GB2294307A

GB2294307A - Pressure resistant pipe with corrugated armouring

Info

Publication number: GB2294307A
Application number: GB9518735A
Authority: GB
Inventors: Friedrich Karl Levacher; Gerd Hahne
Original assignee: Felten and Guilleaume Energietechnik AG
Current assignee: Felten and Guilleaume Energietechnik AG
Priority date: 1994-09-13
Filing date: 1995-09-13
Publication date: 1996-04-24
Also published as: DE4432481C1; NO953567L; GB9518735D0; NL1001126A1; NO953567D0; NL1001126C2

Description

2294307 Pressure-resistant pipe with corrugated armouring

The invention concerns a pipe with corrugated armouring based on the generic description of the main claim.

Corrugated metal pipes or corrugated metal sheaths of electrical cables which are equipped with a plastic sheath are described in the German published application DE 14 90 349. The plastic sheath fills out the corrugation valleys. The plastic sheath has a smooth cylindrical surface in the outward direction. The pipe with corrugated armouring constructed in this way lacks any armouring against inadmissibly high tensile forces. With an application of forces from the outside, tensile forces elongate the corrugated pipe and reduce its inside width.

Another example is known in the form of a hose line (DE AS 1625959). This concerns a flexible hose line with an inner lining made of a corrugated plastic tube and an outer overbraid which fills out the gaps between the outer corrugations. The outer braid is made of softer plastic than the material of the corrugated pipe. A reinforcing inlay (made of metal or fabric) is inserted into the outer overbraid. However, the material selected is not suitable for high tensile forces.

The invention is based on the task of creating a corrugated pipe which is capable of withstanding an increased tensile load, which can still be wound onto drums in greater lengths, and which can be used in particular as cable sheaths for gas pressure pipe cables.

The task was solved by a pipe with corrugated armouring exhibiting the characteristics described in the main claim. Advantageous designs and the use for gas pressure pipe cables are indicated in the sub-claims.

The solution proposed is independent of whether the pipe with corrugated armouring has ringed or helical corrugations. The pipe with corrugated armouring can also be used for other purposes in addition to being used as a sheath for gas pressure pipe cables, such as a conveying line for fluid media. An example of the media we have in mind here would be natural gas or oil.

It is proposed to equip the corrugated pipe with armouring which rests on it by means of friction-locking. The armouring absorbs tensile forces. Elongation is prevented. In spite of this, the pipe with corrugated armouring retains good flexibility, so that it can easily be wound onto drums.

1 The pipe with-corrugated armouring can be factory-produced in great lengths (100 to 200 m) as a result of which it is particularly suited to use as an outer sheath for external gas pressure cables.

The longitudinal forces with external gas pressure cables are very high as a result of the gas pressure. For this reason, external gas pressure cables are accommodated inside pressure-resistant steel tubes in sections of around 20 metres in length which are welded together after being laid. The power cable is then drawn in.

The armouring for external gas pressure cables in accordance with the invention absorbs the forces applied while this type of cable is being drawn into a prepared cable tunnel or conduit. Similarly, the longitudinal forces which occur as a result of the infeed of pressurised gas are absorbed. The external gas pressure cable can be drawn in directly along with the cable cores, thereby cutting down the need for expensive earthlaying work.

The advantage of an external gas pressure cable which can be wound on drums in accordance with the invention exists, therefore, in the fact that the power cable and pressure pipe are manufactured as a single unit and can be delivered in greater lengths to the building site, laid there and connected by pressure. This allows a reduction in the number of coupling sleeves required.

The pipe with corrugated armouring can be connected by friction-locking at certain points to the cable core or (in the case of a multi-core cable) to the cable cores of the inner cable. If the geometry of the run layout permits, this can take place at the terminations or sleeves or at the end of the cable run using insulating supports. DE 25 39 326 Al, for example, offers a proposal for the type of connection.

A corrosion protection layer can be applied to a metal pipe with corrugated armouring under the inner plastic sheath. However, this should not be applied very thickly, and should not fill out the corrugated valleys so that it does not diminish the adhesion of the armouring.

The design of the armouring can be adapted to the requirements. This is normally done by selecting the length of lay of the armouring wires. In order to obtain the flexibility required in practice for winding onto drums, the length of lay can be selected in such a way that a maximum elongation of the pipe with corrugated armouring is limited to, for example, 0. 1 percent.

The plastic sheath on the pipe with corrugated armouring consists of an inner and an outer plastic sheath between which the armouring is located. The two plastic sheathes are connected to each other permanently by mechanical means on the armouring via th ' e gaps in the relatively exposed armouring for the purpose of transmitting force from the inside towards the outside. The inner plastic sheath can, for example, be made of polyettlylene and should preferably have a cylindrical outer surface.

2 The armouring consists of a wire mesh of high tensile strength or of wires wound in reverse lay made of metal, plastic or glass fibres. Meshed wires or wires, inserted with lays have the crucial advantage, compared to armouring elements which are only drawn in the longitudinal direction in the plastic sheath, that an elongation of the pipe with corrugated armouring can be reliably absorbed and caught by the armouring. The transmission of force occurs in the same way as with a draw stocking. An essential aspect of the invention is that even slight tensile forces or elongations are transmitted and exert a pinching effect on the plasticembedded armouring.

The inner plastic sheath just slightly exceeds the outer dimensions of the corrugation peaks of the pipe with corrugated armouring, the outer diameter of the inner plastic sleeve is preferably a mayimum of 2 mm larger than the outer diameter across the corrugation peaks on the pipe with corrugated armouring. On a relative scale, this corresponds to approx. 1 % of the outer diameter of the pipe with corrugated armouring in the case of a diameter of 200 mm.

The elasticity of the plastic sheathes is sufficiently high that the pipe with corrugated armouring still retains sufficient flexibility in order to be able to be wound onto drums.

The invention is described in more detail in the sole figure.

The figure shows a pressure-tight version of a pipe with corrugated armouring 1. It is equipped with a firmly attached coating, the outer surface of which is cylindrically smooth, and which extends down into the corrugation valleys and exceeds the dimensions of the peaks of the corrugations only by a relatively small degree (inner plastic sheath 2). The dovetailing of the plastic sheath with the corrugated valleys produces a well-fitting connection on the pipe with corrugated armouring. Metal or plastic can be selected as the material of the pipe with corrugated armouring. What is important is its stability under pressure with fluid media (gas or liquid). The corrugations may be parallel or of the thread-type. The reference symbol F indicates the dimension with which the inner plastic sheath 2 exceeds the outer diameter of the corrugation peaks.

The armouring 3 designed to absorb the tensile forces is situated on the inner plastic sheath 2. It can exist in the form of a mesh or wires wound in reverse-lay. The armouring has a relatively small degree of coverage 4, if possible less than 50%, preferably 113, so that there are sufficiently large gaps 4 through which the external plastic sheath 5 is connected with the inner plastic sheath 2. The two plastic sheathes 2, 5 thereby create a mechanically stable unit. The armouring 3 is completely embedded in plastic. The material of the inner and outer sheathes is preferably made of the same plastic. The connection of the two sheathes 2, 5 can be arranged by means of a welding process with correspondingly high temperatures and be reinforced by means of a moulding process. For both plastic sheathes 2, 5, it is also possible to use crosslinkable plastics. In this case, the crosslinking process is undertaken only after the armouring has been embedded and after mounting of the outer sheath.

The wires 3 of the mesh can be made of metal, preferably steel, or of plastic with a high tensile strength (for example Keviar) or of glass fibres.

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Claims

PRESSURE-RESISTANT PIPE WITH CORRUGATED ARMOURING 1. Pressure-resistant pipe with corrugated armouring with a plastic sheath inserted into the recesses of the pipe with corrugated armouring, characterized by the fact that the inner plastic sheath (2) rests friction-locked on the corrugated pipe (1), that an armouring (3) formed with gaps (4) lies on the plastic inner sheath (2), on top of % -- ich a plastic sheath (5) is located which is permanently welded mechanically to the inner plastic sheath (2) via the gaps in the armouring.
2. Pressure-resistant pipe with corrugated armouring based on Claim 1, characterized by the fact that the inner plastic sheath (2) is made of polyethylene.
3. Pressure-resistant pipe with corrugated armouring based on one of the Claims 1 or 2, characterised by the fact that the armouring (3) is made of a wire mesh of high tensile strength or wires wound in reverse-lay.
4. Pressure-resistant pipe with corrugated armouring based on Claim 3, characterized by the fact that the wire mesh of the armouring (3) is made of metal fibres, plastic fibres or glass fibres.
5. Pressure-resistant pipe with corrugated armouring based on one of the previous claims, characterised by the fact that the degree of coverage (4) of the armouring is less than 50 %.
6. Pressure-resistant pipe with corrugated armouring based on one of the previous claims, characterized by the fact that the outer diameter of the inner plastic sheath (2) is a maximum of 2 per cent greater than the outer diameter of the peaks of the corrugations of the pipe with corrugated armouring.
7. Pressure-resistant pipe with corrugated armouring based on one of the previous claims, characterised by the fact that a thin corrosion protection coating exists on a metal pipe with corrugated armouring (1) under the inner plastic sheath (2).
8. Use of a pipe with corrugated armouring based on one of the previous claims, characterised by the fact that it is used as an external pressure pipe (10) of a external gas pressure cable.

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9. External gas pressure cable based on Claim 8, characterised by the fact that the pipe vAth corrugated armouring (1) is connected by frictionlocking preferably at the terminations to a cable core - or in the case of a multi-core cable - to the cable cores.
10. Use of a pipe with corrugated armouring based on one of the previous claims, characterised by the fact that it is used as a conveying line for fluid media.