CONTROL SYSTEM FOR REGULATING WATERWORKS PRESSURE

Abstract

A control system for regulating fluid flow and pressure downstream a waterworks main valve includes a variable orifice device disposed upstream a pressure reducing pilot. The variable orifice device is in fluid communication with the pressure reducing pilot and a cover chamber of the main valve. Opening and closing the variable orifice device causes the main valve to modulate and the pressure of fluid downstream the main valve to be changed while avoiding pressure oscillations during the transition between pressure setpoints.

Claims

1. A control system for regulating fluid flow and pressure downstream a waterworks main valve, comprising: a pressure reducing pilot having an inlet thereof in fluid communication with a cover chamber of the main valve and an outlet thereof in fluid communication with fluid downstream the main valve; and a variable orifice device disposed upstream the pressure reducing pilot and having an inlet in fluid communication with fluid upstream the main valve and an outlet thereof in fluid communication with the inlet of the pressure reducing pilot and the cover chamber of the main valve; wherein increasingly opening the variable orifice device increases flow to the pressure reducing pilot and/or the cover chamber of the main valve, causing the main valve to close and the downstream pressure to be reduced.

2. The control system of claim 1, wherein the pressure reducing pilot has a preselected set point establishing a maximum downstream pressure, and wherein opening the variable orifice device adjusts pressure of fluid downstream the main valve below the maximum downstream pressure.

3. The control system of claim 1, wherein the variable orifice device has a variable orifice defined at least in part by a movable stem disposed between an inlet and an outlet of the variable orifice device.

4. The control system of claim 3, wherein the stem is tapered.

5. The control system of claim 1, including a fixed orifice disposed upstream the pressure reducing pilot.

6. The control system of claim 5, wherein an inlet of the fixed orifice is in fluid communication with fluid upstream the main valve and an outlet of the fixed orifice is in fluid communication with the inlet of the pressure reducing pilot and the cover chamber of the main valve.

7. The control system of claim 6, wherein the outlets of the variable orifice device and the fixed orifice are in fluid communication with each other.

8. The control system of claim 1, wherein the variable orifice device is motor-operated.

9. The control system of claim 8, including an electronic controller that controls the motor of the variable orifice device to selectively open and close the variable orifice device.

10. A control system for regulating fluid flow and pressure downstream a waterworks main valve, comprising: a pressure reducing pilot having an inlet thereof in fluid communication with a cover chamber of the main valve and an outlet thereof in fluid communication with fluid downstream the main valve, wherein the pressure reducing pilot has a preselected set point establishing a maximum downstream pressure; a fixed orifice disposed upstream of the pressure reducing pilot and having an inlet in fluid communication with fluid upstream the main valve and an outlet thereof in fluid communication with the inlet of the pressure reducing pilot and the cover chamber of the main valve; and a motor-operated variable orifice device disposed upstream the pressure reducing pilot and having an inlet in fluid upstream the main valve and an outlet thereof in fluid communication with the inlet of the pressure reducing pilot and the cover chamber of the main valve; wherein increasingly opening the variable orifice increases flow to the cover chamber of the main valve, causing the main valve to close and the downstream pressure to be reduced.

11. The control system of claim 10, wherein the variable orifice device having a variable orifice defined at least in part by a movable stem disposed between an inlet and an outlet of the variable orifice device.

12. The control system of claim 11, wherein the variable orifice device stem is tapered.

13. The control system of claim 10, including an electronic controller that controls the motor of the variable orifice device to selectively open and close the variable orifice device.

14. A method for retrofitting a pressure control system of a waterworks main valve, comprising the steps of: providing a pressure control system comprising a pressure reducing pilot having an outlet in fluid communication with fluid downstream the main valve and an inlet in fluid communication with a cover chamber of the main valve, and a fixed orifice disposed upstream the pressure reducing valve having an inlet in fluid communication with fluid upstream the main valve and an outlet in fluid communication with the main valve cover chamber and the inlet of the pressure reducing pilot, wherein the pressure reducing pilot has a preselected set point establishing a maximum downstream pressure; and installing a motor-operated variable orifice device upstream of the pressure reducing valve, an inlet of the variable orifice device being in fluid communication with fluid upstream the main valve and an outlet thereof in fluid communication with the inlet of the pressure reducing valve and the main valve cover chamber, wherein increasingly opening the variable orifice increases flow to the cover chamber of the main valve, causing the main valve to close and the downstream pressure to be reduced.

15. The method of claim 14, including the step of installing the variable orifice device in parallel with the fixed orifice.

16. The method of claim 14, wherein the variable orifice device has a movable stem disposed between the inlet and outlet thereof and at least partially defining a variable orifice.

17. The method of claim 16, wherein the stem is tapered.

18. The method of claim 14, including the step of using an electronic controller to control the motor of the variable orifice device to selectively open and close the variable orifice device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings illustrate the invention. In such drawings:

[0029] FIG. 1 is a cross-sectional and diagrammatic view of a prior art plumbing arrangement for waterworks pressure modulation control;

[0030] FIG. 2 is a perspective view of a pressure modulation control system incorporating a variable orifice device, in accordance with the present invention;

[0031] FIG. 3 is a partially sectioned view of the system of FIG. 2;

[0032] FIG. 4 is a cross-sectional view of a variable orifice device used in accordance with the present invention;

[0033] FIG. 5 is an enlarged cross-sectional view of area “5” of FIG. 4;

[0034] FIG. 6 is a schematic diagram illustrating a fluid flow and pressure modulation control system embodying the present invention;

[0035] FIG. 7 is a schematic diagram illustrating a fluid flow and pressure modulation control system embodying the present invention; and

[0036] FIG. 8 is a schematic diagram illustrating a fluid flow and pressure modulation control system embodying the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The present invention, as shown in the accompanying drawings for purposes of illustration, resides in a pressure reducing valve control system utilizing a variable orifice for pressure modulation control. The invention addresses a market demand for a low-power modulating pressure regulating type valve or a control system, such as having an application for a pressure management type valve or control system that can monitor the downstream pressure conditions and adjust or monitor those pressure conditions based on fluid demand situations throughout the system. An example would be in a water distribution or waterworks system where demand is high during the day and drops off at night. During nighttime or low-demand situations, it may be desirable to lower the water pressure to reduce water loss in the system, such as due to leaks throughout the system which may be attributed to old piping or poor seals at piping junctions or the like. By lowering the water pressure during low demand conditions, less water is lost through pipe leaks, etc.

[0038] Moreover, utilizing a variable orifice device minimizes the potential for causing pressure oscillations during the transition between pressure set points. In the system of the present invention, the pressure regulating or reducing pilot is not used to transition between pressure set points, but rather behaves more like a fixed orifice and working in this manner is less likely to overrespond or overcompensate when transitioning between pressure set points. The system of the present invention is configured so that the variable orifice is used to change the downstream pressure set point from the baseline or maximum pressure set point of the regulating pilot control.

[0039] More particularly, the system incorporates a motor operated variable orifice device 200 in combination with a fixed orifice 118 and a pressure reducing pilot 116 to change the downstream pressure set point from the baseline set point of the pressure reducing or regulating pilot, reducing or preventing pressure oscillations and overresponse when transitioning between pressure set points. By using a motor operated variable orifice device, less power is required to adjust the variable orifice opening as the variable orifice does not need to overcome the heavy spring forces of a conventional motor operated pressure regulator, so a low-powered motor can be utilized.

[0040] With reference now to FIGS. 2 and 3, the system of the present invention incorporates a variable orifice device 200, which is typically motor operated, upstream of the pressure reducing or regulating control 116. As used herein, “upstream” refers to fluid that has not passed through the seat 106 and “downstream” refers to fluid which has passed through the seat 106 of the main valve 100. Thus, the variable orifice device 200 is in fluid communication with fluid upstream of the main valve, which can include fluid which is in the main valve but which has not yet passed through the seat 106 of the main valve 100 and could also include fluid which is upstream of the main valve 100, although typically it will be understood that the fluid is diverted to the variable orifice device 200 which has entered into the inlet 102 of the main valve 100 but not yet passed through the seat 106 thereof. By contrast, the pressure reducing control 116 is disposed downstream of the variable orifice device 200 and is in fluid communication with fluid that has passed through the seat 106 of the main valve 100. Typically, this fluid is still within the main valve 100 before it leaves the outlet 104 thereof, but it will be understood that the fluid could be downstream from the main valve 100 as well.

[0041] Typically, the variable orifice device 200 is plumbed to the fixed orifice 118, such as in parallel with the fixed orifice 118, such that the fluid outlet of the fixed orifice 118 and the fluid outlet of the variable orifice device 200 both direct fluid to an inlet of the pressure reducing control 116 and/or the cover chamber 114 of the main valve 100. This is particularly the case when an existing pressure control system having a pressure reducing control 116 and a fixed orifice 118 is already in place and a variable orifice device 200 is incorporated into the existing system as a retrofit in order to accomplish the present invention.

[0042] However, it will be understood that the use of the variable orifice device 200 can eliminate the need for the fixed orifice 118 as all of the fluid can be directed through the variable orifice device 200 and the variable orifice of the variable orifice device be opened or closed so as to control the amount of fluid which is directed to the cover chamber 114 and/or inlet of the pressure reducing control pilot 116. In this case, the variable orifice device 200 would always be open at least to a minimum extent corresponding to what would be the equivalent of a fixed orifice. The variable orifice could then be opened, in accordance with the invention, to introduce additional fluid into the cover chamber 114 or to the pressure reducing control pilot 116 to increase fluid into the cover chamber 114, resulting in closure of the main valve 100 and a reduction of fluid flow through the main valve 100 and thus decreasing the downstream pressure, in accordance with the invention.

[0043] Pressure management is achieved by communication between a process controller 300 and the motor operated variable orifice control device 200, such as via an electrical lead 302 which extends between the process controller 300 and a motor of the variable orifice device 200 which opens and closes a variable orifice of the variable orifice device 200. Leads 304 and 306 may also extend between the process controller 300 and a flow meter and a pressure transducer, where a process controller algorithm is used with the motor operated variable orifice device 200 to adjust system pressure to the desired set point value, such as a higher set point for daytime pressures and a lower set point for nighttime pressures. As there are no heavy spring forces or adjustment screw thread friction forces typical of a motor operated pressure regulator or control device, the operating power of the motor used with the variable orifice device 200 is significantly lower than the power required for traditional motor operated pressure regulator control devices.

[0044] With continuing reference to FIGS. 2 and 3, in a typical embodiment upstream fluid is conveyed through a fluid conduit 308 to the fixed orifice 118. The fluid may pass through a strainer or a filter 312, which may be integrally formed with the fixed orifice 118. In the embodiment illustrated in FIGS. 2 and 3, a fluid conduit 310 extends between the strainer and/or fixed orifice 118 to an inlet of the variable orifice device 200. The fluid may pass through a strainer or filter 312. Moreover, a shut-off valve 314 may be incorporated to override the activity of the motor operated variable orifice pilot device 200 and return the downstream pressure set point to the maximum set point value initially established by the pressure reducing pilot 116. However, in normal operation mode of the present invention, the shut-off valve 314 remains open. Additional shut-off valves 314 may be incorporated into the system as needed or desired, such as between the outlet of the variable orifice device 200 and the fluid conduits passing to the main valve cover chamber 114 and/or the pressure reducing control pilot 116.

[0045] There may also a fluid conduit 316 extending between the outlet of the fixed orifice 118 and outlet of the variable orifice device 200 and the control chamber 114 of the main valve to the inlet 318 of the pressure reducing pilot control 116. As mentioned above, an outlet 320 of the pressure reducing control pilot 116 is in fluid communication with fluid downstream of the main valve 100, such as by means of fluid conduit 322.

[0046] With reference now to FIG. 4, a cross-sectional view of an exemplary variable orifice device 200 is shown. The variable orifice device 200 includes a fluid inlet 202 which is in fluid communication with fluid upstream the main valve. The variable orifice device 200 also includes a fluid outlet 204 which as mentioned above is in fluid communication with the inlet of the pressure reducing pilot 116 and the cover chamber 114 of the main valve. A movable stem 206 is disposed between the inlet 202 and outlet 204 of the variable orifice device 200 to define a variable orifice 210 disposed in the passageway between the inlet 202 and the outlet 204. A small motor 212 of the variable orifice device 200 is used to raise and lower, or otherwise move, the stem 206 to open and close the passageway comprising the variable orifice between the inlet 202 and outlet 204.

[0047] The variable orifice feature of the motor operated variable orifice pilot 200 can be designed so the flow area change through the variable orifice opening 210 is as sensitive as desired. One method of controlling the sensitivity of the flow area through the variable orifice 210 is with tapering the stem 206. The tapered stem portion 208 is used to increase or decrease the flow area through the orifice by travelling axially through a fixed orifice opening. Customizing the taper of the stem feature allows the change in variable opening to be optimized for sensitivity. This sensitivity optimization can be important when making a change to the downstream pressure set point of the main valve 100. By maximizing the sensitivity of the variable orifice 210, changes in downstream pressure set point can be more precisely controlled which makes it less likely to cause pressure oscillations in the downstream piping when transitioning between set points.

[0048] With continuing reference to FIGS. 4 and 5, the variable orifice device 200 uses a tapered stem 206 to vary the flow area through the orifice 210. When fully extended, as shown, the flow through the orifice 210 is fully restricted and pressure regulation is under command of the pressure regulating pilot 116. When the stem 206 travels upwardly, flow area through the orifice 210 increases and the pressure regulation set point is now under the command of the motor operated variable orifice device 200.

[0049] Adding a motor operated variable orifice pilot device 200, in accordance with the present invention, is a way to change the regulation relationship of the fixed orifice 118 and pressure reducing or regulating pilot 116. By adding a motor operated variable orifice pilot device 200 to the pilot plumbing, such as in a parallel arrangement with the fixed orifice 118 this adds to or permits an increase to the flowing area of the fixed orifice 118. By adding a motor operated variable orifice pilot 200, the ratio of flow areas between the fixed orifice 118 and pressure reducing pilot 116 can be changed. By means of the motor operated variable orifice pilot 200 the flow area can be incrementally increased which modifies the area ratio value.

[0050] This change in flow area relationship in the pilot plumbing changes the dynamics of the relationship between a fixed orifice 118 and the pressure reducing pilot 116. The pressure reducing pilot 116 can only partially compensate for the increase in flow from the motor operated variable orifice pilot device 200 and therefore the excess flow is directed into the main valve (Item 1) cover chamber causing the main valve 100 to modulate towards the closed position. This activity causes the downstream pressure to drop which establishes a new lower downstream pressure set point.

[0051] At this point the decrease of the outlet pressure forces the spring decompression of the pressure reducing pilot 116 accordingly, until the combined flow area relationship between the fixed orifice 118 associated variable orifice 210 and the pressure reducing pilot 116 is recovered. Or as previously explained, [ΔP.sub.1-CH] and [ΔP.sub.CH-2] are equal. Except now [ΔP.sub.1-CH] is defined as the pressure differential value between the main valve cover chamber 114 and the combination of the fixed orifice 116 and variable orifice 210. The downstream pressure is still under control of the pressure reducing pilot 116, but at a lower set point generated by the motor operated variable orifice pilot device 200. At this point the downstream pressure set point is no longer under command of the pressure reducing pilot 116. The downstream pressure set point is now determined by the motor operated variable orifice pilot device 200.

[0052] Increasing the opening of the variable orifice 210 continues to lower the downstream pressure set point. If the variable orifice 210 is opened sufficiently the combined flow area of the fixed orifice 116 and motor operated variable orifice pilot device 200 can be greater than the flow area capacity of the pressure reducing pilot 116 which can cause the main valve 100 to close. This arrangement allows the downstream pressure set point to be adjusted from the baseline high pressure set point all the way down to a zero or near zero set point when the main valve closes. Therefore the lowest outlet pressure modulated value by the motor operated variable orifice pilot device 200 is reached when the combined flow area of the fixed orifice 116 and motor operated variable orifice pilot device 200 is practically equal to the flow area capacity of the pressure reducing pilot 116.

[0053] In addition to the unique pilot plumbing arrangement the motor operated variable orifice device 200 is used as the means to change the downstream pressure set point from a baseline value, as described above. The command to change the downstream pressure set point is typically determined from a process controller 300 where the downstream pressure values and flow values are monitored by means of a pressure transducer 324 and flow meter 326.

[0054] A variable orifice device 200 may be incorporated into an existing pressure regulating valve system to create the control system of the present invention or the control system of the present invention, incorporating the variable orifice device 200, may be plumbed and arranged in a variety of manners. In each case, however, the variable orifice device 200 will be in fluid communication with fluid upstream of the main valve 100 and plumbed or disposed upstream of the pressure reducing or regulating pilot 116 to accomplish the objectives of the invention. When a fixed orifice 118 is either already incorporated into the existing pressure reducing valve system or incorporated into the control system of the present invention, it also is in fluid communication with fluid upstream the main valve 100 and plumbed or disposed upstream of the pressure reducing pilot 116. Fluid from the outlets of the variable orifice device 200 and the fixed orifice 118 converge with each other or are otherwise directed to the inlet of the pressure reducing pilot 116 or the cover chamber 114 of the main valve 100 if the fluid flow exceeds the pressure reducing control pilot's throughput.

[0055] With reference to FIG. 6, an exemplary pilot plumbing arrangement for a control system with a motor operated variable orifice pilot device 200 for pressure modulation control and a manually operated pressure reducing control pilot 116 for a fixed or base line pressure control set point is shown. FIG. 6 shows a system with a motor operated variable orifice pilot device 200 where for multiple pressure set point applications the downstream pressure set point is determined by adjusting the opening of the motor operated variable orifice pilot device 200. For this system design, a variable orifice device 200 is used in combination with a fixed orifice 118 where flow through the variable orifice and fixed orifice, plumbed in parallel, can travel either into the main valve cover 114 or through a pressure reducing pilot 116.

[0056] In this arrangement a baseline pressure set point is established by closing the motor operated variable orifice pilot device 200 so that during this set point process all flow from the pilot plumbing enters through the fixed orifice 118. Typically the baseline maximum prescribed pressure set point is established at any flow rate through the main valve 100 being understood that it is corresponding to or representing the prescribed pressure at high flow (high demand) condition. The baseline pressure set point is the highest desired downstream pressure set point for the application. During this baseline pressure set point step the flow rate through the seat (orifice) of the pressure reducing pilot 116 modulates until it is balanced (or equal to) the flow rate through the fixed orifice 118. In this initial set point step, the downstream pressure is maintained at the set point value for all flow conditions. When the flow rate through the seat of the pressure reducing pilot 116 is less than the flow rate of the fixed orifice 118, part of the flow through the fixed orifice 118 is directed into the main valve cover chamber 114 causing the main valve 100 to modulate towards the closed position which in turn causes pressure on the outlet 104 of the main valve to drop.

[0057] The plumbing arrangement of the control system may include strainers 312, one-way flow controls 328 and other components as deemed necessary or desirable. The control system plumbing arrangement may also include one or more isolation valves (such as a ball valve) 314 used as a means to disable flow through the variable orifice device 200. When the isolation valve 314 is open downstream pressure set point values are under command of the variable orifice device 200 where an increase in flow area through the variable orifice tends to lower the downstream pressure set point and a decrease in flow area through the variable orifice tends to raise the downstream pressure set point. When the isolation valve 314 is closed downstream pressure values are under command of the pressure reducing pilot 116. Flow through the variable orifice device 200 is blocked. In this condition downstream pressure set point is fixed at the baseline pressure set point value of the pressure reducing pilot 116. Closing the isolation valve 314 can be used to either adjust the baseline pressure set point or as a means to override the motor operated variable orifice pilot device 200.

[0058] With reference to FIG. 7, another pilot plumbing arrangement for a pressure reducing valve control system with a motor operated variable orifice pilot device 200 for pressure modulation control and a manually operated pressure reducing control 116 or a fixed or baseline pressure control set point is shown. In this arrangement, the outlet of the motor operated variable orifice pilot device 200 is connected by a tee between the main valve cover chamber 114 and the inlet of the manually operated pressure reducing control 116.

[0059] With reference now to FIG. 8, another pilot plumbing arrangement for a pressure reducing valve control system with a motor operated variable orifice pilot device 200 for pressure modulation control and a manually operated pressure reducing control 116 or a fixed or baseline pressure control set point is shown. In this arrangement, the outlet of the motor operated variable orifice pilot device 200 is connected to a boss on the main valve cover chamber 114. Fluid communication to the pressure reducing control 116 occurs through the piping connected to an opposing boss of the main valve cover chamber 114.

[0060] For control systems that use a pressure regulating pilot 116 in combination with a variable orifice device 200 and a fixed orifice 118, a change in downstream pressure set point is achieved by making an adjustment to the motor operated variable orifice control device 200. The pressure reducing control 116 is used to establish the baseline or highest pressure set point whereas the motor operated variable orifice control device 200 is used to establish pressure set points lower than the baseline. The position of the motor operated variable orifice control device 200 in the pilot plumbing of the control system is such that it is working in parallel with the fixed orifice 116. To work in a parallel flow path arrangement the motor operated variable orifice control device 200 can be plumbed in a variety of manners, as shown above.

[0061] In each of the control system arrangements, upstream fluid flow, such as flow from the valve inlet 102, enters the control system pilot plumbing and is directed through the fixed orifice 118 and the variable orifice device 200. Flow from these orifices is directed to the inlet of the pressure reducing control 116 or the cover chamber 114 of the main valve 100. The amount of flow into or out of the main valve cover chamber 114 is dependent on the flow area and pressure differential through the seat of the pressure reducing control 116. As explained above, the flow into the main valve cover chamber 114 occurs when the total flow rate (volume) through the fixed orifice 118 and variable orifice device 200 is greater than the flow rate through the seat of the pressure reducing control 116. This flow condition causes the main valve 100 to modulate towards the closed position which lowers the downstream pressure. Flow out of the main valve cover chamber 114 occurs when the total flow rate through the fixed orifice 118 and variable orifice device 200 is less than the flow rate through the seat of the pressure reducing control 116. This flow condition causes the main valve 100 to modulate towards the open position which raises the downstream pressure. A stable downstream pressure is obtained when the total flow rate (volume) through the combination of the fixed orifice 118 and variable orifice device 200 is equal to the flow area through the seat of the pressure reducing control 116. In all cases of flow rate change, the change transitions and downstream pressure are stable with no noticeable fluctuations or erratic behavior in downstream pressure values. The outlet pressure of the main valve is stable during the transition step even if there are minor flow oscillations occurring during the transition period.

[0062] Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.