JPH0322638Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an improvement of the joint structure of double piping used for transporting cryogenic fluids such as liquid hydrogen.

[Prior Art] Conventionally, vacuum insulated double piping is used to transport cryogenic fluids such as liquid hydrogen. A lip seal flange is used at the joint of the inner pipe through which the cryogenic fluid of this double piping passes.

FIG. 6 is a cross-sectional view of a main part of a joint structure using a lip seal flange 21 (hereinafter simply referred to as a flange).
A protrusion 23 is provided along the periphery of 2.

The flanges 21 are faced to each other with a small gap 24 maintained between the flange contact surfaces 22, and seal welding 25 is performed at the tip of the protrusion 23 to seal the flanges 21 together. Inner tubes 26 are each joined to the flange 21 by butt welding, and a vacuum heat insulating section 28 is formed between the inner tube 26 and the outer tube 27.

By the way, an oxide film is generated on the back surface of the welded portion of the seal weld 25 due to welding heat. If this oxide film falls off, there is a risk that it will be mixed into the cryogenic fluid passing through the inner tube 26, so when seal welding 25 is performed, the inner tube 26 is filled with inert gas.
By back-sealing the back side of the weld, the formation of an oxide film is prevented.

[Problems to be solved by the invention] However, in the above joint structure, in order to perform back sealing, it is necessary to fill the entire length of the inner pipe 26 with inert gas, so a large amount of inert gas is required. Moreover, air remains in the minute gap 24 between the flanges 21 and it is difficult for the inert gas to reach the tip of the protrusion 23, making it impossible to obtain a sufficient back sealing effect and forming an oxide film on the back surface of the weld. There was a problem with that.

The purpose of this invention is to provide a joint structure that eliminates the above problems.

[Means for Solving the Problems] In this invention, lip seal flanges having protrusions extending outward along the periphery of the flange abutment surfaces are placed facing each other, and the tips of the protrusions are seal welded to seal the flanges. In a joint structure that is sealed and connects inner pipes of double piping, an annular groove is carved on the flange contact surface, and between the outer surface of one of the facing flanges and the annular groove. It has a communicating hole.

[Function] It is configured as described above, and inert gas is supplied from the communication hole, and while adjusting the supply pressure, the inert gas fills the entire minute gap on the flange contact surface. After back sealing, seal welding is performed on the tip of the protrusion.
Prevents the formation of an oxide film on the back side of the weld.

[Example] Hereinafter, an example of this invention will be described with reference to the drawings.
FIG. 1 shows a first embodiment, in which lip seal flanges 1a and 1b (same as above, hereinafter simply referred to as flanges) have protrusions 3a extending outwardly along the peripheries of flange contact surfaces 2a and 2b. , 3b are provided, and the flange contact surfaces 2a, which face each other while maintaining a minute gap 4,
2b is provided with annular grooves 5a and 5b around the entire circumference of the contact surface. A socket 6 is attached to the outer surface of one flange 1a of the pair of flanges 1a and 1b, and a communication hole 7 for supplying inert gas is bored between the socket 6 and the annular groove 5a. In addition, 13
is an inner pipe, 14 is an outer pipe, and the inner pipe 13 is joined to the flanges 1a and 1b by butt welding,
A vacuum heat insulating section 15 is formed between the inner tube 13 and the outer tube 14.

With the above structure, an inert gas such as argon gas is supplied from the socket 6 to the communication hole 7, and the entire minute gap 4 is filled through the annular grooves 5a and 5b to perform back sealing. Thereafter, seal welding 8 is performed on the tips of the projections 3a and 3b. During this welding, inert gas is continuously supplied to prevent outside air from entering the minute gap 4.

FIG. 2 shows a second embodiment, which has a structure in which an annular groove 5a is carved only in the flange 1a, and is a joint structure in which the structure of the opposing flange 1b is simplified.

FIG. 3 shows a third embodiment, in which a wide annular groove 9a is carved in the flange 1a, and a wide annular groove 9a is carved in the flange 1b.
has a joint structure in which an annular protrusion 10b that fits into a part of the annular groove 9a is provided, and by fitting the annular groove 9a and the annular protrusion 10b, shearing force acting on the flanges 1a and 1b is reduced. absorbs the external force applied to the seal weld 8, and also reduces the external force applied to the flange 1.
a, 1b are stably combined.

FIG. 4 shows a fourth embodiment, which shows the protrusion 3
Annular grooves 11a, 11b are carved close to the tips of a, 3b, and the back surface of the seal weld 8 and the annular grooves 11a, 1
This is a joint structure in which the inner surfaces of 1b are substantially the same plane, and the seal weld 8 is prevented from becoming brittle due to the notch effect caused by the minute gap 4, and the joint toughness is improved.

FIG. 5 is a drawing showing an example of sealing the socket 6, and when the seal welding 8 is completed, the plug 12 is sealed.
into socket 6, and then connect plug 12 and socket 6.
are sealed by welding 16.

[Effects of the invention] This invention is constructed as described above, and inert gas is supplied from the communication hole to fill the minute gap on the flange contact surface, and the supply pressure of the inert gas can be easily adjusted. Therefore, the effectiveness of the back seal can be improved, the formation of an oxide film is prevented, and the inside of the pipe is kept clean. Furthermore, since the inert gas needs to be supplied only to the minute gap on the back side of the weld, the amount of inert gas required is small, and the amount of inert gas used can be reduced significantly.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of the joint structure of the first embodiment of the present invention, Fig. 2 is a longitudinal sectional view of the main part of the second embodiment, and Fig. 3 is a longitudinal sectional view of the main part of the third embodiment. 4 is a longitudinal sectional view of the main part of the fourth embodiment, FIG. 5 is a sectional view showing an example of socket sealing, and FIG. 6 is a longitudinal sectional view of a conventional joint structure. . 1a, 1b...lip seal flange, 2a, 2
b...Flange contact surface, 3a, 3b...Protrusion, 4...
Minute gaps, 5a, 5b, 9a, 11a, 11b...
Annular groove, 6... Socket, 7... Inert gas communication hole, 8... Seal welding, 10b... Annular protrusion, 12
...Plug, 13...Inner tube, 14...Outer tube, 15...Vacuum insulation part, 16...Welding.

Claims (1)

[Scope of utility model registration request] A joint structure in which lip seal flanges provided with protrusions along the periphery of the flange abutting surfaces are faced to each other, and the tips of the protrusions are seal welded to join the inner pipes of the double piping, an annular groove opening in the flange contact surface; a communication hole bored in one flange to communicate the annular groove with the outside of the flange;
A vacuum insulated double piping joint structure characterized by having means for feeding an inert gas with an adjusted feeding pressure into the annular groove from the outside of the flange through the communication hole during seal welding of the tip of the protrusion. .