CN202483903U - Liquefied natural gas (LNG) immersed pump - Google Patents

Abstract

An LNG submersible pump, comprising a shell, the shell is provided with a liquid inlet, an air inlet, and a liquid discharge port, the shell is provided with a pump jacket, and a vacuum interlayer is provided between the shell and the pump jacket, and the pump The jacket is provided with a pump body, and the infusion tube on the pump body is connected to the liquid discharge port. The casing is provided with a liquid discharge pipe extending into the pump jacket, and the bottom end of the liquid discharge pipe is located at the bottom of the pump jacket. The utility model adopts a centrifugal structure pump body with high rotating speed and light weight. The designed LNG submersible pump is stable and reliable in the working process without leakage. The working state of the motor in the low temperature environment is good. There is no combustion and explosion problem, the motor bearing is well lubricated, and the pump is less affected by thermal stress. Its structure is designed in such a way that the shielded motor and the pump body are all submerged in the cryogenic liquid to achieve zero leakage. The pump will meet the requirements of large flow rate and high outlet pressure, with good structure and overall performance, and can be widely used in various low-temperature processes.

Description

LNG submersible pump

technical field

The utility model relates to an LNG submersible pump. the

Background technique

LNG is the abbreviation of Liquefied Natural Gas (LNG). The natural gas is frozen to about -162°C under normal pressure, which can make it into liquid, that is, liquefied natural gas. It is formed after the natural gas is purified (dehydration, dehydrogenation, deacid gas), and the process of throttling, expansion and external cold source refrigeration is used to make methane into liquid. The volume of LNG is about 1/620 of its gaseous volume. Therefore, liquefied natural gas is an effective way of storage and transportation of natural gas, and has developed rapidly in recent years. As a new type of vehicle fuel, LNG is popularized and applied in China, and the prospect is quite considerable. The main equipment of the LNG vehicle filling station are: LNG storage tank, LNG cryogenic pump and LNG filling machine. LNG storage tank is a double-layer vacuum insulation container. At present, the domestic technology is mature, and it can produce tanks with a size of 50-200m3. However, the development of LNG cryogenic pumps and LNG dispenser equipment started relatively late in China and currently mainly relies on imports. The LNG submersible pump is a kind of core power output equipment that installs the pump and the motor in a sealed metal container to achieve zero leakage, avoid explosive environments, and eliminate ignition conditions for transporting liquefied natural gas and related cryogenic liquids. The key issues to be solved in the development include: research on electrical equipment of LNG submersible pump, mainly research on low-temperature electrical insulation materials and low-temperature cables, research on sealing technology of electrical connections, research on lubrication and cooling technology of submersible motors, and low-temperature working characteristics of motors Research on several aspects; the research on the pump body of LNG submersible pump is mainly the study of the law of LNG cavitation in the pump, the design and optimization of the impeller and inducer structure of the cryogenic submersible pump, and the research on the self-balancing mechanism of the LNG submersible pump. the

The biggest feature of the LNG submersible pump is that the pump and the motor are integrally installed in a sealed metal container, and the impeller is directly installed on the main shaft of the motor, so that it becomes a whole without a shaft seal, so there is no LNG leakage problem. Due to the low temperature and flammable characteristics of LNG, the delivery pump must not only be able to withstand low temperature performance, but also have higher requirements for the airtightness and electrical safety performance of the pump. Since the inlet and outlet of the pump are connected to the delivery pipeline with a flange structure, the sealing problem is the sealing of the electrical connection. In addition, the lubrication and cooling of the motor in low-temperature LNG, the possible gasification of LNG in the pump body, and the balance problems caused by the motor rotor and the impeller of the pump body sharing the same shaft, etc., make LNG submersible pumps different from ordinary pump bodies. Solving these problems is the key to developing LNG submersible pumps. the

Contents of the invention

The utility model aims to solve the above-mentioned shortcomings of the prior art, and provides an LNG submersible pump, which has a reasonable structural design, good sealing and balance, and can operate safely for a long time under low temperature conditions. the

The utility model adopts the technical scheme to solve the technical problem: this LNG submersible pump includes a shell, the shell is provided with a liquid inlet, an air inlet, and a liquid discharge port, and a pump jacket is arranged inside the shell, and the shell There is a vacuum interlayer between the pump jacket and the pump jacket. The infusion tube on the pump body is connected to the discharge port, and the casing is provided with a discharge pipe extending into the pump jacket. The bottom end of the liquid tube is at the bottom of the pump jacket. the

The pump body includes a pump shaft, and the pump shaft is installed on the bearing of the fixed plate. The fixed plate is equipped with a thrust balance mechanism installed outside the pump shaft, and a throttling ring is arranged under the thrust balance mechanism. The joints between the throttling rings are respectively provided with an upper wear ring and a lower wear ring. For the balance of axial thrust, the thrust balance mechanism TEM (Thrust Equalizing Mechanism) is used to balance the axial thrust. The diameter of the upper wear ring of TEM is larger than that of the lower wear ring, so that the resultant force is upward during high-speed rotation, so all rotating parts on the pump shaft Moving upward, the throttle ring of the impeller is adjusted to reduce its distance from the fixed plate, restricting the flow through the wear ring and causing the upper chamber pressure to increase. Due to the increase of the pressure of the upper lock chamber, the thrust is downward at this time, and the rotating part moves downward again, so the distance between the fixed plate and the throttle ring of the impeller becomes larger, and the pressure of the upper lock chamber decreases. After repeated and continuous self-adjustment by TEM, the spherical thrust bearing lubricated by LNG can be operated in the state of zero axial thrust, which greatly improves the reliability of the bearing and prolongs the service life of the LNG submersible pump. the

The cables on the pump body lead to the outside of the casing, and the casing is sealed with an explosion-proof junction box for connecting cables. Since the power cable of the motor needs to be connected externally, the external packaging of the power cable needs to be absolutely sealed. In order to adapt to the low temperature environment, the cable uses polyester tape and polyethylene composite paper as the insulation layer, which can make it resistant to low temperature and not easy to age and deform. The sealing of the power cable part connected to the outside of the housing adopts a special seal combining double O-ring seal, compression seal and self-tightening seal to ensure reliable sealing. In order to reduce the wiring links, the connection between the stator and the housing is directly connected by enameled wire After insulation treatment, it is clamped on the copper terminal, and an explosion-proof junction box is connected behind the sealing device to prevent LNG from leaking along the cable from the connection to the junction box and encountering sparks and explosion. In order to achieve the effect of sealing and explosion-proof, the design is Two nitrogen sealing protection systems are installed at the external cables and junction boxes to block possible leakage channels of LNG. If the first N2 protection fails, the second N2 sealing system can still work normally, but when the first N2 protection fails, its pressure changes significantly, thus alarming the safety monitoring device. the

The beneficial effects of the utility model are: the utility model adopts a centrifugal structure pump body with high rotating speed and light weight. The designed LNG submersible pump is stable and reliable in the working process without leakage, and the working and running state of the motor in the low temperature environment is good. The external sealing of the power cable is reliable and safe, there is no problem of combustion and explosion, the motor bearing is well lubricated, and the pump is less affected by thermal stress. Its structure is designed in such a way that the shielded motor and the pump body are all submerged in the cryogenic liquid to achieve zero leakage. The pump will meet the requirements of large flow rate and high outlet pressure, with good structure and overall performance, and can be widely used in various low-temperature processes. the

Description of drawings

Fig. 1 is the sectional view of the whole of the utility model;

Fig. 2 is a partial sectional view of the pump body of the present invention.

Explanation of reference signs: shell 1, pump jacket 2, vacuum interlayer 3, pump body 4, infusion tube 4-1, liquid inlet 5, air inlet 6, liquid outlet 7, explosion-proof junction box 8, cable 9 , Drain pipe 10, pump shaft 11, bearing 12, fixed plate 13, thrust balance mechanism 14, throttle ring 15, upper wear ring 16, lower wear ring 17. the

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described:

Referring to the accompanying drawings: this LNG submersible pump includes a casing 1, which is provided with a liquid inlet 5, an air inlet 6, and a liquid outlet 7, and the casing 1 is provided with a pump jacket 2. 1 and the pump jacket 2 are provided with a vacuum interlayer 3, and the pump jacket 2 is provided with a pump body 4, and the infusion tube 4-1 on the pump body 4 is connected to the liquid outlet 7, and the casing 1 is provided with A drain pipe 10 extending into the pump jacket 2 , the bottom end of the drain pipe 10 is located at the bottom of the pump jacket 2 . The pump body 4 includes a pump shaft 11, the pump shaft 11 is installed on the bearing 12 of the fixed plate 13, wherein the fixed plate 13 is provided with a thrust balance mechanism 14 installed outside the pump shaft 4, and a throttling ring is arranged under the thrust balance mechanism 14 15, where the thrust balance mechanism 14, the connection between the pump body 4 and the throttle ring 15 are respectively provided with an upper wear ring 16 and a lower wear ring 17. A cable 9 leading to the outside of the casing 1 is provided on the pump body 4 , wherein an explosion-proof junction box 8 connecting the cable 9 is sealed and installed on the casing 1 .

1.1 Solving problems related to cryogenic submersible motors

Since the motor is immersed in the low temperature liquid, it is necessary to ensure that the motor cannot be broken down in the low temperature liquid, firstly, between the stator and the rotor, and then between the turns. The gap between the silicon steel sheets of the motor is insulated, the cable coil is made of enameled wire with resin insulating varnish, and the enameled wire of resin insulating varnish is treated at low temperature with liquid nitrogen to ensure the insulation performance of the motor. The space of the motor stator is foamed with low-temperature glue. Prevent partial discharge and corona damage to the winding.

Since the power cable of the motor needs to be connected externally, the external packaging of the power cable needs to be absolutely sealed. In order to adapt to the low temperature environment, the cable uses polyester tape and polyethylene composite paper as the insulation layer, which can make it resistant to low temperature and not easy to age and deform. The sealing of the power cable part connected to the outside of the housing adopts a special seal combining double O-ring seal, compression seal and self-tightening seal to ensure reliable sealing. In order to reduce the wiring links, the connection between the stator and the housing is directly connected by enameled wire After insulation treatment, it is clamped on the copper terminal, and an explosion-proof junction box is connected behind the sealing device to prevent LNG from leaking along the cable from the connection to the junction box and encountering sparks and explosion. In order to achieve the effect of sealing and explosion-proof, the design is Two nitrogen sealing protection systems are installed at the external cables and junction boxes to block possible leakage channels of LNG. If the first N2 protection fails, the second N2 sealing system can still work normally, but when the first N2 protection fails, its pressure changes significantly, thus alarming the safety monitoring device. the

1.2 Solve the balance problem of LNG submersible pump

  When designing LNG submersible pumps, the negative effects of fluid and mechanical aspects due to unbalanced forces must be taken into account. When designing and manufacturing, unbalanced forces should be eliminated as much as possible. Since the structure of the LNG submersible pump is that the motor and the impeller are coaxial, the unbalanced axial thrust and radial force generated during the high-speed operation of the motor will directly affect the service life of the pump and motor, and at -196°C In this cryogenic environment, the bearing cannot be lubricated with lubricating oil, but a small amount of LNG is introduced to avoid the heating and lubrication of the bearing. The axial thrust and radial force affect the state of the liquid film, which can easily cause serious damage. wear and tear.

For the balance of the axial thrust, a thrust balancing mechanism (Thrust Equalizing Mechanism, TEM) is used to balance the axial thrust, as shown in Figure 2: the diameter of the upper wear ring of the TEM is larger than that of the lower wear ring, so that the resultant force is upward during high-speed rotation. As a result all rotating parts on the pump shaft move upwards, at which point the throttle ring adjustment of the impeller narrows its distance from the stationary plate, restricting flow through the wear ring and causing an increase in upper lock chamber pressure. Due to the increase of the pressure of the upper lock chamber, the thrust is downward at this time, and the rotating part moves downward again, so the distance between the fixed plate and the throttle ring of the impeller becomes larger, and the pressure of the upper lock chamber decreases. After repeated and continuous self-adjustment by TEM, the spherical thrust bearing lubricated by LNG can run in the state of zero axial thrust, which greatly improves the reliability of the bearing and prolongs the service life of the LNG submersible pump. the

The balance of radial force is realized by using symmetrical diffuser blades. The low-temperature LNG flows out of the impeller and enters the axial diffuser, which has good hydraulic symmetry. Since the diffuser is symmetrical to the fluid, it has perfect hydraulic symmetry in its flow range. When the pump reaches the design flow rate, the radial force of the submersible LNG pump acting on the impeller is theoretically zero. the

1.3 Solution to cavitation problem

In order to prevent cavitation at the suction port of the pump and reduce fluid resistance at the suction port, a helical deflector is installed at the suction port. The whole pump is installed in a stainless steel container, which has the function of separating gas and liquid, and is manufactured according to the pressure vessel standard. The suction port of the pump is located at a lower position to ensure that the suction port is in the liquid. The application of the helical deflector and the stainless steel container enables the LNG pump to achieve the proper net suction head (NPSHR), which is conducive to improving the hydraulic characteristics, reducing the pump’s requirements for the net suction head, and preventing the suction of the pump from Cavitation occurs.

1.4 Solution to thermal stress problem

When the LNG submersible pump is started, the thermal stress may cause the pump to crack and lock and cannot rotate, which will damage the pump. In order to prevent this phenomenon, the cantilever type can be used in the structure, so that the whole shrinks to the top in the low temperature environment, and the matching parts of the pump body are selected with materials with similar thermal expansion coefficients to avoid the phenomenon of locking cracks caused by different shrinkage degrees in the low temperature environment; at the same time, through The temperature sensor monitors the pump outlet temperature in real time, adjusts the front and rear valves of the pump according to the outlet temperature display, and controls the pump pre-cooling time. Experiments show that this method is quite effective in solving thermal stress problems.

Although the present invention has been illustrated and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made within the scope of the claims. the

Claims (3)

1. LNG immersed pump; Comprise housing (1); Housing (1) is provided with liquid entering hole (5), suction port (6), liquid port (7), it is characterized in that: be provided with pump chuck (2) in the said housing (1), be provided with vacuum sandwich (3) between housing (1) and the pump chuck (2); Be provided with the pump housing (4) in the pump chuck (2); Indusion tube (4-1) on the pump housing (4) is connected on the liquid port (7), and said housing (1) is provided with the liquid-discharging tube (10) that stretches in the pump chuck (2), and the bottom of liquid-discharging tube (10) is positioned at the bottom of pump chuck (2).

2. LNG immersed pump according to claim 1; It is characterized in that: the said pump housing (4) comprises pump shaft (11); Pump shaft (11) is installed on the bearing (12) of fixed plate (13); Said fixed plate (13) is provided with and is installed in the outer thrust-balancing mechanism (14) of pump shaft (4); Thrust-balancing mechanism (14) below is provided with restrictor ring (15), and the joint between said thrust-balancing mechanism (14), the pump housing (4) and the restrictor ring (15) is respectively equipped with wear ring (16), following wear ring (17).

3. LNG immersed pump according to claim 1 is characterized in that: the said pump housing (4) is provided with and leads to the outer cable (9) of housing (1), is sealed and installed with the anti-explosion terminal box (8) of conjunction cable (9) on the said housing (1).

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