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Coupling for vent gas cooled transfer lines
RESEARCHANDTECHNICALNOTES Coupling for vent gas cooled transfer lines H. Walter
The use of vent gas cooled transfer lines for liquid helium is of interest wherever: a. Longer distances between the coolant storage or the liquefier and the cryostat are unavoidable.
6
8
b. The liquid is not transferred continuously but at certain intervals.
2
5
7
c. The amount of vent gas from the cryostat is sufficiently large. For intermittent transfer superinsulated transfer lines have disadvantages due to the long time necessary for the establishment of temperature equilibrium. From the point of manufacturing as well as of operation, it is desirable to compose a long transfer line from handy shorter sections. In the following a coupling for such sections is described, which has been found efficient in our laboratory. As usual, both parts to be coupled comprise a liquid carrying inner tube, 1, which is surrounded by the radiation shield, 2, attached to the vent gas tube, 3, and a vacuum jacket, 4. The vacuum jacket of the female part extends by 400 mm over the end of the liquid carrying tube and by 200 mm over the end of the vent gas tube, which both open into the inner stepped sleeve, 5, confining the insulation vacuum. The male part fits with its correspondingly stepped vacuum jacket into the sleeve, 5, and is connected to the female part by means of the flange, 6. The adjusting rod, 7, helps to find the proper position when both parts are coupled. The coupling is sealed in three positions. The O-ring, 8, provides a vacuum-tight seal against the atmosphere. Seal 9, 10, which consists of a ring, 9, at the male part fitting into the annular groove, 10, at the female part, is a shrink seal. That means, that the ring can be inserted into the groove at room temperature, but is tightly pressed against the inner wall of the groove at low temperatures due to the difference in contraction of both materials (eg ring: Teflon, KELF; plate with groove: stainless steel). Since the upper annular space, 11, between the male and female part of the coupling is thus effectively sealed against the lower annular space, 12, The author is with the Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 1000 Berlin 33, West Germany. Paper received 20 February 1978.
CRYOGENICS.
MAY
1978
Cross section A - B
-0
[
\\
9
Io A 4
Crosssection C-D ~
H I II I I II D-
12
13
I 2
.LD Fig. 1 Diagramto show the coupling of transfer lines both ends of the vent gas tubes, 3, can be inserted into each other without any seal. The liquid carrying inner tubes, 1, are connected by a bellows valve, 13. This valve, which provides a coarse seal for the liquid, has proved superior to a simple plug-in connection, especially during cool-down of the coupling.
315
The use of vent gas cooled transfer lines for liquid helium is of interest wherever: a. Longer distances between the coolant storage or the liquefier and the cryostat are unavoidable.
6
8
b. The liquid is not transferred continuously but at certain intervals.
2
5
7
c. The amount of vent gas from the cryostat is sufficiently large. For intermittent transfer superinsulated transfer lines have disadvantages due to the long time necessary for the establishment of temperature equilibrium. From the point of manufacturing as well as of operation, it is desirable to compose a long transfer line from handy shorter sections. In the following a coupling for such sections is described, which has been found efficient in our laboratory. As usual, both parts to be coupled comprise a liquid carrying inner tube, 1, which is surrounded by the radiation shield, 2, attached to the vent gas tube, 3, and a vacuum jacket, 4. The vacuum jacket of the female part extends by 400 mm over the end of the liquid carrying tube and by 200 mm over the end of the vent gas tube, which both open into the inner stepped sleeve, 5, confining the insulation vacuum. The male part fits with its correspondingly stepped vacuum jacket into the sleeve, 5, and is connected to the female part by means of the flange, 6. The adjusting rod, 7, helps to find the proper position when both parts are coupled. The coupling is sealed in three positions. The O-ring, 8, provides a vacuum-tight seal against the atmosphere. Seal 9, 10, which consists of a ring, 9, at the male part fitting into the annular groove, 10, at the female part, is a shrink seal. That means, that the ring can be inserted into the groove at room temperature, but is tightly pressed against the inner wall of the groove at low temperatures due to the difference in contraction of both materials (eg ring: Teflon, KELF; plate with groove: stainless steel). Since the upper annular space, 11, between the male and female part of the coupling is thus effectively sealed against the lower annular space, 12, The author is with the Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 1000 Berlin 33, West Germany. Paper received 20 February 1978.
CRYOGENICS.
MAY
1978
Cross section A - B
-0
[
\\
9
Io A 4
Crosssection C-D ~
H I II I I II D-
12
13
I 2
.LD Fig. 1 Diagramto show the coupling of transfer lines both ends of the vent gas tubes, 3, can be inserted into each other without any seal. The liquid carrying inner tubes, 1, are connected by a bellows valve, 13. This valve, which provides a coarse seal for the liquid, has proved superior to a simple plug-in connection, especially during cool-down of the coupling.
315