Water leak detection and shut-off method and apparatus using differential flow rate sensors

• US 8,749,393 B1
• Filed: 02/14/2011
• Issued: 06/10/2014
• Est. Priority Date: 02/14/2011
• Status: Active Grant

• Current Assignee: Control Air Conditioning Corporation
• Original Assignee: Control Air Conditioning Corporation
• Inventors: Tollefson, Robin
• Primary Examiner(s): Lieu, Julie
• Application Number:
  US12/931,869
• Time in Patent Office: 1,212 Days
• US Class Current: 340/605
• CPC Class Codes: A62C 35/60 wet, i.e. containing extinguishing material even when not in use
• CPC Class Codes: A62C 35/68 Details, e.g. of pipes or valve systems valves in general F16K
• CPC Class Codes: A62C 37/50 Testing or indicating devices for determining the state of readiness of the equipment
• CPC Class Codes: F17D 5/02 Preventing, monitoring, or locating loss
• CPC Class Codes: G01M 3/243 for pipes
• CPC Class Codes: G01M 3/2807 for pipes G01M3/2892, G01M3/30 take precedence
• CPC Class Codes: G01M 3/2815 using pressure measurements
• CPC Class Codes: G01M 3/2876 for valves G01M3/30 takes precedence
• CPC Class Codes: G01M 3/3254 using a flow detector G01M3/3245, G01M3/3272 take precedence
• CPC Class Codes: Y10T 137/7727 Excessive flow cut-off
• CPC Class Codes: Y10T 137/7734 Fluid opened valve requiring reset
• CPC Class Codes: Y10T 137/7759 Responsive to change in rate of fluid flow
• CPC Class Codes: Y10T 137/776 Control by pressures across flow line valve

Abstract

A method and apparatus for detecting leakage of flowing liquids from pipes includes an upstream flow-rate sensor positioned between a source of a flowing liquid which is conducted from a source to a destination terminal such as a VAV heat exchanger, and a downstream flow-rate sensor positioned between an outlet port of the destination terminal and a return line for the flowing liquid. The apparatus includes electronic control circuitry which is responsive to a differential flow-rate between upstream and downstream measured flow rates which exceeds a predetermined limit value in removing a valve-opening signal to the upstream shut-off valve, thus closing the valve to interrupt flow of liquid through the valve if the differential flow-rate signifies a leak. Optionally, the apparatus also includes a downstream shut-off valve positioned between the destination terminal and a return line, which is also closed in response to a differential flow-rate exceeding the limit value.

Claims

1. A method for detecting leakage of fluid delivered from a source through a first, source conduit to a destination terminal and returned from the destination terminal through a second, return conduit, said method comprising;

a. measuring a first flow rate of fluid through said source conduit at a first, upstream location to obtain a first, upstream flow rate value,

b. measuring a second flow rate of fluid through said return conduit at a second location downstream from said first location, to obtain a second, downstream flow rate value,

c. comparing said first and second flow rate values to obtain a difference value therebetween, said step of comparing said first and second flow rate values to obtain a difference value therebetween including the step of subtracting said second, downstream flow rate value from said first, upstream flow rate value to obtain a differential flow rate value,

d. determining whether or not said differential flow rate value of said first and second flow rate values exceeds a predetermined limit value, and

e. generating an alarm status signal if said differential flow rate value exceeds said predetermined limit value, said step of determining whether said differential flow rate value exceeds said predetermined limit value including the step of inputting said differential flow rate value to a first input node of a comparator, inputting said limit value to a second input node of said comparator, said comparator being configured to output said alarm status signal if said first input node value exceeds said second input node value.

2. The method of claim 1 further including the step of interrupting flow of said fluid through said return conduit in response to said alarm status signal.

3. The method of claim 1 wherein said comparator has a dead band equal to said predetermined limit value, and said comparator producing at an output node thereof said alarm status signal if the difference value between said first and second flow rate values exceeds said dead-band value of said comparator.

4. The method of claim 2 wherein said step of interrupting flow of fluid through said source conduit in response to said alarm status signal includes the step of shutting off flow of fluid at a location upstream of said first, upstream flow rate sensor.

5. The method of claim 4 further including the step of interrupting flow of fluid through said return conduit, said step including shutting off flow of fluid at a location downstream of said second, downstream flow rate sensor.

6. An apparatus for detecting leakage of liquid delivered from a source to a destination terminal through a first, source conduit and returned from the destination terminal through a second, return conduit, said apparatus comprising;

a. a first, upstream flow rate sensor for measuring a first flow rate of liquid from a source of flowing liquid through said upstream flow rate sensor to a destination terminal,

b. a second, downstream flow rate sensor for measuring a second flow rate of liquid from said destination terminal, and

c. a comparator for determining a difference value between said first and second flow rate values and outputting an alarm status signal if said difference value exceeds a predetermined limit value, said comparator having a first signal input node connected to a signal output node of said first flow rate sensor, a second signal input node connected to a signal output node of said second flow rate sensor, and an output node on which said alarm status signal occurs if the difference between said first and second flow rate value signals exceeds said predetermine limit value.

7. The apparatus of claim 6 further including at least a first valve having an inlet port connected to said source and an outlet port connected to said first flow rate sensor, said first value being operatively interconnected to said comparator, said valve shutting off flow through said source conduit in response to said alarm status signal.

8. The apparatus of claim 7 wherein said first valve is further defined as being an electrically actuated solenoid value.

9. The apparatus of claim 8 wherein said first valve is further defined as being a normally closed valve, whereby interruption of electrical power to said valve causes a spring within said valve to close said valve.

10. The apparatus of claim 7 further including a second valve, said second valve having an inlet port connected to an outlet port of said second, downstream flow rate sensor.

11. The apparatus of claim 6 wherein said comparator is further defined as being a software application implemented in a digital computation apparatus.

12. The apparatus of claim 6 wherein said comparator is further defined as being an electronic circuit.

13. The apparatus of claim 6 wherein said first and second flow rate sensors are each further defined as being a Pitot-tube type sensor.

14. An apparatus for detecting a leakage of liquid from a terminal destination supplied with flowing liquid from a source through a source conduit and shutting off flow of liquid through said source conduit in response to a detection of a leak, said apparatus comprising;

a. a first, upstream remotely actuatable shut-off valve having an inlet port connected to said source of flowing liquid,

b. a first, upstream flow rate sensor having an inlet port connected to an outlet port of said first upstream valve, and an outlet port connected to an inlet port of a destination terminal,

c. a second, downstream flow rate sensor having an inlet port connected to an outlet port of said destination terminal,

d. an electronic control module having;

i. a first interrupt input port electrically connected to an output terminal of said first upstream flow rate sensor for receiving a first upstream electrical flow-rate signal proportional to a first upstream flow-rate of liquid through said source conduit,

ii. a second interrupt input port electrically connected to an output terminal of said second, downstream flow-rate sensor for receiving a second downstream electrical flow rate signal proportional to said second, downstream flow rate of liquid from said destination terminal,

iii. first, upstream shut-off valve actuator circuitry electrically connected to input terminals of said first, upstream shut-off valve,

iv. first, upstream valve shut-off circuitry for providing an input signal to said first, upstream shut-off valve actuator circuitry which causes said circuitry to output a valve-opening signal to said valve, and

v. comparator circuitry for comparing said first and second flow-rate sensor signals, said comparator having a first signal input node connected to said first interrupt port, a second signal input node connected to said second interrupt port, and an output node for outputting a signal to said first shut-off valve circuitry to remove said valve-opening signal if a difference between said first and second flow-rate sensor signals indicates a difference between first and second flow-rates that exceeds a predetermined limit value.

15. The apparatus of claim 14 further including;

a. a second, downstream remotely actuatable shut-off valve, and

b. second, downstream shut-off valve control circuitry for providing an input signal to said second, downstream shut-off valve circuitry which causes said circuitry to output a valve-opening signal unless said comparator circuitry outputs a signal to said second valve control circuitry indicating a difference between first and second flow-rates which exceeds a predetermined limit value.

16. The apparatus of claim 15 wherein said first and second shut-off valves are normally closed, spring actuated solenoid valves.

17. The apparatus of claim 14 wherein said electronic control module includes micro-processor control logic.