Apparatus and method for inline leak detection and quantification

A method for detecting a leak in a pipeline wall comprising:

• providing a leak detecting pig apparatus comprising:
• an outer housing having a first end, a second end, a first inner diameter and first outer diameter;
• a front seal stack coupled to the first end of the outer housing, positioned to seal against an inner surface of a pipeline;
• a rear seal stack coupled to the second end of the outer housing positioned to seal against the inner surface of the pipeline, such that an annular space defined between the front seal stack, the rear seal stack, the first outer diameter of the outer housing, and the inner pipeline surface defines an annular control volume;
• a fluid path fluidly coupled between the control volume, and the rear of the apparatus, in fluid communication with a flow meter;
• the flow meter, positioned to measure a flow rate through the fluid path;
• a rear pressure sensor positioned to measure a first absolute pressure P1 in the pipeline behind the rear seal stack;
• a control volume pressure sensor positioned to measure a second absolute pressure P2 in the annular control volume;
• and
• a front pressure sensor positioned to measure a third absolute pressure P3 in the pipeline in front of the front seal stack;
• passing said apparatus through the bore of a pipeline, driven by a fluid flow in the pipeline;
• measuring the absolute pressures of P1, P2 and P3;
• measuring any fluid flow through the flow meter;
• measuring distance traveled by the apparatus;
• recording said pressures, fluid flow rates and distances with the aid of microcontroller PCBs;
• and
• downloading and analyzing said measurements with a PC at the end of measurement run;
• a first pressure port behind the rear seal stack in fluid communication with a first pressure flow path PFP1 between the rear seal stack and the first pressure sensor P1;
• a second pressure port and a second pressure flow path PFP2 between the control volume CV and the second pressure sensor P2;
• a third pressure port in front of the front seal stack in fluid communication with a third pressure flow path PFP3 located between a sealed pressure bulkhead and the third pressure sensor P3 and between a first inner instrument housing within the outer housing and a second inner instrument housing;
• wherein absolute pressure values from each location can be read directly by the pressure sensors P1, P2 and P3
• wherein said pressure sensors P1, P2 and P3 measure absolute pressures at a plurality of locations of the pig as it passes through the pipeline;
• wherein said flow meter measures any fluid flow through the pig into the control volume as it passes through the pipeline;
• and
• determining the location and quantifying a leak flow rate;
• wherein a leak in the pipeline is detected when P1>P2 and the flow meter measures flow rate F>0 through the control volume.

A pipeline leak detecting pig apparatus for detecting leaks in the wall of a pipeline, the apparatus comprising:

• an outer housing having a first end, a second end, a first inner diameter and first outer diameter;
• a first inner instrument housing within the outer housing having a first inner instrument housing end, a second inner instrument housing end, a first inner instrument housing inner diameter and a first inner instrument housing outer diameter;
• wherein the first inner instrument housing outer diameter, the first inner diameter of the outer housing and a bulkhead create a pressure vessel within the leak detecting pig apparatus in communication with the pressurized fluid within the pipeline at rear of the leak detecting apparatus;
• a front seal stack coupled to the first end of the outer housing, positioned to seal against an inner surface of a pipeline;
• a rear seal stack coupled to the second end of the outer housing positioned to seal against the inner surface of the pipeline, such that an annular space defined between the front seal stack, the rear seal stack, the first outer diameter of the outer housing, and the inner pipeline surface defines an annular control volume;
• a fluid path fluidly coupled between the control volume and the rear of the apparatus, in communication with a flow meter;
• wherein the flow meter resides in the inner instrument housing and the fluid path to the control volume passes through the inner instrument housing and the pressure vessel and is in fluid communication with the control volume via a flow tube;
• the flow meter, positioned to measure a flow rate through the fluid path;
• wherein said flow meter measures for any fluid flow through the pig from the rear of the apparatus into the control volume;
• and
• wherein a leak in the pipeline can be detected when the flow meter measures flow rate F>0 through the control volume.

A method for detecting a leak in a pipeline wall comprising:

• providing a leak detecting pig apparatus comprising:
• an outer housing having a first end, a second end, a first inner diameter and first outer diameter;
• a front seal stack coupled to the first end of the outer housing, positioned to seal against an inner surface of a pipeline;
• a rear seal stack coupled to the second end of the outer housing positioned to seal against the inner surface of the pipeline, such that an annular space defined between the front seal stack, the rear seal stack, the first outer diameter of the outer housing, and the inner pipeline surface defines an annular control volume;
• a fluid path fluidly coupled between the control volume and the rear of the apparatus, and in fluid communication with a flow meter and the pipeline behind the apparatus;
• the flow meter, positioned to measure a flow rate through the fluid path;
• an odometer for measuring distance traveled by recording pulses for each flow rate recorded;
• a first pressure port behind the rear seal stack in fluid communication with a first pressure flow path PFP1 between the rear seal stack and a first pressure sensor P1;
• a second pressure port and a second pressure flow path PFP2 between the control volume CV and a second pressure sensor P2;
• a third pressure port in front of the front seal stack in fluid communication with a third pressure flow path PFP3 located between a sealed pressure bulkhead and a third pressure sensor P3 and between a first inner instrument housing within the outer housing and a second inner instrument housing;
• passing said apparatus through the bore of a pipeline, driven by a fluid flow in the pipeline;
• measuring any fluid flow through the flow meter;
• measuring distance traveled by the apparatus;
• recording said fluid flow rates and distances with the aid of microcontroller PCBs;
• and
• downloading and analyzing said measurements with a PC at the end of measurement run;
• wherein said flow meter measures any fluid flow through the pig, from the rear of the apparatus into the control volume as it passes through the pipeline;
• and
• determining the location and quantifying a leak volume;
• wherein a leak in the pipeline is detected when the flow meter measures flow rate F>0 through the control volume.