GB1590782A

GB1590782A - Insulated pipelines

Info

Publication number: GB1590782A
Application number: GB4023577A
Authority: GB
Original assignee: Pont a Mousson SA
Current assignee: Pont a Mousson SA
Priority date: 1976-10-04
Filing date: 1977-09-28
Publication date: 1981-06-10
Also published as: JPS5344959A; JPS5437331B2; DE2743635C2; DD131874A5; NL7710806A; FI772919A; NL178273C; SE7710775L; AT371581B; CA1096418A; IT1091203B; DE2743635A1; SE439678B; CH614514A5; ATA703077A; FI72191B; FI72191C

Description

(54) INSULATED PIPELINES (71) We, PoNT-AoUssoN S.A., a Societe anonyme organised under the laws of France, of 91 Avenue de la Liberation, 54000 Nancy, France, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to an insulated pipeline for the conveyance of fluids at high temperatures.

Thermally insulated pipes are already known. By way of example, French Patent 2 042 814 discloses a pipe comprising a foam of thermally insulating plastics material which sticks firstly to an inner pipe and and secondly to an outer protecting cover and which covers the major part of the pipe but terminates at a certain distances from each of the ends of the pipe in an inclined surface of frustoconical shape.

It is an object of the present invention to provide a pipe line comprising pipes of the above type which is particular well-suited to the transportation of hot fluids.

According to the present invention there is provided an insulated pipeline for the conveyance of fluids at high temperatures, comprising a plurality of sections slidably interconnected, each section comprising a foam of thermally insulating plastics material which is adhered to an inner pipe and an outer protective cover and which covers the major part of the section but terminates a predetermined distance from each end of the section in an inclined surface of frustoconical shape, characterised in that the outer cove is constituted by a relatively rigid cover which terminates before each frustoconical surface and a jacket is provided for protecting each of the frustoconical surfaces of the foam, the jacket being fixed at one end to the outer cover and connected at the other end to the inner pipe, said jacket having sufficient elasticity to follow the expansion of the inner pipe and the inner surface of the foam adhered thereto as the inner pipe is hated, whilst the outer cover and the foam adhered thereto remains stationary.

In a first embodiment of the invention, the outer cover is formed by a strip of bitumen or a mixture of bitumen and elastomer provided with a non-woven reinforcement and wound externally in the form of a spiral on the plastics material foam.

In a second embodiment of the invention, the outer cover is constituted by a layer of non-cellular polyurethane placed around the layer of insulating foam by spraying. This ensures a perfect seal of the cover and facilitates manufacture of the insulated pipe.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partial view, in axial section, of an insulated pipe embodying the invention Figure 2 is a half view, also in axial section, of the connection between the ends of the two adjacent pipes according to the embodiment of figure 1; Figure 3 is a partial view, in axial section, of an insulating pipe according to another embodiment of the invention; and Figure 4 is a half view, also in axial section, of the connection between the ends of two adjacent pipes according to the em embodiment of figure 3.

The insulated pipe shown in figure 1 comprises an inner pipe- 1 made of cast-iron, preferably spheroidal graphite cast-iron, known as ductile cast-iron, which pipe has a large diameter, i.e. a diameter greater than 300 mm and possibly reaching 1200 and even 1600 mm. This pipe is intended for the transportation of water or fluid, at high temperatures which may reach 1200C, over a distance of the order of 1 or more Kilometres, the pipe preferably being buried.

The inner surface of the pipe 1 is provided with an inner coating 2, for example a coating of cement mortar, the nature and quality of which depends on the type of circuit in which the insulating pipe is mounted, as well as on the quality and nature of the fluid conveyed.

Sticking to the outer surface of the pipe 1 is a layer of insulating material 4, preferably constituted by relatively rigid polyurethane foam having a depth of 30 to 50 mm for example. The polyurethane, or other plastics material, intended to form the insulating foam is applied by being sprayed cold onto the pipe 1 which is rotated. By way of example, this plastics material has the formulation proposed by the ENODIM company, under the reference MR 2109, such that it adheres well to the cast-iron. Furthermore, the foam formed subsequent to this cold spraying operation on the pipe has a density which is higher at the interfaces, i.e. in contact with the cast-iron and on its outer surface, than throughout its mass. The foam formed in this way preferably has a density of the order of 80 to 120 kg/m3 which gives it the quality of mechanical strength without increasing its thermal conductivity to an excess extent.

This layer of insulating foam 4 is surrounded by a protective outer cover 6 preferably composed of bitumen or a mixture of bitumen and elastomer and provided with a reinforcement constituted for example by glass fibres or non-woven polyester. This cover is preferably a SOPRALENE cover provided by the SOPREMA company. It is wound hot in the shape of a spiral around the outer surface of the foam, to which it sticks. This cover is in fact sufficiently flexi- ble to follow possible local projections of the foam without breaking or cracking. It is also able to withstand perforation by roots and the like, owing to the presence of the reinforcement provided by the non-woven material. The tensile strength of this cover is of the order of 300 Newtons/cm. Its elastic elongation is from 8 to 10%.

On the opposite side to the foam, the cover 6 comprises anchoring ridges 8 preferably formed by a surface encrustation of gravel, naturally of a very small size, which facilitates anchorage of the latter in the ground. This small gravel also prevents sticking of the strip intended to form the cover when it is wound on a bobbin before being placed on the pipe. Furthermore, it prevents the action of ultraviolet rays which would be able to damage the material constituting the cover, when it is exposed to the light.

Referring now to Figure 2 the cover 6, like the foam 4, does not cover the entire length of the pipe 1, but stops at a certain distance from each of the ends of the pipe 1, in order to expose the smooth end 10, as well as the socket end 12, respectively provided at each of its ends and intended to provide for the connection of adjacent pipes. In the vicinity of each of these ends, the foam 4 terminates in a surface 14 which is inclined with respect to the general axis of the pipe and has a substantially frustoconical shape. This surface is covered by a jacket 16 of corresponding shape, which is retained under the cover 6 at one of its ends and fixed to the pipe both by sticking and by means of a clamping collar 20 at its other end. The jacket 16 is made of a material which is able to withstand high temperatures and in particular temperatures of the order of 1200C at which the pipe operates. This material must also have good tensile strength and sufficient flexibility to deform without being damaged under the effect of thermal expansions of the pipe.

Butyl rubber, or more simply butyl, is a material which fulfils these requirements, although other rubbers may also be used, for example ethylene propylene rubber.

The outer surface of the smooth end 10 is covered with a coating 22 which covers its entire surface and extends below the collar 20 and the end of the jacket 16. This coating is produced from a material having both a low coefficient of friction with the elastomeric joints and sufficient mechanical strength to withstand heating to a temperature of the order of 1200 without loosing its frictional qualities. This coating is preferably a fluorinated polymer or difluorinated polyvinylidene referred to by the initials DERV. A coating of the same material or similar material 24 also covers the outer surface of the socket 12 extending below the collar 20 and the end of the jacket 16. This coating is also extended on to the end of the socket 12 and on to the inner surface of the socket 12. This inner surface comprises a recess for receiving a gasket 26 intended to be compressed between the smooth end 10 and the socket 12 of adjacent pipes when connected. The recess for receiving the gasket 26 is defined at its inner end by an inner shoulder 28 of the socket 12 and at its outer end by an abutment rim 30 formed at the free end of this same socket 12. The base of the recess is formed by a cylindrical surface 32 which may be cast in one-piece but which is preferably bored-out in order to have more restricted diametral tolerances about a diameter depending on the desired compression of the gasket 26 at the time of connection.

In the region of the abutment shoulder 30 the cylindrical base 32 comprises a groove 34 in which a heel of the gasket 26 is fitted, which allows the latter to be absolutely immobilised in its position of use. The active part of this gasket is in turn in contact with the surface 32.

As shown clearly in figure 2, when twd adjacent ends of insulating pipes are cón- nected, the smopth end 10 of one, which is provided with a coating 22, is engaged in the socket 12 of the other and slides along the gasket 26 which it compresses.

The diameter of the abutment shoulder 30 is greater than the outer diameter of the coating 22 on the smooth end 10, such that the smooth end 10 easily penetrates the socket 12 with a slight diametral clearance limiting eccentricities, and therefore compression. In the same manner, the diameter of the cylindrical surface 32 is chosen in order to ensure radial compression of the gasket 26 which is at least greater than 5%, but does not exceed 25 %, whatever the manufacturing tolerances of the smooth end. The gasket 26 itself may be made by moulding from an ethylene-propylenediene-methylene mixture, or from any other similar material able to withstand high temperatures, for example "EPDM 5512" sold by KLEBER COLOMBES.

Manufacture of the insulated pipes takes place in the factory and the completed pipes may be easily stored until such time as they are required. When it is desired to lay the pipes, a first pipe is placed in the ground, in order that the outer cover 6 may be anchored in the ground, by means of the anchouring ridges 8. Onto the smooth end 10 of this first pipe there is fitted the socket 12 of a second pipe, such that the gasket 26 is clamped between the socket 12 and smooth end 10 of these two pipes, thus ensuring that their connection is sealed. Additional insulation (not shown) may be placed around the head of the socket 12 and collars 20. An appropriate number of identical pipes may thus be fixed end-to-end over the desired length, which may reach several Kilometres.

When in use, water or fluid at high temperature travels through the inner pipes I and causes heating of the latter, i.e. causes their thermal expansion. Under the effect of this expansion, the smooth end 10 tends to slide under the gasket 26 in the direction of the inside of the socket 12. The nature of the coating 22 allows this sliding, whilst nevertheless ensuring a constant sealed contact between the latter and the gasket, such that the seal is never destroyed by the thermal expansion.

However, this expansion causes deformation of the insulating foam 4 at its interface with the pipe 1 in order to accompany the latter. On the other hand, the protective cover 6 remains absolutely stationary owing to its anchorage and also remains relatively cold since it is protected from the heat by the presence of the insulating foam 4. Nevertheless, the insulating foam 4 has sufficient flexibility to be able to deform and follow the expansion of the pipe 1 without becoming detached from the fixed cover 6. Furthermore, the jacket 16 is also sufficiently resilient to adapt to the expansion of the pipe 10 whilst remaining rigidly connected to the end of the cover 6, which enables the insulation to withstand considerable thermal expansions without the danger of being damaged and consequently to retain its efficiency for a prolonged period of time.

Furthermore, at the time of introduction of the smooth end into the socket, it is easy to reserve a sufficient axial distance between these two members in order to allow a relatively considerable thermal expansion of the pipes when the temperature of the whole of the pipe line rises. The expansion of each pipe is thus absorbed at the point of connection to an adjacent pipe without the danger of it being transmitted from one pipe to another and accumulating thus causing considerable drawbacks at certain points.

The invention thus makes it possible to provide an insulating pipe of large diameter, manufactured in the factory in an arrangement formed or rigidly connected members in which there is no danger of separation and which are able to withstand high temperatures. It is also possible to produce pipe lines of great length by connecting a number of similar pipes without using specialised devices such as expansion bends or bellows to ensure joining of the latter. Naturally, in certain applications, it is still possible to use insulating pipes according to the invention comprising two smooth ends 10, their connection taking place by means of a sleeve or equivalent member facilitating expansion. In a pipe line produced in this way, there is no danger of an absence of seal or loss of resistance to heat, even if the pipe line is very long and it is thus particularly well-suited to carrying fluids over long distances. It is clear that the simplicity of assembly on the ground, added to the ease of transportation of the insulating pipe, considerably reduces the manufacturing and maintenance costs of pipe lines produced by means of the pipe according to the invention.

In addition, the jackets 16 divide the insulation of the pipe into compartments, so that no passage of humidity can occur and detach the foam, even in the case of failure of the attached insulation place around the junction of adjacent pipes.

The insulating pipe Ta of figure 3 has a diameter of between 150 and 1200 to 1600 mm. It differs from the pipe of figure 1 solely by the composition of the protecting and sealing outer cover 6".

In fact, the cover 6" is constituted by a layer of polyurethane varnish, which is a non-cellular polyurethane and which is thus compact and sealed. The polyurethane cover 6" is applied around the layer of insulating foam 4 according to a known technique of spraying. Polyurethane is a product not comprising a solvent, with two components (a polyol and an isocyanate). This is why spraying is carried out with a gun for two components, preferably by means of an automatic gun without air. Polyurethane sold under the trade name "POLYSTAL" by the Societe Technique d'Applications Chimiques (S.T.A.C.) may be used by way of example and this product may be sprayed with a thickness of 1 to several millimetres.

Figure 4 shows a direct junction between two insulating pipes Ta and Tta. This junction has a structure and method of assembly identical to that described with reference to figure 2, apart from the composition of the cover 6".

As in the case of figure 2, when used, water or fluid at high temperatures travels through the inner pipes 1 and la and causes heating of the latter, i.e. causes their thermal expansion Under the effect of this expansion, the smooth end 10 tends to slide under the gasket 26 in the direction of the inside of the socket 12. The nature of the coating 22 facilitates this sliding whilst ensuring constant sealed contact between the latter and the gasket, such that the seal is in no way destroyed by the thermal expansion.

The expansion caused by the passage of a hot fluid through the pipes Ta, Tta causes a deformation of the insulating foam 4 at its interface with the pipe 1 in order to accompany the latter. On the other hand, the outer cover 6" is not heated since it is thermally insulated by the presence of the foam. In addition, the method of burying the pipes and the nature of the earth in which they are buried is sufficient, in many cases, to ensure sufficient anchorage of the cover 6", by friction, despite the absence of ridges on the outer surface of the latter.

The choice of polyurethane makes it possible to obtain the desired coefficient of friction between the cover and the earth.

However, the insulating foam 4 has sufficient flexibility to be able to deform and follow the expansion of the pipe 1 without becoming detached from the fixed cover 6".

Furthermore, the jacket 16 is also sufficiently resilient to adapt to the expansion of the pipe 10 whilst remaining rigidly connected to the end of the cover 6", which allows the insulation to withstand considerable thermal expansions without any danger of being damaged and consequently to retain its effectiveness over a prolonged period of time. In other words, the combination of the foam, of the relatively rigid and fixed cover and of the terminal resilient jackets makes it possible, as in the embodiment of figures 1 and 2, to accommodate the radial gradient of expension within the foam between the pipe and the fixed cover.

The embodiment of figures 3 and 4 has the same advantages as that of figures 1 and 2, to which are added further advantages, described hereafter, due to the composition of the cover 6".

The layer of polyurethane 6" constituting the outer cover is applied by spraying. The latter is carried out quickly and easily and is not hindered by possible irregularities of the outer surface of the layer of insulating foam 4. It should also be noted that the waiting period, i.e. the time at the end of which it is possible to handle the pipe without damaging the coating, is short, of the order of 5 minutes. This method of construction also provides an important advantage: to apply the layer of polyurethane forming the cover 6", it is possible to use the same equipment as that which serves for applying the insulating layer 4, or very similar equipment. The seal obtained by the cover 6" is absolute even at the ends of the pipe, since this cover 6" covers the end of each jacket 16 and the attachment of the cover to the foam 4 is excellent, greater than the cohesion of this foam: in the case of tearing stress, the coating yields within the foam 4 rather than at the interface between the latter and the cover 6".

WHAT WE CLAIM IS: 1. An insulated pipeline for the conveyance of fluids at high temperatures, comprising a plurality of sections slidably interconnected, each section comprising a foam of thermally insulating plastics material which is adhered to an inner pipe and an outer protective cover and which covers the major part of the section but terminates a predetermined distance from each end of the section in an inclined surface of frustoconical shape, characterised in that the outer cover is constituted by a relatively rigid cover which terminates before each frustoconical surface and a jacket is provided for protecting each of the frustoconical surfaces of the foam, the jacket being fixed at one end to the outer cover and connected at the other end to the inner pipe, said jacket having sufficient elasticity to follow the expansion of the inner pipe and the inner surface of the foam adhered thereto as the inner pipe is heated, whilst the outer cover and the foam adhered thereto remains stationary.

2. An insulated pipeline according to claim 1, characterised in that the foam has a greater density at the interfaces with the inner pipe and the cover than within its mass.

3. An insulated pipeline according to claim 1 or 2, characterised in that the jacket is connected to the inner pipe by a securing collar.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. spraying. Polyurethane is a product not comprising a solvent, with two components (a polyol and an isocyanate). This is why spraying is carried out with a gun for two components, preferably by means of an automatic gun without air. Polyurethane sold under the trade name "POLYSTAL" by the Societe Technique d'Applications Chimiques (S.T.A.C.) may be used by way of example and this product may be sprayed with a thickness of 1 to several millimetres. Figure 4 shows a direct junction between two insulating pipes Ta and Tta. This junction has a structure and method of assembly identical to that described with reference to figure 2, apart from the composition of the cover 6". As in the case of figure 2, when used, water or fluid at high temperatures travels through the inner pipes 1 and la and causes heating of the latter, i.e. causes their thermal expansion Under the effect of this expansion, the smooth end 10 tends to slide under the gasket 26 in the direction of the inside of the socket 12. The nature of the coating 22 facilitates this sliding whilst ensuring constant sealed contact between the latter and the gasket, such that the seal is in no way destroyed by the thermal expansion. The expansion caused by the passage of a hot fluid through the pipes Ta, Tta causes a deformation of the insulating foam 4 at its interface with the pipe 1 in order to accompany the latter. On the other hand, the outer cover 6" is not heated since it is thermally insulated by the presence of the foam. In addition, the method of burying the pipes and the nature of the earth in which they are buried is sufficient, in many cases, to ensure sufficient anchorage of the cover 6", by friction, despite the absence of ridges on the outer surface of the latter. The choice of polyurethane makes it possible to obtain the desired coefficient of friction between the cover and the earth. However, the insulating foam 4 has sufficient flexibility to be able to deform and follow the expansion of the pipe 1 without becoming detached from the fixed cover 6". Furthermore, the jacket 16 is also sufficiently resilient to adapt to the expansion of the pipe 10 whilst remaining rigidly connected to the end of the cover 6", which allows the insulation to withstand considerable thermal expansions without any danger of being damaged and consequently to retain its effectiveness over a prolonged period of time. In other words, the combination of the foam, of the relatively rigid and fixed cover and of the terminal resilient jackets makes it possible, as in the embodiment of figures 1 and 2, to accommodate the radial gradient of expension within the foam between the pipe and the fixed cover. The embodiment of figures 3 and 4 has the same advantages as that of figures 1 and 2, to which are added further advantages, described hereafter, due to the composition of the cover 6". The layer of polyurethane 6" constituting the outer cover is applied by spraying. The latter is carried out quickly and easily and is not hindered by possible irregularities of the outer surface of the layer of insulating foam 4. It should also be noted that the waiting period, i.e. the time at the end of which it is possible to handle the pipe without damaging the coating, is short, of the order of 5 minutes. This method of construction also provides an important advantage: to apply the layer of polyurethane forming the cover 6", it is possible to use the same equipment as that which serves for applying the insulating layer 4, or very similar equipment. The seal obtained by the cover 6" is absolute even at the ends of the pipe, since this cover 6" covers the end of each jacket 16 and the attachment of the cover to the foam 4 is excellent, greater than the cohesion of this foam: in the case of tearing stress, the coating yields within the foam 4 rather than at the interface between the latter and the cover 6". WHAT WE CLAIM IS:

1. An insulated pipeline for the conveyance of fluids at high temperatures, comprising a plurality of sections slidably interconnected, each section comprising a foam of thermally insulating plastics material which is adhered to an inner pipe and an outer protective cover and which covers the major part of the section but terminates a predetermined distance from each end of the section in an inclined surface of frustoconical shape, characterised in that the outer cover is constituted by a relatively rigid cover which terminates before each frustoconical surface and a jacket is provided for protecting each of the frustoconical surfaces of the foam, the jacket being fixed at one end to the outer cover and connected at the other end to the inner pipe, said jacket having sufficient elasticity to follow the expansion of the inner pipe and the inner surface of the foam adhered thereto as the inner pipe is heated, whilst the outer cover and the foam adhered thereto remains stationary.

4. An insulated pipeline according to

claim 1, 2 or 3, characterised in that the said sections comprise a male end constituted by a smooth end covered by a coating of heat-resistant plastics material adapted for sealed frictional contact with a gasket.

5. An insulated pipeline according to any one of claims 1 to 4, characterised in that the said sections comprise a female end comprising a recess covered by a coating of heat-resistant plastics material for receiving a gasket.

6. An insulated pipeline according to any one of claims 1 to 5, characterised in that the jacket for protecting the end of the insulating foam is constituted by a sheet of rubber.

7. An insulated pipeline according to any one of claims 1 to 6, characterised in that the insulating foam is sprayed cold onto the inner pipe and is formed of a foaming material such as polyurethane and has a density of the order of 80 to 120 kg/m3.

8. An insulated pipeline according to any one of claims 1 to 7, characterised in that the cover is wound externally in the form of a spiral on the plastics material foam.

9. An insulated pipeline according to any one of claims 1 to 8, characterised in that the cover comprises anchoring ridges on its outer surface.

10. An insulated pipeline according to claim 9, characterised in that the anchoring ridges on the cover are formed by gravel encrusted in its outer surface, which ensures axial anchorage to the earth.

11. An insulated pipeline according to any one of claims 1 to 10, characterised in that the outer cover is formed by a strip of bitumen or a mixture of bitumen and elastomer provided with a non-woven reinforcement.

12. An insulated pipeline according to claim 5, characterised in that the recess for receiving the gasket comprises a bored base whose diameter ensures maximum compression of the gasket by 25%.

13. An insulated pipeline according to claim 5, characterised in that the female end of the said sections comprises an abutment whose diameter relative to that of the male end of the said sections depends on the desired compression for the gasket.

14. An insulated pipeline according to any one of claims 1 to 7, characterised in that the cover is constituted by a layer of non-cellular polyurethane.

15. An insulated pipeline according to claim 14, characterised by the fact that the cover is applied around the layer of insulating foam by spraying.

16. An insulated pipeline according to any one of claims 1 to 15, characterised in that the cover extends longitudinally in order to cover the end of each jacket.

17. An insulated pipeline substantially as hereinbefore described with reference to Figs. 1 and 2 or Figs. 3 and 4 of the accompanying drawings.