Method for Producing Single Insulated Pipes with an Improved Water-Stop

Abstract

Disclosed herein is a method for producing insulated pipes having an improved protection of the insulation material. The pipe system comprises an inner pipe with a longitudinal axis extending from a first end of the inner pipe to a second end of the inner pipe, the inner pipe comprising a middle section, a first end section at the first end of the inner pipe, and a second end section at the second end of the inner pipe, a layer of inner coating covering the inner pipe, the layer of inner coating comprising one or more inner coating sub layers, one or more layers of insulation material covering the layer of inner coating such that the insulation layer covers the middle section of the inner pipe covered by the inner coating, and the ends of the insulation layer tapers towards the end sections, and the end sections comprises a section with an exposed layer of inner coating.

Claims

1. A method for producing insulated pipes comprising an inner pipe, a casing layer and insulation material, where the insulated pipe has an improved protection of the insulation material, the method comprising the steps of: a) providing a pipe system comprising: an inner pipe with a longitudinal axis (L) extending from a first end of the inner pipe to a second end of the inner pipe, the inner pipe comprising a middle section, a first end section at the first end of the inner pipe, and a second end section at the second end of the inner pipe; a layer of inner coating covering the inner pipe, the layer of inner coating comprising one or more inner coating sub layers; one or more layers of insulation material covering the layer of inner coating such that: the insulation layer covers the middle section of the inner pipe covered by the inner coating, and ends of the insulation layer tapers towards the end sections, and the end sections comprises a section with an exposed layer of inner coating; b) positioning a jaw around the exposed layer of inner coating at the first end section of the inner pipe; c) heating the exposed layer of inner coating using the jaw to a temperature near or above a welding temperature of materials which the inner coating and a casing layer are made of; d) removing the jaw; e) covering the exposed layer of inner coating and the insulation layer with a layer of casing extruded from a casing extruder; f) positioning a jaw around the exposed layer of inner coating at the second end section of the inner pipe; g) heating the exposed layer of inner coating using the jaw to the temperature near or above the welding temperature of the materials which the inner coating and the casing layer are made of; h) removing the jaw, and i) covering the exposed layer of inner coating at the second end section of the inner pipe with a layer of casing extruded from the casing extruder.

2. The method according to claim 1, wherein the casing is extruded onto the exposed layers of inner coating and the insulation layer by moving the pipe past the casing extruder or by moving the casing extruder along the longitudinal axis (L) of the pipe.

3. The method according to claim 1, wherein the steps b) to e) and steps f) to i) are performed concurrently.

4. The method according to claim 1, wherein the pipe system is rotated along the longitudinal axis (L) of the pipe while: the pipe system and the casing extruder moves in relation to each other, and the layer of casing is extruded onto the exposed layers of inner coating and the insulation layer, whereby the casing layer is applied onto the pipe system in a spiral, wherein the rotation of the pipe system and the movement of the pipe system and the extruder in relation to each other is adjusted such that there is an overlap between consecutive casing layers of between 1-10 cm, or between 3-8 cm, or between 4-6 cm or at 5 cm.

5. The method according to claim 1, wherein the pipe system is positioned on a line moving the pipe system in a longitudinal direction (L) towards and past the casing extruder during the production of the insulated pipe.

6. The method according to claim 4, wherein the pipe system is constantly being rotated (R) around the longitudinal axis (L) as the pipe system moves along the line.

7. The method according to claim 1, wherein after the jaw is positioned around the exposed layer of inner coating in step b) or f), the jaw moves along with the pipe system in the longitudinal direction (L) at the same speed as the pipe system before the jaw is removed in step d) and h).

8. The method according to claim 1, wherein removing the jaw in step d) and h) is done when the distance between the jaw and the casing extruder is less than 5 cm, or between 1-5 cm or between 1-2 cm.

9. The method according to claim 1, wherein the jaw (204) is heated using radiant heating.

10. The method according to claim 1, wherein end joining tools positioned between two inner pipes are used to connect inner pipes, thereby forming a pipeline comprising a number of interconnected inner pipes, and wherein the end joining tools are removed again after the pipe system has been fully covered by the casing layer thereby proving a number of separated insulated pipes.

11. The method according to claim 1, wherein the inner coating and/or the casing is polypropylene (PP) or polyethylene (PE).

12. The method according to claim 1, wherein the thickness of the inner coating is between 2-10 mm.

13. The method according to claim 1, wherein the insulation material is polyurethane (PUR) foam.

14. The method according to claim 1, wherein the welding temperature to which the exposed layer of inner coating is heated in step c) and g) is between 180-240 C.

15. The method according to claim 1, wherein the temperature to which the inner coating is heated in step c) and g) is measured by an infrared thermometer.

16. The method according to claim 1, wherein one or more pressure rolls are applied onto the layer of casing applied over the exposed layer of inner coating in step e) and i) pressuring the casing closer to the inner coating.

17. The method according to claim 16, wherein the one or more pressure rolls are also applied onto the layer of casing applied over the entire pipe.

18. The method according to claim 16, wherein only one pressure roll is applied.

19. The method according to claim 16, wherein two or more pressure rolls are applied.

20. The method according to claim 19, wherein a first pressure roll is applied onto the layer of casing applied over the exposed layer of inner coating in step e) and i) pressuring the casing closer to the inner coating, and a second pressure roll is applied onto the layer of casing applied over the middle section of the pipe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIGS. 1, 2A-B and 3 illustrate a different angle view of a single pipe produced by the method according to the invention.

[0028] FIGS. 4-5 illustrate the method for producing an insulated pipe.

[0029] FIG. 6 illustrates a jaw used in the method for producing an insulated pipe.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] In FIG. 1 a single insulated pipe 100 produced by the method according to the invention is shown in a longitudinal cross sectional view. FIGS. 2A-B show the close up of the pipe 100 marked with the circle in the cross sectional view in FIG. 1. In FIG. 2A, the pipe is nearly finished whereas in FIG. 2B, the last finishing touch of milling the edge has been performed. FIG. 3 illustrates the pipe 100 in an isometric view showing the different layers.

[0031] The pipe 100 comprises an inner carrier pipe 102 of metal, normally steel, with a layer of inner coating 104. The inner coating layer 104 may be a three-layer coating, which may comprises a thin epoxy layer placed directly on the outside of the inner carrier pipe 102 in order to protect against corrosion, a polypropylene (PP) based layer, and a layer of glue in between the epoxy and the PP based layers holding these two layers together. As an alternative to using the PP-based material in the three-layer coating, polyethylene (PE) based materials or other polymeric materials can also be used. Thus, in one or more embodiments, the material of the inner coating is polypropylene or polyethylene (PE).

[0032] In one or more embodiments, the thickness of the inner coating is between 2-10 mm.

[0033] In one or more embodiments, the thickness of the inner coating is between 2.5-8 mm.

[0034] In one or more embodiments, the thickness of the inner coating is between 3-6.5 mm.

[0035] In one or more embodiments, the thickness of the inner coating is between 3-5 mm.

[0036] The pipe 100 also comprises a thermal insulation layer 106. The insulation layer is normally a polyurethane foam layer. Thus, in one or more embodiments, the insulation material is polyurethane (PUR) foam. The insulation layer 106 may consist of one or more layers of solid or partly foamed thermoset or thermoplastic polymers.

[0037] On the outer part of the pipe 100, a layer of casing 108 is present. The casing layer 108 may also comprise a thin outer layer of rough coating 110. Both the casing 108 and the rough coating 110 is normally of a PP-based material or a PE-based material. The rough coating 110 will normally consist of very small pieces of material applied to the casing 108 in order to provide the pipe 100 with a rough surface to increase friction when handled, e.g. lifted and/or turned around, during the assembly and/or insertion into the water. Thus, in one or more embodiments, the material of the casing is PP or PE. PP or PE is preferred as a sealed interface between two layers of PP or PE, respectively, can withstand the high temperatures inside the pipe, when the pipe is used to transport e.g. subsoil and at the same time withstand the low temperatures of the sea when put on or below the seabed.

[0038] The inner pipe 102 comprises a middle section 103 extending over the main part of the pipe in a longitudinal direction L, and two end sections including a first end section 105a at a first end of the inner pipe 102 and a second end section 105b at a second end of the inner pipe 102.

[0039] Towards the end sections 105a, 105b, the thermal insulation layer 106 is tapered thereby creating an assembly face 107 for joining the inner coating 104 and the casing 108 at the end sections 105a, 105b. This provides an effective sealing of the insulation layer 106.

[0040] The method for producing the insulated pipe 100 shown in FIGS. 1-3 are illustrated in FIGS. 4-6. FIG. 5 is a close-up of the area marked with the dotted circle in FIG. 4.

[0041] The production method comprises a number of steps, where first a number of pipe systems, at least one pipe system, are provided. The pipe system comprises an inner pipe 102, a layer of inner coating 104 covering the inner pipe 102, and one or more layers of insulation material 106 covering the layer of inner coating 104 as described above.

[0042] The inner pipes 102 are normally connected end to end using end joining tools 112 inside or outside the inner pipes 102, thereby forming one long pipeline comprising a number of interconnected inner pipes 102. In FIG. 5, an example of an inner joining tool 112 is shown. In one or more embodiments, end joining tools 112 positioned between two inner pipes 102 are used to connect inner pipes 102, thereby forming a pipeline comprising a number of interconnected inner pipes 102. The end joining tools 112 will normally be removed again after the pipe system has been fully covered by the casing layer 108 (as described in the following) thereby providing a number of separated insulated pipes 100.

[0043] The pipe line is positioned on a line moving the pipe system(s) in the direction along the longitudinal axis of the pipe systems indicated by the arrow with the marking L. This may be done using a number of slightly pitched rollers (not shown in the figures), which rotates. As the rollers rotate, the pipe systems(s) also rotate as indicated in FIG. 4 with the R arrow. Due to the pitch of the rollers, the pipe system(s) are moved forward along the line in the direction L. Typically the pipe system(s) are moved forward 3-8 cm per revolution.

[0044] As an alternative to moving the pipe system(s) forward, the different extruders for applying the different layer onto the inner pipe (see the following text for details), may instead be moved in the opposite direction of L combined a rotation of the inner pipe(s) 102.

[0045] Each of the inner pipes 102 are covered with a layer of inner coating comprising one or more inner coating sub layers. Applying the layer of inner coating onto the inner pipe is performed prior to connecting the inner pipes 102. Thus, the inner pipes 102 can be received pre-coated before the method described herein is started or the pre-coating can be setup to occur close by or in direct connection to the pipe line used here.

[0046] The inner pipe(s) 102 with a layer of inner coating 104 is covered with one or more layers of insulation material 106 such that the insulation layer 106 covers the middle section 103 of the inner pipe 102 covered by the inner coating 104. The end sections 105a, 105b of the inner pipe comprises an exposed layer of inner coating and an additional section at the very ends of the inner pipes, where the inner pipes are exposed, i.e. not covered by the exposed layer of inner coating. The insulation material is applied forming tapered ends towards the sections 105a, 105b of the inner pipe (102).

[0047] The insulation layer 106 may be applied using spray application 202 as shown in FIG. 4. Thus, in one or more embodiments covering the layer of inner coating with one or more layers of insulation material is done by spray application using one or more insulation layer sprayers 202 while the pipe is rotated along the longitudinal axis L. Two or more layers of insulation material 106 can possibly be applied.

[0048] Alternatively, the a mould may be used for foaming in. After foaming in a mould, the mould is removed and a pipe with the inner coating layer 104 an the insulation layer 106 is obtained and ready for use in the method according to this invention. Thus, in one or more embodiments, covering the layer of inner coating with one or more layers of insulation material is done by positioned a mould around the inner pipe, foaming in the mould and subsequently removing the mould.

[0049] After applying the one or more layers of insulation material 106 in one of the above described manners or in an alternative manner not described herein, a jaw 204, 204 is positioned around the exposed layer of inner coating 104 at the first end section 105a of the inner pipe 102. The jaw 204 heats a section of the exposed layer of inner coating 104 to a temperature near or above the welding temperature of the materials which the inner coating and the casing 108, 110 (applied in a later step) are made of.

[0050] When heating the exposed layer of inner coating 104 it is important that the inner coating has a thickness preventing that the underlying inner pipe 102 extracts the heat yielding a too low temperature of the inner coating 104. The previous attempts to weld casing and coating layers together using e.g. a welding band proved quite difficult, if not impossible, as the inner carrier pipe absorbed much of the heat from the inner coating with the consequence that the casing was heated too severely allowing it to overheat while the coating remained inadequately heated. By heating the exposed layer of inner coating 104 prior to applying the casing, the previously observed problems with an overheated casing and a cold inner coating are avoided. Also, the previously required pre-heating of the inner pipe prior to the welding of the inner coating and the casing is also avoided. In some embodiments, the inner pipe may be heated before applying the insulation layer to ensure a good reaction of this. Furthermore, the reaction of the insulation foam is applied directly before the method of this invention is started, heats the inner pipe further.

[0051] Just before a layer of casing 108 is applied to the first end 105a section of the inner pipe 102, the jaw 204 is removed and the exposed layer of inner coating 104 and the insulation layer 106 is covered with a layer of casing 108 extruded from a casing extruder 206. Possibly a second layer of coating 110 is applied on top of the inner coating 108. This layer can be an extruded layer of a thin outer ruffled coating layer 110, which is sprinkled onto the first coating layer 108.

[0052] As the front most end of the pipe system and the casing extruder 206 are moved towards each other in the direction L, and the front most end of the pipe system pass the casing extruder 206 (thereby covering the insulation layer 106 with a coating layer), a jaw 204 is positioned around the exposed layer of inner coating 104 at the second end section 105b of the inner pipe. This jaw 204 can be the same as the first mentioned jaw 204 used for heating up the first end section 105a of the inner pipe 102 or alternatively a second jaw 204.

[0053] In the same manner as with heating the inner coating 104 at the first end section 105a with the jaw 204, the exposed layer of inner coating at the second end section 105b is heated using the jaw 204 to a temperature near or above the welding temperature of the materials which the inner coating 104 and the casing layer 108, 110 are made of.

[0054] The jaw 204 is subsequently removed and the exposed layer of inner coating 104 at the second end section 105b of the inner pipe 102 is covered with a layer of casing 108 extruded from the casing extruder 206.

[0055] In one or more embodiments, the pipe system is positioned on a line moving the pipe system in a longitudinal direction L towards and pass the casing extruder 206 during the production of the insulated pipe 100. The pipe system may be constantly being rotated R around the longitudinal axis L as the pipe system moves along the line.

[0056] In one or more embodiments, after the jaw 204, 204 is positioning around the exposed layer of inner coating 104, 104, the jaw 204, 204 moves along with the pipe system in the longitudinal direction L at the same speed as the pipe system before the jaw 204, 204 is removed.

[0057] In one or more embodiments, removing the jaw 204, 204 is done when the distance between the jaw 204, 204 and the casing extruder 206 is less than 5 cm. In some embodiments, the distance is between 1-5 cm. In some embodiments, the distance is between 1-2 cm.

[0058] FIG. 6 shows an example of a jaw 204 which can be used in the above method. The jaw 204 in FIG. 6 represent the jaws 204, 204.

[0059] In one or more embodiments, the jaw 204, 204 is heated using radiant heating.

[0060] In one or more embodiments, the welding temperature to which the exposed layer of inner coating 104, 104 is heated is between 180-240 C.

[0061] In one or more embodiments, the welding temperature to which the exposed layer of inner coating 104, 104 is heated is between 200-240 C.

[0062] In one or more embodiments, the welding temperature to which the exposed layer of inner coating 104, 104 is heated is between 220-240 C.

[0063] In one or more embodiments, the welding temperature to which the exposed layer of inner coating 104, 104 is heated is between 230-240 C.

[0064] In one or more embodiments, the welding temperature to which the exposed layer of inner coating 104, 104 is heated is 235 C.

[0065] In one or more embodiments, the casing 108 is extruded onto the exposed layer of inner coating 104, 104 and the insulation layer 106 by moving the pipe system pass the casing extruder 206.

[0066] In one or more embodiments, the casing 108 is extruded onto the exposed layer of inner coating 104, 104 and the insulation layer 106 by moving the casing extruder 206 along the longitudinal axis L of the pipe system.

[0067] In one or more embodiments, the pipe system is rotated along the longitudinal axis L of the pipe while the pipe system and the casing extruder 206 moves in relation to each other, and the layer of casing 108 is extruded onto the exposed layers of inner coating 104, 104 and the insulation layer 106. In this manner, the casing layer 108 is applied onto the pipe system in a spiral, wherein the rotation of the pipe system and the movement of the pipe system and the extruder in relation to each other is adjusted such that there is an overlap between consecutive casing layers.

[0068] In one or more embodiments, the overlap between consecutive casing layers is between 1-10 cm.

[0069] In one or more embodiments, the overlap between consecutive casing layers is between 3-8 cm.

[0070] In one or more embodiments, the overlap between consecutive casing layers is between 4-6 cm.

[0071] In one or more embodiments, the overlap between consecutive casing layers is 5 cm.

[0072] In one or more embodiments, the temperature to which the coating is heated is measured by an infrared thermometer.

[0073] In one or more embodiments, one or more pressure rolls 208 are applied onto the layer of casing applied over the exposed layer of inner coating pressuring the casing 108 closer to the inner coating 104, 104. This occurs primarily in the welding zone.

[0074] In one or more embodiments, the one or more pressure rolls 208 are also applied onto the layer of casing applied over the entire pipe. Thus, pressure roll(s) are used over the entire pipe and not just in the welding zone area.

[0075] In one or more embodiments, only one pressure roll 208 is applied. Thus the same pressure roll may sufficiently be used for applying a pressure on the casing over the entire pipe.

[0076] In one or more embodiments, two or more pressure rolls 208, 209 are applied. As is illustrated in FIG. 6, the pressure roll 209 may be a larger pressure roll than the pressure roll 208. The larger pressure roll 209 may be used for the applying a pressure onto the casing layer(s) covering the middle section 103 of the pipe, whereas the smaller pressure roll 208 may be used in the welding zone, where the insulation material 106 tappers towards.

[0077] In one or more embodiments, a first pressure roll 208 is applied onto the layer of casing applied over the exposed layer of inner coating in step e) and i) pressuring the casing 108 closer to the inner coating 104, and a second pressure roll 209 is applied onto the layer of casing applied over the middle section of the pipe.

[0078] In a final step, the welded edge part of the welded inner coating and the casing is chamfered to form a tapered end 109 using a milling device. This gives the manufacture the possibility to inspect the welding between inner coating and the casing.

[0079] Also disclosed herein is an insulated pipe produced using the method described above

REFERENCES

[0080] 100 Pipe [0081] 102 Inner carrier pipe [0082] 103 Middle section of the inner pipe [0083] 104, 104, 104 Inner coating [0084] 105a, 105b End sections of the inner pipe [0085] 106 Thermal insulation layer [0086] 107 Assembly face [0087] 108 Casing [0088] 109 Tapered end of the welded edge part [0089] 110 Thin outer coating [0090] 112 End joining tools [0091] 200 Production line [0092] 202 Insulation material sprayer [0093] 204, 204, 204 Jaw [0094] 206 Casing extruder [0095] 208 Pressure roll [0096] 209 Pressure roll [0097] L Longitudinal direction [0098] R Rotational direction