Study On The Method Of Detection And Location Of Ship Pipeline Leakage

With the increases of demands in ship safe, the fault diagnosis technique of mechanical and electrical equipment in ship has been developed and applied continuously. The ship pipelines are usually worked in the moist, damp and vibration circumstances, which are often eroded easily and cause leakages. Now the leakages of pipeline in ship are mainly depend on the worker's inspecting, so the leakages are not usually found and treated. The theory and technique of pipeline leakage are developed very quickly, which has been used in oil and natural gas pipelines. This research has displayed the tremendous safe and economic action, but there is rare research in ships pipeline leakage and no more mature technique. Therefore, this dissertation aimed at a central cooling system of ships, the mainly contents of this dissertation are shown as follow.(1) Research on the method of ship pipeline leakage diagnostic based on the fluid network theory. The principle of central cooling system has been analyzed in this dissertation, and its compute model was built up applying the fluid network theory. The main parameters can be calculated by this model of all points, and leakage status can be determined when the examined pressure and flowrate are high than a certain valve. The experimental results showed that this method has high accuracy, and it can carry on judging to the very small leakiness point.(2) Application of wavelet transform in leak for pipelines. Wavelet transform has been used for the detection of signal singularity and felting, the deficiency of hard threshold and soft-threshold were discussed in this dissertation based on the wavelet transform. The model of threshold has been also improved. It proved that this model is an effective method.(3) Research on the wave speed and regulation of negative pressure wave. At the method based on negative pressure wave of examining leakage in ship pipeline, the negative pressure wave speed is a very important parameter. It is not only related to the physical properties of fluid, but is also affected by the size of pipeline, machine characteristic etc. Because pressure wave speed is influenced by a lot of factors, so far there is not a good method which can satisfy the accuracy of the wave speed. Aiming at the ships special piping, the formula of negative pressure wave speed considering the piping transforms and the air exists has been put forward. The influence factors of wave speed have been analyzed by MATLAB. The experimental results were matched with the actual engineering.(4) Detection method experimental research. Leakage monitoring and positing experimental system has been designed based on the correlation analysis technique using the virtual instrument technique. Methods of negative pressure wave and fluid network of leakage monitoring were examined respectively. The results showed two methods are feasibly.