| Our country is rich in fresh water resources, but with a large population the quantity per capita is far below the world average. In addition, the uneven temporal and spatial distribution of water resources brings about severe regional water shortage, which altogether have impeded the people's living standards improvement and the urban economic construction. Based on all the above, during recent years, a number of long-distance diversion objects have been constructed in which the water hammer proctetion has been of great concern. The paper gives a brief introduction of water hammer when Pump is Cut off calculations, the most common in water hammer and on this basis, conducts analysis and research of the drying and nonstop models through practical projiect cases.1) For the time being, the most usual method of water hammer calculation is power algorithm, which is based on the characteristics method. Method of characteristics applies the characteristic equation derived from basic differential equations of water hammer to make calculated characteristic line parameters of each point in the pipeline. For special points, it also has to list the boundary condition equations for the characteristic equation simultaneous solution.2) In water hammer electric algorithms, the operating parameters of pumping stations under various conditions are requested. Nevertheless, the overall characteristic curve of pump obtained by experiments can not be directly quoted by the computer. Through the mathematics of discrete points from the curve out, and then interpolation of two discrete points, the acquired parameters of the pump can be used to run the computer on the overall characteristic curve of pump for a comprehensive simulation.3) When the pipeline pressure is reduced to the saturation water vapor pressure, the water will vaporize so that a continuous water column separation occurs, followed by separation of the water column to bridge, and then the generation of water hammer of cavities collapsing causes a huge pressure rising in pipes, as is the water hammer of cavities collapsing. This paper investigates water hammer calculation, analyzes and compares the calculation results of step-up of two mathematical models:broken water hammer model and the model of non-breaking water hammer to conclude a reasonable model.4) After application of the two mathematical model to Fugu second, third pumping station water pipelines and analysis of the simulation calculation results, it is concluded that the calculation model of non-breaking water hammer dose not accord with the reality with small boost and the pressure change bears a resemblence to that of waterpipes when pumps operate well. Hence, it is insecure in prctice and broken water hammer calculation model is superior.5) For the calculation of the practical project cases, according to the acccidental power failure maximum head envelope that are derived from the broken water hammer model, it is extremely insecure to take no water hammer protection measures. Reasonable water hammer protections are supposed to obtained through calculation to control the pressure within the pipeline pressure-bearing capacity. The boundary protection conditions should be confirmed through theoretical analysis and futhermore, experimental validation.
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