Liquid line break control system and method

• US 3,952,759 A
• Filed: 08/14/1974
• Issued: 04/27/1976
• Est. Priority Date: 08/14/1974
• Status: Expired due to Term

• Current Assignee: M & J Valve Company
• Original Assignee: M & J Valve Company
• Inventors: Ottenstein, Sidney Allan
• Primary Examiner(s): Schwadron, Martin P.
• Assistant Examiner(s): Miller, Robert J.
• Application Number:
  US05/497,248
• Time in Patent Office: 622 Days
• Field of Search: 137/12, 137/14, 137/2, 137/1, 137/487.5, 235/151.34, 73/40.5 R
• US Class Current: 137/12
• CPC Class Codes: F16K 37/00 Special means in or on valves or other cut-off apparatus for indicating or recording operation thereof, or for enabling an alarm to be given
• CPC Class Codes: F17D 5/06 using electric or acoustic means
• CPC Class Codes: G01M 3/2815 using pressure measurements
• CPC Class Codes: Y10T 137/0379 By fluid pressure
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

System and method for automatically closing flow control valves and/or actuating an alarm in the event of a leak or break in a liquid pipeline. The occurrence of a leak or break is determined first by detecting the negative pressure wave which accompanies the leak or break and then by monitoring the rate of static pressure drop on the downstream side of the valve. False alarms and undesired valve closing in response to normal disturbances in the line are avoided by distinguishing between negative pressure waves originating on the upstream and downstream sides of the valve and responding only to the negative waves of downstream origin. Additional protection is provided by continuously monitoring the static pressure on the upstream side of the valve and closing the valve and/or actuating the alarm in the event that pressure falls and remains below a predetermined level.

Claims

1. In a method for controlling the operation of a valve controlling fluid flow in a pipeline to close the valve in the event of a leak or break in the line, the steps of:

monitoring the static fluid pressure in the pipeline to detect the occurrence of a negative pressure wave originating on the downstream side of the valve, distinguishing said wave from a like wave originating on the upstream side, monitoring the rate of static pressure drop on the downstream side in the event that a negative pressure wave originating on that side of the valve is detected, and closing the valve in the event that the pressure on the downstream side decreases faster than a predetermined rate after the negative pressure wave is detected.

2. The method of claim 1 wherein a negative pressure wave originating on the downstream side of the valve is detected by sensing the static pressure in the pipeline on the upstream and downstream sides of the valve and providing an output signal in the event of a rapid drop in the downstream pressure followed by a corresponding drop in the upstream pressure.

3. The method of claim 1 together with the additional steps of monitoring the level of the static pressure on the upstream side of the valve and closing the valve in the event that said pressure falls below a predetermined level.

4. The method of claim 1 wherein a pumping station is connected to the pipeline on the upstream side of the valve and shut-down of the pipeline in response to a negative pressure wave generated by normal operation of the pumping station is avoided by the steps of sensing the static pressures at points on the upstream and downstream sides of the valve, said points being spaced apart by a predetermined distance, detecting the arrival of a negative pressure wave at each of said points, and responding to the wave only in the event that it arrives at the downstream point at a predetermined time before it arrives at the upstream point.

5. The method of claim 1 together with the additional steps of monitoring the level of the static pressure on the upstream side of the valve and inhibiting valve closure in the event that the pressure exceeds a predetermined level.

6. In a system for controlling the operation of a valve controlling the flow in a pipeline to close the valve in the event of a leak or break in the line:

means for detecting the occurrence of a negative pressure wave originating on the downstream side of the valve, and distinguishing said wave from a like wave originating on the upstream side, means for monitoring the rate of static pressure drop on the downstream side in the event that a negative pressure wave originating on that side of the valve is detected, and means for initiating closure of the valve in the event that the pressure on the downstream side decreases faster than a predetermined rate after the negative pressure wave is detected.

7. The system of claim 6 wherein the means for detecting the occurrence of a negative pressure wave comprises means for detecting falling static pressures on the upstream and downstream sides of the valve and means for providing an output signal in the event that a falling pressure is detected on the downstream side and thereafter a falling pressure is detected on the upstream side.

8. The system of claim 6 further including means for monitoring the pressure on the upstream side of the valve and providing a signal for closing the valve in the event that said pressure falls below a predetermined level.

9. The system of claim 6 further including means for monitoring the level of the static pressure on the upstream side of the valve and inhibiting valve closure in the event that the pressure exceeds a predetermined level.

10. In a method for controlling the operation of a valve controlling the flow in a pipeline to close the valve in the event of a leak or break in the line, the steps of:

providing electrical signals corresponding to the static pressures on the upstream and downstream sides of the valve, monitoring the signals to detect falling pressures on the upstream and downstream sides, providing an output signal in the event that a falling pressure is detected on the downstream side and thereafter a falling pressure is detected on the upstream side, monitoring the signal corresponding to the downstream pressure in the event of an output signal to determine whether said pressure is decreasing faster than a predetermined rate, and delivering a control signal for closing the valve in the event that the downstream pressure is decreasing faster than the predetermined rate.

11. The method of claim 10 further including the steps of monitoring the signal corresponding to the upstream pressure and delivering a control signal for closing the valve in the event that said pressure drops below a predetermined level.

12. The method of claim 10 further including the step of selectively applying the control signal to an alarm to actuate the same.

13. The method of claim 10 further including the steps of monitoring the signal corresponding to the upstream pressure and delivering an inhibit signal for preventing valve closure in the event that the pressure exceeds a predetermined level.

14. In a system for controlling the operation of a valve controlling the flow in a pipeline to close the valve in the event of a leak or break in the line:

means for providing electrical signals corresponding to the static pressures on the upstream and downstream sides of the valve, means responsive to the signals for detecting falling pressures and providing an output signal in the event of a falling pressure on the downstream side followed by a falling pressure on the upstream side, and means for monitoring the downstream pressure signal in the event of an output signal and delivering a control signal to initiate closure of the valve in the event that the downstream pressure decreases faster than a predetermined rate.

15. The system of claim 14 further including means responsive to the upstream pressure signal for delivering a control signal for initiating closure of the valve in the event that the upstream pressure falls below a predetermined level.

16. The system of claim 14 further including means for monitoring the signal corresponding to the upstream pressure and delivering an inhibit signal for preventing valve closure in the event that the pressure exceeds a predetermined level.

17. The system of claim 14 wherein the means for detecting falling pressures and providing an output signal includes falling pressure detectors for monitoring the signals corresponding to pressure on the upstream and downstream sides and delivering output signals in the event that the pressure signals change in a predetermined manner, first timing means for delivering an output signal a predetermined time after the occurrence of an output signal from the falling pressure detector for the downstream side of the valve, second timing means for delivering a signal of predetermined duration in response to the output signal from the first timing means, and gating means responsive to signals from the second timing means and the upstream falling pressure detector for delivering an output signal upon conjoint receipt of an output signal from said detector and a signal from said timing means.

18. The system of claim 17 wherein the first and second timing means are one-shot multivibrators.

19. The system of claim 14 further including an alarm and means for applying the control signal to the alarm to actuate the same.

20. The system of claim 19 wherein the means for applying the control signal comprises switch means for selectively applying the signal to initiate closure of the valve or to actuate the alarm.