A method for detecting small leaks or thefts in a pipeline, comprising the following steps:
- forming energy waves in a fluid within a pipeline using a pump or a compressor which travel in the fluid towards an outlet end of the pipeline and defining an energy flow line to be the front of an energy wave which enters the inlet of the pipeline and travels along the pipeline centerline;
- calculating the speed of the energy flow line;
- determining the energy density loss across the leak location directly based on the leaked amount of the fluid on the energy flow line while the interest energy wave section continues to travel towards the outlet of the pipeline, and is detected by sensors at the outlet end of the pipeline, the differences between the measured flows and between the total energies at the both ends of the energy flow line providing information on the leaked amount of the fluid;
- determining the energy density change across the leak location reflecting the leaked amount change on the energy flow line due to an enlarged leaking or the theft valve closing, and determining whether the theft valve is closed;
- detecting pipeline leakage as follows:
- monitoring the measured flow data at both ends of the pipeline to identify flow changes greater than a predetermined strength and duration that occur at different ends within a given time frame;
- and
- determining if a leak or a theft has occurred by the performing following steps:
- determining a phantom leak-started-time at the inlet and outlet of the pipeline when the outlet end flow decreases and the inlet end flow increases, thereby denoting a leak or a theft valve opening event;
- determining a phantom theft-valve-closed time at the inlet and outlet of the pipeline when the outlet end flow increases and the inlet end flow decreases, thereby denoting a theft valve closing event;
- and
- determining if a leak has occurred by:
- defining the first leaking energy flow line for a new leak as the earliest energy flow line that is affected by the new leak that passes the leak location at a leak-started-time and also passes the outlet sensors at the measured phantom leak-started-time related to the new leak at the outlet side of the pipeline;
- detecting the pump response or compressor response to a first expansion pressure wave at the measured phantom leak-started-time at the inlet side of the pipeline as the first expansion pressure wave originated by the new leak passes the inlet sensors and reaches the pump or the compressor after the system response time to the expansion pressure waves with the inlet sensors;
- tracing back the first leaking energy flow line and the trajectory of the first expansion pressure wave line to determine an estimated leak location and leak-starting-time based on the intersection of the two lines;
- determining a leak verification time as the time that the first leaking energy flow line would be expected to pass the outlet sensors of the pipeline if no leak was present;
- calculating the time difference between the leak verification time and the measured phantom leak-started-time at the outlet side to determine the size and location of the new leak and to verify the existence of the leak if the estimated and the measured phantom leak-started-time at the outlet side are within a predetermined tolerance;
- determining an amount of leaked fluid based on the accumulation of each measured flow difference between the two ends of each energy flow line that passes the outlet sensors after the measured phantom leak-started-time at the outlet side of the pipeline;
- and
- when a leak is detected, if the discharge flow increase of the pump or the compressor is smaller than its tested capacity to respond leaking related expansion waves, determining if a new leak exists by:
- measuring the overall flow and determining if the leak is in a different leak location, and is therefore a new leak and or if the detected new leak has the same leak location as the previously detected one determining that the previously detected leak has become larger;
- or
- determining if a theft has occurred by:
- defining the last leaking energy flow line for a new theft as the latest energy flow line that is affected by the new theft that passes the theft location at the theft-valve-closed-time, and also pass the outlet sensors at the measured phantom theft-valve-closed-time related to the new theft at the outlet side of the pipeline;
- detecting the pump response or the compressor response to the last compression pressure wave at the measured phantom theft-valve-closed time at the inlet side of the pipeline as the last compression pressure wave originated by the theft valve closing at the theft-valve-closed-time passes the inlet sensors and reaches the pump or the compressor;
- estimating a theft location and a theft-valve-closed-time for the new theft based on their intersection of the last leaking energy flow line and the trajectory of the last compression pressure wave;
- determining a theft verification time based on an expected time that the last leaking energy flow line would pass the outlet sensors of the pipeline if no theft was present;
- calculating the time difference between the theft verification time and the measured phantom theft-valve-closed-time at the outlet side to determine the size and location of the new theft and verifying a theft if the estimated and the measured phantom theft-valve-closed-time at the outlet side are within a predetermined tolerance;
- determining the amount of leaked fluid based on the accumulation of the measured flow difference between the two ends of each energy flow line that passes the outlet sensors during a phantom theft-duration between the phantom leak-started-time and the phantom theft-valve-closed-time at the outlet side, where the phantom theft-duration is the difference between the theft verification time and the leak verification time;
- and
- after a theft is detected, if the discharge flow decrease of the pump or the compressor is higher than a reference 0 level, detecting additional new thefts as following:
- based on the measured overall flow, if the detected new theft has a different theft location, determining that it is a new theft and if the detected new theft has the same theft location as the previously detected one, determining that the previously detected theft valve closing was not fully closed.