprising a plane mirror. Multiple mirrors may be provided in addition to focusing lenses, some of which may be fixed in position. The mirror 11 is positioned in the path of light exiting an input port 12 that receives an end 13 of a fibre. The light path is indicated by a dashed line in Figure 3. The mirror 11 is fixed to a base through an actuator 14 such as an electric motor or pair of motors so that it can be tilted about two or three orthogonal axes to steer the beam of light. The base is located within a protective housing 15 that has an optically transparent window 16 through which light reflected from the mirror can pass to impinge on the inner surface of the tube. The housing 15 in this example comprises a cylindrical can which has an outer diameter that is smaller than the bore of the pipe. The actuator 14 is controlled by a small microcontroller 16 located within the housing 15 of the texture head. This in turn responds to control signals received at an input port 16a from the external controller 20 to move the mirror 11 and hence to steer the light beam to different positions on the inner wall of the tube 100. This is done in synchronization with the emission of the pulses. This causes portions of the inner surface of the tube 100 to be vaporized by the light pulses to leave a pattern of concavities on the inner surface. The input signals are supplied by an electrical cable (not shown) that connects the texture head 10 to the remotely located controller. By rotating the mirror 11 the treatment head in Figure 4 can apply a pattern of concavities over the whole circumference of the pipe 100 covering a defined length. To apply the pattern to the whole of the inner surface the treatment head must be moved along the pipe so that a pattern can be applied to an adjacent section, and this repeated for the whole length of the pipe. In some arrangements the movement of the optical elements 11 may be insufficient to texture an entire circumferential patch of the inner surface of the pipe. In this case a displacement means may be provided that include a further actuator may be provided to rotate the entire treatment head around the axis of the pipe each time a patch has been textured. For instance, if the patch can be applied to 180 degrees of the inner circumference, this additional actuator will be configured to rotate the treatment head through 180 degrees and two patches will be applied. If it can only apply over 90 degrees, the treatment head will be rotated four times with an angle of 90 degrees each time. In an alternative, the base carrying the optical elements may rotate within the housing of the treatment head around an axis coincident with the axis of the pipe. The movement of the treatment head relative to the pipe in this first embodiment is achieved by providing a displacement means in the form of a set of wheels 17 that are fixed to the housing and locate the treatment head 10 centrally in the pipe. The wheels can be rotated by an electric motor 18 that receives control signals from the microcontroller. This allows the treatment head 10 to be held stationary as texture is applied and moved along the pipe between the application of patches. Again, the microcontroller may respond to external control signals received to control movement of the texture head within the pipe. Figure 5 is a flow chart of the steps that can be performed by the apparatus shown in Figures 1 to 4 to apply a texture to the entire inner wall of an intermediate pipe. Prior to performing the method, the laser is connected to an end of a fibre and the other end connected to the treatment head. In a first step 200 the treatment head is placed into the bore of the pipe. The treatment head is the centralized relative to the pipe axis if required. The treatment head can be initially fed into the bore by hand as it is very mobile and restrained only by the flexible fibre and the electrical cable that connects it to the controller. In a second step 210 the controller sends timing instructions to the laser to cause the laser to generate a sequence of ultrashort feeding laser pulses and feeding the pulses into one end of an optical fibre network that is connected at an opposite end to the input port of the treatment head. The timing instructions may be set by a computer data file stored in a memory accessible to the controller. In a third step 220, the controller sends signals to the microcontroller of the treatment head to cause the actuator means of the treatment head to move the optical element or elements in synchronization with the pulses to produce a texture pattern on a region of the inner wall using a process of laser surface texturing. This movement steers the laser pulses over a region of the inner surface of the tube to apply a pattern of concavities. This step is performed in parallel with the first step. Once the whole of a region has been textured in this way a further step 230 is performed in which the treatment head is moved relative to the inner surface of the pipe. This movement is again controlled by the controller. Where the treatment head includes an actuator to move itself along the pipe, as shown in Figure 3, these signals are sent to the microcontroller of the texture head. Where the propulsion means is located away from the texture head, as shown in Figure 4, to move the pipe these signals are sent to that remote propulsion means. When the propulsion means is moving the laser is turned off so that it is not outputting any pulses. Once the relative position of the texture head and pipe have reached their new position the method steps 200 to 220 are repeated. In this way adjacent regions are textured to form a complete stitched pattern that may be continuous over the whole of the inner surface of the pipe. The assemblies described above can be used to generate a range of interior textures. One assembly may be used to provide different textures by running appropriate commands on the controller, or the controller may be hardcoded to produce a single texture pattern. Example 1 - Pipe with Antimicrobial / anti-biofouling properties In this example, a digital texture pattern is applied having the properties listed in table 1. The pattern is produced using laser ablation with radiation in a wavelength of around 1060nm and very short pulse durations in the femtosecond range. The pulses are generated continuously, and they are scanned over the surface to form the required concavities. Figure 6 details the size of the features present in a minimum unit of an exemplary self-tessellating pattern and Figure 7 shows the pattern applied to a surface. This pattern has been shown to give the inner surface of a pipe antimicrobial properties and help to keep the surface clean. The pipe inner surface has full area coverage in this parameter range. In a modification it is possible to provide for uneven / non uniform pattern lengths with the same parameters. Wavelength 1,020-1,090 nm Pulse duration 200-2000 fs Frequency 100-2,000 kHz Spot size 20-70 pm Speed 0.5-4 m / s Pulse energy Fluence 0.1-5 J / cm2 Passes 1-30 Hatch pitch Table 1 Example 2 - Pipe that encourages Laminar flow, reduced noise / vibration In this example, a regular repeating series of pits, parallel lines or chevrons are aligned to the direction of fluid flow at 20-200pm pitch, depth 10-100pm. As with the second example a beam size of 20-70pm is used. Also, as with the second example the laser parameters are chosen for low thermal input <200ns pulse duration, pulse energy > material ablation threshold but <5x ablation threshold. Figure 8 shows seven different patterns that may be created using circular concave dimples of fixed size arranged in a regular pattern. Example3- Pipe with Anti-icing, hydrophobic, corrosion resistant and self-cleaning properties In this example, a digital texture pattern is applied that comprises a series of parallel lines or cross hatch at 20-200pm pitch, depth 10-100pm. The lines are formed by laser ablation using a beam size of 20-70pm. The laser parameters are chosen for low thermal input <200ns pulse duration, pulse energy > material ablation threshold but <5x ablation threshold. Figures 9 and 10 show how the pattern alters the shape of a droplet of water on the surface of a 316L stainless steel sample of pipe walling demonstrating that an improved wettability can be achieved on the inner surface of a pipe. The skilled person will understand that the examples given are not to be considered limiting to the scope of protection which is defined by the claims. Various laser powers and pulse durations may be used as required to modify the surface with desired features. The features themselves as indicated in the three examples may be arranged in a pattern and have shapes and sizes- in particular depths and widths- that are chosen according to the desired properties of the pipe surface.

Claims

1. A pipe suitable for conveying a material from one opening of the pipe to another opening, the pipe having an inner surface and an outer surface,in which at least a portion or the whole of the inner surface of the pipe is provided with a digitally defined pattern of texture features.

2. A pipe according to claim 1 in which the texture features comprise concavities in the form of dimples or that comprise open ended concavities.

3. A pipe according to claim 1 or claim 2 in which each texture feature has a width between 5 micrometers and lOOmicrometres with an area coverage of the pipe inner surface from 10-90%.

4. A pipe according to any preceding claim in which the digitally defined pattern of surface features is applied to the surface using laser ablation in a process known as laser surface texturing.

5. A pipe according to any preceding claim in which the pattern provides the surface of the pipe with one or more of the following enhanced properties or function: a biocidal function, an anti-fouling property, non-stick properties by decreasing the surface energy of the pipe surface compared with an untextured equivalent surface, resistance to corrosion by decreasing water contact angle compared with an untextured equivalent surface, and a reduced resistance to the flow of liquid through the pipe by reducing the contact area between the liquid and the pipes surface.

6. A pipe according to any preceding claim in which the inner surface comprises a metal or metal alloy.

7. A pipe according to claim 6 comprising a seamless drawn metal tube.

8. A pipe according to any one of claims 1 to 5 comprising an extrusion.

9. A pipe according to claim 8 comprising a polymer material.

10. A pipe according to any preceding claim suitable for delivery of liquid fuel including but not limited to gasoline, diesel, biodiesel, ethanol, or hydrogen, or suitable for use for delivery of food or drink products, or suitable for use in carrying coolant for the purpose of cooling equipment or machinery such as but not limited to motors, battery modules, nuclear reactors, laser systems etc.

11. A method of manufacture of a pipe suitable for conveying a material from one opening of the pipe to another opening, the pipe having an inner surface and an outer surface, the method comprising: providing a stock material,processing the stock material to form an intermediate pipe defining the inner and outer surfaces, andforming a digitally defined pattern of texture features on the inner surface of the intermediate pipe using a process of laser texturing to form a pipe according to the first aspect.

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