Water shock relief valve is an automatic valve to reduce the impact of water shock and effectively protect the safe and smooth operation of pipelines. In long-distance oil pipelines, switching valves too quickly, sudden stopping of pumps, pipe cleaners suddenly jammed, etc. will cause sudden changes in the flow rate of oil in the pipeline, this change produces a pressure wave in the pipeline quickly transfer.

Water strike means that in the pressurized pipeline, the liquid flow rate changes dramatically caused by the phenomenon of large fluctuations in pressure, in essence, the liquid in the pipeline kinetic energy and pressure energy conversion. Water strike on the oil pipeline is a direct hazard to lead to pipeline overpressure, including two cases: one is the water strike pressure wave may make the pipeline pressure exceeds the maximum allowable working pressure, so that the pipeline rupture; the second is the decompression wave may make the steady state operation of the lower pressure pipe pressure down to the saturation vapor pressure of the liquid, resulting in part of the vaporization caused by the separation of the liquid flow. The pressure wave generated by the water strike, in the pipeline to 1000 ~ 1200m / s speed propagation, in the pipeline liquid flow suddenly stopped caused by the water strike pressure rise rate of up to 1MPa / s, the water strike pressure rise of up to 3MPa. The propagation of the wave of the water strike so that the pressure value superimposed on the original hydraulic pressure, resulting in localized pipeline overpressure, vibration and pipeline rupture, damage to equipment, threatening the safety of pipeline operation. Pipeline operation safety.

Domestic and foreign long-distance pipeline development trend is the pipeline network and closed transport, which makes the long-distance pipeline hydraulic system more complex, more likely to form a water strike. In order to effectively prevent the phenomenon of water strike, to ensure the safe operation of long-distance pipeline, long-distance pipeline must have a perfect pressure relief system, in addition to the use of regulating valves to regulate the inlet and outlet pressure and pressure overrun protection, the extensive use of water pressure relief valve to prevent the pipeline pressure is too high. When the liquid in the pipeline water strike, and reach the set value of the water pressure relief valve, water pressure relief valve quickly open, part of the medium into the pressure relief tank. Due to the opening of the water pressure relief valve so that the pipeline liquid pressure energy is released, so that the intensity of the water pressure wave is weakened, and therefore play a role in protecting the pipeline and the purpose of equipment safety.

Water-strike pressure relief valve consists of two parts: the valve body and the driving unit. The main valve generally adopts the axial flow form, according to the type of its driving force, the water strike pressure relief valve is divided into electromagnetic, pilot-operated and nitrogen loading type.

Pilot operated water strike relief valve, belongs to self-operated relief valve, its driving force is the medium pressure in the pipeline, the pressure point of pilot operated water strike relief valve is in the upstream pipeline of the water strike relief valve, through the induction conduit, the pressure is transferred to the pilot valve. The drive unit consists of a pilot valve, an induction conduit, a pressure gauge and several control valves.

Pilot operated pressure relief valves are driven by the pressure in the pipeline, and it is crucial to ensure that the pressure conduit is unobstructed, which requires that the medium in the pipeline is of low viscosity and free of impurities, so pilot operated pressure relief valves are mainly used in the pipeline of refined oil products. In order to ensure that the pressure pilot tube is smooth, electric heating and insulation devices can be added to the pilot tube.

Nitrogen-loaded water strike pressure relief valve is shown in Figure 2. The driving force is nitrogen, and there is a complete set of nitrogen driving unit. The driving unit mainly includes nitrogen supply system, lead pipe, pressure gauge, filling valve, pressure relief valve, cut-off valve and temperature difference compensation bottle. The structure of nitrogen-loaded water-shock pressure relief valve is relatively complex, nitrogen is easy to leak, and maintenance is cumbersome. This type of water-shock pressure relief valve can be applied in asphalt, crude oil and heavy lubricating oil pipelines.