Working principle and application of closed liquefied petroleum gas pump

1. Overview of fully enclosed liquefied petroleum gas pumps


With the development of the petroleum industry, the domestic fuels of urban and rural residents in China have gradually replaced coal with liquefied petroleum gas, and the application of canned liquefied petroleum gas is becoming more and more popular. As a result, LPG stations have sprung up like mushrooms. The currently used canning equipment is a single-acting vane type rotor pump. The shaft seal adopts two single-end mechanical seals, one side is used as a shaft seal to prevent leakage of liquefied petroleum gas, and one side seals the bearing to ensure grease lubrication of the bearing. From the application situation, the pump mechanical seal has wear and leakage problems, the tank area tastes great, causing pollution to the environment; in addition, the sealing replacement operation is cumbersome and unsuitable for overhaul. Based on the principle of permanent magnet transmission, the author has extended the technology to the rotor pump based on the successful application of non-leakage magnetic centrifugal pumps, valves, reactors, etc., and designed a fully enclosed liquefied petroleum gas pump to achieve no seal. Fully enclosed, absolutely sealed. In addition to canned liquefied petroleum gas, the pump can also transport volatile liquids and petroleum products of various properties such as liquid hydrocarbons, liquid ammonia, and propylene.


2. How the pump works


The fully enclosed liquefied petroleum gas pump is a single-acting sliding vane pump. The working principle is shown in Figure 1. Mainly composed of the pump body 1, the inner sleeve 2, the rotor 3, the shaft 4, the sliding piece 5, the side plate 6 (not shown) and the like. There is an eccentric distance e between the inner sleeve and the rotor. The sliding piece is placed in the rotor slot and can slide along the groove. When the rotor rotates, the sliding piece is pressed against the inner wall of the inner sleeve by its own centrifugal force, and the inner surface of the inner sleeve and the outer surface of the rotor A plurality of closed working chambers are formed between the sliding piece and the end faces of the two side plates. When the rotor rotates counterclockwise, the sliding piece on the right side gradually protrudes, and the volume between the adjacent two sliding pieces gradually increases to form a partial vacuum, and the liquid is sucked in. The mouth enters the studio, which is the suction process of the pump. The sliding piece on the left side is gradually pressed into the groove by the inner sleeve, and the closed volume between the adjacent two sliding pieces is gradually reduced, and the liquid is pushed out of the discharge port, which is the pumping process of the pump. The rotor is turned one revolution and a suction press is completed. Between the suction and discharge chambers of the pump, there is a section of oil seal that separates the suction chamber from the pressure chamber. The displacement Q of the pump is proportional to the eccentricity e and the rotational speed n of the pump. Therefore, the eccentricity and the rotational speed can be used to adjust the displacement or to make a series of products to meet the needs of different working conditions.


The fully enclosed liquefied petroleum gas pump is a rotary positive displacement pump, and the displacement is constant at a certain speed. For a pump with a number of slides larger than 4, the displacement pulsation is small. As the pressure difference increases, the displacement decreases slightly; the fluid viscosity m has little effect on the efficiency η. These two points are significantly better than centrifugal pumps. Figure 2 shows the performance curve of the vane pump.


3. Transmission and sealing principle


The power is driven by a gear motor, a flexible coupling 5, and an external magnetic rotor 4. The inner wall of the outer magnetic rotor is provided with a permanent magnet, and the magnetic flux passes through the sealing cover 3 to drive the inner magnetic rotor 2, and the inner magnetic rotor and the pump rotor are mounted on the same shaft. Permanent magnets of different polarities are alternately arranged on the inner and outer magnetic rotors, and the principle of homosexual repulsive and opposite-phase attracting is maintained to maintain accurate synchronous rotation. When the external torque does not exceed the designed magnetic torque, the inner and outer magnetic rotors do not slip. The sealing cover is similar to the end cover and is connected to the pump body by a static seal. The pump shaft does not need to extend out of the casing, and the pumping fluid is completely enclosed in the pump body and the sealing cover, completely eliminating the leakage problem of the mechanical seal, and changing the seal to static Sealed, so it is called unsealed, fully enclosed, and absolutely sealed.

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