JPH04155160A - liquid helium depressurizer - Google Patents

Abstract

PURPOSE:To prevent the entrainment of liquefied helium on the suction side of a pressure-reducing pump, by a method wherein for vaporized helium gas, a baffle plate is provided at the outlet of a liquid helium reserver. CONSTITUTION:Herium gas in low temperature and high pressure, which is fully cooled in a herium-refrigerating machine 1, passes a liquefing line 2 and expands through a valve 3 for Joule-Thomson cooling effect. After that, a part thereof is turned into liquefied helium, is decelerated through a divergent pipe 4 and is stored as liquid helium 5. On the other hand, helium gas evaporated by the heat load of a superconductive magnet 7 placed in a liquid helium reserver 6, passes a cylindrical baffle plate 8, is properly compressed by a pressure-reducing pump 9 and is returned to the suction side of the helium-refrigerating machine 1. When a liquid level is low in the time of the supply of the liquid helium, the helium gas in low temperature entrains the liquefied helium and they are scattered. In this case, since a divergent pipe 4 is provided at the outlet part of the liquefying line 2, the liquefied helium is not directly entrained on the suction side of the pressure-reducing pump 9. In the case where the liquid helium is sufficiently exists, since the liquefied helium is interrupted by the baffle plate 8, such a matter as the liquefied helium directly enters the suction side of the pressure-reducing pump 9 does not occur.

Description

[Detailed description of the invention] [j! TECHNICAL FIELD The present invention relates to a liquid helium decompression device, and particularly to a liquid helium depressurization device 1i11+ suitable for depressurizing a liquid helium generated by a refrigeration device in a helium liquid.

[Conventional technology]

Conventional equipment is cryogenic, Mol 24. Al (19
As shown in the FuC-sheet described on pages 29 to 35 of 89), there is a configuration in which liquid helium supply piping from the helium refrigerator at the source is installed at the inlet of the liquid helium tank, and a decompression pump is installed at the helium gas outlet. It becomes.

[MS that the invention attempts to solve]

The above-mentioned conventional technology does not take into account the method of supplying liquefied helium to liquid helium I, and there is also the problem that liquefied helium gets mixed into the suction side of the pressure reducing pump, causing the suction pressure to fluctuate.

An object of the present invention is to provide a structure in which liquefied helium does not get mixed into the suction side of a vacuum pump, thereby improving the reliability of the vacuum pump.

[Means for solving the problem] In order to achieve the above purpose, liquefied helium is
A cylindrical bubble plate is installed at the suction port of the depressurizing valve to prevent liquefied helium from being sucked in even if it is scattered on the suction side of the pressure pump.

Furthermore, in order to achieve the above object, an expansion pipe is provided at the inlet of the helium tank for liquefied helium to prevent the liquefied helium from scattering to the suction side of the pressure reducing pump.

[For production]

Since a cylindrical bubble plate is installed at the vacuum pump suction port of the liquid helium tank, it is possible to prevent liquefied helium from getting mixed in even if liquid helium scatters, and the suction pressure of the vacuum pump can be prevented from fluctuating. do not have.

Further, when liquefied helium is supplied to the liquid helium tank, since a expansion tube is provided at the liquid helium inlet, the liquefied helium is stored in the liquid helium tank while being gradually depressurized. Therefore, since liquefied helium is not scattered on the suction side of the decompression pump, the suction pressure of the decompression pump does not fluctuate, and the bearings of the decompression pump do not suffer from load fluctuations, allowing stable rotation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In steady state, helium refrigeration! ! Reference numeral 11 is composed of a compressor, a plurality of heat exchangers, and a plurality of cold generating means (for example, an expansion terpino) (not shown).
The low-temperature, high-pressure helium gas that has been sufficiently cooled by the ef passes through the liquefaction rhino 2 and erodes into I11 at the Joule-Tomtsuno valve 3, and a portion of it becomes liquefied helium. C and stored as liquid helium 5.

On the other hand, helium gas evaporated by the heat load of the superconducting magnet 7 installed in the liquid helium tank 6 passes through a cylindrical pub full plate 8 and is pumped by a centrifugal pressure reducing pump 9 (the structure of which will be explained in the second section). The helium is appropriately compressed and returned to the suction side of the JJL machine 1 in a cycle of s&:.

The above explanation is for the case where the heat load is in a steady state, but when liquid helium is being supplied (when the liquid level is low), the liquid helium tank 6 is in a state where liquefied helium and low-temperature helium gas are entrained and scattered. It is. In this case, in this embodiment, the expansion pipe 4 is provided at the outlet of the liquefier rhino 2, so 1! Wetted helium is not entrained into the suction side of the vacuum pump 9. Also, when there is enough liquid helium, the heat load on the superconducting magnet becomes large, and liquefied helium is entrained from the liquid surface and mixed into the suction side of the decompression pump 9! The most cylindrical baffle plate 8
I was disturbed by that! There is no way for wetted helium to enter the suction side of the vacuum pump 9.

According to this embodiment, even when liquid helium is supplied or when the heat load on the helium tank becomes large, liquefied helium will not be mixed into the suction side of the pressure reducing pump. Therefore, the pressure on the suction side of the decompression pump does not fluctuate.
This has the effect of stably rotating the bearings of the decompression pump without causing load fluctuations, which in turn has the effect of improving the damage resistance of the entire system, including the refrigerator.

FIG. 2 shows the structure of the pressure reducing pump shown in FIG. 1. The bearings (journal bearing 13, thrust bearing 12) housing the high-frequency motor (motor rotor 14 and motor stator 15) are placed on the room temperature side, and the impeller 16 is placed on the low temperature side. ■ is the connector of the dynamic cable and is usually connected to the inverter. This implementation unit uses a dynamic pressure gas bearing, so there is no helium contamination with oil or the like. When the impeller 16 rotates at high speed, the gas flow is
Low-temperature helium gas is sucked in from the suction section 17 of the vacuum pump, is adiabatically compressed by the innovator, and is led to other components from the discharge section.

Therefore, in the structure of a vacuum pump using a gas bearing as in this embodiment, if liquefied helium gets into the suction part and vaporizes during the process, the suction pressure will increase by 10 times (4, lat
The densities of helium gas and liquid helium at m are about 10 times different. ), causing pressure fluctuations that exceed the load capacity of the gas bearing, resulting in seizure of the bearing.

Other embodiments are shown in FIGS. 3 to 6. Components that are the same as those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

In the embodiment shown in FIG. 3, a disc-shaped baffle plate 8' is provided within a cylindrical baffle plate 8. Therefore, even if liquefied helium entrained in helium gas enters from the opening IgA of the pub full plate 8, the second
The 1 jol of liquefied helium does not collide with the baffle plate 8' and enter the suction side of the vacuum pump 9. According to this embodiment, the liquid helium ellipse does not enter the suction side of the pressure reducing pump even in a state where liquefied helium and helium gas are entrained. Therefore, the pressure on the suction side of the decompression pump does not fluctuate, resulting in stable rotation.

FIG. 4 shows another embodiment. In this embodiment, the liquid helium tank 6 is equipped with a liquid gauge for measuring the liquid level of the liquid helium 4, and when the liquid level rises above the set liquid level, the controller 4 sends a signal to rotate the decompression pump 9. The configuration is such that it can be stopped. Therefore, when the amount of liquid helium 4 increases due to a decrease in heat load and the cylindrical baffle plate 8 becomes immersed in liquid helium, the vacuum pump is stopped to protect the vacuum pump 9. According to this embodiment, the pressure on the suction side of the decompression pump does not fluctuate, and when the heat load decreases, the decompression pump is stopped as punishment for liquefied helium entering the suction side of the decompression pump. This has the effect of further increasing reliability.

FIG. 5 shows another embodiment. In this embodiment, the pressure reducing pump 9
A buffer tank is provided on the suction side. Even if liquefied helium is entrained and mixed with helium gas on the suction side of the vacuum pump, Buffer Tac I can absorb the sudden pressure f movement. Therefore, this embodiment has the effect of alleviating fluctuations in the suction pressure of the vacuum pump, and has the effect of increasing the reliability of the vacuum pump.

FIG. 6 shows another embodiment. In this example, the liquefaction line 2
is in communication with the lower part of the liquid helium tank 6. Therefore, liquefied helium does not directly enter the suction side of the pressure reducing pump 9 during liquid supply. According to this embodiment, with a simple structure, it is possible to prevent liquefied helium from entering the suction side of the vacuum pump during liquid supply, and it is possible to alleviate fluctuations in the suction pressure of the vacuum pump.

〔Effect of the invention〕

According to this embodiment, liquefied helium is not directly entrained into the suction side of the vacuum pump. In addition, the pressure on the suction side of the pressure reducing pump does not fluctuate, and there are no load fluctuations on the bearings of the pressure reducing pump, which has the effect of providing stable rotation, which in turn increases the reliability of the entire system, including the refrigerator. It has the effect of improving sex.

[Brief explanation of drawings]

Figure 1 shows an embodiment of the present invention in which 5 kilos of liquefied helium is depressurized.
FIG. 2 is a structural diagram of a pressure reducing pump according to the present invention, and FIGS. 3 to 6 are flow diagrams showing liquefied helium pressure reducing apparatuses according to other embodiments of the present invention. 6... Expansion tube, 6... Liquid helium tank, 8... Pub full plate, 8'... Bent full plate, 9... Decompression pump, I... ...Liquid level needle, B...Controller, I...Baphwatank representative Patent attorney Masao Ogawa Figure 1 Figure 5 Figure 6

Claims (1)

[Claims] 1. A Joule-Thomson expansion valve for liquefying helium gas provided at the final stage on the high-pressure side of a helium liquefaction refrigeration system, and a liquefied helium expansion valve disposed downstream of the Joule-Thomson expansion valve. A refrigeration system comprising a liquid helium tank for storing the helium gas, and a decompression pump that reduces the pressure of the helium gas evaporated due to heat load in the liquid helium tank and exhausts it to a low-pressure side return arrangement of the helium liquefaction refrigeration system. A liquid helium decompression device characterized in that a baffle plate is provided at an outlet of the liquid helium tank for gas. 2. The liquid helium decompression device according to claim 1, wherein a buffer tank is provided on the suction side of the decompression pump. 3. The rotation of the depressurizing pump is controlled by a level gauge of the liquid helium tank, claim 1, item 4. Claim 1, wherein an expansion pipe is provided at the liquefied helium inlet of the liquid helium tank. The liquid helium decompression device described. 5. The liquid helium decompression device according to claim 1, wherein the liquefied helium inlet portion is provided at the lower part of the liquid helium tank. 6. A Joule-Thomson expansion valve for liquefying helium gas provided at the final stage on the high-pressure side of the helium liquefaction refrigeration device, and a liquid helium tank for storing liquid helium in consideration of the downstream side of the Joule-Thomson expansion valve. , a decompression pump that reduces the pressure of the helium gas evaporated due to heat load in the liquid helium tank and exhausts it to a low-pressure side return pipe of the helium liquefaction refrigeration system, the liquefied helium inlet portion of the liquid helium tank; A liquid helium decompression device characterized by having an expansion tube.