Real time remote sensing pressure control system using periodically sampled remote sensors

• US 5,540,555 A
• Filed: 10/04/1994
• Issued: 07/30/1996
• Est. Priority Date: 10/04/1994
• Status: Expired due to Fees

• Current Assignee: Fifeco, Inc.
• Original Assignee: Unosource Controls Incorporated
• Inventors: Corso, Anthony B., Elliott, G. Mark
• Primary Examiner(s): Gluck, Richard E.
• Assistant Examiner(s): THAI, XUAN MARIAN
• Application Number:
  US08/318,040
• Time in Patent Office: 665 Days
• Field of Search: 417/18, 417/44.2, 417/53, 137/567, 165/22
• US Class Current: 417/44.2
• CPC Class Codes: E03B 11/00 Arrangements or adaptations of tanks for water supply water-butts E03B3/03; storage aspects B65D, B65G, F17B, F17C; foundations E02D27/38; construction or assembling of bulk storage containers employing civil engineering techniques E04H7/00; tower aspects E04H12/00
• CPC Class Codes: F04B 2205/06 Pressure in a (hydraulic) circuit
• CPC Class Codes: F04B 2205/07 Pressure difference over the pump
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine
• CPC Class Codes: Y10T 137/86027 Electric
• CPC Class Codes: Y10T 137/86163 Parallel

Abstract

A real time remote sensing pressure control system is provided which uses periodically sampled remote sensors to generate a bias signal that modifies the base setpoint of a proportional-integral controller that controls variable speed pumps. This control scheme saves energy by slowing the rotational speed of the variable-speed secondary pumps during periods of light system demand. The system can be provided with more than one zone of system loads (such as chilled or hot water coils) and a remote pressure sensor (gauge or differential) can be provided at each of those zones. In addition, a local pressure sensor (gauge or differential) is provided at the primary and secondary pumps. The process variable signals detected by the remote pressure sensors is communicated by a building automation system or other type of data highway, which inherently delays the real time nature of those sensed signals and only periodically provides an update of those signals. To provide stable control of the variable speed pumps, the local pump controller utilizes the local pressure sensor'"'"'s signal to control the speed of those pumps in a stable manner, and a bias signal is provided based upon the periodically updated remote signals from the remote pressure sensors of each zone. In a typical multi-zone control system, the zone requiring the greatest pressure change is selected and its signal is used to create the necessary bias signal that is used to control the variable speed pumps. This control scheme can be utilized in booster pressure systems or other pumping systems in which more than one pumping location must supply water or other liquids to remotely located and diverse loads. In an alternate embodiment, a real time remote sensing pressure control system is provided that utilizes more than one water and pumping source at remote locations from one another to supply a common distribution system. This distribution system can either be a non-recirculating system, such as a potable water system, or can be a recirculating system in which some or all of the liquid is to be returned to the source, such as in chemical plants or oil refineries.

Claims

1. A water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a return pipe connected to the suction side of said primary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one system load having a supply and return line, said water system comprising:

(a) a local differential pressure sensor connected to said supply pipe and to said return pipe, said local differential pressure sensor including an output that generates a first signal related to the differential pressure across the local differential pressure sensor;

(b) a remote differential pressure sensor connected to the supply and return lines at each of said at least one system load, said remote differential pressure including an output that generates a second signal related to the differential pressure across the remote differential pressure sensor;

(c) a remote control panel located near each of said at least one system load, said remote control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit being configured to receive the second signal generated by the output of said remote differential pressure sensor, said second processing circuit additionally having a communications output device that transmits information corresponding to said signal; and

(d) a local control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said first processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive the first signal generated by the output of said local differential pressure sensor, said first processing circuit additionally having a communications input device that receives said information transmitted by said communications output device at the remote control panel, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the values of said first and second signals.

2. The water system as recited in claim 1, wherein said first and second signals are electrical signals.

3. The water system as recited in claim 1, wherein said first and second signals are pneumatic signals.

4. A water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a return pipe connected to the suction side of said primary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one system load having a supply and return line, said water system comprising:

(a) a local differential pressure sensor connected to said supply pipe and to said return pipe, said local differential pressure sensor including an output that generates a first signal related to the differential pressure across the local differential pressure sensor,

(b) a remote differential pressure sensor connected to the supply and return line at each of said at least one system load, said remote differential pressure including an output that generates a second signal related to the differential pressure across the remote differential pressure sensor;

(c) a remote control panel located near each of said at least one system load, said remote control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit being configured to receive the second signal generated by the output of said remote differential pressure sensor, said second processing circuit additionally having a communications output device that transmits information corresponding to said second signal; and

(d) a local control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said first processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive the first signal generated by the output of said local differential pressure sensor, said first processing circuit additionally having a communications input device that receives said information transmitted by said communications output device at the remote control panel, said first processing circuit being configured to provide a setpoint for each of said at least one system load, wherein the setpoint represents the desired pressure for that system load, said first processing circuit being configured to determine the magnitude of deviation between the actual differential pressure sensed by each said remote differential pressure sensor and said setpoint for each corresponding system load based upon the information received from said communications output device at the remote control panel and its associated setpoint, said deviation creating a third signal, said first processing circuit using said third signal to modify said first signal to create a fourth signal, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

5. The water system as recited in claim 4, wherein said first and second signals are electrical signals.

6. The water system as recited in claim 4, wherein said first and second signals are pneumatic signals.

7. A water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a return pipe connected to the suction side of said primary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one zone containing a system load having a supply and return line, said water system comprising:

(a) a local differential pressure sensor connected to said supply pipe and to said return pipe, said local differential pressure sensor including an output that generates a first signal related to the differential pressure across the local differential pressure sensor;

(b) a remote differential pressure sensor connected to the supply and return line at each of said at least one zone, said remote differential pressure including and output that generates a second signal related to the differential pressure across the remote differential pressure sensor;

(c) a remote control panel located near each of said at least one zone, said remote control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit being configured to receive the second signal generated by the output of said remote differential pressure sensor, said second processing circuit additionally having a communications output device that transmits information corresponding to said second signal; and

(d) a local control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said first processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive the first signal generated by the output of said local differential pressure sensor, said first processing circuit additionally having a communications input device that receives said information transmitted by said communications output device at the remote control panel, said first processing circuit being configured to provide a setpoint for each of said at least one zone, wherein the setpoint represents the desired pressure for that zone, said first processing circuit being configured to determine the zone requiring the greatest amount of correction to bring the actual differential pressure of a particular zone to its set point, and to create a third signal corresponding to the magnitude of said greatest amount of correction required based upon the information received form said communications output device at the remote control panel and its associated setpoint, said first processing circuit using said third signal to modify said first signal to create a fourth signal, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

8. The water system as recited in claim 7, wherein said first and second signals are electrical signals.

9. The water system as recited in claim 7, wherein said first and second signals are pneumatic signals.

10. A water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a return pipe connected to the suction side of said primary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one zone containing a system load having a supply and return line, said water system comprising:

(a) a local differential pressure sensor connected to said supply pipe and to said return pipe, said local differential pressure sensor including an output that generates a first signal related to the differential pressure across the local differential pressure sensor.

(b) a remote differential pressure sensor connected to the supply and return line at each of said at least one zone, said remote differential pressure including an output that generates a second signal related to the differential pressure across the remote differential pressure sensor;

(c) a remote control panel located near each of said at least one zone, said remote control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit being configured to receive the second signal generated by the output of said remote differential pressure sensor, said second processing circuit additionally having a communications output device that transmits information corresponding to said second signal; and

(d) a local control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said first processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive the first signal generated by the output of said local differential pressure sensor, said first processing circuit additionally having a communications input device that receives said information transmitted by said communications output device at the remote control panel, said first processing circuit being configured to provide a setpoint for each of said at least one zone, wherein the setpoint represents the desired pressure for that zone, said first processing circuit being configured to determine the zone having the highest load, and to create a third signal corresponding to the magnitude of said highest load based upon the information received from said communications output device at the remote control panel, said first processing circuit using said third signal to modify said first signal to create a fourth signal, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

11. The water system as recited in claim 10, wherein said first and second signals are electrical signals.

12. The water system as recited in claim 10, wherein said first and second signals are pneumatic signals.

13. A water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one system load having a supply line, said water system comprising:

(a) a local pressure sensor connected to said supply pipe, said local pressure sensor including an output that generated a first signal related to the pressure at the local pressure sensor;

(b) a remote pressure sensor connected to the supply line at each of said at least one system load, said remote pressure including an output that generates a second signal related to the pressure at the remote pressure sensor;

(c) a remote control panel located near each of said at least one system load, said remote control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit being configured to receive the second signal generated by the output of said remote pressure sensor, said second processing circuit additionally having a communications output device that periodically transmits information corresponding to said second signal; and

(d) a local control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said first processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive in real time the first signal generated by the output of said local pressure sensor, said first processing circuit additionally having a communications input device that periodically receives said information transmitted by said communications output device at the remote control panel, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the values of said first and second signals.

14. The water system as recited in claim 13, wherein said first processing circuit is further configured to provide a setpoint for each of said at least one system load, wherein the setpoint represents the desired pressure for that system load, said first processing circuit also being configured to determine the magnitude of deviation between the actual pressure sensed by each said remote pressure sensor and said setpoint for each corresponding system load based upon the information received from said communications output device at the remote control panel and its associated setpoint, said deviation creating a third signal, said first processing circuit using said third signal to modify said first signal to create a fourth signal, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

15. The water system as recited in claim 13, wherein said at least one system load is contained within at least one zone;

said first processing circuit is further configured to provide a setpoint for each of said at least one zone, wherein the setpoint represents the desired pressure for that zone, said first processing circuit being configured to determine the zone requiring the greatest amount of correction to bring the actual pressure of a particular zone to its setpoint, and the create a third signal corresponding to the magnitude of said greatest amount of correction required based upon the information received from said communications output device at the remote control panel and its associated setpoint, said first processing circuit using said third signal to modify said first signal to create a fourth signal, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

16. The water system as recited in claim 13, wherein said at least one system load is contained within at least one zone;

said first processing circuit is further configured to provide a setpoint for each of said at least one zone, wherein the setpoint represents the desired pressure for that zone, said first processing circuit being configured to determine the zone having the highest load based upon the information received from said communications output device at the remote control panel, said first processing circuit using said third signal to modify said first signal to create a fourth signal, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

17. A method for controlling a water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a return pipe connected to the suction side of said primary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one system load having a supply and return line, said water system comprising:

(a) measuring the differential pressure across said supply and return pipes and creating a first signal related to this local differential pressure;

(b) measuring the differential pressure across said supply and return lines at each of said at least one system load and creating a second signal related to this remote differential pressure;

(c) communicating said second signal at periodic intervals to a control panel;

(d) communicating said first signal in real time to said control panel; and

(e) controlling the speed of said at least one variable speed secondary pump based upon the values of said first and second signals.

18. The method as recited in claim 17, further comprising the steps of providing a setpoint for each of said at least one system load, wherein the setpoint represents the desired differential pressure for that system load;

determining the magnitude of deviation between the actual differential pressure measured at each said one system load and its corresponding setpoint based upon said second signal and its associated setpoint, said deviation creating a third signal;

modifying said first signal based upon the value of said third signal to create a fourth signal; and

controlling the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

19. The method as recited in claim 17, further comprising the steps of grouping said at least one system load into at least one zone;

providing a setpoint for each of said at least one system zone, wherein the setpoint represents the desired differential pressure for that zone;

determining the zone requiring the greatest amount of correction to bring the actual pressure of a particular zone to its setpoint, said determination creating a third signal corresponding to the magnitude of said greatest amount of correction required based upon information, including said second signal, received by said control panel;

using said third signal to modify said first signal to create a fourth signal; and

controlling the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

20. The method as recited in claim 17, further comprising the steps of grouping said at least one system load into at least one zone;

providing a setpoint for each of said at least one system zone, wherein the setpoint represents the desired differential pressure for that zone;

determining the zone having the highest load, and creating a third signal corresponding to the magnitude of said highest load based upon information, including said second signal, received by said control panel;

using said third signal to modify said first signal to create a fourth signal; and

controlling the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

21. A method for controlling a water system of the type that includes at least one primary pump, at least one heat exchanging device, at least one variable speed secondary pump, a supply pipe connected to the discharge side of said variable speed secondary pump, at least one system load having a supply line, said water system comprising:

(a) measuring the pressure at said supply pipe and creating a first signal related to this local pressure;

(b) measuring the pressure at said supply line at each of said at least one system load and creating a second signal related to this remote pressure;

(c) communicating said second signal at periodic intervals to a control panel;

(d) communicating said first signal in real time to said control panel; and

(e) controlling the speed of said at least one variable speed secondary pump based upon the values of said first and second signals.

22. The method as recited in claim 21, further comprising the steps of providing a setpoint for each of said at least one system load, wherein the setpoint represents the desired pressure for that system load;

determining the magnitude of deviation between the actual pressure measured at each said one system load and its corresponding setpoint based upon said second signal and its associated setpoint, said deviation creating a third signal;

modifying said first signal based upon the value of said third signal to create a fourth signal; and

controlling the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

23. The method as recited in claim 21, further comprising the steps of grouping said at least one system load into at least one zone;

providing a setpoint for each of said at least one system zone, wherein the setpoint represents the desired pressure for that zone;

determining the zone requiring the greatest amount of correction to bring the actual pressure of a particular zone to its setpoint, said determination creating a third signal corresponding to the magnitude of said greatest amount of correction required based upon information, including said second signal, received by said control panel;

using said third signal to modify said first signal to create a fourth signal; and

controlling the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

24. The method as recited in claim 21, further comprising the steps of grouping said at least one system load into at least one zone;

providing a setpoint for each of said at least one system zone, wherein the setpoint represents the desired pressure for that zone;

determining the zone having the highest load, and creating a third signal corresponding to the magnitude of said highest load based upon information, including said second signal, received by said control panel;

using said third signal to modify said first signal to create a fourth signal; and

controlling the speed of said at least one variable speed secondary pump based upon the value of said fourth signal.

25. A water system of the type that includes a plurality of zones each containing a water source, at least one variable speed pump per said water source, at least one system load, a pipe from each of said plurality of water sources to said at least one system load, said water system comprising:

(a) a first pressure sensor connected to one of said pipes, said first pressure sensor having an output that generates a first signal related to the pressure at said first pressure sensor;

(b) a master control panel associated with a first one of said zones, said master control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive said first signal, said first processing circuit having a communications input/output device that transmits and receives information related to said water system, said first processing circuit being configured to provide a setpoint for said first zone;

(c) a second pressure sensor connected to another of said pipes, said second pressure sensor having an output that generates a second signal related to the pressure at said second pressure sensor;

(d) at least one slave control panel, the first one of said slave control panels being associated with a second one of said zones, said first slave control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit further including a controller that controls the speed of a pump, said second processing circuit being configured to receive said second signal, said second processing circuit having a communications input/output device that transmits and receives information related to said water system, said second processing circuit being configured to provide a setpoint for said second zone;

(e) a data highway that communicates information to and from each of said master and slave control panels;

(f) said first processing circuit additionally being configured to determine each of the setpoints and actual pressures for all zones within said water system, then to determine a bias value needed by said water system so that said at least one variable speed pump that is presently operating is controlled in a manner to satisfy the setpoints at all of said zones, said first processing circuit being configured to transmit said bias value to said at least one slave control panel via the data highway, said first processing circuit using said bias value to modify the setpoint for said first zone accordingly to control said at least one variable speed pump associated with said first zone; and

(g) each of said at least one slave control panel'"'"'s second processing circuit additionally being configured to receive said bias value from the data highway, said second processing circuit using said bias value to modify the setpoint for said second zone accordingly to control said at least one variable speed pump associated with said second zone.

26. The water system as recited in claim 25, wherein said first processing circuit is further configured to determine the deviation between the actual pressure and the setpoint for each said zone, said deviation occurring in all zones being used to determine said bias value.

27. The water system as recited in claim 25, wherein said first processing circuit is further configured to determine the zone requiring the greatest amount of correction to bring the actual pressure of a particular zone to its setpoint, and to create a third signal corresponding to the magnitude of said greatest amount of correction required within said water system, said first processing circuit using said third signal to determine said bias value.

28. The water system as recited in claim 25, wherein said first processing circuit is further configured to determine the zone having the highest load, and to create a third signal corresponding to the magnitude of said highest load within said water system, said first processing circuit using said third signal to determine said bias value.

29. The water system as recited in claim 26, wherein the corresponding processing circuit of the one of said master and slave control panels that is associated with the zone that presently is incurring the greatest underpressure deviation ignores said bias value.

30. The water system as recited in claim 27, wherein the corresponding processing circuit of the one of said master and slave control panels that is associated with the zone that presently is requiring the greatest amount of correction to bring its actual pressure to its setpoint ignores said bias value.

31. The water system as recited in claim 28, wherein the corresponding processing circuit of the one of said master and slave control panels that is associated with the zone that presently is incurring the highest load ignores said bias value.

32. A method for controlling a water system of the type that includes a plurality of zones each containing a water source, at least one variable speed pump per said water source, at least one system load, a pipe from each of said plurality of water sources to said at least one system load, said method comprising the steps of:

(a) measuring the pressure at one of said pipes associated with a first one of said zones and providing a first setpoint for said first zone;

(b) measuring the pressure at another of said pipes associated with a second of said zones and providing a second setpoint for said second zone; and

(c) determining each of the setpoints and actual pressures for all zones within said water system, then determining a bias value needed by said water system so that said at least one variable speed pump that is presently operating is controlled in a manner to satisfy the setpoints at all of said zones, and modifying the setpoint for each of said zones accordingly, utilizing said bias value.

33. The method as recited in claim 32, further comprising the steps of creating a first signal related to the pressure at said first zone, creating a second signal related to the pressure at said second zone, and communicating at least one of said signals and said setpoint values between zones at periodic intervals, while controlling said at least one variable speed pump in real time.

34. The method as recited in claim 32, further comprising the steps of determining the deviation between the actual pressure and the setpoint for each said zone, and using said deviation occurring in all zones to determine said bias value.

35. The method as recited in claim 34, further comprising the step of ignoring said bias value at the zone that presently is incurring the greatest underpressure deviation.

36. The method as recited in claim 32, further comprising the steps of determining the zone requiring the greatest amount of correction to bring the actual pressure of a particular zone to its setpoint, and using the magnitude of said greatest amount of correction required within said water system to determine said bias value.

37. The method as recited in claim 36, further comprising the step of ignoring said bias value at the zone that presently is requiring the greatest amount of correction to bring its actual pressure to its setpoint.

38. The method as recited in claim 32, further comprising the steps of determining the zone having the highest load, and using the magnitude of said highest load within said water system to determine said bias value.

39. The method as recited in claim 38, further comprising the step of ignoring said bias value at the zone that presently is incurring the highest load.

40. A fluid pumping system of the type having a pumping station that includes at least one variable speed pump, a discharge pipe connected to said pumping station, a system load having a supply line, said discharge pipe being connected to said supply line, said fluid pumping system comprising:

(a) a first pressure sensor connected to said discharge pipe, said first pressure sensor including an output that generates a first signal related to the pressure across the first pressure sensor;

(b) a second pressure sensor connected to the supply line at said system load, said second pressure sensor including an output that generates a second signal related to the pressure across the second pressure sensor;

(c) a second control panel located near said system load, said second control panel having a second processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said second processing circuit being configured to receive the second signal generated by the output of said second pressure sensor, said second processing circuit additionally having a communications output device that transmits information corresponding to said second signal; and

(d) a first control panel having a first processing circuit which includes a memory circuit, input/output circuits, and a clock circuit that measures real time, said first processing circuit further including a controller that controls the speed of a pump, said first processing circuit being configured to receive the first signal generated by the output of said first pressure sensor, said first processing circuit additionally having a communications input device that receives said information transmitted by said communications output device at the second control panel, said first processing circuit being configured to control the speed of said at least one variable speed secondary pump based upon the values of said first and second signals, said first processing circuit using a predetermined setpoint at which the desired pressure of the system load is to be maintained, said first signal being used as a bias for said setpoint.