APPARATUS FOR MONITORING FLOW OF A FLUID ALONG A CONDUIT

Abstract: Apparatus (1) for monitoring flow of fluid, such as domestic water, along a conduit (2) (shown in dashed lines) comprising a piston and cylinder arrangement (3) having a plurality of free pistons, in the embodiment shown two pistons (4 and 5), and port means (6) which are so arranged with respect to the pistons (4) and (5) that an inlet port is always open during strokes of each piston (4 or 5) so that fluid flow is continuous along the conduit (2).

Description: APPARATUS FOR MONITORING FLOW OF A FLUID ALONG A CONDUIT The indention relates to apparatus for monitoring flow of a fluid along a conduit, and to a system including such apparatus. The conduit may contain water or gas, which is for example part υf a domestic water or gas supply. Present flυw meters for water flow measurement do not lend themselves without considerable increasing in manufacturing costs to high accuracy at low flow rates, generally are not susceptible of supporting a remote information logger, and in any event do not readily meet the criteria laid down in BS 5728 (amendment 1-1985) Class D. Domestic water flow meters according to this standard are required to have a nominal flow rate of 1.0 m 3 /hr. This requires a starting flow rate of 0.00375 m 3 /h. a minimum flow rate υf 0.0075 m 3 /h, above which accuracy ' is to be within +/~5% rate to a transiton flow rate of 0.0115 m 3 /h . above which accuracy is to be within +/-2% rate to a maximum flow rate of 2.0 m 3 /h. Pressure loss accordingly is to be a maximum of 1 bar' at the maximum flow rate and a maximum of 0.25 bar at the nominal lυw rate. Domestic water pipework internal diameter is in the United Kingdom nominally 15 mm with a tolerance of +/-1 mm. At minimum and maximum flυw rates, mean fluid pipework velocities are therefore 0.012 m/s and 3 * 1 m/s based on 15 mm dia. Corresponding Reynolds numbers with water at ambient conditions are 135 and 36,000. The flow in the pipework therefore goes from laminar to turbulent over the flow range. Turndown: maximum flow rate/minimum flow rate i.s very high at 267 : 1. The present flow meters used in the United Kingdom and elsewhere, are generally rotary piston meters. They usually comprise a cylindrical measurement chamber with a partition plate separating the inlet from the outlet port. The piston is also cylindrical and has numerous holes in its support so that liquid is able to flow on both sides of the piston. The piston is guided within the measuring chamber by the circulation of the piston hub or peg between an outer and inner boss. The slot in the piston for the partition plate confines motion relative to the plate to one plane. The motion of the piston is thus oscillatory. As the flow meter entraps fixed quantities of liquid outside and inside the piston each revolution, the rate of flow is proportional to rotational velocity. Operation of this meter over a wide turndown depends on close tolerances to give sufficiently low internal leakage especially as the leakpaths are constrained to be short relative to breadth because of the rounded geometry. Furthermore the tolerance structure is complex to keep mechanical friction low. ' For example the tolerances on the piston hub, the internal diameter of the outer boss confining its path, the 0D of the piston and the ID of the measuring chamber must be such that the piston outer circumference does not touch and hence rub on the inside circumference of the measuring chamber. Otherwise mechanical friction will go up. This is because the constraining forces are designed to be taken by the hub on the ID of the outer boss, which confines them to a smaller radius arm, so keeping friction torque down. Conversely the piston outer circum erence must be close enough to the inner circumference of the measuring chamber to keep internal leakage low. To achieve Class D Specifications and retain existing maximum flow capability the meter would require even tighter tolerances. Without some form of compensating measure, tightening the clearance between the 0D of the piston and the ID of the measuring chamber would reduce life as less wear at the hub would be required to make the circumferences touch and fractional torque increase. In order to control the complex tolerance structure of this meter cost would considerably increase, with no guarantee on accuracy being increased cυnmensurately. Moreover, it has been estimated that in the Thames Water Authority area alone there could be a significant drop in demand (present day) if there was adoption of universal metering. It is accordingly an object υf the invention to seek to mitigate the disadvantages of the prior meter and to provide a meter, particularly for monitoring the flow of domestic water, which has improved accuracy at low flow rates, is cheaper to manufacture and install than the present meter, which is capable of supporting a remote information logger and which would be acceptable to the consumer. According to a first aspect of the invention there is provided apparatus for monitoring flυw of fluid alυng a conduit, comprising a piston and cylinder arrangement having a plurality of free pistons, and port means which are so arranged with respect to the pistons that an inlet port is open during strokes of each piston so that fluid flow is continuous along the conduit. One free piston may act as the valving for another and vice- versa. There may be two pistons. The pistons may be double-acting. The two pistons may be mounted in a single cylinder with a divider therebetween to provide a respective cylinder part for each piston. The two pistons may each be mounted in a respective separate cylinder. The cylinder parts or cylinder may be coaxial. The cylinder parts or cylinder may comprises two spaced apart shells which are coaxial, and there may be radial partitions between the shells whereby to provide the port means. Each piston may comprise equal diameter piston parts coi ected by reduced section piston parts. The cylinder may be terminated at opposite ends by manifolds which may extend substantially parallel to one another and to the divider. Each manifold may have an extension adapted for connection into the conduit. The extensions may be adapted for coaxial connection with the conduit by screw-threaded connections. The cylinder may comprise moulded components. The components may be extruded aluminium components, or may be plastic components, such as injection mouldings. According to a second aspect of the invention there is provided a system for measuring flow of liquid along a conduit, comprising apparatus as hereinbefore defined and means to sense displacement of the pistons whereby to determine flow of fluid along the conduit. The sensing means may comprise an optical sensing means, a magnetic sensing means, a mechanical sensing means or a capacitative sensing means. The conduit may contain water. Apparatus embodying the invention is hereinafter described, by way of example, with reference to the accompanying drawings. Fig. 1 is perspective, part sectional view, of apparatus according to the invention; Fig. 2 is a cross-sectional view of a cylinder of the apparatus of Fig. 1; Fig. 3 is an end elevational view of an alternative view of the apparatus of Fig. 1; Fig. 4 is a schematic flow diagram of a sequence of operations of the apparatus of Fig. 1? Fig. 5 is a perspective, part sectional view of a second apparatus according to the invention; Fig. 6 is an end view of the apparatus of Fig. 5; Fig. 7 is an end view of a third apparatus according to the invention; Figs. 8 and 9 are perspective, part cross-sectional views of further apparatus according to the invention " ; and Fig. 10 is a schematic flow diagram of a sequence of operations of the apparatus of Fig. 5. In the drawings, like parts are identified by like reference numerals. Referring firstly to Figs. 1-4 of the drawings, there is shown apparatus 1 for monitoring flow of fluid, such as domestic water, along a conduit 2 (shown in dashed lines> ■ comprising a piston and cylinder arrangement 3 having a plurality of free pistons, in the eπibodiment shown two pistons 4 and 5, and port means 6 which are so arranged with respect to the pistons 4 and 5 that an inlet port is always cpen during strokes of each piston 4 or 5 so that fluid flow is continuous along the conduit 2. The piston and cylinder arrangement 3 ccπprises two cylinder parts 7 and 8 which are coaxial, the parts 7 and 8 being separated by a ported divider 9. The cylinder parts 7 and 8 cαπprise two coaxial shells 10 and 11, the annular space 12 between which comprise the port means, with radial walls 13 between the shells 10 and 11 (forming impermeable barriers between different ports of the port means 6 (the walls and ports being omitted from Fig. 1 for clarity)). Each piston 4 and 5 comprises three disc-shaped parts 14 which are parallel of identical diameter, spaced apart and joined by integral connector pieces 15 of reduced diameter. The disc-shaped parts 14 are of such a diameter that they just provide a sliding fit within the inner (as considered in use) shell 10. The inner and outer shells 10 and 11 are of substantially the same length and are terminated by manifolds 16 comprising double-walled ported plates which are substantially parallel to the divider 9 and which include extensions 17 secure to the cylinder 3 by bolts 18, and which have coaxial extensions 19, adapted by threaded external surfaces 20, for connection with the conduit 2 and coaxial therewith. Water thus flows down the conduit 2, through the apparatus 1, which is in-line with the conduit 2. There is means (not shown) for monitoring movement of at least one piston 4 or 5 whereby to measure water flow, and thus consumption, movement of a piston 4 or 5 being dependent on water flow, and thus water consumption. The apparatus 1 with the monitoring means thus provides a measuring system. The monitoring means may be optical, magnetic, mechanical, capacitative or any other suitable means, and can also provide an LCD read-out or any other suitable means either at the meter or at a remote point, or both. The cylinder parts 7 and 8, pistons 4 and 5, partition 9 and manifolds 16 may comprise mouldings, for example plastic or aluminium, and may be injection mouldings. This provides for simplicity and repeatability of construction and use and simplicity of manufacture. In use, the apparatus 1 is mounted in-line in a domestic (say) SUBSTITUTESHEET water supply conduit 2 via the extensions 19. Movement of the pistons 4 and 5 is described with reference to the schematics of Fig. 4, which shows the cylinder split into two notional cylinder parts for simplicity. The left hand extension 19 (as viewed) is assumed to be upstream and the right hand extension downstream, the manifolds respectively adjacent thereto being at A and D. Assuming the pistons 4 and 5 are in their respective positions shown, inlet water is blocked from inlet port II of the port means 6 by the central disc 14 of the piston 4. The water therefore flows into 12, where it finds the inlet port open. It flows through cylinder part 8 to port H of the port means 6, and returns in direction of arrow 'R' to port B of the port means 6, so pushing the piston 4 to the left as viewed. Water is forced out of port A, by this action and hence passes into port G of the cylinder part 8 to the outlet port 03 and hence down the conduit 2. During the later part of the movement of the piston 4, the path between inlet port ' II- and port F opened. Water passes from F into port C in the direction of arrow 'S' to start movement of the piston 5 to the right as viewed, piston 5 so closing off ports 12 and 03 after the piston 4 has reached the end of its stroke. Water is forced from port D of the port means 6 into E and out of 01. During the later part of the movement of piston 5, the path between inlet port 12 and port G is opened. Water passes through G into port A to restart movement of the piston 4, to the right as viewed, so that the piston 4 closes off ports II and 01 after the piston 5 has reached the end of the stroke. When the piston 4 has nearly reached the end of its stroke to the far right as viewed, water again passes from II through E to D to reverse the piston 5. The pistons 4 and 5 thus move freely to and fro within their respective cylinder parts 7 and 8, one piston acting as a valve for the other during this movement as they work in quadrature, and an inlet port of the port means 6 always being open, unobstructed by a piston 4 or 5 so that water ^. O _ s __ * _ •____ * -_-_.£-_ flow is continuous. The port means 6 positioning is such that each piston 4 or 5 travels substantially a full stroke, eve*-, at low flow rates. Referring now to Figs 5-9 of the drawings, there is shown apparatus 100 for monitoring flow of fluid, such as domestic water, along a conduit 2 (shown in dashed lines) comprising a piston and cylinder arrangement 3 having a plurality of free pistons, in the embodiment shown two pistons 4 and 5, and port means 6 which are so arranged with respect to the pistons 4 and 5 that an inlet port is always open during strokes of each piston 4 or 5 so that fluid flow is continuous along the conduit 2. The piston and cylinder arrangement 3 cαtprises two cylinder parts 7 and 8 which are parallel, and the interiors of which are in fluid interconnection via port means 6. The cylinder parts 7 and 8 comprise two shells 10 and a shell 11. In Fig. 6 the shells 10 have S-shaped extension 10' to p rov ide the end port means 6. In Fig. 7 the end port means 6 are provided by the manifolds 16 which have appropriate transverse walls for guiding fluid between the shells 10. There are walls or webs 13 between the shells 10 and 11 (forming impermeable barriers between different ports of the port means 6) . Each piston 4 and 5 corrprises three disc-shaped parts 14 which are parallel of identical diameter, spaced apart and joined by integral connector pieces 15 of reduced diameter. The disc-shaped parts 14 are of such a diameter that they just provide a sliding fit within the shells 10. The inner and outer shells 10 and 11 are of substantially the same length and are terminated by the manifolds 16 which latter include extensions 17 secured to the cylinder 3 by bolts 18, and which have coaxial extensions 19, adapted by threaded external surfaces 20, for connection with the conduit 2 and coaxial therewith. The apparatus 100 thus comprises two pistons 4, 5, and a cylinder block 10 and 13 and a casing 11 which may be moulded from plastic as for example by extrusion. The apparatus also includes two tube plates of the manifolds 16 and the two end covers 17. There is means (not shown) for monitoring movement of at least one piston 4 or 5 whereby to measure water flow, and thus con¬ sumption, movement of a piston 4 or 5 being dependent on water flow, and thus water consumption. The apparatus 1 with the monitoring means thus provides a measuring system. The monitor¬ ing means may be optical, magnetic, mechanical, capacitative or any other suitable means, and can also provide an LCD read-out or any other suitable means either at the meter or at a remote point, or both. The cylinder parts 7 and 8, pistons 4 and 5, and manifolds 16 may comprise mouldings, for example plastic or aluminium, and may be injection mouldings. This provides for simplicity and repeatability of construction and use and simplicity of manufacture. Figs.8 and 9 show apparatus 200 similar to the apparatus 100 in that there is a cylinder block moulded from plastics or alumin¬ ium as by extrusion, although in this embodiment there is a ported divider separating the cylinder parts 7-and 8. The embodi¬ ment 200 of Figs. 8 and 9 is otherwise similar to that of Fig. 5. In use, the apparatus 100 or 200 is virtually identical to the embodiment of Figs. 1 to 4 in that it is mounted in-line in a domestic (say) water supply conduit 2 via the extensions 19. Water thus flows down the conduit 2, through the apparatus 100 or 200, which is in-line with the conduit 2. Movement of the pistons 4 and 5 is described with reference to the schematics of Fig. 10, which shows the cylinder split into two notional cylinder parts for simplicity. As in the embodiment of Figs. 1 to 4, the left hand extension 19 (as viewed) is assumed to be upstream and the right hand extension downstream, the manifolds respectively adjacent thereto being at A and D. Assuming the pistons 4 and 5 are in their respective positions shown, inlet water is blocked from inlet port II of the port means 6 by the central disc 14 of the piston 4 as in Figs. 1 to 4. The water therefore flows into 12, where it finds the inlet port open. It flows through cylinder part 8 to port H of the port means 6, and returns in direction of arrow 'R' to port B of the port means 6, _3 ϊ ■ ϊ∞i >~ ' ■ ϊ.__ so pushing the piston 4 to the left as viewed. Water is forced out of port A, by this action and hence passes into port G of the cylinder part 8 to the outlet port 03 and hence down the conduit 2. During the later part of the movement of the piston 4, the path between inlet port II and port F opened. Water passes from F into port C in the direction of arrow 'S' to start movement of the piston 5 to the right as viewed, piston 5 so closing off ports 12 and 03 after the piston 4 has reached the end of its stroke. Water is forced from port D of the port means 6 into E and out of 01. During the later part of the movement of piston 5, the path between inlet port 12 and port G is opened. Water passes through G into port A to restart movement of the piston 4, to the right as viewed, so that the piston 4 closes off ports • II and 01 after the piston 5 has reached the end of the stroke. When the piston 4 has nearly reached the end of its stroke to the far right as viewed, water again passes from II through E to D to reverse the piston 5. The pistons 4 and 5 thus move freely to and fro within their respective cylinder parts 7 and 8, one piston acting as a valve for the other during this movement as they work in quadrature, and an inlet port of the port means 6 always being open, unobstructed by a piston 4 or 5 so that water flow is continuous. The port means 6 positioning is such that each piston 4 or 5 travels substantially a full stroke, even at low flow rates. At all times in every embodiment one or both of the pistons 4 or 5 is or are clear of an inlet port such that water flow is continuous and one piston commences a new stroke before the other has finshed its current stroke. Also, water between the end faces of the pistons 4 and 5 and the respective end parts of the apparatus (the divider and manifolds) means that there is a cushion of water which effectively prevents any percussive effect of the pistons 4 and 5 engaging the cylinder parts while the pistons are effectively "coupled" by the relatively inccmpressible water to provide positive displacement of the pistons, the movement of only one of which need be monitored, as the pistons are in phase, to provide a measurement which can si ply be related to fluid flow. The flow rate of the water, and thus quantity of water used, can readily be ascertained by measuring movement of a piston by a non-intrusive device. Volumetric output is digital, based on the number of strokes of a piston. It is possible to adjust the size of the apparatus 1, 100 or 200 so that a pulse (one complete cycle of four strokes) corresponds to a verification scale interval at which speed of operation is assessed as 5 cycles/sec. at the nominal desired flow rate of 1.0 m 3 /h. In every embodiment the cylinder 3 may be transparent, to provide for direct visual/optical measurement of movement of a piston 4 or 5. Modifications of the apparatus disclosed may, it will be understood, be envisaged. For example, the cushioning effect provided by the water may be-achieved by mechanical means such as valve means or an elastomeric or rubber end cap or seat on the piston and/or end port means 6.

Claims: CLAIMS 1. Apparatus or monitoring low of fluid along a conduit, comprising a piston and cylinder arrangement having a plurality of free pistons, and port means which are so arranged with respect to the pistons that an inlet port is open during strokes of each piston so that fluid flow is continuous along the conduit. . Apparatus according to Claim 1, wherein one ree piston acts as the valving for another, and vice-versa. 3« Apparatus according to Claim 1 or Claim 2, there being two pistons. 4- Apparatus according to any of Claims 1 to 3, the pistons being double-acting. 5- Apparatus according Claim 4 ? the two pistons being mounted in a single cylinder with a divider therebetween to provide a respective cylinder part for each piston. 6. Apparatus according to Claim 4 . the two pistons each being mounted in a respective separate cylinder. 7. Apparatus according to Claim 5 or Claim 6, the cylinder parts or cylinder being coaxial. 8. Apparatus according to Claim "J , the cylinder parts or cylinder comprising two spaced apart shells which are coaxial, there being radial partitions between the shells whereby to provide the port means. 9« Apparatus according to any of Claims 3 to 8, each piston comprising equal diameter piston parts connected by reduced section piston parts. 10. Apparatus according to Claim 8 or Claim 9, the cylinder being terminated at opposite ends by manifolds which extend substantially parallel to one another and to the divider. 11. Apparatus according to Claim 6, the cylinders being 5 substantially parallel. 12. Apparatus according to Claim 11, the cylinders comprising part of a cylinder block terminated at opposite ends by manifolds which extend substantially parallel to one another. 13. Apparatus according to Claims 11 or 12, the cylinder block 10 comprising the cylinders and a shell encompassing same and spaced therefrom by webs. 14. Apparatus according to Claim 13, the webs comprising, with the cylinders and shell, flow ports, or paths for the fluid. 15. Apparatus according to Claim 14, the cylinders, shell and 15 webs being integral. 16. Apparatus according to any of Claims 10 to 15, each manifold having an extension adapted for connection into the conduit. 17. Apparatus according to Claim 16, the extensions being 20 adapted for coaxial connection with the conduit by screw-threaded connections. 18. Apparatus according to any one of Claims 1 - 15, adapted by a combined inlet and outlet means for connection with the conduit. 25 19. Apparatus according to any preceding Claim, the cylinder comprising moulded components. 20. Apparatus according to Claim 19, the components being extruded aluminium components. 21. Apparatus according to Claim 19, the components being plastic components. 22. Apparatus according to Claim 21, the plastic components 5 being injection mouldings. 23. Apparatus according to Claim 21, the plastic components being extrusions. 24. Apparatus for monitoring flow of fluid along a cylinder, substantially as hereinbefore described with reference to the 10 accompanying drawings. 25. A system for measuring flow of fluid along a conduit, comprising apparatus according to any preceding Claim and means to sense displacement of the pistons whereby to determine flow of fluid along the conduit. 15 26. A system according to Claim 25, the sensing means comprising an optical sensing means. 27. A system according to Claim 26, the sensing means comprising a magnetic sensing means. 28. A system according tc Claim 25, the sensing means 20 comprising mechanical sensing means. 29. A system according to Claim 25, the sensing means comprising a capactitative sensing means. 30. A system according to any of Claims 25 to 29, the conduit containing water. 25 31. A system for measuring flow of fluid along a conduit substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: STORRAR ANDREW MARTIN, STORRAR, ANDREW, MARTIN
Applicants: STORRAR ANDREW MARTIN, THAMES WATER AUTHORITY, STORRAR, ANDREW, MARTIN
Application year: 1987
Main classification: G01F3
IPC codes: G01F3