GB2148447A

GB2148447A - Tubular conduit

Info

Publication number: GB2148447A
Application number: GB08426763A
Authority: GB
Inventors: Jean-Paul Aubert
Original assignee: Coflexip SA
Current assignee: Technip France SAS
Priority date: 1983-10-24
Filing date: 1984-10-23
Publication date: 1985-05-30
Also published as: DK505984D0; IT8423296A1; FR2553859B1; DE3438988A1; NO844228L; FR2553859A1; JPS61500371A; BR8407135A; NL8403239A; IT8423296A0; ES537394A0; IT1177028B; WO1985002001A1; GB8426763D0; DK505984A; ES8600483A1

Abstract

The flexible tubular conduit comprises an inner pipe (1) made of flexible material providing for tighteness characteristics with rspect to the conveyed product, a first assembly of reinforcement armatures (2) providing for resistance characteristics to mechanical stress, a protection coating of flexible material (3) and a second assembly of reinforcing armatures (4) surrounding said coating (3).

Description

SPECIFICATION Flexible tubular conduit The present invention relates to a new flexible tubular conduit which may be employed in particular but not exclusively for the conveyance of hydrocarbons within the frame of the exploration of undersea wells. The flexible tubular conduits in accordance with the invention may, however, be equally well employed in other applications, especially on land, for the conveyance of liquid, powdery or gaseous products.

Various types of flexible tubular conduit are already known. A first type of conduit called "smooth-bore" comprises an inner tube of flexible material intended to ensure tightness with respect to the product being conveyed, a set of reinforcing armouring wound spirally or braided, which ensures resistance to the mechanical stresses of pressure, tension and torsion, the number, nature and arrangement of the armourings being defined as a function of the dimensions and of the use foreseen for the conduit, and finally an outer protective coating generally of flexibel material such as polyethylene or a polyamide. Conduits of this type exhibiting particularly favourable mechanical characteristics are manufactured in great lengths by the Applicant company.

The latter likewise manufacture conduits of "rough-bore" type which besides the components described above include an inner metallic carcase intended for preventing crushing and to protect the flexible sealant sheath against attack by the products being conveyed.

In the case where the conduits are called upon to convey gas, alone or associated with liquids and/or solids, in order to ensure the discharge of the gas which diffuses through the inner tube provision is made to render the outer coating permeable either through holes or by choosing a material having a permeability to gas, which is high with respect to that of the material of the inner tube. It is also known, to provide zones of weakness in the outer coating, especially grooves or blind holes in order to form locations for bursting in the event of overpressure, to offer a preferential passage for the escape of the gas.

The outer protective coating is by its nature incapable of containing the internal pressure prevailing in the conduit in the event of accidental failure of the inner tube and/or the reinforcing armouring.

In this case there is a risk of the flexible conduit bursting with every imaginable consequence for safety, in particular when the fluid being conveyed is aggressive, inflammable or explosive.

The present invention has in view the provision of a flexible tubular conduit which offers increased safety with respect to bursting, avoiding in particular damage to the environment in the event of failure of the inner tube and/or of the reinforcing armouring arranged round it.

The flexible tubular conduit in accordance with the invention includes an inner tube of flexible material which ensures tightness with respect fo the product being conveyed, a first layer of reinforcing armouring which ensures resistance to the mechanical stresses of pressure, tension and torsion, a protective coating of flexible material and a second layer of reinforcing armouring suited to resisting the internal pressure and surrounding the said protective coating.

If desired an outer protective sheath may be provided.

French Patent No. 2 119 266 shows a flexible tubular body which includes two sets of armouring. However, in this construction only the inner armouring exhibits a suitability for resisting the internal pressure, the outer armouring ensuring only resistance to tension and to torque. In the event of failure of the inner armouring under the effect of internal pressure the risk of bursting of the conduit cannot be avoided.

In the present invention, on the contrary, it is understood that the second layer of armouring achieves a second sealing barrier suited to retaining the internal pressure in the event of failure of the first layer of armouring or of the inner tube. The second layer of armouring may have any conventional structure for this type of application, which enables it to ensure the required functions of resistance to the stresses and tension and torsion and to resist in addition to the internal pressure.

The second layer of armouring may comprises a spiral structure which may be seamed or not, of one or more wires, for example, a carcase of metal ribbon or of steel section, two superimposed crosses layers of metallic sections, of flat or round cross-section or stranded, or else a spiral layer which may be seamed or not, associated with two superimposed crossed layers. Such structures are traditional and employed in particular in the conduits produced by the Applicant company.

In one particular advantageous embodiment of the invention the conduit includes a device for detection of the pressure between the inner tube and the second set of armouring.

This pressure detector device is advantageously connected to an alarm actuated in the event of detection of an overpressure corresponding with the destruction of the inner tube and/or of the first layer of armouring.

The simplest embodiment of the pressure detection device is a simple pressure connection associated with a pressure guage.

In a particular advantageous construction when the fluid to be conveyed is a gas or contains gas, the conduit is arranged in order to enable a discharge of leakage towards the outside, of the gas diffusing through the inner tube, the detector device then being sensitive only to an overpressure which exceeds a pre determined threshold level which corresponds with the normal leakage flow, and then causing triggering of an alarm or the closure of valves provided upstream in the conduit.

A choke may also be provided, which is mounted in the leakage detector device and calibrated in such a fashion that the flow of diffused gas passes through it without significant loss of pressure whereas the application of the full discharge from the conduit in the event of failure would bring about high losses of pressure to be detected in the detector device.

In accordance with the invention the detector device may be arranged in the pipe itself or in an end ferrule in which the conduit is mounted.

The invention can be performed in many ways and some embodiments will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic section illustrating the structure of a first embodiment of conduit in accordance with the invention; Figure 2 is a view similar to that in Fig. 1, illustrating a second embodiment of conduit; Figure 3 is a diagrammatic view illustrating an embodiment of a detector device associated with the conduit from Fig. 2; and Figure 4 is a view similar to that in Fig. 3, illustrating a variant upon the detector device.

The "smooth-bore" type of conduit illustrated in Fig. 1 comprises an inner tube of flexible sealant material, for example, polyamide or polyethylene.

Above this inner tube 1 is located a first layer of armouring 2 represented only diagrammatically, which in practice comprises, for example, at least one layer of seamed spiral wires or two superimposed closed layers.

A protective coating generally of flexible material such as polyamide or polyethylene 3 surrounds the layer of armouring 2. Structures of flexible conduit which include the three components described below are at present produced commercially in great lengths by the Applicant company.

In accordance with the invention there is located round the coating 3 a second layer of armouring 4 of the same structure as the layer of armouring 2 or of a different structure.

In the example illustrated the layer of armouring 4 comprises two superimposed crossed layers of steel wire.

Finally an outer protective sheath 5 which if the occasion arises might be omitted, is located round the second layer of armouring.

The structure of the flexible conduit illustrated in Fig. 2 is of "rough-bore" type and comprises besides the components described for the structure from Fig. 1, a spiral inner cracase 6.

In this embodiment once again the layers of armouring 2 and 4 may exhibit the same structure or different structures and these structures may be the same as those of the layers of armouring of the conduit from Fig. 1 or else be different.

In Figs. 3 and 4 the structure of flexible conduit illustrated in Fig. 2 is shown mounted in a connector ferrule 7 with the interposition of sealing rings 8 between the coatings or sheets 1, 3 and 5 of the conduit and the facing bearing surfaces on the ferrule 7. A hollow 9 provided in the ferrule 7 communicates with an annular space 10 outside the first layer of armouring 2. The leakage detector device comprises a choke 11 in the package for the flow of the diffused gas and a guage 12 which detects the pressure prevailing in the annular space 10.

The choke is calibrated in such a fashion that the flow of diffused gas passes through it without significant loss of pressure whereas the application of the full delivery from the conduit, especially in the event of damage to the set of armouring 2, brings about a high loss of pressure.

In the embodiment as Fig. 4 a detector device is illustrated which comprises besides the choke 11 and the pressure guage 12 a regulator 13 which directs the different gases to the open air (the position represented in the Figure) and which in the event of a heavy discharge changes its position (the action being controlled by the control line shown in broken lines) in order to direct the leakage flow towards a storage tank 14.

An adjustable pressure-switch 15 in the event of overpressure actuates an alarm 16 fed by a battery 17. This switch may likewise actuate the closure of valves (not shown) which lie upstream in the flexible conduit, so as to drop the pressure prevailing in the conduit.

Although the invention has been described in connection with particular embodiments it is quite obvious that it is in no way restricted and that numerous variants in form and material may be applied to it without for all that departing either from its scope or from its spirit.

Claims

1. A flexible tubular conduit, characterized in that it includes an inner tube of flexible material which ensures tightness with respect to the product being conveyed, a first layer of reinforcing armouring which ensures resistance to the mechanical stresses of pressure, tension and torsion, a protective coating of flexible material and a second layer of reinforcing armouring suited to resisting the internal pressure and surrounding the said protective coating.

2. A flexible tubular conduit as claimed in claim 1, characterized in that it includes round the second layer of reinforcing armouring an outer protective sheath.

3. A flexible tubular conduit as claimed in claim 1 or claim 2, characterised in that it includes an inner metallic carcase.

4. A flexible tubular conduit as claimed in any one of the preceding claims, characterised in that the second layer of reinforcing armouring exhibits the same structure as the first layer of reinforcing armouring.

5. A flexible tubular conduit as claimed in any one of the preceding claims characterised in that it includes a device for detection of the pressure between the inner tube and the second layer of armouring, the said device being arranged in order in normal operation, to ensure passing of the gas which diffuses through the inner tube.

6. A flexible tubular conduit as claimed in claim 5, characterised in that the detector device is connected to an alarm.

7. A flexible tubular conduit as claimed in claim 5 or claim 6 characterised in that the detector device is associated with means of closure of valves arranged upstream in the conduit.

8. A flexible tubular conduit substantially as described herein with reference to and as shown in Fig. 1, Fig. 2 and Figs. 3 and 4 of the accompanying drawings.