Line-break, control valve, orifice diameter, pressure drop rate, experimental study

Automatic line-break control valve can be used in zones with no access to national electricity network, hazardous or impassable area enclosure, for passive defence conditions or to protect dierent ecosystems such as rivers and ground water, forests and fertile land and etc. The pipeline break causes a growth in oil velocity magnitude and uid pressure reduction consequently but the pressure drop is not a good signal for line break detection because it is low, therefore reference tank is used. The reference tank is connected to the pipeline through a calibrated orice with check valve. The tank pressure is higher than pipeline pressure when pressure reduction occurs by line breaking. If the pressure dierence between tank and pipeline is higher than the sustainable pressure value of diaphragm valve, the valve will be closed by actuator. In this paper, the eects of orice diameter, pipeline initial pressure and pipeline break pressure drop rate on the dierential pressure of diaphragm valve in automatic line-break control valve have been studied with nitrogen by 27 experiments. The dierential pressure of diaphragm valve is increased by the growth of pipeline break pressure drop rate. The occurrence time of maximum dierential pressure of diaphragm valve just depends on orice diameter. The maximum of dierential pressure increases with decrease of orice diameter. The dierential pressure of diaphragm valve increases by decrease of pipeline initial pressure for constant orice diameters and pipeline break pressure drop rates. The curves of maximum dierential pressure generated by dierent pipeline break pressure drop rates are shown for dierent orice diameters and pipeline initial pressure. The values of curves in this diagram with 10 percent safety factor can be used in automatic line-break control valve setting which are installed on gas transportation pipelines because of the nitrogen gas using instead of the natural gas.