How to remove the pump from inside the tank

Abstract

To prevent the inclusion of air in a pump barrel when taking out a pump for delivering liquefied gas from a tank.SOLUTION: A method of taking out a pump in a tank is a method of a pump 3 to the outside in a liquefied gas tank 1 equipped with a structure delivering liquefied hydrogen LH collected in a tank body 10 by using a pump barrel 2 and a pump 3 installed in the tank. The method includes installing a tent 4 on a tank roof 11 so as to cover a barrel opening 2H sealing an upper end portion 22 of the pump barrel 2, making an in-tent space 4A in the tent 4 become a positive pressure environment, opening the barrel opening 2H, hoisting the pump 3 into the tent 4 through the pump barrel 2 by a hoisting device 5 installed on the tank roof 11, sealing the barrel opening 2H, and recovering the hoisted pump 3.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for removing a pump installed in a tank for storing liquefied gas and discharging the liquefied gas in the tank.

Background Art

[0002] For example, a liquefied gas tank for storing liquefied gas such as liquefied hydrogen or liquefied natural gas needs to be equipped with a pump for discharging the liquefied gas in the tank. When discharging liquefied gas through the tank roof, the pump is installed in the tank, and the liquefied gas is sent to the outside through a cylindrical pump barrel penetrating the tank roof (for example, Patent Document 1).

[0003] For maintenance work of the pump, etc., it may be necessary to remove the pump from the tank. In this case, the pump is lifted through the pump barrel, and the pump is removed from the barrel opening at the upper end of the pump barrel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When removing the pump from the barrel opening, it is desirable not to mix air into the pump barrel. In particular, when the liquefied gas stored in the tank is cryogenic liquefied hydrogen, the air entering the barrel from the barrel opening is liquefied or solidified, causing various problems including safety issues.

[0006] An object of the present disclosure is to provide a method for removing a pump for discharging liquefied gas from a tank, which can prevent air from entering the pump barrel. [Means for solving the problem]

[0007] A method for removing a pump from a tank according to one aspect of the present disclosure is a method for removing a pump from a liquefied gas tank having a structure for discharging liquefied gas stored in the tank using a pump barrel that penetrates the tank vertically and a pump installed inside the tank, wherein a tent is installed outside the tank so as to cover the sealed barrel opening at the upper end of the pump barrel, the inside of the tent is made into a positive pressure environment, the barrel opening is opened, and the pump is lifted into the tent through the pump barrel using a lifting device installed outside the tank, the barrel opening is sealed, and the lifted pump is recovered. [Effects of the Invention]

[0008] According to this disclosure, a method for removing a pump for discharging liquefied gas from a tank can be provided that prevents air from entering the pump barrel when the pump is removed from the tank. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing a liquefied gas tank to which the in-tank pump extraction method of this disclosure is applied. [Figure 2] Figure 2 is a process chart showing the procedure for removing the pump from the tank. [Figure 3] Figure 3 is a cross-sectional view showing part of the process for removing the pump from the tank. [Figure 4] Figure 4 is a cross-sectional view showing part of the process for removing the pump from the tank. [Figure 5] Figure 5 is a cross-sectional view showing part of the process for removing the pump from the tank. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of the tank pump extraction method according to the present disclosure will be described in detail based on the drawings. The tank to which the extraction method of the present disclosure is applied is a liquefied gas tank that stores low-temperature liquefied gas. The stored liquefied gas is, for example, liquefied hydrogen, liquid helium, liquid nitrogen, liquefied natural gas, liquefied petroleum gas, or liquefied ammonia. In particular, the extraction method according to the present disclosure is suitable for application to a liquefied gas tank that stores liquefied hydrogen.

[0011] [Tank structure] First, with reference to Figure 1, the structure of the liquefied gas tank 1 to which the in-tank pump extraction method of this disclosure is applied will be described. The liquefied gas tank 1 illustrated in Figure 1 is a tank for storing cryogenic liquefied hydrogen LH, and is a flat-bottomed tank with a multi-shell structure that is installed on the ground. The liquefied gas tank 1 comprises a tank body 10 for storing liquefied hydrogen LH, a pump barrel 2 which is a structure for discharging liquefied hydrogen LH from the tank body 10, and a submersible pump 3 which is installed inside the tank body 10 and immersed in the liquefied hydrogen LH.

[0012] The tank body 10 has a storage space for storing liquefied hydrogen LH. Although Figure 1 shows a simplified single-shell structure, the actual tank body 10 has a multi-shell structure such as a double-shell or triple-shell structure. In the case of a double-shell structure, the tank body 10 consists of an outer tank erected on a foundation, an inner tank enclosed within the outer tank, and a cooling layer between the outer tank and the inner tank. The liquefied hydrogen LH is stored inside the inner tank. The cooling layer is filled with a powder insulation material such as granular perlite and a low-boiling-point gas. In the case of a triple-shell structure, the tank body 10 has an intermediate tank between the outer tank and the inner tank. In addition, the tank body 10 may be a tank with a shape other than a flat bottom, or a tank that is buried underground, etc.

[0013] The pump barrel 2 is a cylindrical body installed so as to penetrate the tank body 10 vertically, and serves as a discharge pipe for discharging liquefied hydrogen LH from the tank body 10 to the outside. The pump barrel 2 comprises a barrel interior space 2A, which is the internal space through which the liquefied hydrogen LH flows, a lower end portion 21 located near the bottom plate of the tank body 10 and immersed in the liquefied hydrogen LH, and an upper end portion 22 that extends upward through the tank roof 11. The barrel interior space 2A extends vertically between the lower end portion 21 and the upper end portion 22 and has an inner diameter that allows the pump 3 to pass through.

[0014] Pump 3 is housed in the barrel space 2A near the lower end 21. A foot valve 23 is attached to the intake opening at the lower end 21 of the pump barrel 2. Pump 3 is positioned on top of the foot valve 23, and the weight of pump 3 causes the foot valve 23 to hang down, opening the intake opening at the lower end 21. As shown by the arrows in Figure 1, pump 3 takes in liquefied hydrogen LH from the tank body 10, increases the pressure, and sends the liquefied hydrogen LH into the barrel space 2A.

[0015] A discharge port 24 is provided near the upper end 22 of the pump barrel 2. A barrel opening 2H is provided at the upper end of the pump barrel 2, connecting the internal barrel space 2A to the external space. When the liquefied gas tank 1 is in operation, the barrel opening 2H is sealed by the head plate 25. When the pump 3 is operated, liquefied hydrogen LH is discharged from the internal barrel space 2A through the discharge port 24.

[0016] On the other hand, during maintenance work on the pump 3, the head plate 25 is removed and the barrel opening 2H is opened. The pump 3 is lifted through the pump barrel 2 and removed from the barrel opening 2H. When the weight of the pump 3 is no longer applied due to the lifting, the foot valve 23 rises and seals the intake opening at the lower end 21. After the maintenance work is completed, the pump 3 is lowered through the pump barrel 2 from the barrel opening 2H and installed on top of the foot valve 23. After that, the barrel opening 2H is sealed with the head plate 25.

[0017] [Method for Removing Pump] As described above, when removing the pump 3 installed in the tank body 10 during maintenance work or the like, it is necessary to open the barrel opening 2H. At this time, air can enter the pump barrel 2. In this embodiment, since the tank body 10 stores liquefied hydrogen LH, the air (nitrogen and oxygen) that has entered the pump barrel 2 is liquefied or solidified, causing various problems including safety issues. Therefore, in this embodiment, a method for preventing the entry of air into the pump barrel 2 when removing the pump 3 from the tank body 10 is shown.

[0018] Figure 2 is a process chart showing the procedure of an embodiment of the method for removing the in-tank pump according to the present disclosure. First, as a preparatory work, a tent 4 is temporarily installed on the tank roof 11 (step S1). Figure 3 is a cross-sectional view showing the implementation status of step S1. The tent 4 is assembled by, for example, a sheet material such as a woven fabric, a fiber-reinforced resin sheet, or a resin sheet with excellent airtightness, and an aggregate that supports this sheet material, and is a structure that partitions an in-tent space 4A isolated from the atmosphere. Note that the tent 4 may be any structure that can be temporarily installed outside the tank body 10 and removed relatively easily, and may be constructed by assembling prefabricated plate materials, for example.

[0019] The tent 4 is installed so as to cover the barrel opening 2H sealed by the head plate 25 at the upper end of the pump barrel 2. That is, the tent 4 is assembled so that the barrel opening 2H is located in the in-tent space 4A. This is to prevent the direct communication between the barrel inner space 2A and the atmosphere through the barrel opening 2H when the head plate 25 is removed, and to interpose the in-tent space 4A between the two. Although not shown in the figure, the tent 4 is provided with a door for the operator to enter and exit the in-tent space 4A. A pre-room for isolating the in-tent space 4A and the outside air when the door is opened and closed may be provided outside the door.

[0020] When temporarily installing the tent 4, a deck 40 is installed on the tank roof 11 so as to surround the upper end 22 of the pump barrel 2. The deck 40 includes a vertical frame 41 serving as a support column and a horizontal frame 42 for supporting the tent 4 from below. The horizontal frame 42 is installed at a position lower than the barrel opening 2H. The deck 40 may be temporarily installed during maintenance like the tent 4, or may be permanently installed on the tank roof 11. The tent 4 is assembled on the horizontal frame 42. There is no limitation on the shape of the tent 4 as long as it surrounds the barrel opening 2H, and for example, it can be set in the shape of a rectangular parallelepiped, a sector, a cylinder, a semi - circular shape, or a gable roof shape.

[0021] The tent 4 is provided with an air inlet hole 43 and an exhaust hole 44. The air inlet hole 43 is an opening for taking gas into the inner space 4A of the tent 4. The exhaust hole 44 is an opening for exhausting gas from the inner space 4A of the tent. In the present embodiment, an inert gas such as nitrogen gas is supplied to the air inlet hole 43. That is, the air supply pipe 61 of the gas replacement device 6 is connected to the air inlet hole 43. The gas replacement device 6 is a facility for replacing the inner space 4A of the tent with an inert gas environment, and includes a supply source of inert gas, an air supply pump, a flow rate adjustment valve, and the like. Note that the gas replacement device 6 may also supply a gas other than an inert gas, such as helium gas or hydrogen gas.

[0022] After the installation of the tent 4 is completed, a process of making the inside of the tent 4 a positive pressure environment is executed (process S2). There is no limitation on the method of creating a positive pressure environment, but in the example of FIG. 3, an example of making the inner space 4A of the tent a positive pressure environment by continuously supplying an inert gas into the tent 4 is shown. That is, a large amount of inert gas is supplied from the air supply pipe 61 of the gas replacement device 6 through the air inlet hole 43 of the tent 4 into the inner space 4A of the tent. At the same time, the gas in the inner space 4A of the tent containing the supplied inert gas is discharged from the exhaust hole 44 of the tent 4. Note that a schematic exhaust pipe for guiding the exhaust to an appropriate place is connected to the exhaust hole 44. As a result, the inner space 4A of the tent is replaced with an inert gas and becomes a positive pressure environment by the supply pressure of the inert gas. The supply of the inert gas continues until at least the subsequent step S7 in which the barrel opening 2H is sealed.

[0023] Next, the process of pushing the liquefied hydrogen LH in the pump barrel 2 into the tank body 10 is performed (step S3). When the liquefied gas tank 1 is in operation, liquefied hydrogen LH is present in the barrel space 2A. Generally, except when discharging liquefied hydrogen LH, the liquefied hydrogen LH is present in the barrel space 2A up to the same height as the liquid level in the tank body 10. From the viewpoint of reducing the lifting resistance of the pump 3 and suppressing liquid entrapment, it is desirable that no liquid is present in the barrel space 2A. In step S3, the gas of the stored liquefied gas, hydrogen gas in this embodiment, is supplied from the discharge port 24 to the barrel space 2A. Pushed by the supplied hydrogen gas, the liquefied hydrogen in the barrel space 2A is returned to the tank body 10. This step S3 can be performed as needed and may be omitted. In other words, the pump 3 may be lifted while liquefied hydrogen LH is present in the barrel space 2A.

[0024] Subsequently, the head plate 25 is removed and the barrel opening 2H is opened (step S4). Before this opening, it is desirable to set the pressure in the tent interior space 4A to a pressure lower than the pressure in the barrel interior space 2A. This prevents the inert gas in the tent 4 from entering the pump barrel 2 due to the pressure difference between the tent interior space 4A and the barrel interior space 2A. Therefore, the generation of liquefied or solidified inert gas in the pump barrel 2 can be prevented. On the other hand, hydrogen gas in the barrel interior space 2A may enter the tent interior space 4A. The hydrogen gas that enters the tent interior space 4A is discharged from the exhaust port 44 along with nitrogen gas.

[0025] Next, the process of lifting the pump 3 through the pump barrel 2 is performed (process S5). Figure 4 is a cross-sectional view showing the execution of process S5. A lifting device 5 installed outside the tank body 10 is used to lift the pump 3. The lifting device 5 includes a drum 51 that rotates forward and backward around an axis, and a lifting wire 52 wound around the drum 51. The lifting wire 52 is unwound by the forward rotation of the drum 51, and the lifting wire 52 is wound back up by the reverse rotation of the drum 51. The lifting wire 52 hangs down into the barrel space 2A through the barrel opening 2H, and the end of the lifting wire 52 is connected to the pump 3.

[0026] The lifting device 5 is installed vertically above the pump barrel 2. A pair of support columns 45 are erected on the horizontal frame 42 of the deck 40 for the installation of the lifting device 5. The support columns 45 extend to a position higher than the tent 4. A horizontal beam 46 is installed between the pair of support columns 45, extending horizontally. A pair of hoist rails 53, extending vertically in the plane of Figure 4, are attached to the horizontal beam 46. Movable rollers 54 that hold the drum 51 are engaged with the hoist rails 53. The drum 51 can move horizontally along the hoist rails 53. The lifting device 5 may also be a type in which a crane equipped with an arm to hold the drum 51 and a pivot axis for the arm is permanently installed on the tank roof 11. Although Figure 4 shows an example in which the lifting device 5 is installed outside the tent 4, the lifting device 5 may also be installed inside the tent 4.

[0027] Figure 4 shows the state in which the pump 3 is lifted to approximately the midpoint of the vertical direction of the pump barrel 2 by winding the suspension wire 52 connected to the pump 3 onto the drum 51. The foot valve 23 rises when the weight of the pump 3 is no longer applied, sealing the intake opening at the lower end 21. In this embodiment, the suspension wire 52 passes through the top surface of the tent 4 and hangs down into the tent interior space 4A and the barrel interior space 2A. It is desirable to place a sealing member at the point of penetration that can maintain airtightness while allowing the suspension wire 52 to slide.

[0028] Next, the lifting device 5 continues to lift the pump 3, and the process of bringing the pump 3 into the tent 4 is performed (process S6). Figure 5 is a cross-sectional view showing the execution of process S6. The pump 3 is lifted above the barrel opening 2H and brought into the tent interior space 4A. After that, the barrel opening 2H is sealed (process S7). That is, the head plate 25 is attached to the barrel opening 2H, separating the barrel interior space 2A from the tent interior space 4A.

[0029] Subsequently, a step is performed in which the pump 3 is held inside the tent 4 for a predetermined time (step S8). Liquid hydrogen may remain inside the pump 3 after it has been lifted from the pump barrel 2. For this reason, the pump 3 may be held inside the tent 4, and the inert gas continuously supplied to the tent space 4A may be used as a purge gas to purge the liquid hydrogen remaining inside the pump 3.

[0030] Subsequently, the process of recovering the pump 3 (process S9) and the process of removing the tent 4 (process S10) are carried out. The recovery of the pump in process S9 is the work of lowering the pump 3, which has been removed from the pump barrel 2 and is suspended on the tank roof 11, to the ground. The removal of the tent 4 in process S10 is the work of dismantling the tent 4 that has been assembled on the deck 40. Process S9 and process S10 may be carried out in any order. That is, the removal of the tent 4 can be carried out before the recovery of the pump 3, simultaneously with the recovery, or after the recovery.

[0031] Step S9 can be performed using the lifting device 5 used to lift the pump 3. In this case, an extension is provided that extends the hoist rail 53 to the radially outer side of the tank body 10. In step S9, the drum 51 with the pump 3 suspended is moved to the extension. Then, the drum 51 is rotated to unwind the lifting wire 52, thereby lowering the pump 3 to the ground.

[0032] Another embodiment of step S9 is to install a crane around the liquefied gas tank 1 and use the crane to lower the pump 3. In this case, the pump 3, which has been lifted into the tent 4 by the lifting device 5, is moved out of the tent 4, and the pump 3 is connected to the crane's lifting wire and lowered. Alternatively, the tent 4 is dismantled after the pump 3 has been lifted, the lifting wire 52 is replaced with the crane's lifting wire, and the pump 3 is lowered. Or, the drum 51 with the pump 3 attached may be lowered by the crane.

[0033] According to the method for removing the tank pump described above, a tent 4 is installed so as to cover the barrel opening 2H of the pump barrel 2, which is sealed by the head plate 25, and the space 4A inside the tent 4 is made into a positive pressure environment. As a result, the space 4A inside the tent is interposed between the space 2A inside the barrel and the atmosphere, and the pressure difference between the space 4A inside the tent and the atmosphere prevents air from the surrounding tank from entering the tent 4. In this state, the barrel opening 2H is opened and the pump 3 installed inside the tank body 10 is lifted up through the pump barrel 2. Therefore, it is possible to prevent air present around the tank body 10 from mixing into the pump barrel 2.

[0034] Furthermore, in the extraction method described herein, a tent 4 is temporarily erected on the tank roof 11 when the pump 3 is extracted, and the tent 4 is removed when or after the pump 3 is recovered. In other words, instead of permanently installing a structure to cover the barrel opening 2H on the tank roof 11, the tent 4 is temporarily erected on the outside of the tank body 10 and removed after the extraction of the pump 3 is completed. In this way, since the tent 4 is installed on the tank roof 11 only when the pump 3 is extracted during maintenance, etc., there is an advantage in that the shape of the tank body can be simplified.

[0035] [Summary of this disclosure] The specific embodiments described above include disclosures having the following configurations.

[0036] A method for removing a pump from a tank according to one aspect of the present disclosure is a method for removing a pump from a liquefied gas tank having a structure for discharging liquefied gas stored in the tank using a pump barrel that penetrates the tank vertically and a pump installed inside the tank, wherein a tent is installed outside the tank so as to cover the sealed barrel opening at the upper end of the pump barrel, the inside of the tent is made into a positive pressure environment, the barrel opening is opened, and the pump is lifted into the tent through the pump barrel using a lifting device installed outside the tank, the barrel opening is sealed, and the lifted pump is recovered.

[0037] In this method, a tent is set up to cover the sealed barrel opening, creating a positive pressure environment within the tent. The pressure difference between the tent and the atmosphere prevents air from surrounding the tank from entering the tent. In this state, the barrel opening is opened and the pump inside the tank is lifted, preventing air from surrounding the tank from entering the pump barrel.

[0038] In the above method for removing the pump from the tank, after sealing the barrel opening, the pump can be held in the tent for a predetermined time before being recovered.

[0039] This method allows for the purging of any liquefied gas remaining inside a pump by holding it suspended inside the tent for a predetermined period of time.

[0040] In the method for removing the pump from the tank described above, the tent may be removed when the pump is recovered or after it has been recovered.

[0041] This method involves temporarily erecting a tent outside the tank and removing it after the pump has been removed. In other words, the tent is only installed outside the tank when the pump needs to be removed, such as during maintenance, which allows for a simpler tank design.

[0042] In the above method of extracting the pump from the tank, a positive pressure environment can be created inside the tent by continuously supplying an inert gas into the tent while simultaneously discharging the inert gas from the tent.

[0043] This method makes it possible to maintain positive pressure inside the tent while constantly purging it with an inert gas.

[0044] In the above method of extracting the pump from the tank, it is desirable to set the pressure inside the tent to a pressure lower than the pressure inside the pump barrel.

[0045] This method prevents inert gas from entering the pump barrel from inside the tent due to the pressure difference between the inside of the tent and the inside of the pump barrel. [Explanation of symbols]

[0046] LH Liquefied Hydrogen 1. Liquefied gas tank 10 Tank body (tank) 2 pump barrels 2A Barrel interior space 2H barrel opening 25 Headplate 3 pumps 4 tents 4A Tent interior space 5. Lifting device 6. Gas replacement device

Claims

1. A method for removing a pump in a liquefied gas tank, which has a structure for discharging liquefied gas stored in the tank using a pump barrel that penetrates the tank vertically and a pump installed inside the tank, A tent is set up outside the tank so as to cover the sealed barrel opening at the upper end of the pump barrel. The inside of the tent is kept under positive pressure, and the pressure inside the tent is set to a pressure lower than the pressure inside the pump barrel. The barrel opening is opened, and the pump is lifted into the tent through the pump barrel using a lifting device installed outside the tank. A method for removing a pump from a tank, comprising sealing the barrel opening and recovering the lifted pump.

2. In the method for removing a pump from a tank according to claim 1, A method for removing a pump from a tank, comprising sealing the barrel opening, holding the pump inside the tent for a predetermined time, and then retrieving the pump.

3. In the method for removing a pump from a tank according to claim 1 or 2, A method for removing a pump from a tank, comprising removing the tent during or after the recovery of the pump.

4. In the method for removing a pump from a tank according to any one of claims 1 to 3, A method for removing a pump from a tank, comprising continuously supplying an inert gas into the tent while simultaneously discharging the inert gas from the tent to create a positive pressure environment inside the tent.

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