When the buried high pour point oil pipeline is running, it is inevitable to avoid pipeline failures and the pipeline should be shutdown. After shutdown oil temperature dropped and viscosity increased, oil gelling happens, it will cause the accident "condensing tube". For high pour-point oil pipeline can start after shutdown, it should ensure the safety shutdown time of the pipeline and corresponding in the restart pressure. So it is necessary to guide the production practice and pipeline safe operation.
The composition and properties of phosphate cement, the requirement of its materials needed are discussed. Its compositional materials are heavy burnt magnesia and polyphosphatic solution. The effect of features, the amount of magnesium oxide and phosphate on the cement properties are described. It can be used in large fabrication repairing and in industrial waste disposal.
The mechanism for phosphate cement hydraulic reaction is determined. The microscopic process is described by means of scanning electronic microscope, X-ray diffraction analysis,infrared spectrophotometry and differential heat analysis. The results show the three main phases are present, i.e. hydromagnesium phosphates, Mg (OH)2and MgO phase. The type, structure, and amount of every phase play an important role in phosphate cement properties. Hydromagnesium phosphate phase structure has a close relation to phosphate cement setting and hardening. The development of strength has much to do with the formed crystalline directing.
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