JP7603548B2 - Low temperature liquefied gas pumping equipment - Google Patents

Description

The present invention relates to a low-temperature liquefied gas pumping device that pumps low-temperature liquefied gas, such as liquid helium, from a storage tank that stores the gas.

In research at universities and other institutions, low-temperature liquefied gases are used as refrigerants. In particular, liquid helium is the refrigerant that can achieve the lowest temperatures, and is therefore used in a variety of research projects, primarily in the field of physics.

After being used as a refrigerant, liquid helium becomes helium gas. Because helium is a valuable resource, the helium gas used as a refrigerant is collected at a helium supply center within a research institute or university, where it is refined and re-liquefied.
The reliquefied helium is temporarily stored in a large helium tank (e.g., 5,000 L). When it is to be used again for research, it is pumped into small containers (e.g., 100 L) and distributed to each laboratory.

When pumping liquid helium from a large helium tank to a small container, a vacuum insulated pipe called a pumping pipe is used. It is possible to pump liquid helium by using the pressure difference between the large helium tank and the small container, but this takes a long time if a large amount of liquid helium needs to be pumped.
Therefore, research institutes that use a lot of liquid helium use pumping equipment with an immersion pump attached to the end of a pumping tube, and the liquid helium is pumped out using the power of the pump.

An example of such a conventional pumping device will be described with reference to Fig. 5. Fig. 5 shows a conventional low-temperature liquefied gas pumping device 37 provided in a storage tank 3 for storing liquid helium, with Fig. 5(a) being a plan view and Fig. 5(b) being a front view.
As shown in FIG. 5(b), a conventional low-temperature liquefied gas pumping device 37 includes a pumping pipe 5 having one end inserted into a storage tank 3 in which liquid helium, which is a low-temperature liquefied gas, is stored and the other end extending outside the storage tank 3, a pump 7 that pumps up the liquid helium in the storage tank 3 and discharges it into the pumping pipe 5, and a Wilson seal 9 that is provided at the opening of the storage tank 3 and seals the periphery of the pumping pipe 5 while allowing the pumping pipe 5 to rotate.

The pumping pipe 5 is a triple-structure vacuum insulated pipe consisting of an insertion section 5a inserted into the storage tank 3, a horizontal section 5b bending from the insertion section 5a and extending horizontally, and a hanging section 5c bending from the horizontal section 5b and extending downward. A pump 7 is attached to the tip of the innermost pipe of the insertion section 5a (hereinafter referred to as the "innermost pipe"), and when the pumping pipe 5 rotates around the Wilson seal 9 (see FIG. 5(a)), the pump 7 also rotates in conjunction with it.
In the figure, reference numeral 15 denotes a pumping pipe support member that supports the horizontal portion 5b of the pumping pipe 5, reference numeral 39 denotes a lead wire that supplies power to the pump 7, and reference numeral 41 denotes a feedthrough for airtightly introducing the lead wire 39 into the pumping pipe 5.

In the above, the pump 7 is supported by the pumping pipe 5, but Patent Document 1 discloses an example in which the pump 7 is supported by another member.
In Patent Document 1, the pump is supported by a support member fixed to the lid member of the storage tank, and the pump is connected to the pumping pipe via a flexible tube. In the above example, the pump and the pumping pipe are connected via a flexible tube having flexibility, so that even if the pump is fixed to the support member, the pumping pipe can be rotated in the same manner as in the example of Figure 5.

JP 2021-25591 A

In the case of the conventional low-temperature liquefied gas pumping device 37 of FIG. 5, one end of the innermost pipe of the pumping pipe 5 is immersed in liquid helium, so that it is thin-walled to reduce heat intrusion, making it difficult to attach the heavy pump 7.
In addition, since the insertion portion 5a of the pumping tube 5 is supported by the Wilson seal 9, if the weight of the pump 7 is large, the deterioration of the Wilson seal 9 will be accelerated.

Furthermore, if the discharge port 21 of the pump 7 is not located at the center of the top surface of the pump 7, or if the center of gravity of the pump 7 is significantly deviated from the central axis of the insertion portion 5a of the pumping tube 5, an eccentric load is generated on the Wilson seal 9. The eccentric load on the Wilson seal 9 increases as the weight of the pump 7 increases. When the eccentric load increases, the frictional force generated between the pumping tube 5 and the Wilson seal 9 also increases, so that the force required to rotate the pumping tube 5 also increases, resulting in poor operability.
For the reasons mentioned above, the conventional low-temperature liquefied gas pumping device 37 shown in FIG. 5 has many limitations on the weight and center of gravity of the pump 7, the position of the discharge port 21, and the like.

The technology in Patent Document 1 solves the above problem, but since there is a limit to how much the flexible tube can deform, it is necessary to restrict the rotation range of the pumping tube during operation.

In addition, it is necessary to use a flexible tube with a certain length or more, but as mentioned above, flexible tubes have a deformation limit and cannot be bent tightly. Therefore, in order to attach the low-temperature liquefied gas pumping device of Patent Document 1 to a storage tank, it is necessary to provide a large opening in the storage tank, which raises concerns about increasing the amount of heat entering the storage tank.

As described above, the technology of Patent Document 1 solves the problems of the conventional low-temperature liquefied gas pumping device 37 in Figure 5, but there is room for improvement in terms of the rotation range of the pumping pipe and heat entering the storage tank, etc.
Therefore, a new technique is required to solve the problems of the conventional low-temperature liquefied gas pumping device 37 shown in FIG.

The present invention was made to solve these problems, and aims to provide a cryogenic liquefied gas pumping device that can reduce eccentric loads on the Wilson seal by relaxing restrictions on the pump's weight, center of gravity, and outlet position.

(1) The low-temperature liquefied gas pumping device of the present invention comprises a pumping pipe having one end inserted into a tank in which low-temperature liquefied gas is stored and the other end extending outside the tank, a pump supported directly or indirectly on the pumping pipe to discharge the low-temperature liquefied gas in the tank to the pumping pipe, and a Wilson seal provided at an outlet of the tank for extracting the low-temperature liquefied gas and sealing the periphery of the pumping pipe while the pumping pipe is in a rotatable state, characterized in that the device comprises a bearing provided above the Wilson seal and supporting the pumping pipe rotatably coaxially with the Wilson seal.

(2) In addition, in the above (1), the bearing is supported by a stand arranged to surround the Wilson seal, the stand is made up of multiple segments, and at least one of the segments is configured to be removable while supporting the bearing.

(3) In addition, in the above (1) or (2), the bearing is supported by a stand arranged to surround the Wilson seal, and the stand has an inspection window that allows the Wilson seal to be viewed.

(4) In addition, in any of the above (1) to (3), the pump is indirectly supported on the pumping pipe via a pump support member, the upper end of which is fixed to the pumping pipe and the lower end of which supports the pump.

(5) Furthermore, in any of the above (1) to (4), a flexible tube is provided between the pump outlet and the pumping pipe.

In the present invention, a bearing is provided above the Wilson seal to support the pumping tube so that it can rotate coaxially with the Wilson seal. This alleviates restrictions on the weight, center of gravity, and location of the discharge port of the pump, and reduces the load and eccentric load on the Wilson seal. This allows a variety of pumps to be used, improves operability when rotating the pumping tube, and reduces wear and deterioration of the Wilson seal.

1 is a diagram illustrating a low-temperature liquefied gas pumping device according to an embodiment of the present invention. FIG. FIG. 2 is a perspective view showing a stand portion of FIG. 1 . 3 is a diagram showing a state in which one divided piece is removed from the stand in FIG. 2. FIG. FIG. 13 is a diagram showing another aspect of the pedestal. FIG. 1 is a diagram illustrating a conventional low-temperature liquefied gas pumping device.

1, a low-temperature liquefied gas pumping device 1 according to an embodiment of the present invention includes a pumping pipe 5 for pumping out low-temperature liquefied gas from a storage tank 3 in which the low-temperature liquefied gas is stored, a pump 7 for discharging the low-temperature liquefied gas in the storage tank 3 to the pumping pipe 5, a Wilson seal 9 provided at an outlet for taking out the low-temperature liquefied gas from the storage tank 3, a bearing 11 for supporting the pumping pipe 5 rotatably coaxially with the Wilson seal 9, and a stand 13 for supporting the bearing 11 and provided to surround the Wilson seal 9. Each of the above components will be specifically described below.
In the following, an example will be described in which the low-temperature liquefied gas stored in the storage tank 3 is liquid helium.
Moreover, the same parts as those in the conventional low-temperature liquefied gas pumping device 37 in FIG. 5 are given the same reference numerals, and the description thereof will be omitted.

<Suction pipe>
The pumping pipe 5 is a triple-walled vacuum insulated pipe having one end inserted into the storage tank 3 and the other end extending outside the storage tank 3. The liquid helium pumped up by the pump 7 flows through the innermost pipe of the pumping pipe 5 and is pumped out of the storage tank 3.

As in the conventional example of FIG. 5 , the pumping pipe 5 is composed of an insertion section 5a which penetrates the Wilson seal 9 and is inserted into the tank 3, a horizontal section 5b which bends and extends horizontally from the insertion section 5a, and a hanging section (not shown) which bends and extends downward from the horizontal section 5b, and the horizontal section 5b is supported by a pumping pipe support member 15 which has a wheel at its lower end.
A user can rotate the dip tube 5 by grasping and moving the dip tube support member 15 .

<Pump>
The pump 7 is immersed in the liquid helium in the storage tank 3 to pump up the liquid helium, pressurize the pumped liquid helium, and discharge it into the pumping pipe 5.

In this embodiment, assuming that a relatively large liquid helium pump will be used, a pump support member 17 is provided to support the pump 7. The pump support member 17 has the pump 7 attached to its lower end, and its upper end attached to the outermost piping of the pumping pipe 5 (hereinafter referred to as the "outermost pipe") by means of a mounting fixture 19.
By using the pump support member 17, the pump 7 can be attached to the outermost pipe of the pumping pipe 5, which has a relatively high strength, so that the weight limit for the pump 7 can be relaxed compared to when the pump 7 is attached to the thin-walled innermost pipe.
In addition, since the pumping pipe 5 to which the pump 7 is attached is supported by the bearings 11, the load is not applied to the Wilson seal 9 as in the conventional example, and the weight limit of the pump 7 can be further relaxed.

In addition, when the pump 7 is attached directly to the innermost pipe of the pumping pipe 5 as in the conventional example, the wall thickness of the innermost pipe needs to be set so that it has the minimum strength to support the pump 7. However, in this embodiment, such strength is not required, so the wall thickness can be made thinner than in the conventional example, reducing heat intrusion.

The material of the pump support member 17 preferably has a lower thermal conductivity than the pumping pipe 5. Since the weight of the pump support member 17 does not affect the load on the Wilson seal 9, the material of the pump support member 17 can be selected without considering the weight. Therefore, a glass fiber composite material, which is relatively heavy but has excellent insulating properties and great strength even at low temperatures, can be used.

The above is an example in which the pump 7 is indirectly supported by the pumping pipe 5 via the pump support member 17, but if the pump 7 is small and lightweight, the pump 7 may be directly supported by the innermost pipe of the pumping pipe 5, as in the conventional example shown in Figure 5.

1 has a discharge port 21 for discharging pressurized liquid helium provided on the side surface of pump 7, and discharges the liquid helium horizontally. For this reason, an introduction pipe 23 is attached to discharge port 21 for introducing the liquid helium discharged horizontally and discharging it vertically, and introduction pipe 23 is connected to the innermost pipe of pumping pipe 5 via a flexible tube 25.
By providing the flexible tube 25 between the discharge port 21 of the pump 7 and the pumping pipe 5, the flexible tube 25 absorbs vibrations of the pump 7, making it difficult for the vibrations to propagate to the innermost pipe of the pumping pipe 5. In addition, the flexible tube 25 also absorbs thermal contraction of the introduction pipe 23, so the risk of damage to the pumping pipe 5 can be reduced compared to the case where the flexible tube 25 is not provided.

<Wilson Seal>
The Wilson seal 9 seals the periphery of the scooping tube 5 while the scooping tube 5 is in a rotatable state. In the storage tank 3 of this embodiment, a first cover member 27 is provided at the opening of the storage tank 3, and a small-diameter opening smaller in diameter than the opening of the storage tank 3 is formed in the center of the first cover member 27. A cylindrical protrusion 29 protruding in a cylindrical shape is provided at the edge of the small-diameter opening. A second cover member 31 is provided at the upper end (the outlet of the present invention) of the cylindrical protrusion 29, and the Wilson seal 9 is provided on the second cover member 31. That is, the Wilson seal 9 of this embodiment air-tightly seals the portion where the scooping tube 5 passes through the second cover member 31.

The helium gas generated by the evaporation of the liquid helium in the storage tank 3 is at a low temperature (approximately -269°C), and since helium atoms are very small, leakage is likely to occur. Under these conditions, the Wilson seal 9 is a suitable member that can rotate the pumping tube 5 while ensuring airtightness, and is commonly used.

In addition, by providing a cylindrical protrusion 29 and a second cover member 31, each having a smaller diameter than the first cover member 27, on the first cover member 27 as shown in FIG. 1, when replacing the pump 7, the second cover member 31 having a smaller diameter can be opened to perform the work, which makes the work easier than if the first cover member 27 having a larger diameter was opened.
However, if the cylindrical protrusion 29 and the second lid member 31 are not provided, the opening of the storage tank 3 serves as the outlet of the present invention, and a Wilson seal 9 may be provided on the first lid member 27 to hermetically seal the space between the pumping pipe 5 and the first lid member 27.

<Bearings>
The bearing 11 is provided at the upper end of the stand 13 and supports the pumping pipe 5 above the Wilson seal 9 so as to be rotatable coaxially with the Wilson seal 9. Although the type of the bearing 11 is not limited in the present invention, a thrust bearing is used as the bearing 11 in this embodiment.

The bearing 11 is configured by sandwiching a plurality of rolling members 11a, such as balls or rollers, arranged and held in a ring shape between two ring members (a first ring member 11b and a second ring member 11c). The first ring member 11b is fixed to the insertion portion 5a of the scooping tube 5 and rotates together with the scooping tube 5. The second ring member 11c is fixed to the upper surface of the stand 13 so that the center of the second ring member 11c coincides with the center of the Wilson seal 9.

By providing the bearing 11 configured as described above, the insertion portion 5a of the pumping pipe 5 is supported by the bearing 11 and the stand 13. Therefore, the weight of the pumping pipe 5 and the pump 7 and pump support member 17 attached to the pumping pipe 5 is placed on the bearing 11 and the stand 13, which reduces the load on the Wilson seal 9 compared to the conventional example, and reduces wear on the Wilson seal 9.

Furthermore, as shown in FIG. 1, when the pump 7 is attached to the outermost pipe of the scooping pipe 5 via a pump support member 17, or when a pump 7 having a horizontal discharge port is used, the direction of the load applied to the scooping pipe 5 generally does not coincide with the rotation axis of the scooping pipe 5.
In this case, in the conventional example of Fig. 5 not having a bearing 11, a large eccentric load is applied to the Wilson seal 9, and a large frictional force is generated in the O-ring of the Wilson seal 9. As a result, the operability when rotating the pumping pipe 5 is significantly reduced, and the wear and deterioration of the Wilson seal 9 is accelerated, requiring frequent maintenance.

In this regard, in this embodiment, the bearing 11 keeps the scooping tube 5 centered relative to the Wilson seal 9, which improves operability when rotating the scooping tube 5 and further reduces wear on the Wilson seal 9, which is expected to extend the maintenance interval.

<Frame>
The stand 13 is provided to surround the Wilson seal 9 and supports the bearing 11 above the Wilson seal 9 .
The base 13 of this embodiment is composed of two divided pieces 13a as shown in Fig. 2. Each divided piece 13a has a strength such that one divided piece 13a can support the bearing 11 even when the other divided piece 13a is removed, and one divided piece 13a can be removed while still supporting the bearing 11 as shown in Fig. 3.

This makes it easy to visually inspect and maintain the Wilson seal 9 on a daily basis without placing any more load on it than would be placed on it during normal operation, and allows for early detection of problems such as leaks.

Figures 2 and 3 show an example in which the stand 13 is made up of two divided pieces 13a, but the stand 13 may be made up of three or more divided pieces 13a. In that case, it is preferable to make at least one divided piece 13a removable while supporting the bearing 11.

As another embodiment of the stand 13, as shown in FIG. 4, a stand 35 having an inspection window 33 through which the Wilson seal 9 can be viewed may be used.
By providing an inspection window 33 in the frame 35 as shown in FIG. 4, it becomes possible to visually check and perform maintenance on the Wilson seal 9 without disassembling the bearing 11 and the frame 35.

Incidentally, even in the case of the stand 13 constituted by the divided pieces 13a as shown in Figs. 2 and 3, the above-mentioned inspection window 33 may be provided in the divided pieces 13a.
However, in this embodiment, as described above, the load and eccentric load applied to the Wilson seal 9 are reduced, so that it is expected that the frequency of required maintenance will also be reduced.

As described above, in this embodiment, the load and eccentric load on the Wilson seal 9 can be reduced by providing a bearing 11 that supports the insertion portion 5a of the scooping tube 5 and centers the scooping tube 5 to the axis of the Wilson seal 9. This prevents wear and deterioration of the Wilson seal 9 and improves operability when rotating the scooping tube 5. In addition, it is possible to attach the pump 7 to the outermost tube of the scooping tube 5 via a pump support member 17 as shown in Figure 1, which relaxes restrictions on the weight, center of gravity, and position of the discharge port of the pump 7, allowing the use of various types of pumps 7.

REFERENCE SIGNS LIST 1 Low-temperature liquefied gas pumping device 3 Storage tank 5 Pumping pipe 5a Insertion portion 5b Horizontal portion 5c Hanging portion 7 Pump 9 Wilson seal 11 Bearing 11a Rolling member 11b First annular member 11c Second annular member 13 Frame 13a Divided piece 15 Pumping pipe support member 17 Pump support member 19 Mounting metal fitting 21 Discharge port 23 Inlet pipe 25 Flexible tube 27 First cover member 29 Cylindrical protruding portion 31 Second cover member 33 Inspection window 35 Frame (other embodiments)
37 Low-temperature liquefied gas pumping device (conventional example)
39 Lead wire 41 Feedthrough

Claims (4)

A cryogenic liquefied gas pumping device comprising: a pumping pipe having one end inserted into a tank in which a cryogenic liquefied gas is stored and the other end extending outside the tank; a pump supported directly or indirectly on the pumping pipe and discharging the cryogenic liquefied gas in the tank to the pumping pipe; and a Wilson seal provided at an outlet for extracting the cryogenic liquefied gas from the tank and sealing the periphery of the pumping pipe while the pumping pipe is rotatable,
a bearing provided above the Wilson seal and supporting the pumping tube rotatably coaxially with the Wilson seal;
The bearing is supported by a frame arranged to surround the Wilson seal, the frame being made up of a plurality of divided pieces, and at least one of the divided pieces is configured to be removable while supporting the bearing. 2. The cryogenic liquefied gas pumping apparatus according to claim 1 , wherein the platform has an inspection window through which the Wilson seal can be viewed. The pump is indirectly supported on the pumping pipe via a pump support member,
3. The low-temperature liquefied gas pumping device according to claim 1, wherein the pump support member has an upper end fixed to the pumping pipe and a lower end supporting the pump. 4. The low-temperature liquefied gas pumping device according to claim 1, further comprising a flexible tube provided between the discharge port of the pump and the pumping pipe.

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