Liquid pressure reducing valve

Abstract

A spring loaded regulator (1) has a body (2) containing a chamber (3) to which an inlet (4) opens via an inlet aperture (5). The inlet is connected to a pressurised mains water supply (6). An outlet (7) of the chamber is connected to a pipe network (8) for local water distribution. The regulator has a flow pressure regulating plate (9) disposed opposite the inlet aperture (5). A diaphragm (10) is secured to the plate (9) to form a seal with an upper portion (11) and a lower portion (12) of the body (2). The regulating plate has a guide rod (14) extending downwardly therefrom to a guide (16) in the inlet aperture (5). A compression spring (21) acts at its lower end (22) on the top of the diaphragm (19). The upper end (23) of the spring abuts a spring drive member (24) at the end of a drive tube (25) of a servo (26). The drive tube is housed in a fixed tube (27) of the servo and is fixedly connected to the upper portion (11) of the regulator body (2). A threaded spindle (28) remote from the spring is journaled for axial alignment in the drive tube within the fixed tube. An electric motor (29) and gearbox (30) are arranged to drive the spindle. A nut (31) is fixedly connected to the remote end of the drive tube (25). Thus, the spring drive member can be advanced to further compress the spring or retracted to release compression. The pipe system (8) of the local distribution network extends downstream of the outlet (7). A flow meter (32) and a pressure sensor (33) are located in the pipe system adjacent the outlet. They are electronically connected to a controller (34). A remote pressure sensor (35) is also connected to the controller at a remote point (36) of the pipe system (8).

Description

[0001] The present invention relates to a liquid pressure reducing valve, in particular but not exclusively for water pipes.

[0002] Loss of water from a main pipe is a problem due to the age of the main pipe system and damage to the main pipe and associated equipment. Many main pipes are old and have many leak points. Even newer main pipes can develop leaks. As would be expected, the flow of a leak is greatest when the water pressure is highest. However, the inventors noticed a simple correlation between, on the one hand, the pressure required downstream of the regulator and, on the other hand, the flow in the local network in which the regulator is located between the high pressure area supply and the local network to maintain a given minimum pressure at the far points of the local network. The required regulating pressure and the flow on the side downstream of the regulator are generally linearly dependent. Nonetheless, the inventors know of no pressure regulators that are controlled in dependence on the flow through them, except for the following.

[0003] In a prior proposal in GB 2,176,316, to the extent of its abstract, it is disclosed that:

[0004] Apparatus for controlling the flow of water through a pipe (26) comprising a valve (29) and an orifice plate (37) and supplying a water distribution system comprises a governor (1) for actuating a pilot valve (14) in a servo system controlling the valve (29). The governor (1) has two diaphragms (5) and (6) connected by a tension spring (7) whose extension is dependent on the flow through the orifice plate (37). The first diaphragm (5) operates a valve member (13) of the pilot valve (14) and is subjected to a pressure differential caused by the flow through the orifice plate (37). The second diaphragm (6) is loaded by a compression spring (8) whose displacement is dependent on the control pressure at a tap (38) in the pipe (26). The movement of the valve member (14) is a combination of the displacements of the two diaphragms (5 and 6) and, as the amount of water increases, the control pressure at the tap (38) is raised.

[0005] It is an object of the present invention to provide an improved liquid pressure reducing valve.

[0006] According to the present invention, there is provided a fluid pressure reducing valve apparatus comprising:

[0007] • a spring loaded regulator having:

[0008] • a body containing a chamber,

[0009] • a liquid supply aperture into the chamber and a liquid outlet aperture out of the chamber,

[0010] • a regulating plate opposite the aperture for the supply of liquid acting thereon,

[0011] • a spring for urging the plate towards the aperture, and

[0012] • a diaphragm between the regulating plate and the body for closing the chamber between the regulating plate and the body and for taking up the regulating pressure in the chamber when in use,

[0013] • a controllable motor drive acting between the body and the end of the spring remote from the regulating plate,

[0014] • a flow meter downstream of the outlet; and

[0015] • a controller arranged to receive flow data from the flow meter and to control the servo motor to withdraw the distal end of the spring in dependence on the flow measured by the flow meter;

[0016] The above arrangement is such that on an increase in demand flow, the regulating plate is partially withdrawn to maintain downstream pressure on such an increase, and vice versa.

[0017] Preferably, the controllable motor drive is a servo motor drive.

[0018] The invention is particularly applicable to water pipes where the fluid is liquid, particularly water. The inventors envisage that the invention is applicable to liquid and gaseous hydrocarbon fluids.

[0019] The controller can be adapted to calculate servo motor action in the spring positioning in dependence on a substantially linear downstream pressure and flow rate relationship. The calculation can be based on a pressure to be achieved in the spring servo positioning; or solely on the spring servo positioning. Alternatively, it can be adapted to servo motor action in dependence on a look-up table of downstream pressure and flow rate. Again, the look-up table can include pressure values to be achieved, but preferably includes spring positions in terms of servo revolutions.

[0020] In order to assist in understanding the invention, specific embodiments thereof will now be described by way of example and with reference to the accompanying drawings in which:

[0021] Figure 1 is a schematic cross-sectional side view of a pressure regulator of the present invention, Figure 2 ,

[0022] Figure 2 is a schematic cross-sectional side view of a pressure regulator of the present invention,

[0023] Figure 3 is a similar arrangement on a smaller scale, including a controller and a line from a remote pressure sensor,

[0024] Figure 4 is a typical pressure graph required to be imposed in a network to achieve a constant remote pressure with different demand flows, and

[0025] Figure 5is a schematic view of a main water pipe with the regulator of the invention and a number of customer water taps and leak points.

[0026] Referring to the drawings, the spring loaded regulator 1 has a body 2 containing a chamber 3. An inlet 4 opens into the chamber via an inlet aperture 5. The inlet is connected to a high pressure main water pipe 6. An outlet 7 from the chamber is connected to a pipe network 8 for local distribution of water to individual consumers. The regulator has a flow pressure regulating plate 9 disposed opposite the inlet aperture 5. A diaphragm 10 is secured to the plate 9 and projects therefrom into the body, forming a seal with the upper 11 and lower 12 parts of the body 2. The chamber 3 is thus sealed between the upper and lower parts.

[0027] The regulating plate has a guide rod 14 extending downwardly therefrom into a guide 16 in the inlet aperture 5. The rod extends through both the regulating plate and the diaphragm. The rod carries a nut 17 at its top end. The nut 17 is supported on a spring centring washer 18 and a diaphragm sealing clamp plate 19. This arrangement keeps the regulating plate centred above the inlet aperture 5.

[0028] In a variant, a separate regulating plate 109 is provided on the lower rod 14 opposite the aperture. The diaphragm keeps the plate 9 / 109 centred above the aperture 5.

[0029] A compression spring 21 acts at its lower end 22 on the top of the clamp plate 19. The spring is held more or less compressed as described below. It thus remains around the centring washer 18. Its upper end 23 abuts a spring drive member 24 at the end of a drive tube 25 of a servo 26. The drive tube is contained in a fixed tube 27 of the servo, which is fast with the upper part 11 of the regulator body 2. A lead screw 28 remote from the spring is journalled for axial alignment in the drive tube within the fixed tube. A motor 29 and gearbox 30 are arranged to drive the lead screw. A nut 31, preferably a circulating ball nut, is fast with the remote end of the drive tube 25, which is keyed to the fixed tube to prevent rotation. Thus, by corresponding rotation of the motor and lead screw, the spring drive member can be advanced to further compress the spring or retracted to decompress.

[0030] The pipe system 8 of the local distribution network extends downstream of the outlet 7. A flow meter 32 and pressure sensor 33 adjacent the outlet are located in the pipe system 8. The flow meter 32 and pressure sensor 33 are electronically connected to a controller 34. A remote pressure sensor 35 is also connected to the controller at a remote point 36 of the pipe system 8.

[0031] Along the pipework there are various leakage points 37 whose flow rate increases with pressure and with the number of user taps 38 and so on. It is these leakage points that are the main determinant of the flow rate at the pressure regulator 1. If it is of the type that permanently sets the pressure to be sufficient to maintain at the furthest point 36 in the network, then this pressure will exacerbate the leakage points 37 regardless of the user flow rate at the taps 38.

[0032] In this embodiment of the invention, the overall pressure reducing valve arrangement includes not only the regulator 1 and flow meter 32 but also a controller 38 for controlling the regulator via the servo motor in dependence on the flow rate as measured by the flow regulator and indeed a remote pressure sensor 35 which is not strictly necessary to the invention.

[0033] When the regulator is set to provide the required furthest point pressure for varying flow rates, many local distribution networks such as network 8 have previously been measured and exhibit a pressure / flow rate characteristic as shown in Figure 1. Figure 4 Due to leakage points there is rarely an ideal low pressure point 41 for zero flow rate. The actual low pressure point 42 can be measured at night when user demand is negligible. Further flow and pressure readings 43 can be taken during periods of more and less usage by adjusting the regulator to provide sufficient furthest point pressure.

[0034] In practice the pressure flow graph is essentially a straight line with a slope or gradient and an offset equal to the zero flow rate offset. The graph can be represented by the following equation:

[0035] The pressure required by the regulator = zero flow rate pressure + measured flow rate x graph gradient (in pressure per unit flow rate).

[0036] This is surprising because one would expect the adjustment of the regulator to change the measured flow rate. However, this is a second order effect because the main determinant of flow rate is user usage. By contrast, leakage flow rate is small and is kept below what it could be by keeping the pressure in the network below the value that would set it to ensure that its furthest point is adequate at maximum flow rate. That value would result in excessive flow rate and excessive leakage for all other flow rates.

[0037] The spring 21 in the regulator acts against the force exerted by the diaphragm 10 which is subjected to the pressure to be regulated. The upstream pressure exerted on the regulating plate 9 is substantially constant and is small compared to the diaphragm force. Therefore, shortening the spring by an amount proportional to the change in required pressure can provide this change, bearing in mind that only a small movement of the regulating plate is required for a significant change in pressure drop at the outlet orifice. Therefore, for practical purposes, the linear movement of the end of the spring acted upon by the servo motor will result in a linear change in the regulated pressure. The controller can therefore be set to move the end of the spring linearly in dependence on the flow rate.

[0038] If the zero flow pressure and the gradient of the measured flow profile are unknown, the controller can be set to adjust the regulation pressure periodically for different flow rates to establish the pressure required to achieve a sufficiently far point pressure. For this purpose, a connection is made with a remote pressure sensor 35 and a near range pressure sensor 33, in the former case a local wireless connection is suitable.

[0039] The controller can be equipped with a memory. This memory is suitable for recording the pressure and flow profile instead of just storing the offset and gradient and using this as a look-up table for the pressure, which should be adjusted in accordance with the measured flow rate.

[0040] The sensor 33 can be used to fine-tune the servo motor control to achieve the required pressure in accordance with the measured flow rate.

Claims

1. A fluid pressure reducing valve apparatus comprising: • a spring loaded pressure reducing valve having: • a body containing a chamber, • a liquid supply aperture leading into the chamber directly connected to a high pressure mains water supply and a liquid outlet leading from the chamber, • a regulating plate opposite the liquid supply aperture and in use subject to the supply liquid acting thereon, • a spring for urging the regulating plate towards the liquid supply aperture, and • a diaphragm between the regulating plate and the body for closing the chamber between the regulating plate and the body and in use subject to the regulating pressure in the chamber; • a controllable motor drive acting between the body and the end of the spring remote from the regulating plate; • a flow meter downstream of the outlet; and • a controller arranged to receive flow data from the flow meter and to control a servo motor to withdraw the distal end of the spring in dependence on the flow measured by the flow meter, the above arrangement being such that on an increase in demand flow the regulating plate is partially withdrawn to maintain downstream pressure on such an increase in demand flow and vice versa. The apparatus is suitable for reducing the pressure of water.

2. The fluid pressure reducing valve apparatus according to claim 1, wherein The controllable motor drive is a servo motor drive.

3. The fluid pressure reducing valve device according to claim 1 or 2, wherein The controller is suitable for calculating the action of the servo motor drive in spring positioning in dependence on a substantially linear downstream pressure and flow rate relationship.

4. The fluid pressure reducing valve apparatus according to claim 3, wherein The calculation is based on the pressure to be achieved in respect of servo positioning of the spring.

5. The fluid pressure reducing valve apparatus according to claim 4, wherein The calculation is based solely on servo positioning of the spring.

6. The fluid pressure reducing valve apparatus according to claim 4, wherein The calculation is based on a look up table of downstream pressure and flow rate.

7. The fluid pressure reducing valve apparatus according to claim 4, wherein The look up table includes: (a) pressure values to be achieved; or (b) spring positions expressed in servo revolutions.

8. The fluid pressure reducing valve apparatus according to claim 7, wherein The regulating plate is provided adjacent a central region of the diaphragm, a guide rod extending into a centring guide in the liquid supply aperture.

9. The fluid pressure reducing valve apparatus according to claim 1, wherein The regulating plate is provided on a guide rod spaced from the diaphragm, the guide rod extending from the diaphragm into a centring guide in the liquid supply aperture.

10. The fluid pressure reducing valve apparatus according to claim 1, wherein The spring is a compression spring acting on a side of the diaphragm remote from the liquid supply aperture.

11. The fluid pressure reducing valve apparatus according to claim 1, wherein The spring is a tension spring acting on a side of the diaphragm proximate to the liquid supply aperture.

12. The fluid pressure reduction valve apparatus of claim 1, wherein, The controllable motor drive comprises a nut and screw arrangement arranged to act on the spring at an end remote from the diaphragm and actuatable by a motor of the controllable motor drive.

13. The fluid pressure reduction valve apparatus of claim 1, wherein, 14. The fluid pressure reducing valve apparatus of claim 1 in combination with a remote pressure sensor for measuring the downstream pressure to be maintained. ​

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