MULTILAYER TUBE AND USE THEREOF FOR FLUID TRANSPORTATION AT MEDIUM PRESSURE

Abstract

A multilayer tube for fluid transportation may include, from an interior of the multilayer tube to an exterior of the multilayer tube: an inner layer including at least one polyamide in admixture with at least one elastomer; an adhesive layer; and/or a layer including at least one polyolefin. In a system for transporting fluids at medium pressure, a plurality of multilayer tubes may be joined together by electro-soldered joints formed by the at least one polyamide. A multilayer tube may be used for transporting hydrocarbons within an extraction site, from the extraction site to a refinery, or within the extraction site and from the extraction site to the refinery. A multilayer tube may be used for transporting water, distributing the water, or transporting and distributing the water.

Claims

1. A multilayer tube for fluid transportation, the multilayer tube comprising, from an interior of the multilayer tube to an exterior of the multilayer tube: an inner layer comprising at least one polyamide in admixture with at least one elastomer: a first adhesive layer; and a first layer comprising at least one first polyolefin.

2. The multilayer tube of claim 1, further comprising: a second layer, comprising at least one second polyolefin, internal to the inner layer and bonded to the inner layer by a second adhesive layer.

3. The multilayer tube of claim 1, wherein the at least one first polyolefin is high density polyethylene (HDPE) or medium density polyethylene (MDPE), haying a density greater than or equal to 0.926 g/cm.sup.3 and less than or equal to 0.970 g/cm.sup.3.

4. The multilayer tube of claim 1, wherein the at least one polyamide is selected from: (a) PA-6, 10, obtainable by polycondensation of hexamethylenediamine and 1,10-decandioic acid; (b) PA-6, 12, obtainable by polycondensation of hexamethylenediamine and 1,12-dodecandioic acid; (c) PA-9, 12, obtainable by polycondensation of 1,9-diamine-nonane and 1,12-dodecandioic acid; (d) PA-10, 10, obtainable by polycondensation of 1,10-diamine-decane and 1,10-decandioic acid; and (e) PA-10, 12, obtainable by polycondensation 1,10-diamine-decane and 1,10-dodecandioic acid.

5. The multilayer tube of claim 1, wherein the at least one polyamide comprises PA-6 or PA-6, 6.

6. The multilayer tube of claim 1, wherein an amount of the at least one elastomer is greater than or equal to 3% by weight and less than or equal to 30% by weight with respect to a total weight of the admixture.

7. The multilayer tube of claim 1, wherein the at least one elastomer is selected from: ethylene/propylene copolymers (EPR) and ethylene/propylene/diene terpolymers (EPDM).

8. The multilayer tube of claim 1, wherein the at least one elastomer is a copolymer or terpolymer comprising greater than or equal to 5% by weight of ethylene and less than or 25% by weight of ethylene, and greater than or equal to 75% of propylene and less than or equal to 95% by weight of propylene.

9. The multilayer tube of claim 1, wherein the at least one elastomer is grafted with an amount greater than or equal to 0.05% by weight and less than or equal to 5% by weight of at least one mono- or bi-carboxylic acid containing ethylenic unsaturation or aderivative thereof.

10. The multilayer tube of claim 1, wherein the first adhesive layer comprises a polyolefin grafted with at least one mono- or bi-carboxylic acid containing an ethylenic unsaturation or a derivative thereof.

11. The multilayer tube of claim 1, wherein the inner layer has a standard dimension ratio (SDR) value greater than or equal to 7 and less than or equal to 26.

12. The multilayer tube of claim 1, wherein the first layer has a thickness greater than or equal to 0.1 mm and less than or equal to 5 mm.

13. The multilayer tube of claim 1, wherein the first adhesive layer has a thickness greater than or equal to 0.05 mm and less than or equal to 2 mm.

14. A system for transporting fluids at medium pressure, the system comprising: a plurality of multilayer tube according to a claim 1; wherein the multilayer tubes are joined together by electro-soldered joints formed by at least one polyamide.

15. Use of the multilayer tube of claim 1 for transporting hydrocarbons within an extraction site, from the extraction site to a refinery, or within the extraction site and from the extraction site to the refinery.

16. Use of the multilayer tube of claim 1 for transporting water, distributing the water, or transporting and distributing the water.

17. The multilayer tube of 1, wherein the at least one polyamide comprises: (a) PA6, 10, obtainable by polycondensation of hexamethylenediamine and 1,10-decandioic acid; (b) PA6, 12, obtainable by polycondensation of hexamethylenediamine and 1,12-decandioic acid; (c) PA9, 12, obtainable by polycondensation of hexamethylenediamine and 1,12-decandioic acid; (d) PA10, 10, obtainable by polycondensation of hexamethylenediamine and 1,10-decandioic acid; or (e) PA-10, 12, obtainable by polycondensation of 1,10-diamine-decane and 1,10-dodecandioic acid.

18. The multilayer tube of claim 2, wherein the at least one first polyolefin is the same as at least one second polyolefin.

19. The multilayer tube of claim 2, wherein the at least one first polyolefin differs from the at least one second polyolefin.

20. The multilayer tube of claim 8, wherein the at least one elastomer further comprises less than or equal to 10% by weight of diene.

Description

[0047] The present invention shall now be illustrated with particular reference to the following figures, in which:

[0048] FIG. 1 is a cross-section view of a tube according to a first embodiment of the present invention;

[0049] FIG. 2 is a cross-section view of a tube according to a second embodiment of the present invention.

[0050] With reference to FIGS. 1 and 2, the multilayer tube (1) in accordance with the present invention comprises, from the interior to the exterior: an inner layer (2) comprising at least one polyamide in admixture with at least one elastomer; a first adhesive layer (3); a first layer (4) comprising at least one polyolefin. According to the embodiment illustrated in FIG. 2, the multilayer tube (1) further comprises a second layer (6) comprising at least one polyolefin placed internally with respect to the inner layer and bonded to the inner layer by a second adhesive layer (5).

[0051] The following working examples are provided merely with the purpose of illustrating the present invention and must not be intended to limit the scope of protection of the attached claims.

EXAMPLE 1

[0052] A multilayer tube was made by coextrusion of different polymer materials by means of a multi-head extruder; the multilayer tube consisted of the following layers, from the exterior to the interior:

[0053] a first layer made up of MDPE (product Eltex TUB172Ineos, having a density equal to 0.939 g/cm.sup.3), with a thickness equal to 1 mm;

[0054] a first adhesive layer made up of linear low density polyethylene (LLDPE) grafted with maleic anhydride (product Bynel 4157DuPont), with a thickness equal to 0.1 mm;

[0055] an inner layer, having a thickness equal to 5.3 mm and DTR=17, made up of a mixture between: (i) a polyamide 6, 10 modified with a functionalized elastomer EPR (product Zytel RS LC 4601DuPont); and (ii) a polyamide 6, 10 as such (product Zytel RS LC 3090DuPont) (weight ratio (i):(ii)=1:2);

[0056] a second adhesive layer identical to the first one;

[0057] a second layer that made up of MDPE identical to the first one.

[0058] The tube thus produced was tested for resistance to internal pressure exerted by a fluid at different temperatures, according to standard UL 971 (Standard for Nonmetallic Underground Piping for Flammable Liquids). The results obtained are the following (pressure up to tube burst):

TABLE-US-00001 TABLE 1 Temperature Burst pressure ( C.) (bar) 23 80 60 62 80 48 95 37

[0059] According to the aforementioned standard UL 971, also a crush resistance test, a drop test and an impact test of the same tube kept at low temperature (30 C.), were also carried out. The tube passed all the aforementioned tests.

[0060] The same tube was also tested for pressure resistance over time according to standard ISO 16486 (safety factor: 1.7). The results are shown in Table 2, where the duration represents the test time without observing damage on the tube, whereas the minimum duration is that required by the standard:

TABLE-US-00002 TABLE 2 Pressure Temperature Minimum duration Duration (bar) ( C.) (hours) (hours) 26.5 80 165 3000 46.8 20 1000 2000

[0061] Segments of the same tube were joined by electro-soldered joints made from polyamide, and subjected to tensile tests according to standard ASTM F1973. The pulling force necessary for separating the two segments was measured to be 85,000 N. The joined segments were also subjected to decohesion tests at different temperatures (10 C., +50 C. and +23 C.) according to standard ISO 13954: the tests were passed in all cases.