GB2337367A

GB2337367A - Elongated tubular product,suac as in particular an installation conduit

Info

Publication number: GB2337367A
Application number: GB9919234A
Authority: GB
Inventors: Christian Blanc; Eric Pirony; Claude Trichard
Original assignee: Novoplastic SA
Current assignee: Novoplastic SA
Priority date: 1997-03-14
Filing date: 1998-03-13
Publication date: 1999-11-17
Anticipated expiration: 2018-03-13
Also published as: UA57069C2; DE19882152T1; ES2154612A1; RU2189098C2; GB2337367B; AU6923498A; RO120440B1; LT4659B; PL334903A1; CZ251099A3; FR2760814B1; SK283429B6; FR2760814A1; CH693801A5; EE9900407A; SK121499A3; TR199902238T2; HUP0002341A3; KR20000076210A; ID22695A

Abstract

The invention concerns an elongated tubular product with the same cross section along its whole length, comprising a solid tube (1) made of at least a plastic material, both sufficiently flexible to be wound and unwound, and sufficiently rigid to resist a centripetal or centrifugal radial force, said solid tube comprising, on the inside and/or on the outside, a surface coating (3) whose free surface constitutes a friction surface and comprising a plastic matrix in which is distributed a lubricant. The invention is characterised in that, with synergistic effect, the particles (4) of a solid lubricant are distributed in the plastic matrix, at least partly flush at the free surface of the surface coating, and a liquid lubricant compatible with the plastic matrix, is dispersed in the surface coating, practically without wetting the free surface of the latter.

Description

ELONGATE TUBULAR PRODUCT, ESPECIALLY OF THE INSTALLATION DUCT TYPE The

present invention relates to an elongate tubular product, having in general the same cross section over its entire longitudinal direction, and comprising a solid tube consisting of at least one plastic, which is both sufficiently flexible for it to be wound up and unwound and sufficiently rigid for it to withstand a centripetal or centrifugal radial force.

From the above generic definition, the present invention should be understood to encompass under the same concept, for example, equally well an installation duct, for one or more cables or one or more pipes, subsequently contained in the said installation duct, as a protective sheath for one or more cables, for example power cables.

Moreover, from the terms "cables" and "pipes", the present invention should be understood to cover any duct which allows, in general, transfer or transport of a flow, whether this is of a fluid (water or gas, for example), of energy (electricity, for example), or else of information or signals (video transmission via optical cable, for example), or of data in the form of electrical signals, be they analogue, digital, etc.

In order to introduce and define the present invention, reference is now given, by way of example, to installation ducts and/or to cables or pipes installed in the said ducts.

In order to limit the amount of civil engineering work, and in particular the number of jointing chambers, it is known to lubricate the friction surface, corresponding to the inner surface of the solid tube forming the installation duct and/or the outer surface of the protective sheath, for example the cable protection sheath. This makes it possible in fact to increase the length of tube which can be installed.

This lubrication is generally provided by a surface layer on the inside and/or outside of the tube, the free surface of which constitutes a friction surface.

Various solutions have been proposed for this purpose.

According to document W093/14546, the surface layer consists of a lubricating film or coating, either in solid or liquid form. In the case of a solid lubricating coating, this may, for example, be a plastic matrix made of polyethylene in which solid particles, for example graphite particles, may be distributed. In the case of a liquid lubricating coating, this may, for example, oil.

Document EP-0,326,711 describes a solution comparable to that defined above, in the sense that the solid surface layer constitutes the internal layer of a tube coextruded with an external layer.

According to document DE-3,539,304, the surface layer, consisting of a grease or paste which is lubricating, but adherent, is added and remains on the inside of the tube.

This lubricating paste or grease itself consists of a mixture of a liquid lubricant and particles of a solid lubricant.

The subject of the present invention is an elongate tubular product, with permanent, almost dry lubrication of the friction surface or surfaces of the solid tube, significantly decreasing the frictional forces, including those compared with the solutions identified and discussed above.

For this purpose, according to the invention, a synergistic action has been discovered between:

- on the one hand, particles of a solid-type lubricant, which are distributed in the plastic matrix of the surface layer and are at least partly flush with the free surface of the latter; and be a silicone-based 3 - on the other hand, a liquid-type lubricant, compatible with the plastic matrix, which lubricant is dispersed in the surface layer virtually without wetting the free surface of the latter.

The observed synergistic effect may be explained by the fact that the particles of the solid lubricant which are flush with the surface are as it were lubricated in turn by the liquid lubricant wetting them.

By virtue of the present invention, installation duct becomes, as it were, a general-purpose duct in the sense that it is compatible, without any other modification, with all the current installation techniques, whether they be pulling techniques, for example using a small cable, or blowing techniques, for example using a pig, or by blowing-pushing.

Moreover, when the solid lubricant is an electrical conductor, the lubricating system according to the invention makes it possible to eliminate, at least in part, the static charges generated by the friction between the duct and the cable while the latter is being installed.

The present invention following secondary characteristics:

an therefore has the the solid lubricant has a lamellar structure, and is, for example, graphite, or else has a polymeric structure with oriented long straight chains, and is, for example, a polytetrafluoroethylene; the particles of the solid lubricant are microspheres having a diameter of at most 20 gm, and preferably of between 1 and 15 gm; - the licluid lubricant is preferably, but not exclusively, a silicone; it has a viscosity of at most 1000 centistokes, at room temperature, and, for example, of between 10 and 1000 centistokes, the thickness of the film of liquid lubricant on the free surface of the surface layer not exceeding 1 gm; - the solid lubricant_constitutes a filler; - 4 the surface layer is irregular over the perimeter of the solid tube and corresponds, for example, to longitudinal ribs or grooves; however, this same surface layer may be continuous over the perimeter of the solid tube.

Preferably, it is the solid tube which consists of just the plastic matrix in which, on the one hand, particles of the dry lubricant are distributed, these particles being partly flush with at least one, inner or outer, free surface and constituting a dry-friction surface, and, on the other hand, a liquid lubricant is diffused, virtually without wetting either the outer surface or the inner surface of this same matrix.

According to this preferred solution, the solid lubricant constitutes a filler, the proportion by weight of which is at least equal to 5% of the plastic matrix, especially between 5% by weight and 20% by -weight of this same matrix.

still according to this same preferred solution, the matrix includes, in the diffused state, a liquid lubricant, which constitutes as it were an additive, its proportion being at least equal to 0.02% by weight of the plastic matrix, and especially between 0. 02% by weight and 0.08% by weight of this same matrix. In this case, by way of example, the solid lubricant/liquid lubricant proportion is at least equal to 5% and is especially between 5% and 20%.

The present invention will now be described with reference to the appended drawing, in which:

- Figure 1 shows diagrammatically, in axial section, an installation duct according to the invention; - Figure 2 shows, in axial section, a sheath for protecting a cable according to the invention; and - Figure 3 shows, in cross section, an installation duct according to the invention, but in another embodiment of the latter.

According to Figure 1, an installation duct consists of a solid -or rigid.-.tube 1, made of a filled plastic (for example, high-density polyethylene)., which is both sufficiently flexible in order for it to be wound up and unwound and sufficiently rigid in order for it to withstand a centripetal or centrifugal radial force. This solid tube has a dry-friction surface corresponding to its inner surface.

According to the present invention, at least one surface layer 3 is formed in the solid tube 1, the free surface of this surface layer 3 constituting the dry-friction surface (inner surface 2). This surface layer comprises a plastic matrix, corresponding to that of the solid tube, in which particles 4 (microspheres) of a solid lubricant are distributed, these particles being partly flush with the free surface 2.

According to another embodiment of an installation duct according to the invention, shown in Figure 3, the latter comprises three concentric layers 6, 7 and 8, optionally made of respectively different plastics, namely the outer layer 7, the inner layer 6, in which the surface layer 3 is incorporated, and the other, middle layer or interlayer 8. The surface layer 3 is discontinuous over the perimeter of the solid tube 1 and comprises, for example, longitudinal ribs 9 or corresponding longitudinal adjacent grooves.

However, of course, this same surface layer 3 may be continuous over the perimeter of the solid tube 1.

As shown in Figure 4, the surface layer 3 is obtained by spraying or diffusing, inside the tube 1, after extrusion but in the viscoelastic phase, the solid lubricant in particulate form and mixed with the liquid lubricant.

In this way, the solid lubricant and the liquid lubricant are incorporated in the plastic matrix of the tube, at least on the surface.

EXAMPLE 1

A tube made of high-density polyethylene (HDPE), (commercial reference DAPLEN 4610 from the French company PCD), having an inside diameter of 27 mm and a thickness of 3 mm, is extruded on a CMS60 machine from the company Cincinatti.

A suspension of a polytetrafluoroethylene (PTFE) powder (commercial reference UNILUB T3 from the company Uniflon) having an average particle size of 16 im, in a silicone oil (commercial reference 47V100 from the company Pennwhite) having a viscosity of 100 centistokes, is sprayed in divided form, at the exit of the extrusion head, into the extruded tube while it is still viscoelastic. The PTFE powder represents 20% by weight (PTFE) with respect to the oil.

The friction coefficient between the internal surface of such a tube and a sheath made of HDPE (same commercial reference as above) is 0.075.

Everything else being equal, the PTFE powder and the silicone oil act synergistically in order to decrease the friction coefficient since:

- the friction coefficient obtained without treatment of the internal surface of the tube is 0.19; - the friction coefficient obtained with just silicone oil being sprayed is 0.102.

EXAMPLE 2:

An 8 mm cable is pushed by blowing, with a pig, into a 2400 m installation duct made of high-density polyethylene (HDPE), having an inside diameter of 26 mm and a thickness of 2.2 mm. In the first case, the inner surface of the installation duct is coated with the liquid lubricant (silicone oil) identified in Example 1. In the second case, the inner surface is coated with a solid lubricant powder identical to that in Example In the first case, it is not possible to install a length of cable exceeding 400 m, whereas in the second case it was possible to install lengths of cable ranging up to 700 m, all other things being equal.

- 7 EXAMPLE 3:

An installation duct, made of high-density polyethylene, having an inside diameter of 27 mm and a thickness of 3 mm, for an installed cable of 17.6 mm outside diameter, is used with the inner surface of the duct coated firstly with a silicone oil having a viscosity of 100 cP, secondly with a Teflon G powder having a particle size of 10 gm and thirdly with a mixture of powder in the aforementioned oil, with a level of 10% by weight of a powder with respect to the oil.

In the three cases, the friction coefficients measured during the pushing/ conveying of the cable are is 0.102, 0.071 and 0.0061, respectively.

EXAMPLE 4:

An installation duct made of high-density polyethylene, having an inside diameter of 27 mm and a thickness of 3 mm, for an installed cable of 17.6 mm outside diameter, is used with the inner surface of the duct coated with a lubricating mixture consisting of a liquid lubricant (silicone) having a viscosity of 100 cP and an increasing proportion by weight of a solid lubricant (Teflon 0 powder) having the same particle size as previously, namely 5, 10, 15 and 20% by weight, respectively.

In the above four cases, the friction coefficients measured during the blowing/conveying of the cable are 0.086, 0.085, 0.089 and 0.090, respectively.

Claims

1. Elongate tubular product, having the same cross section over its entire longitudinal direction, comprising a solid tube (1) consisting of at least one plastic, which is both sufficiently flexible for it to be wound up and unwound and sufficiently rigid for it to withstand a centripetal or centrifugal radial force, the said solid tube having, on the inside and/or the outside, a surface layer (3), the free surface of which constitutes a friction surface, the said surface layer comprising a plastic matrix in which a lubricant is dispersed, characterized in that, synergistically, on the one hand, particles (4) of a solid-type lubricant are distributed in the plastic matrix, these particles being at least partly flush with the free surface of the surface layer, and, on the other hand, a liquid-type lubricant, compatible with the plastic matrix, is dispersed in the surface layer, virtually without wetting the free surface of the latter.

2. Tubular product according characterized in that the liquid silicone.

3. Tubular product according characterized in that the liquid lubricant has a viscosity of at most 1000 centistokes, at room temperature, and, for example, of between 10 and 1000 centistokes.

4. Tubular product according to Claim 1, characterized in that the particles (4) of the solid lubricant are microspheres having a diameter of at most gm, and preferably of between 1 and 15 gm.

5. Tubular product according to Claim 1, characterized in that the solid tube (1) consists of just the plastic matrix in which particles (4) of the dry lubricant are distributed, these particles being to Claim 1 ' lubricant is a to Claim 1 ' 9 partly flush with at least one, inner or outer, free surface (2) constituting a dry-friction surface.

6. Tubular product according to Claim 5, characterized in that the solid lubricant consists of a filler, the proportion of which is at least equal to 5 % by weight, and comprised between 5 and 20 % by weight of said matrix.

7. Tubular product according to Claim 5, characterized in that the liquid lubricant is essentially in the liquid state and is diffused into the plastic, virtually without wetting either the outer surface or the inner surface of the sci:ld mat.rix.

8. Tubular product according to Claim -7, characterized in that the liquid lubricant consists of an additive, the proportion of which is at least equal to 0.02% by weight of the plastic matrix, and especially between 0.02% and 0.08%' by weight of the said matrix.

_9. Tubular product according to Claim 81 characterized i ii that the solid lubricant/liquid lubricant proportion is at the utmost equal to 5%.

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