Flexible pipe body layer and method of producing same
View Patent ↗A flexible pipe body layer and method of producing a flexible pipe body layer are disclosed. The method includes coextruding an inner sub-layer and an outer sub-layer, wherein the inner sub-layer and outer sub-layer comprise a polymer, and wherein the inner sub-layer has a lower modulus of elasticity than the outer sub-layer.
1. A method of producing a flexible pipe body, comprising:
providing a tubular layer by coextruding an inner sub-layer and an outer sub-layer, wherein the inner sub-layer and outer sub-layer comprise a polymer, and wherein the inner sub-layer has a lower modulus of elasticity than the outer sub-layer, and wherein the inner sub-layer comprises a material having a yield strength that is between 30% and 70% lower than the outer sub-layer; and
wherein the inner sub-layer and outer sub-layer are chemically bonded together, directly during coextrusion, and wherein the inner sub-layer comprises PVDF, HDPE, PA-11, PA-12, PEX, PEEK, PPS, FEP or a mixture thereof, and the inner sub-layer and outer sub-layer comprise different grades or different forms of the same polymer, and
further comprising forming an armour layer over a radially outer portion of the tubular layer, the armour layer having gaps between adjacent windings thereof.
2. A method as claimed in claim 1 wherein the step of chemically bonding comprises bonding the inner sub-layer indirectly to the outer sub-layer via a tie layer.
3. A method as claimed in claim 1 further comprising co-extruding a further sub-layer between the inner and outer sub-layers, wherein the further sub-layer has a modulus of elasticity intermediate that of the inner and outer sub-layers.
4. A method of producing a flexible pipe body comprising providing the tubular layer as claimed in claim 1 , and forming an outer sheath over the armour layer.
5. A method of producing a flexible pipe comprising providing a flexible pipe body as claimed in claim 4 and attaching one or more end fitting thereto.
6. A tubular layer for a flexible pipe body as claimed in claim 1 , wherein the tubular layer for a flexible pipe body is capable of withstanding internal pressures of 55 MPa or more.
7. A method as claimed in claim 1 , wherein the inner sub-layer and outer sub-layer are directly chemically bonded together.
8. A method as claimed in claim 7 , wherein the inner sub-layer and outer sub-layer comprise different grades of the same polymer.
9. A method as claimed in claim 8 , wherein the inner sub-layer and outer sub-layer comprise different grades of PVDF.