Acoustic Leak Detection in Force Mains via Negative Pressure Inversion
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Solution Overview
Problem
Current technologies for detecting leaks in pressurized wastewater force mains and water distribution systems are inefficient due to high background noise, signal attenuation, and the inability to detect small leaks, especially under transient conditions and in environments with undissolved gases and variable acoustic propagation velocities.
Innovation Solution
The method involves creating negative pressure in the pipe by shutting down the pump, allowing external fluid to enter and generate noise at leak locations, which is then detected using acoustic leak noise correlation techniques with hydrophones or vibration sensors, enabling the analysis of signals to determine leak locations without the interference of pump noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic leak noise correlation is used under positive pipe pressure, then leak detection is possible, but high background noise from pumps and signal attenuation prevent detection of small leaks
Solution Approach 1:
The patent inverts the conventional approach by creating negative pressure conditions in the pipe instead of maintaining positive pressure. This reversal causes external fluid to be drawn into the pipe through leaks, generating acoustic signals that are detectable above the noise floor without pump interference
Solution Approach 2:
The system utilizes periodic pump shutdown cycles to create transient negative pressure conditions. During these periodic intervals when pumps are off, the acoustic environment is quiet enough to detect leak signals, transforming a continuous noise problem into a periodic detection opportunity
2Measurement precision
If mass balance, pressure analysis, or temperature monitoring technologies are used, then leak detection capability is improved, but implementation cost increases significantly
Solution Approach 1:
The system uses existing acoustic correlation hardware and software infrastructure to detect leaks, making the existing technology serve a new purpose (negative pressure leak detection) rather than requiring entirely new expensive measurement systems
Solution Approach 2:
The patent changes the pressure parameter from positive to negative, transforming the operating conditions of existing acoustic correlation systems to enable small leak detection without requiring new hardware or software developments
3Stress or pressure
If pump operates continuously to maintain positive pressure, then pipe remains pressurized for normal operation, but pump noise interferes with acoustic leak detection
Solution Approach 1:
The system employs periodic pump shutdowns during which acoustic leak detection is performed. This creates alternating phases of pressurization (when pumps run) and detection (when pumps are off), eliminating the conflict between maintaining pressure and detecting leaks
Solution Approach 2:
The system maintains continuous monitoring capability by utilizing every pump shutdown cycle for acoustic detection, ensuring that leak detection is an ongoing process rather than a periodic interrupt, thereby maintaining security while enabling detection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively detects both small and large leaks without requiring pipe excavation, reduces implementation costs, and can be easily integrated with existing hardware and software, providing continuous monitoring and accurate leak location identification.
Implementation Method 1
Following pump shutdown, negative internal pressure develops in force mains due to the fact that the wastewater continues to flow along the mains by inertia
Implementation Method 2
acoustic leak noise correlation techniques with hydrophones or vibration sensors, enabling the analysis of signals to determine leak locations
Implementation Method 3
acoustic leak noise correlation techniques with hydrophones or vibration sensors, enabling the analysis of signals to determine leak locations
Data Source
AI summary
A method of detecting leakage in a force main involves placing at least two spaced sensors on the force main. Liquid is pumped through the pipe by means of a pump. The pump is shut down for an interval of time, and during the period following pump shutdown while negative pressure is present in the pipe, signals are generated at the sensors due to noise or vibration resulting from fluid being drawn into the pipe. The position of a leak in the pipe is determined by correlating the leak noise signals generated while the pipe is under negative pressure. Alternatively, the invention can be applied to a pressurized pipe, in which case conditions of negative pressure can be deliberatively created for a period to draw in fluid from the outside.