(1) Properties of liquefied petroleum gas

① The density of gaseous liquefied petroleum gas is higher than that of air, and it accumulates and diffuses near the ground after leakage. Easy to diffuse, the explosion limit of liquefied petroleum gas is about 2% ~ 9%, and the lower explosion limit is low. Once leaked, liquefied petroleum gas can quickly form explosive mixed gas in a small area, which is very dangerous.

② Liquefied petroleum gas is lighter than water.

(3) Liquefied petroleum gas has high saturated vapor pressure and fast gasification speed, and can absorb a lot of heat in a short time in the process of changing from liquid to gas. If sprayed on the human body, it will cause local cooling of the skin surface and cause frostbite.

(2) Process principle

Because liquid LPG is lighter than water, if there is leakage at the valve, flange and joint at the bottom of the storage tank, water can be injected into the storage tank through the process pipeline, and LPG can be hoisted with water to isolate LPG from the leakage point, thus reducing the possibility of LPG leaking to the surrounding environment [2, 3]. To gain time for the implementation of measures such as blocking and dumping tanks, and reduce the amount of liquefied petroleum gas sprayed and the damage to operators.

(3) Process flow

See figure 1 for the process flow. The water pump is connected with the fire hose and the fire pool to ensure the continuity and reliability of water supply. Check valves must be installed on two pipes at the pump outlet. Once the pressure of liquefied petroleum gas pipeline is high, liquefied petroleum gas will not flow back into the fire water pipeline. The saturated vapor pressure of liquefied petroleum gas at room temperature is high, about 0.4 MPa ~ 0.8 MPa, so the pump with high lift should be selected to ensure the water can enter the storage tank smoothly. A standby pump should be connected in parallel, and the two pumps can work at the same time in case of danger, which is more reliable.

(4) the implementation of the process

Once leakage is found in production, find the leakage point, and judge that other methods are difficult to implement, immediately start the pump to inject water. If the leakage point is small, the temperature around the leakage point drops rapidly due to the rapid gasification and heat absorption of liquefied petroleum gas during the leakage process, and the water freezes when it reaches the leakage point, which can play the role of temporary plugging. If the crack at the leakage point is too big to form an ice plug, continue to fill the water storage tank. Because liquefied petroleum gas is lighter than water, the water injected into the storage tank will lift liquefied petroleum gas to the water surface and isolate it from the leakage point. At this time, the leakage point is not mainly pure liquefied petroleum gas, and then other methods are used to stop the leakage. In the process of plugging, the pressure relief valve at the top of the storage tank can be opened to release gaseous liquefied petroleum gas, which is not easy to cause danger and reduce the pressure in the storage tank.

(5) Advantages of the process ① This process is simple, quick to start, quick to take effect, easy to realize and can play an emergency role.

(2) The liquid ejected from the leakage point is mainly water, which reduces the ejection amount of LPG in the process of plugging, delays the formation of explosive mixed toughness, reduces the risk of frostbite of operators, reduces the operation difficulty, and wins time for implementing measures such as plugging and dumping tanks.

(3) The implementation of air dispersion reduces the pressure at the leakage point, which is convenient for plugging.