JPH0681996B2 - Method for removing permeated gas from flexible composite pipe - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for removing permeated gas from a flexible composite pipe that transports a high-pressure fluid such as petroleum or natural gas.

[Prior art]

Conventionally, iron pipes have been widely used as pipes for transporting gas and oils containing gas components, but flexible composite pipes have recently come into use because they can be easily laid on the sea floor. Came. As shown in FIG. 1, this pipe is provided on a plastic inner pipe 1 with a circumferential reinforcing armor 2a for increasing pressure resistance and an axial reinforcing armor mainly for withstanding tension.
This is a flexible composite tube 4 having a structure in which a metal reinforcing layer 2 composed of 2b and a plastic outer sheath 3 for corrosion protection and external damage prevention is further provided.

In general, plastics have different degrees, but cannot completely shield the gas, and the gas diffuses and permeates in the plastic. The higher the pressure and temperature, the larger the gas permeation amount tends to be.

Therefore, also in the composite pipe 4, the gas in the plastic inner pipe 1 gradually passes through the wall of the inner pipe during the transportation of the pressurized fluid. Of course, also in the outer sheath 3, the gas permeates and is released to the outside of the sheath, but since the amount thereof is smaller than the permeation amount from the plastic inner tube 1, the gap between the plastic inner tube 1 and the outer sheath 3 (metal The gas is accumulated and pressurized in the armor void 5 of the reinforcing layer.

[Problems to be solved by the invention]

However, when the accumulated gas pressure becomes high, the outer sheath 3 bursts, and the original role of the sheath is no longer fulfilled. In addition, if O ₂ , H ₂ S, CO ₂ etc. are mixed in the permeated gas, metal reinforcement There is a drawback that the layer 2 is corroded and the life of the composite pipe 4 is shortened.

In order to eliminate such a defect, there is a method of locally providing a thin wall portion on the outer sheath 3 to promote gas permeation, but the outer sheath 3 is more likely to be punctured than the thin wall portion. Also, there is a method of using a material having good permeability such as silicon rubber as the outer sheath, but there is a problem in moldability and mechanical properties, and neither method is effective.

[Means for solving problems]

The present invention has been made to solve the above-mentioned problems, and one end of a flexible composite pipe formed by providing a metal reinforcing layer on a plastic inner tube and applying an outer sheath to the plastic inner tube and the outer sheath The carrier gas is supplied to the space between the two to convey the permeated gas that permeates into the space from the plastic inner pipe to the other end of the flexible composite pipe, and the permeated gas is transmitted from the other end to the outside of the flexible composite pipe. To remove the permeated gas of the flexible composite pipe.

[Action]

In this way, when carrier gas is supplied to the space between the plastic inner tube and the outer sheath, the gas that permeates from the plastic inner tube into this space flows from one end of the composite pipe to the other as the carrier gas flows. Since it is transported quickly, the permeated gas does not accumulate in the void.
Therefore, it is possible to prevent the outer sheath from bursting and the metal reinforcing layer from being corroded.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings. The flexible composite pipe to which the present invention is applied is the one shown in FIG. 1 described above, and the end joints 6 and 7 shown in FIG. 2 are attached to both ends of the composite pipe 4. The joints 6 and 7 are attached to the exposed end of the plastic inner pipe 1 of the flexible composite pipe 4 by a packing 8
And a cap 11 which is airtightly fitted to the end of the outer sheath 3 by a packing 10 and screwed into the joint body 9 and which has a gas insertion hole 11a. A plug 12 is fitted to the exposed end of the circumferential reinforcing armor 2a of the metal reinforcing layer 2 to press the packing 8.
Shows an engaging collar that bends the exposed end of the axial reinforcing armor 2b outward in a U-shape and engages with it to restrain the axial movement of this armor.

A carrier gas supply source 15 such as a gas cylinder or an air conditioner press is connected via a valve 14 to the gas insertion hole 11a of the terminal joint 6 attached to one end of the flexible composite pipe 4, and the flexible composite pipe 4 The gas insertion hole 11a of the terminal joint 7 attached to the terminal is opened or provided with a check valve (not shown) (see FIG. 3).

Next, the method of the present invention will be described. During the pressurized transportation of a fluid such as petroleum containing a gas or a gas component into the flexible composite pipe 4, a valve is used.
By opening 14, the carrier gas A such as air or nitrogen gas is supplied from the terminal joint 6 to the space 5 between the plastic inner tube 1 and the outer sheath 3 and constantly circulates in the space in the longitudinal direction. On the other hand, the permeated gas B that has permeated from the inside of the plastic inner tube 1 into the void 5 is conveyed to the terminal joint 7 of the other terminal as the carrier gas A flows, and is discharged from the gas insertion hole 11a to the outside of the flexible composite tube, for example, into the atmosphere. The gas is released and released, and the permeated gas B is removed (degassed). The carrier gas A may be supplied to the gap 5 intermittently instead of continuously.

When the carrier gas A is supplied to the space 5 between the plastic inner tube 1 and the outer sheath 3 as described above, the permeated gas B is not accumulated in the space 5 to prevent the outer sheath 3 from rupturing and the metal reinforcing layer 2 from corroding. can do. If, for example, nitrogen gas is used as the carrier gas A or if the carrier gas A is constantly flowed, it is more effective in preventing corrosion of the metal reinforcing layer 2, and nitrogen gas is also effective in preventing deterioration of the plastic inner tube and the plastic outer sheath. is there. Also terminal fitting 7
If a check valve is attached to the gas insertion hole 11a, there is less risk of water intrusion even when the terminal joint 7 is underwater, and the waterproof treatment such as covering the terminal joint 7 with a waterproof cover can be omitted or reduced. You can Also, unlike a relief valve, the use of a check valve has a large opening and closing frequency, so there is no risk that microorganisms etc. will adhere to the valve operating part and it will not operate, gas pressure will rise and sheath rupture and corrosion of the metal reinforcing layer will not occur. The inconvenience caused can be more surely prevented.

The terminal joints 6 and 7 may be provided not only at the end of the flexible composite pipe 4 but also at the intermediate connecting portion of the composite pipe. In this case, part of the intermediate connecting portion also serves as the terminal joint.

〔The invention's effect〕

As described above, the present invention supplies the carrier gas from one end of the flexible composite pipe to the gap between the plastic inner pipe and the outer sheath, and the permeated gas that permeates into the gap from the plastic inner pipe. Since the permeated gas is carried to the other end of the composite pipe and released from the other end to the outside of the flexible composite pipe, the permeated gas is transferred from one end of the composite pipe to the other end as the carrier gas flows. It will be transported quickly, preventing permeate gas from accumulating in the voids.
Therefore, there is no increase in gas pressure in this void, the outer sheath does not burst, the metal reinforcing layer does not corrode or stress cracks occur, and the life of the flexible composite pipe increases and aftercare becomes easy. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a flexible composite pipe to which the present invention is applied,
FIG. 2 is a longitudinal sectional view of the terminal joint, and FIG. 3 is an explanatory view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Plastic inner tube, 2 ... Metal reinforcement layer, 3 ... Outer sheath, 4 ... Flexible composite tube, 5 ... Void, 6 ... Terminal joint, 7 ...
Terminal joint, A ... Carrier gas, B ... Permeation gas.

Claims (1)

[Claims] 1. A plastic gas is supplied from one end of a flexible composite pipe in which a metal reinforcing layer is provided on a plastic inner tube and an outer sheath is applied, to a gap between the plastic inner tube and the outer sheath, and the plastic gas is supplied. A flexible composite characterized in that a permeated gas that permeates from the inner pipe into the void is carried to another end of the flexible composite pipe, and the permeated gas is discharged from the other end to the outside of the flexible composite pipe. Method for removing permeated gas from pipes.