JPH04219587A - Seal structure - Google Patents

Abstract

PURPOSE:To surely prevent an accident of leakage of cryogenic fluid staying inside a pipeline to the exterior through seals with a gas pressure in a permanent pipe coupling or separation coupling of the pipeline where the cryogenic fluid flows by constituting the seals in a dual structure, and supplying gas into a space defined by the seals from the exterior. CONSTITUTION:In a coupling portion of a cryogenic fluid pipeline, gas, which is harmless even in the case of leakage to the exterior and is free from icing or chemical reaction even in the case of leakage to the interior, is introduced into a space defined by two seals in a seal portion having a dual structure. A gas pressure inside the space is kept higher than a pressure of cryogenic fluid staying inside the pipeline, thereby preventing any leakage of the cryogenic fluid.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is used, for example, in cryogenic propellant piping systems for rockets and related ground equipment, or piping systems in plants that handle noxious or dangerous fluids that must never leak to the outside. , relates to a seal structure suitable for use in permanent joints, separation joints, detachable joints, etc.

0002

[Prior Art] It is difficult to completely prevent leakage from cryogenic propellant piping joints in rockets or related ground equipment, etc., and various seals have been developed so far.
A double combination of these seals was used to achieve a more reliable leak-proofing effect.

0003

[Problem to be solved by the invention] Since there is no substance that has excellent elasticity at extremely low temperatures like rubber at room temperature, even if various devised seals are used in duplicate, If the cryogenic fluid is only used for this purpose, as long as the pressure of the cryogenic fluid is higher than the outside air pressure, there is a possibility that it will leak through both of the double seals to the outside.

[0004] In fact, there have been several instances in which fluid hydrogen leaked through both seals of a double seal, resulting in aborted rocket launches. In particular, problems often occur with separation joints that cannot be tightened with bolts to apply sufficient surface pressure to the seal.

Among cryogenic propellants, fluid hydrogen is particularly
Because the temperature is as low as 253 degrees Celsius, it is difficult to stop the leak with just a combination of seals as in the past, but if it leaks, it will explode in a wide range of mixture ratios with air, and it will be dangerous because it will ignite with a small ignition energy. Therefore, there was a need for a joint with a new sealing structure that would absolutely prevent leakage to the outside.

[0006]

SUMMARY OF THE INVENTION The present invention provides a seal structure in which a pressure higher than that of the cryogenic propellant is introduced into the middle portion of the double seal.

That is, the seal structure of the present invention uses double seals in the joints of the piping system through which cryogenic fluid flows, and applies a pressure higher than the cryogenic fluid pressure to the space sandwiched between the two seals. to guide the gas.

[0008] The type of gas used in this case is that it does not cause any harm even if it leaks to the outside, does not freeze even if it leaks into the cryogenic fluid,
Also, select one that does not chemically react with cryogenic fluids. For example, if the cryogenic fluid is liquid hydrogen, helium gas,
In the case of fluid oxygen, helium gas or nitrogen gas is suitable. Furthermore, there are various control means for controlling the gas pressure, such as means using a pressure regulating valve or means using a safety valve that operates within a constant pressure range.

[0009]

[Operation] In the first embodiment shown in FIG.
The two are bolted together, one face seal 13 and one shaft seal 14 are used in duplicate, and gas pressure controlled by a pressure regulating valve 17 is introduced into the space between the double seals.

[0010] Here, an inert gas controlled to a pressure Pg that is always higher than the cryogenic fluid pressure Pl by a pressure regulating valve 17 is supplied to the face seal 13 and the shaft seal 14 through a small hole 15 provided in the pipe 16 and the flange 12. Supplied to the space between.

This ensures that if the shaft seal 14 is defective and a leakage condition occurs, the higher pressure inert gas leaks toward the cryogenic fluid, and vice versa (leakage of the cryogenic fluid to the outside). doesn't happen. Therefore, if the seal 13 is incomplete and a leak could occur, the inert gas will leak to the outside, and the cryogenic fluid in the main pipe will not leak to the outside.

In the case of cryogenic propellant piping for rockets or related ground equipment, if an inert gas that does not freeze at that temperature is selected, a small amount of inert gas will be mixed in compared to the flow rate of the cryogenic propellant. However, there is no practical problem.

[0013] The gas pressure control means may be a means using a pressure regulating valve, a pressure control means using a safety valve that operates within a constant pressure range, such as shown in the second embodiment, or other pressure control means. good.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. First example

FIG. 1 is a perspective view showing the configuration of a first embodiment of the present invention. This is a bolt-on flange joint that does not allow leakage, and can be applied to locations where cryogenic propellant must never leak to the outside.

In the first embodiment shown in FIG. 1, the flanges are bolted together, one face seal and one shaft seal are used dually, and a pressure regulating valve is installed in the space between the double seals. This shows an example of a configuration in which a gas pressure controlled by .

In FIG. 1, a flange A11 and a flange B12 are connected by bolts, and a face seal 13 and a shaft seal 14 are connected by bolts.
A gas pressure Pg controlled by a pressure regulating valve 17 is guided to the space sandwiched between the face seal 13 and the shaft seal 14 through the small hole 15 between the double seals and the pipe 16.

At this time, the inert gas, which is controlled to a pressure Pg that is always higher than the cryogenic fluid pressure Pl by the pressure regulating valve 17, is supplied to the face seal 13 and shaft seal 14 through the gas supply pipe 16 and the thin hole 15 provided in the flange 12. Supplied to the space between.

Thereby, when the shaft seal 14 is defective, the higher pressure inert gas supplied to the space leaks toward the cryogenic fluid in the main pipe, thus causing the shaft seal 1
Even if 4 becomes incomplete, the cryogenic fluid in the main pipe will not leak to the outside. Second example

FIG. 2 is a perspective view showing the structure of a second embodiment of the present invention, and the joint portion is the same as that of the first embodiment.
As an inert gas pressure control means, a constant flow rate of gas is caused to flow through the orifice 28, and the amount subtracted from the gas flow rate leaking from the face seal 23 or the shaft seal 24 is set to the safety valve 2.
It is configured to escape from 7.

In FIG. 2, 21 and 22 are flanges A and B which are bolted to each other, and 25 is a small hole formed between the double seal consisting of the face seal 23 and shaft seal 24. , 26 are gas supply piping for supplying inert gas to the space sandwiched between the face seal 23 and the shaft seal 24. Third Embodiment FIG. 3 is a perspective view showing the configuration of a third embodiment of the present invention, which illustrates a seal structure using two shaft seals.

In FIG. 3, 31 is a joint nipple, 32
is a joint socket, 33 and 34 are joint nipples 3, respectively.
a shaft seal provided between 1 and the joint socket 32;
5 is a small hole formed between double seals, 36 is seal 3
This is a gas supply pipe for supplying inert gas to the space sandwiched between 3 and 34.

The seal structure shown in FIG. 3 can be applied to bolted flange joints, but it can also be used between ground equipment and rockets, between rocket jettison tanks and rocket bodies, It is suitable for application to separation joints used between the engine and the rocket body, etc., which are jettisoned after the engine is finished. That is, the joints of the pipes that exchange the cryogenic propellant between them need to be sure that there is no leakage when there is air around them, and they need to come off smoothly when they are separated. For actual application, an appropriate "coupling→dissociation" mechanism is required, although it is not shown in the drawings. As the inert gas pressure control means, the pressure control means of the first and second embodiments described above or other pressure control means can be used. Fourth example

FIG. 4 is a perspective view showing the configuration of a fourth embodiment of the present invention. Here, a seal structure in which a sheet 47 attached to the tip of a bellows 48 is pressed against the seal 44 by the spring force of the bellows 48 is used as one of the double seals, and a normal shaft seal 43 is used as the other. An example of the separation joint used is shown. 41 is a joint nipple, 42 is a joint socket, 45 is a thin hole formed between the double seals, and 46 is a gas supply pipe for supplying inert gas to the space between the seals 33 and 34. In the case of the seal structure shown in FIG. 4 as well, the supply pressure of the inert gas may be controlled using the pressure control means of the first and second embodiments or other pressure control means.

[0025] By using the seal structure of the present invention as described above, it is possible to reliably avoid the problem of leakage of cryogenic fluid to the outside. In other words, it is difficult to prevent cryogenic fluid from leaking from pipe joints because there is no seal that has sufficient elasticity like rubber at room temperature, and it is not possible to apply sufficient seal surface pressure by tightening bolts. This is especially true in the case of separate joints. However, as in the present invention described above, by using double seals and introducing an inert gas controlled to a pressure higher than the pressure of the cryogenic fluid into the space between the two seals, cryogenic Fluid can be completely prevented from leaking. However, inert gas may pass through each of the double seals and leak into the outside and into the cryogenic fluid; however, as long as the gas is inert to the outside, there will be no problem; However, if you choose an inert gas that does not freeze, there is usually no problem.

[0026]

[Effect of the invention] Double seals are used in the joints of pipes through which cryogenic fluid flows, and the space between the two seals is harmless even if it leaks to the outside, and does not freeze if it leaks inside. By introducing a gas that does not cause a chemical reaction at a pressure higher than the pressure of the cryogenic fluid, it is possible to avoid the inconvenience of the cryogenic fluid leaking from the piping and realize a highly reliable cryogenic fluid feeding system.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a first embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of a second embodiment of the present invention.

FIG. 3 is a sectional view showing the configuration of a third embodiment of the present invention.

FIG. 4 is a sectional view showing the configuration of a fourth embodiment of the present invention.

[Explanation of symbols]

11,21...Flange A, 12,22...Flange B, 1
3, 23... Face seal, 14, 24, 33, 34, 43...
Shaft seal, 15, 25, 35, 45...Small hole, 16, 26
, 36, 46...Gas supply piping, 17...Pressure adjustment valve, 27
... Safety valve, 28... Orifice, 31, 41... Joint nipple, 32, 42... Joint socket, 47... Seat, 48...
Bellows.

Claims (1)

[Claims] Claim 1: In a joint used for cryogenic fluid piping, there is a means for doubling the seals, guiding gas to a space sandwiched between the two seals, and controlling the gas pressure in the space to the cryogenic temperature inside the pipe. A pressurized cryogenic seal structure characterized by comprising means for maintaining a pressure higher than fluid pressure.