Fluid inspection apparatus

Abstract

A fluid inspection apparatus 100 configured to define an inspection section of a fluid flow passage 12 of a system 10, comprises a body element 110 having a wall which defines the inspection section,

Description

The present disclosure relates to a fluid inspection apparatus. In particular the disclosure is concerned with a fluid inspection apparatus configured to define an inspection section of a fluid flow passage of a system. Background Many systems incorporate a fluid as part of their operation. For example, water boiler heating circuits, air conditioning units and circuits, underfloor heating systems, hydraulic actuators, water pumps and liquid fuel systems. A common requirement is that the fluid remains free of impurities, for example debris which becomes part of the fluid flow because of corrosion or equipment in the flow shedding parts of the material they are made from. A known way to inspect the fluid is to bleed off a portion of the fluid to visually inspect it. However, this may provide the user with personal safety and material disposal issues (for example if the fluid is hazardous). Filters may also be provided in flow systems, but these only indicate what material has been removed from the flow, not what may remain in it. Both of these methods rely on a relatively high concentration of debris to be present before the presence of the impurity is apparent from a visual inspection. These methods also require a level of technical expertise and confidence that a user may not have. Hence an apparatus that enables a user to get an indication of the quality of the fluid over a range of impurity concentrations while remaining isolated from the fluid, is highly desirable. Summary According to the present disclosure there is provided an apparatus and system as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows. Accordingly there may be provided a fluid inspection apparatus (100) configured to define an inspection section (102) of a fluid flow passage (12) of a system (10). The fluid inspection apparatus (100) may comprise a body element (110) having a wall (112) which defines the inspection section (102), a flow inlet (114) to the inspection section (102) and a flow outlet (116) from the inspection section (102); the inspection section (102) defining an unobstructed flow path (120) between the flow inlet (114) and the flow outlet (116). The fluid inspection apparatus (100) may further comprise the fluid inspection apparatus (100) further comprises an impurity indicator (200) configured to indicate the presence of an impurity in fluid flowing through the flow path (120). The inspection section (102) may define a central flow axis (122) which extends along the extent of the body element (110). The body element (110) may define a first end face (130) spaced apart from a second end face (132) along the extent of the body element (110). The flow inlet (114) may be provided on the first end face (130). The flow outlet (116) may be provided on the second end face (132). The inspection section (102) may extend along the extent of the body element (110). The body element (110) may further comprise a first side (134) and a second side (136), each of the first side (134) and the second side (136) extending from the first end face (130) to the second end face (132), the first side (134) being opposite the second side (136) across the central flow axis (122). The impurity indicator (200) may be located in the first side (134). The second side (136) may define a viewing region (138) to inspect a region of the first side (134) in the vicinity of the impurity indicator (200). The second side (136) of the body element (110) may comprise a transparent portion (180). At least a part of the remainder of the body element (110) maybe opaque or translucent. The body element (110) may be transparent. The first side (134) may define a first flat outer surface (144) and the second side (136) may define a second flat outer surface (146). The body element (110) may be cuboid such that the first flat outer surface (144) is parallel to the second flat outer surface (146). The body element (110) may be formed from a material chosen from a list comprising polyurethane resin, epoxy resin, plastic, polymer, graphene, glass, acrylic, amorphous thermoplastic polymer, polyphthalamide and silicone. The body element (110) material may comprise a thermochromic pigment such that the body element (110) is operable to change colour in response to the temperature of the fluid in the inspection section (102) being above a predetermined value. The body element (110) material may comprise a phosphorescent pigment such that the body element (110) is operable to emit light in response to absorbing light from a light source. The body element (110) may further comprise a light source (300) mounted on and / or embedded in the body element (110), and the fluid inspection apparatus (100) further comprises a power source (400) to operate the light source (300). The power source (400) may comprise a thermoelectric generator (402) operable to generate electricity using heat energy extracted from the fluid passing through the inspection section (102). The impurity indicator (200) may be configured to indicate the presence of a dissolved mineral in the fluid. The impurity indicator (200) may be configured to indicate the presence of particulates in the fluid. The impurity indicator (200) may be a light source (300). The impurity indicator (200) may be a magnet (202). The magnet (202) may be a permanent magnet chosen from a list comprising a neodymium iron boron (NdFeB) magnet, a samarium cobalt (SmCo) magnet, an alnico magnet, a ceramic magnet and a ferrite magnet. The magnet (202) may be an electromagnet. The body element (110) may define a cavity (140) along its length L which extends at least part of the distance between the flow inlet (114) and the flow outlet (116), and the cavity (140) being offset from and fluidly isolated from the flow path (120), the impurity indicator (200) being located in the cavity (140) such that it is fluidly isolated from the flow path (120). The cavity (140) may be provided as a recess (142) on the first flat outer surface (144). The cavity (140) may be provided beneath and covered by material which defines the first flat outer surface (144). The inspection section (102) may have a constant diameter D along its length between the flow inlet (114) and the flow outlet (116). The inspection section (102) may comprise a transparent sheath (160) which extends along at least part of the length L of the inspection section (102), the sheath (160) defining the inspection section (102) flow path (120) and the sheath (160) being bounded by the body element (110), the sheath (160) comprising a different material to the body element (110). The surface roughness of the material may define the flow path (120) of the inspection section (102) has a Ra value of no more than 0.4 micrometres. The flow inlet (114) and / or the flow outlet (116) may comprise a fluid coupling element (170) for fluidly coupling the body element (110) to the fluid flow passage (12) of the system (10). There may also be provided a system (10) comprising the fluid flow passage (12) which is, at least in part, defined by the fluid inspection apparatus (100) according to the present disclosure. The second side (136) of the body element (110) may be positioned between a user viewing position A and the first side (134) of the body element (110). The system (10) may form at least part of: a boiler heating circuit, a heat pump flow and return circuit, an electric boiler heating circuit, a cold water mains supply, a hot water outlet, an air conditioning unit, an air conditioning circuit, an underfloor heating system, an oil filter, a water pump circuit, and / or a fuel system. Hence there is provided an apparatus that enables a user to get an indication of the quality of a fluid in a system over a range of impurity concentrations while remaining isolated from the fluid. Brief Description of the Drawings Examples of the present disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 shows an example system incorporating a fluid inspection apparatus according to the present disclosure; Figure 2 shows a side view of a fluid inspection apparatus according to the present disclosure; Figure 3 shows a perspective view of an example of the fluid inspection according to the present disclosure; Figures 4, 5 show side views of a further example of the fluid inspection apparatus according to the present disclosure; Figure 6 shows a perspective view of the further example of the fluid inspection apparatus according to the present disclosure, as shown in figures 4, 5; Figure 7 shows a plan view of the further example of the fluid inspection apparatus according to the present disclosure, as shown in figures 4, 5, 6; Figure 8 shows a plan view of an additional example of the fluid inspection apparatus according to the present disclosure; Figure 9 shows a plan view of the example of the fluid inspection apparatus as shown in figure 3; Figures 10, 11 illustrate the operation of an impurity indicator of the fluid inspection apparatus of the present disclosure; and Figures 12, 13 illustrate different side views of another example of the fluid inspection apparatus of the present disclosure. Detailed Description The present disclosure relates to a fluid inspection apparatus configured to define an inspection section of a fluid flow passage. The present disclosure also relates to a system comprising a fluid flow passage which is, at least in part, defined by the fluid inspection apparatus of the present disclosure. By way of non-limiting example, shown in figure 1 is a diagrammatic representation of a system 10 according to the present disclosure. The system 10 comprises a fluid flow passage 12 configured for the flow of a fluid therethrough. As shown in figure 1, the system 10 may comprise a first fluid zone 20 and a second fluid zone 30, the first fluid zone 20 being in fluid communication with the second fluid zone 30 via the fluid flow passage 12, to allow fluid to flow therethrough as indicated by arrows X. The system 10 may form at least part of: a boiler heating circuit, a heat pump flow and return circuit, an electric boiler heating circuit, a cold water mains supply, a hot water outlet, an air conditioning unit, an air conditioning system, and air conditioning circuit, an underfloor heating system, an oil filter for a land, sea or air vehicle, or a water pump circuit, a fuel system for a land, sea or air vehicle. The system 10 may form a part of any flow passage with a fluid passing therethrough. By way of non-limiting example, the first fluid zone 20 may be a fluid reservoir and the second fluid zone 30 may be an apparatus which is fed fluid from the fluid reservoir. Alternatively, the first fluid zone 20 and the second fluid zone 30 may be different parts of the same apparatus, with the fluid flow passage 12 providing fluid communication therebetween. In some examples, there may be provided a further flow passage 40 providing flow communication between the second fluid zone 30 and the first fluid zone 20 to allow fluid to flow therethrough as indicated by arrows Z. As also shown in figure 1, there may be provided a fluid inspection apparatus 100 configured to define an inspection section 102 of the fluid flow passage 12 of the system 10. In a further example, not shown, there may be provided a fluid inspection apparatus 100 according to the present disclosure configured to define an inspection section 102 of the further flow passage 40 of the system 10. The fluid inspection apparatus 100 according to the present disclosure may be configured to operate with a fluid which is transparent or at least partially transparent. In an example in which the system 10, as shown in figure 1, forms at least part of a boiler heating circuit comprising a boiler and heating units (for example radiators), the boiler may define the first fluid zone 20 and the heating units may define the second fluid zone 30. Hence in such a system there may be provided a fluid inspection apparatus 100 in the flow path from the boiler to the heating units. Alternatively or additionally there may be provided a fluid inspection apparatus 100 in the return path from the boiler to the heating units. As shown in figures 2 to 11, the fluid inspection apparatus 100 may comprise a body element 110 having a wall 112 which defines the inspection section 102. The wall 112 may also define a flow inlet 114 to the inspection section 102 and a flow outlet 116 from the inspection section 102. That is to say, the inspection section 102 is a flow passage or flow duct. The inspection section 102 may define an unobstructed flow path 120 between the flow inlet 114 and the flow outlet 116. That is to say, there is nothing provided in the flow path 120 between the flow inlet 114 and the flow outlet 116. As illustrated in figures 1,2, the flow inlet 114 and / or the flow outlet 116 may comprise a fluid coupling element 170 for fluidly coupling the body element 110 to the fluid flow passage 12 of the system 10. That is to say, a fluid coupling element 170 for fluidly coupling the body element 110 to the fluid flow passage 12 of the system 10 may extend from each of the flow inlet 114 and / or the flow outlet 116. The fluid inspection apparatus 100 may further comprise an impurity indicator 200. The impurity indicator 200 is configured to indicate the presence of an impurity in fluid flowing through the flow path 120. The impurity indicator 200 may be configured to indicate the presence of one or more impurities in fluid flowing through the flow path 120. In the present disclosure the term “impurity” is intended to mean a material which is not part of the desired or required composition of the fluid and that may impair the performance of the system 10 which it flows through. The impurity detector 200 may be a passive device. That is to say, the impurity detector may have no moving parts. The impurity detector 200 may be chemically inert. The impurity detector 200 may be a solid state device. In one example, the impurity indicator 200 is configured to indicate the presence of a dissolved mineral in the fluid. For example, in a system in which the fluid is water, the impurity indicator 200 may be configured to indicate the presence of a calcium carbonate dissolved in the water. In another example the impurity indicator 200 is configured to indicate the presence of particulates in the fluid. For example, the impurity indicator 200 may be configured to indicate the presence of metal particles in the water. The impurity indicator 200 may be configured to indicate the presence of magnetic particles in the water. The impurity indicator 200 may be provided as a magnet 202, which is effective for the attraction of dissolved calcium carbonate and magnetic particles / debris. In a further example (and as described below) the impurity indicator 200 may be provided as a light source 300. In examples in which the impurity indicator 200 is provided as a magnet 202, the magnet 202 may be a permanent magnet 202 chosen from a list comprising a neodymium iron boron (NdFeB) magnet 202, a samarium cobalt (SmCo) magnet 202, an alnico magnet 202, a ceramic magnet 202 and a ferrite magnet 202. The magnet 202 may be an electromagnet. In an example of the present disclosure, as shown in figures 3 to 9, the body element 110 defines a cavity 140 (for example an elongate cavity 140) along a length L of the body element 110, wherein the cavity 140 extends at least part of the distance between the flow inlet 114 and the flow outlet 116. The cavity 140 may extend along the full length L of the body element 110 between the flow inlet 114 and the flow outlet 116. The inspection section 102 (i.e., the flow path 120) may have a constant diameter D along its length between the flow inlet 114 and the flow outlet 116. The cavity 140 is offset from, and fluidly isolated from, the flow path 120. Hence, in use, the cavity 140 is fluidly isolated from fluid passing through the flow path 120. The impurity detector 200 may be configured to fit snugly within the cavity 140. Hence the impurity detector 200 may be provided as a flat elongate cuboid to match the dimensions of the cavity 140. The impurity detector 200 (e.g., magnet 202), when located in the cavity 140, is fluidly isolated from the flow path 120 (and hence, in use, is fluidly isolated from fluid passing through the flow path 120). The impurity detector 200 (e.g., magnet 202) may extend part of the distance along the cavity 140. The impurity detector 200 (e.g., magnet 202) may extend along the full length L of the body element 110 between the flow inlet 114 and the flow outlet 116. As illustrated in figures 2, 4, 5, 10, 11, the inspection section 102 may define a central flow axis 122 which extends along the extent of the body element 110. Hence the flow path 120 may be centred on, or at least encompass, the central flow axis 122. The body element 110 may define a first end face 130 spaced apart from a second end face 132 along the extent of the body element 110. The flow inlet 114 may be provided on the first end face 130 and the flow outlet 116 may be provided on the second end face 132 such that the inspection section 102 extends along the extent of the body element 110. The body element 110 may further comprise a first side 134 and a second side 136, each of the first side 134 and the second side 136 extending from the first end face 130 to the second end face 132, the first side 134 being opposite the second side 136 across the central flow axis 122. The impurity indicator 200 may be located in the first side 134. The impurity detector 200 may be flush with the material of the first side 134 when located within the cavity 140. The second side 136 may define a viewing region 138 to inspect a region of the first side 134 in the vicinity of the impurity indicator 200. In one example, as shown in figure 8, the second side 136 of the body element 110 comprises a transparent portion 180 and at least a part of the remainder of the body element 110 is opaque. That is to say, the body element 110 may be opaque except for the transparent portion 180. In another example, not shown, the second side 136 of the body element 110 comprises a transparent portion 180 and at least a part of the remainder of the body element 110 is translucent. That is to say, the body element 110 may be translucent except for the transparent portion 180. In both examples the transparent portion 180 may extend from an outer surface of the body element 110 (e.g., the second side 136) to the inner surface of the flow path 120. That is to say, the transparent portion 180 may define a window through which a user can see the region of the flow path 120 on the other side of the body element 110 which is adjacent to the impurity indicator 200. In another example (as illustrated in the figures) the body element 110 may be transparent. That is to say, the body element 110 may be made of a clear or substantially clear material through which a user can see the region of the flow path 120 adjacent to the impurity indicator 200. As illustrated in figures 7, 8 the inspection section 102 may comprise a transparent sheath 160 which extends along at least part of the length L of the inspection section 102. That is, the sheath 160 defines the inspection section 102 of the flow path 120 and the sheath 160 is bounded by the body element 110. The sheath 160 may be provided as a tube section. The sheath 160 may be provided with a constant outer diameter and / or a constant inner diameter along its length. The sheath 160 may comprise a different material to the body element 110. By way of non limiting example, the sheath 160 may be made of acrylic. The sheath 160 may have a greater thermal tolerance than the material of the body element 110 material. The sheath 160 may be configured to thermally insulate the material of the body element 110 from the fluid flowing through the flow path 120. The surface finish ofthe material which defines the flow path 120 of the inspection section 102 may be machined and / or polished to be smooth. The finish is configured such that debris and / or pollutants do not adhere to the surface ofthe flow path 120. For example, the surface roughness ofthe material which defines the flow path 120 ofthe inspection section 102 may have an Ra value of no more than 0.4 micrometres. In all examples, and as shown in figure 1, when the fluid inspection apparatus 100 is fitted to the system 10, the second side 136 ofthe body element 110 may be positioned between a user viewing position A and the first side 134 ofthe body element 110. Hence the system is configured so a user may look through the viewing region 138 (e.g., the second side 136) to inspect a region of the first side 134 in the vicinity of the impurity indicator 200. The fluid for inspection with the inspection apparatus 100 according to the present disclosure, when pure / clean should be transparent or at least partially transparent so that a viewer can see through the fluid across the flow path 120. The first side 134 may define a first flat outer surface 144 and the second side 136 may define a second flat outer surface 146. The first flat outer surface 144 and / or the second flat outer surface 146 may be machined and / or polished. That is to say, the first flat outer surface 144 and / or the second flat outer surface 146 may be clear of surface irregularities such that they are optically clear. The body element 110 may have any suitable shape provided a user can see through from one side to another side to see a region of the first side 134 in the vicinity of the impurity indicator 200. The body element 110 may be a polyhedron or substantially polyhedron, wherein the first flat outer surface 144 may be parallel to the second flat outer surface 146. As illustrated in the figures the body element 110 may be cuboid or substantially cuboid. Hence the first flat outer surface 144 may be parallel to the second flat outer surface 146. In other examples the body element 110 may be cylindrical. In the examples of figures 4 to 8 the cavity 140 is provided as a recess 142 on the first flat outer surface 144. In such an example the impurity indicator 200 is fixed in place in the recess 142. The impurity indicator 200 may be fixed in place by any appropriate means. The impurity indicator 200 may be fixed in place with a fixing member (e.g. screw, bolt, clip). The impurity indicator 200 may be fixed in place with an adhesive. In the examples of figures 4, 5 metal studs 60 are provided embedded in the material of the body element 110 to which the impurity indicator 200 is fixed / engaged. In examples in which the impurity indicator 200 is a magnet 202, the impurity indicator 200 is held in place by magnetic attraction between the metal studs 60 and the magnet 202. In the example of figure 9 the cavity 140 is provided beneath and covered by material which defines the first flat outer surface 144. Hence the impurity indicator 200 is located in the cavity 140, effectively embedded in the material of the body element 110. The body element 110 may be formed from a material chosen from a list comprising polyurethane resin, epoxy resin, plastic, polymer, graphene, glass, acrylic, amorphous thermoplastic polymer, polyphthalamide and silicone. The material of the body element 110 may extend from the first end face 130 to the second end face 132. The body element 110 material may comprise a thermochromic pigment such that the body element 110 is operable to change colour in response to the temperature of the fluid in the inspection section 102 being above a predetermined value. The body element 110 material may comprise a phosphorescent pigment such that the body element 110 is operable to emit light (i.e., glow) in response to absorbing light from a light source. In an example illustrated in figure 6, the body element 110 may further comprise a light source 300 mounted on and / or embedded in the body element 110. The body element 110 may further comprise a power source 400 to operate the light source 300. That is to say, the fluid inspection apparatus 100 may further comprise a light source 300 mounted on and / or embedded in the body element 110. The fluid inspection apparatus 100 may further comprise a power source 400 to operate the light source 300. The light source 300 may be provided in / on the body element 110 in addition to a magnet 202 or other impurity indicator 200. That is to say the fluid inspection apparatus may comprise a magnet 202 and a light source 300. In a further example, as shown in figures 12, 13, the impurity indicator 200 may be provided as a light source 300. The light source 300 may be provided in the cavity 142, The light source may comprise a number of light emitting elements 310 (for example Light Emitting Diodes LEDs). The light source 300 may be configured to emit a specific wavelength (or range of wavelengths) of light which illuminate a target impurity. For example the light source 300 may be configured to emit ultra-violet light to illuminate target impurities (for example particulates of a particular colour or composition, or chemicals) in the fluid. The power source 400 may be mounted on and / or embedded in the body element 110. In one example the power source 400 may be a battery. In another example the power source 400 may comprise a thermoelectric generator 402 operable to generate electricity using heat energy. Depending on where the thermoelectric generator 402 is mounted, the heat energy may be extracted from fluid passing through the inspection section 102 and / or absorbed from the environment around the fluid inspection apparatus 100. Figures 10, 11 illustrate the operation of an impurity indicator 200 of the fluid inspection apparatus 100 of the present disclosure. Figures 10, 11 show a side view of an example of the fluid inspection apparatus 100 of the present disclosure, as viewed through the viewing region 138. That is to say, figures 10,11 are a view of the second side 134 through which a user would look to inspect a region of the first side 134 in the vicinity of the impurity indicator 200 (as shown in figure 1). The flow path 120 and the impurity indicator 200 are shown in broken lines. Initially, as shown in figure 10, the surface of the flow path 120 of the inspection section 102 is clean. However, as material (e.g., dissolved material and / or particulates) in the system 10 fluid passes over the material of the body element 110 which covers the impurity indicator 200, a proportion of the impurity is attracted towards the impurity indicator 200. That is to say, the impurity indicator 200 is configured to attract pollutants in the fluid, and so the pollutants adhere to the surface ofthe flow path 120 of the inspection section 102 adjacent to the impurity indicator 200. For example, if the impurity indicator 200 is a magnet 202 and the fluid is water, some of the material dissolved in the water (for example calcium carbonate) is deposited on the surface ofthe flow path 120 adjacent to the impurity indicator 200 (as illustrated by the strip of deposit 80 in figure 11). In another example, if the impurity indicator 200 is a magnet 202 and there are magnetic particles in the fluid, some ofthe particles are deposited on the surface ofthe flow path 120 adjacent to the impurity indicator 200 (as illustrated by the strip ofthe deposit 80 in figure 11). Hence when, as illustrated in figure 1, a user looks through the viewing region 138 (e.g., the second side 136) to inspect a region ofthe first side 134 in the vicinity ofthe impurity indicator 200, the presence or absence ofthe strip ofthe deposit 80 will inform a user as to whether there are pollutants / impurities in the fluid, even if the fluid looks clean. With this information a user can decide what action to take (for example determine the source ofthe pollutant / impurity and remove it). The surface ofthe flow path 120 may be cleaned to remove the strip ofthe deposit 80. Additionally, a user can see by looking at the fluid inspection apparatus 100 whether the fluid is “clean” or heavily polluted (for example if the fluid which should be transparent is translucent or opaque). In examples where present, the light source 300 may further assist a user in detecting the present of a target impurity, for example by reflecting light off the target impurity and / or causing the impurity to glow, fluoresce or otherwise be highlighted in the fluid flow. Hence there is provided an apparatus that enables a user to get an indication of the quality of a fluid in a system over a range of impurity concentrations while remaining isolated from, and not having to interact with, the fluid. The apparatus allows a user to visually inspect the fluid in a system without the need to extract a fluid sample, saving the user personal safety and disposal issues (for example if the fluid is hazardous). The fluid inspection apparatus ofthe present disclosure allows a user to view the fluid as it flows through a system. Hence the presence of a large amount of pollutant will be self evident for example because it will be easy to identify that the fluid looks different to how it looks in a clean and pure state. The impurity indicator enables a user to identify material which may otherwise be undetectable in the fluid flow by collecting a sample of the material for a user to observe. The fluid inspection apparatus ofthe present disclosure requires no technical expertise from the user, since all the user needs to do is view the fluid and / or region adjacent the impurity indicator through the transparent material ofthe fluid inspection apparatus. Illumination of the body element 110 of the fluid inspection apparatus 100 (for example using the light source 300) may assist with examining the fluid composition and / or the region adjacent the impurity indicator 200. In examples in which the body element 110 comprises a phosphorescent pigment, this may further help to illuminate the fluid and / or the region adjacent the impurity indicator 200. It may also serve to guide and remind a user to inspect the fluid. Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. C LA I MS 1 A fluid inspection apparatus (100) configured to define an inspection section (102) of a fluid flow passage (12) of a system (10), wherein the fluid inspection apparatus (100) comprises: a body element (110) having a wall (112) which defines the inspection section (102), a flow inlet (114) to the inspection section (102) and a flow outlet (116) from the inspection section (102); the inspection section (102) defining an unobstructed flow path (120) between the flow inlet (114) and the flow outlet (116); and the fluid inspection apparatus (100) further comprises an impurity indicator (200) configured to indicate the presence of an impurity in fluid flowing through the flow path (120). 2 A fluid inspection apparatus (100) as claimed in claim 1 wherein: the inspection section (102) defines a central flow axis (122) which extends along the extent of the body element (110); the body element (110) defines a first end face (130) spaced apart from a second end face (132) along the extent of the body element (110); the flow inlet (114) is provided on the first end face (130) and the flow outlet (116) is provided on the second end face (132) such that the inspection section (102) extends along the extent of the body element (110); and the body element (110) further comprises a first side (134) and a second side (136), each of the first side (134) and the second side (136) extending from the first end face (130) to the second end face (132), the first side (134) being opposite the second side (136) across the central flow axis (122); the impurity indicator (200) is located in the first side (134); and the second side (136) defines a viewing region (138) to inspect a region of the first side (134) in the vicinity of the impurity indicator (200). 3 A fluid inspection apparatus (100) as claimed in claim 2 wherein the second side (136) of the body element (110) comprises a transparent portion (180). 4 A fluid inspection apparatus (100) as claimed in claim 3 wherein at least a part of the remainder of the body element (110) is opaque or translucent. 5 A fluid inspection apparatus (100) as claimed in claim 1 or claim 2 wherein the body element (110) is transparent. 6 A fluid inspection apparatus (100) as claimed in any one of claims 2 to 5 wherein the first side (134) defines a first flat outer surface (144) and the second side (136) defines a second flat outer surface (146). 7 A fluid inspection apparatus (100) as claimed in claim 6 wherein the body element (110) is cuboid such that the first flat outer surface (144) is parallel to the second flat outer surface (146). 8 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the body element (110) is formed from a material chosen from a list comprising polyurethane resin, epoxy resin, plastic, polymer, graphene, glass, acrylic, amorphous thermoplastic polymer, polyphthalamide and silicone. 9 A fluid inspection apparatus (100) as claimed in claim 8 wherein the body element (110) material comprises a thermochromic pigment such that the body element (110) is operable to change colour in response to the temperature of the fluid in the inspection section (102) being above a predetermined value. 10 A fluid inspection apparatus (100) as claimed in claim 8 or claim 9 wherein the body element (110) material comprises a phosphorescent pigment such that the body element (110) is operable to emit light in response to absorbing light from a light source. 11 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the body element (110) further comprises a light source (300) mounted on and / or embedded in the body element (110), and the fluid inspection apparatus (100) further comprises a power source (400) to operate the light source (300). 12 A fluid inspection apparatus (100) as claimed in claim 11 wherein the power source (400) comprises a thermoelectric generator (402) operable to generate electricity using heat energy extracted from the fluid passing through the inspection section (102). 13 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the impurity indicator (200) is configured to indicate the presence of a dissolved mineral in the fluid. 14 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the impurity indicator (200) is configured to indicate the presence of particulates in the fluid. 15 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 14 wherein the impurity indicator (200) is a light source (300). 16 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 14 wherein the impurity indicator (200) is a magnet (202). 17 A fluid inspection apparatus (100) as claimed in claim 16 wherein the magnet (202) is a permanent magnet chosen from a list comprising a neodymium iron boron (NdFeB) magnet, a samarium cobalt (SmCo) magnet, an alnico magnet, a ceramic magnet and a ferrite magnet. 18 A fluid inspection apparatus (100) as claimed in claim 16 wherein the magnet (202) is an electromagnet. 19 A fluid inspection apparatus (100) as claimed in any one of claims 16 to 18 wherein the body element (110) defines a cavity (140) along its length L which extends at least part of the distance between the flow inlet (114) and the flow outlet (116), and the cavity (140) being offset from and fluidly isolated from the flow path (120), the impurity indicator (200) being located in the cavity (140) such that it is fluidly isolated from the flow path (120). 20 A fluid inspection apparatus (100) as claimed in claim 19 when dependent on claim 6 wherein the cavity (140) is provided as a recess (142) on the first flat outer surface (144). 21 A fluid inspection apparatus (100) as claimed in claim 19 when dependent on claim 6 wherein the cavity (140) is provided beneath and covered by material which defines the first flat outer surface (144). 22 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the inspection section (102) has a constant diameter D along its length between the flow inlet (114) and the flow outlet (116). 23 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the inspection section (102) comprises a transparent sheath (160) which extends along at least part of the length L of the inspection section (102), the sheath (160) defining the inspection section (102) flow path (120) and the sheath (160) being bounded by the body element (110), the sheath (160) comprising a different material to the body element (110). 24 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the surface roughness of the material which defines the flow path (120) of the inspection section (102) has a Ra value of no more than 0.4 micrometres. 25 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the flow inlet (114) and / or the flow outlet (116) comprise a fluid coupling element (170) for fluidly coupling the body element (110) to the fluid flow passage (12) of the system (10). 26 A system (10) comprising the fluid flow passage (12) which is, at least in part, defined by the fluid inspection apparatus (100) as claimed in any one of claims 1 to 25. 27 A system (10) as claimed in claim 26 when dependent on claim 6 wherein the second side (136) of the body element (110) is positioned between a user viewing position A and the first side (134) of the body element (110). 28 A system (10) as claimed in claim 26 or claim 27 wherein the system (10) forms at least part of: a boiler heating circuit, a heat pump flow and return circuit, an electric boiler heating circuit, a cold watermains supply, a hot water outlet, an air conditioning unit, an air conditioning circuit, an underfloor heating system, an oil filter, a water pump circuit, and / or a fuel system. Amendments to the claims have been filed as follows:

Claims

1 A fluid inspection apparatus (100) configured to define an inspection section (102) of a fluid flow passage (12) of a system (10), wherein the fluid inspection apparatus (100) comprises:a body element (110) having a wall (112) which defines the inspection section (102), a5 flow inlet (114) to the inspection section (102) and a flow outlet (116) from the inspection section (102); the inspection section (102) defining an unobstructed flow path (120) between the flow inlet (114) and the flow outlet (116); andthe fluid inspection apparatus (100) further comprises an impurity indicator (200) configured to indicate the presence of an impurity in fluid flowing through the flow path (120);10 wherein:the body element (110) further comprises a first side (134) and a second side (136),the first side (134) being opposite the second side (136) across the flow path (120);the body element (110) defines a cavity (140) along its length L in the first side (134) which extends at least part of the distance between the flow inlet (114) and the flow outlet (116), 15 and the cavity (140) being offset from and fluidly isolated from the flow path (120), the impurity indicator (200) being located in the cavity (140) such that it is fluidly isolated from the flow path (120);the impurity indicator (200) is a magnet (202); andthe second side (136) defines a viewing region (138) to inspect the surface of the 20 inspection section (102) adjacent to the impurity indicator (200).2 A fluid inspection apparatus (100) as claimed in claim 1 wherein:the inspection section (102) defines a central flow axis (122) which extends along the extent of the body element (110);25 the body element (110) defines a first end face (130) spaced apart from a second endface (132) along the extent of the body element (110);the flow inlet (114) is provided on the first end face (130) and the flow outlet (116) is provided on the second end face (132) such that the inspection section (102) extends along the extent of the body element (110); and30 each of the first side (134) and the second side (136) extend from the first end face (130)to the second end face (132), the first side (134) being opposite the second side (136) across the central flow axis (122).3 A fluid inspection apparatus (100) as claimed in claim 1 or claim 2 wherein the secondside (136) of the body element (110) comprises a transparent portion (180).4 A fluid inspection apparatus (100) as claimed in claim 3 wherein at least a part of the 5 remainder of the body element (110) is opaque or translucent.5 A fluid inspection apparatus (100) as claimed in claim 1 or claim 2 wherein the body element (110) is transparent.10 6 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 5 wherein the firstside (134) defines a first flat outer surface (144) and the second side (136) defines a second flat outer surface (146).7 A fluid inspection apparatus (100) as claimed in claim 6 wherein the body element (110) 15 is cuboid such that the first flat outer surface (144) is parallel to the second flat outer surface (146).LO CM8 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the body element (110) is formed from a material chosen from a list comprising polyurethane 20 resin, epoxy resin, plastic, polymer, graphene, glass, acrylic, amorphous thermoplastic polymer,polyphthalamide and silicone.9 A fluid inspection apparatus (100) as claimed in claim 8 wherein the body element (110) material comprises a thermochromic pigment such that the body element (110) is operable to25 change colour in response to the temperature of the fluid in the inspection section (102) being above a predetermined value.10 A fluid inspection apparatus (100) as claimed in claim 8 or claim 9 wherein the body element (110) material comprises a phosphorescent pigment such that the body element (110) is 30 operable to emit light in response to absorbing light from a light source.11 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the body element (110) further comprises a light source (300) mounted on and / or embedded inthe body element (110), and the fluid inspection apparatus (100) further comprises a power source (400) to operate the light source (300).12 A fluid inspection apparatus (100) as claimed in claim 11 wherein the power source (400) 5 comprises a thermoelectric generator (402) operable to generate electricity using heat energy extracted from the fluid passing through the inspection section (102).13 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the impurity indicator (200) is configured to indicate the presence of a dissolved mineral in the 10 fluid.14 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the impurity indicator (200) is configured to indicate the presence of particulates in the fluid.15 15 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 14 wherein theimpurity indicator (200) is a light source (300).LO CM16 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 15 wherein the magnet (202) is a permanent magnet chosen from a list comprising a neodymium iron boron20 (NdFeB) magnet, a samarium cobalt (SmCo) magnet, an alnico magnet, a ceramic magnet and a ferrite magnet.17 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 15 wherein the magnet (202) is an electromagnet.18 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 17 when dependent on claim 6 wherein the cavity (140) is provided as a recess (142) on the first flat outer surface (144).30 19 A fluid inspection apparatus (100) as claimed in any one of claims 1 to 17 whendependent on claim 6 wherein the cavity (140) is provided beneath and covered by material which defines the first flat outer surface (144).20 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the inspection section (102) has a constant diameter D along its length between the flow inlet (114) and the flow outlet (116).5 21 A fluid inspection apparatus (100) as claimed in any one of the preceding claims whereinthe inspection section (102) comprises a transparent sheath (160) which extends along at least part of the length L of the inspection section (102), the sheath (160) defining the inspection section (102) flow path (120) and the sheath (160) being bounded by the body element (110), the sheath (160) comprising a different material to the body element (110).1022 A fluid inspection apparatus (100) as claimed in any one of the preceding claims wherein the surface roughness of the material which defines the flow path (120) of the inspection section (102) has a Ra value of no more than 0.4 micrometres.LO CM15 23 A fluid inspection apparatus (100) as claimed in any one of the preceding claims whereinthe flow inlet (114) and / or the flow outlet (116) comprise a fluid coupling element (170) for fluidly coupling the body element (110) to the fluid flow passage (12) of the system (10).24 A system (10) comprising the fluid flow passage (12) which is, at least in part, defined by20 the fluid inspection apparatus (100) as claimed in any one of claims 1 to 23.25 A system (10) as claimed in claim 24 when dependent on claim 6 wherein the second side (136) of the body element (110) is positioned between a user viewing position A and the first side (134) of the body element (110).26 A system (10) as claimed in claim 24 or claim 25 wherein the system (10) forms at least part of: a boiler heating circuit, a heat pump flow and return circuit, an electric boiler heating circuit, a cold watermains supply, a hot water outlet, an air conditioning unit, an air conditioning circuit, an underfloor heating system, an oil filter, a water pump circuit, and / or a fuel system.

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