Leakage detector, leakage detection method, and pipe network monitoring apparatus

A pipe network monitoring apparatus comprising:

• a plurality of leakage detectors each mounted, respectively, at a plurality of locations of a pipe network comprised of pipes and joints, and configured to convert a pressure fluctuation along with movement of a fluid through a pipeline to an electric charge signal;
• a plurality of communication devices each configured to transmit the electric charge signal obtained by a respective one of the leakage detectors;
• and
• a display device configured to receive and display information transmitted from the communication devices, at a remote location,
• wherein each of the leakage detectors comprises a base, a piezoelectric element supported by the base and configured to convert vibration-sounds to an electric signal, and a weight member loaded against the piezoelectric element, wherein the piezoelectric element is made of a polymeric piezoelectric material, and wherein each of the leakage detectors are configured to allow a distance between a support point of the piezoelectric element, supported by a support device, and a load point of the piezoelectric element, loaded by the weight member, to be variably changed in a mechanical manner by a slider to thereby allow the resonant frequency of a system comprising the piezoelectric element and the weight member to be variably changed,
• wherein further,
• a resonant frequency of a system comprising the piezoelectric element and the weight member is set in a range of 10 Hz to 1000 Hz.

A leakage detector for detecting vibration-sounds caused by fluid leakage from a pipeline, comprising a base, a piezoelectric element supported by the base and configured to convert vibration-sounds to an electric signal, and a weight member loaded against the piezoelectric element,

• wherein the piezoelectric element is made of a polymeric piezoelectric material,
• wherein a resonance frequency of a system comprising the piezoelectric element and the weight member is set in a range of 10 Hz to 1000 Hz,
• wherein the piezoelectric element is laminated on at least one of upper or lower surfaces of a reinforcement layer, and
• wherein the piezoelectric element comprises a plurality of film-shaped piezoelectric elements, provided with a thin-film electrode on each of upper and lower sides thereof, that are accordion-folded to form a multi-layered structure comprising three layers.