Abstract: Clam-on and differential pressure flowmeter produces sound waves travelling in axial direction along the pipe wall with the help of natural sound waves conduit in the pipeline excited by wide electronic beam vibrator. When the sound waves(travelling in axial direction) travel further on, they produce sound energy passing through liquid in the form of wide electronic beam, which travels along the pipe wall when reaching the wall opposite and received by the sensor. It takes sound energy longer to reach the opposite sensor when emitted from the upstream direction than from the downstream, just the time difference of which is made use of by the flowmeter in flowrate measurement. The time differential leak detection system (clam on) is refered to as the site detection station which is a series installation. It has not only the time differential flowmeter and a temperature detector but also radio/ satellite as the telecommunication equipment. On top of the functions mentioned above, this system can also perform inspections on flowrate increase, thermal expansion and shrinkage; real time interface inspection can also be done on the screen; display the real volume of each batch flowrate; supervision of the medium being transported can be performed, continuely judging the type and class of the medium; define the leak location and give alarms if any; scrapers can be site inspected by the system, with alarms given if any. The system also has the function of condition monitoring automatically so that fault alarming can be avoided.