What it shows
A fibre cable buried alongside the pipeline acts as a continuous sensor. DAS hears the leak noise, DTS sees the temperature anomaly it creates, and NPW times the pressure drop arriving at the two ends. Set the pipeline and the leak, press play, and compare when each method alarms and where it places the leak.
How each method works
DAS, distributed acoustic sensing. Laser pulses scatter off the fibre, and vibrations change the backscatter. A leak is a persistent broadband noise source, so a bright vertical band appears on the waterfall at the leak position within seconds, with metre-scale resolution.
DTS, distributed temperature sensing. Raman or Brillouin scattering gives temperature every metre. A gas leak cools the soil (Joule-Thomson), a hot product warms it, and a water leak gives only a small contrast with the ground, so DTS is the weakest method for water. It is slow, taking minutes as heat diffuses to the cable, and misses very small leaks.
NPW, negative pressure wave. A sudden leak sends a pressure drop both ways at about 1 km/s. With the arrival times tin and tout at the two ends, the location is x = (L + a·(tin − tout)) / 2, where a is the wave speed. It is fast, but it only sees a sudden onset and needs synchronised clocks.
Read this first
This is a simplified illustration of how the three methods behave. Detection times, location accuracy and sensitivity on a real pipeline depend on the line, the fluid, the cable installation and the instrument settings, and must be confirmed by testing. Figures marked “assumed” are model settings, not measured results.
