DK200901328A

DK200901328A - An unbonded, flexible pipe

Info

Publication number: DK200901328A
Application number: DKPA200901328A
Authority: DK
Inventors: Christensen Claus Dencker; Procida Inger-Margrete; Christensen Martin Damgaard
Original assignee: Nkt Flexibles Is
Priority date: 2009-12-15
Filing date: 2009-12-15
Publication date: 2010-05-21

Claims

1. An unbonded, flexible pipe having a length and comprising from Inside out, a tubular inner sealing sheath, at least one metal armor layer and an outer sealing sheath of a sealing material, said unbonded, flexible pipe comprises at least one stiffened length section comprising a stiffening cover partially or totally surrounding said outer sealing sheath in said stiffened length section, said stiffening cover comprises a layer of a stiffening material having a flexural modulus which Is higher than the flexural modulus of said sealing material, wherein the flexural modulus is determined according to ISO 178, said stiffening cover has a thickness of at least about 3 mm,

2. An unbonded, flexible pipe as claimed in claim 1, wherein said stiffening material has a flexural modulus which Is at least about 100 MPa, such as at least about 125 MPa, such as at least about 150 MPa, such as at least about 200 MPa, such as at least about 250 MPa higher than the flexural modulus of the outer sealing sheath.

3. An unbonded, flexible pipe as claimed In any one of the preceding claims, wherein said stiffening material has a flexural modulus which Is at least about 1000 MPa, such as at least about 1200 MPa, such as at least about 1400 MPa, such as at least about 1500 MPa, such as at least about 1800 MPa, such as at least about 2000 MPa, such as at least about 2500 MPa.

4. An unbonded, flexible pipe as claimed In any one of the preceding claims, wherein said stiffening material is selected from cross-linked and non-cross-llnked polyethylens, said stiffening material preferably being selected from substantially non-cross linked, high density poly ethylene (HDPE) having a density of at least about 940-kg/m3, and medium density poly ethylene (MDPE) having a density of from about 925 kg/m3 to about 940 kg/m3, said stiffening material preferably being a HDPE, more preferably a HDPE having a density of at least about 945 kg/m3.

5. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said stiffening cover comprises two or more materials, preferably arranged In layers, said two or more materials preferably being mechanically and/or chemically bonded to each other.

6. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said stiffening material is a non-fbamed material, preferably said stiffening cover is substantially of non-foamed material(s).

7. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said unbonded, flexible pipe comprises two or more stiffened length sections having equal or different length, and/or stiffness cover.

8. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said unbonded, flexible pipe comprises a first and a second end, at least one of said first and said second end is connected to an end fitting, such that one or more of the layers of the unbonded, flexible pipe are independently fixed to the end fitting, said stiffening cover is not fixed to provide a tight connection to said end fitting.

9. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said stiffness cover is permeable to water such that water can penetrate to the inner side of said stiffness cover, said stiffness cover optionally comprises one or more perforations.

10. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said outer sealing sheath has an outermost surface and said stiffness cover has an outer surface, said outer surface of said stiffness cover has a substantially higher or substantially lower static coefficient of friction (ps) measured according to ASTM D1894 at 23 °C, In wet (wetted with water) condition against itself, compared with the static coefficient of friction of said outermost surface of said outer sealing sheath measured against itself under similar conditions.

11. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said stiffness cover is applied in direct contact with said outer sealing sheath, said stiffness cover preferably being mechanically or chemically bonded to said outer sealing sheath.

12. An unbonded, flexible pipe as claimed in any one of the preceding claims, wherein said stiffness cover is applied by folding or winding onto the outer sealing sheath after the fabrication of the remaining parts of the pipe has been terminated.