METHOD AND APPARATUS FOR MONITORING FLUID FLOW SYSTEMS

• US 3,723,987 A
• Filed: 03/22/1971
• Issued: 03/27/1973
• Est. Priority Date: 03/22/1971
• Status: Expired due to Term

• Current Assignee: Larry F. Barone Jr, Paul E. Patterson, Ross A. Shade
• Original Assignee: Larry F. Barone Jr, Paul E. Patterson, Ross A. Shade
• Inventors: Shade, Ross A., Barone, Larry F. Jr., Patterson, Paul E.
• Primary Examiner(s): Habecker, Thomas B.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US05/126,506
• Time in Patent Office: 736 Days
• Field of Search: 340/242,239,248A 235/151.34 73/196,40.5
• US Class Current: 340/527
• CPC Class Codes: G01M 3/2807 for pipes G01M3/2892, G01M3/30 take precedence

Abstract

A system for detecting leakage in a long pipeline employs meters to generate digital flow signals at stations adjacent inputs and outputs of the pipe system. A scaler function equal to the difference in the input and output flow of the system, as indicated by the meters, is computed when the system is known to be in a leak-free condition. The scaler function is combined with one of the meter representations of system input or output to provide a dynamic balance of input and output, as indicated by the meters. Subsequent deviation from balanced condition is employed to actuate an alarm. Signals from the upstream station are delayed by the amount of time required for a flow disturbance to propagate between input and output stations so as to eliminate effects of such disturbance upon the input-output comparison. Input and output flows are compared concomitantly for both short and long periods to enable rapid detection of large leaks and also detection of much smaller leaks.

Claims

1. The method of monitoring a fluid flow system comprising the steps of generating a first signal representative of flow of fluid in said system at a first station, generating a second signal representative of fluid flow in said system at a second station downstream from said first station, normalizing said signals to a common relative reference at an acceptable flow condition of said fluid system, concomitantly accumulating differential flow totals based upon said normalized first and second signals, over both short and long periods of time, generating a first short-period alarm when the differential flow total accumulated over said short period attains a first value that represents a relatively high leak rate, and generating a second long-period alarm when the differential flow total accumulated over said long period attains a value significantly greater than said first-mentioned value, to thereby indicate a relatively small leak rate occurring over said long period of time.

2. The method of claim 1 including the step of repetitively zeroing both of said accumulated differential flow totals at the end of each consecutive occurrence of said short and long periods, respectively.

3. In a system for characterizing the flow of fluid in a fluid flow system between a plurality of spaced metering stations, the combination comprising first means for generating a first signal representative of fluid flow at one of said stations, second means for generating a second signal representative of fluid flow at another of said stations, means for combining with one of said signals a third signal representing the difference of flow between said one and another of said stations, as indicated by said first and second signals, when said system is in a substantially leak-free condition, a differential accumulator, means for applying said first signal and said combined signals to said accumulator, means responsive to a deviation in said accumulator exceeding a specified constraint for generating a control function, a second differential accumulator for totaling the difference in flow as represented by said first signal and said modulated signal over a first time interval, said first-mentioned differential accumulator totaling the difference of the inputs thereof over a second time interval that is longer than said first time interval, and means for generating a second control function when the difference totaled by said second accumulator exceeds a second constraint, said first-mentioned constraint comprising a selected totalized flow, said second constraint comprising a selected totalized flow that is considerably less than said first totalized flow, whereby said first-mentioned accumulator will cause generation of a control function upon occurrence of leaks of relatively low rate existing for a relatively long time, and said second accumulator will cause generation of a control function upon occurrence of leaks of relatively high rate existing for a relatively short time.

4. The system of claim 3 wherein said means for generating said second control function comprises means for generating first, second and third alarm signals respectively when said second accumulator total exceeds said second constraint at three successive times, means for resetting said second accumulator to zero each time its total exceeds said second constraint, and generating said second control signal upon occurrence of the third one of said alarm signals.

5. The method of monitoring a fluid flow system comprising the steps of observing the system to insure that it is in acceptable condition, flowing fluid through the system from an upstream station to a downstream station thereof, monitoring fluid flow at said upstream and downstream stations to provide upstream and downstream indications of flow, balancing said system and said flow indications, when the system is in an acceptable condition, so as to account for differences in flow parameters at and between said upstream and downstream stations and for relative differences in flow monitoring at said stations, said balancing comprising the modification of at least one of said indications by a factor sufficient to substantially minimize the difference between said indications when said system is in said acceptable condition, relatively delaying said indications, as modified, by an amount sufficient to compensate for the time of propagation of a flow disturbance in said fluid from one of said stations to the other, thereafter monitoring the difference between said indications as so modified, whereby subsequent deviation of said difference will indicate a change in the relative flow of said upstream and downstream stations, and thereby indicate a discrepancy in the system, accumulating said monitored difference to provide indications of flow difference totals over relatively long and short intervals concomitantly, generating a first alarm signal when the long interval flow difference total exceeds a first threshold to thereby indicate relatively small leaks, and generating a second alarm signal when said short interval flow difference total exceeds a second threshold that is considerably smaller than said first threshold to thereby indicate relatively large leaks.