Assembly comprising an end-fitting for terminating an unbonded flexible pipe and an unbonded flexible pipe
The present invention relates to an assembly including an end-fitting for terminating an unbonded flexible pipe and an unbonded flexible pipe. The unbonded flexible pipe includes a first and a second armour layer co-axially arranged, and an electric heating system. The end-fitting includes means for mechanically anchoring the first armour layer to the end-fitting and includes electrical connections for connecting the first armour layer to a power-source. The end-fitting also includes means for mechanically anchoring the second armour layer to the end-fitting. The first and the second armour layers are electrically insulated from each other by at least one electrically insulating layer in the end-fitting and the end-fitting includes a local volume in the end-fitting adjacent to the electrically insulating layer adapted for injection of a functional fluid.
1. An assembly comprising an end-fitting and an unbonded flexible pipe terminated in said end-fitting, said unbonded flexible pipe comprising a first armour layer and a second armour layer co-axially arranged, and an electric heating system,
said end-fitting comprises means that is mechanically anchoring the first armour layer to the end-fitting and said electric heating system comprises electrical connections connecting the first armour layer to a power-source,
said end-fitting is mechanically anchoring the second armour layer to the end-fitting, the first and the second armour layers being electrically insulated from each other by at least one electrically insulating layer in the end-fitting,
wherein the end-fitting comprises a local volume that is defined by a surface of an insulating device, a surface of the end fitting and a surface of the electrically insulating layer, said local volume running continuously in a circular path surrounding a perimeter of the electrically insulating layer in the end-fitting and adjacent to the electrically insulating layer and wherein the local volume comprises a functional fluid selected from the group comprising an electrically insulating fluid, a moisture absorbing fluid and a transformer oil.
2. The assembly according to claim 1 , wherein the end-fitting comprises electrical connections connecting the second armour layer to a power-source.
3. The assembly according to claim 1 , wherein the end-fitting comprises electrical connections connecting the second armour layer with a source selected from the group comprising the power-source connected with the first armour layer, a different power-source and ground.
4. The assembly according to claim 1 , wherein the end-fitting comprises means connecting at least one of the first or second armour layers to ground.
5. The assembly according to claim 1 , wherein the local volume communicates with the exterior surface of the end-fitting via at least one channel.
6. The assembly according to claim 1 , wherein the functional fluid is selected from the group comprising a liquid and an arc suppressing fluid.
7. The assembly according to claim 1 , wherein the functional fluid is FS6 (sulfurhexaflouride) or a halogenated gas such as freon 12.
8. The assembly according to claim 1 , wherein the first armour layer is a carcass.
9. The assembly according to claim 1 , wherein the second armour layer is selected from a pressure armour, a tensile armour, and a combination of tensile armour and pressure armour.
10. The assembly according to claim 1 , wherein the first and the second armour layers are separated by an internal pressure sheath, said internal pressure sheath being the electrically insulating layer.
11. The assembly according to claim 1 , wherein the local volume has volume in the range of about 1 cm3 to about 500 cm3.
12. The assembly according to claim 1 , wherein the functional fluid is injected into the local volume with a pressure from about 0 barg.
13. The assembly according to claim 1 , wherein the electrically insulating layer is an internal pressure sheath and the local volume is placed adjacent to the internal pressure sheath.
14. The assembly according to claim 1 , wherein the local volume is placed at a position between the mechanically anchoring of the first armour layer and the mechanically anchoring of the second armour layer.
15. A method for reducing stray current in an end-fitting arranged for terminating an unbonded flexible pipe comprising a first armour layer and a second armour layer co-axially arranged, and an electric heating system, said end-fitting comprises means arranged for attaching the first armour layer to the end-fitting and comprises electrical connections arranged for connecting the first armour layer to a power-source,
said end-fitting comprises means arranged for attaching the second armour layer to the end-fitting, the first and the second armour layers being electrically insulated from each other by at least one electrically insulating layer,
the pipe comprises a tensile armour located outside an internal pressure sheath, the tensile armour being terminated in a fixation chamber defined between an inner casing and an outer casing of the end-fitting and
wherein said end-fitting comprises a local volume defined by a surface of an insulating device, a surface of the end fitting and a surface of the electrically insulating layer, said local volume running continuously in a circular path surrounding a perimeter of the electrically insulating layer and adjacent to the electrically insulating layer and wherein the local volume is distinct from the fixation chamber, said method comprises the step of injecting a functional fluid into the local volume, wherein the functional fluid is selected from the group comprising an electrically insulative fluid, a moisture absorbing fluid and a transformer oil.
16. The method according to claim 15 , wherein the functional fluid is a gas, such as SF6 (sulfurhexaflouride) or Freon 12.
17. The method according to claim 15 , wherein the functional fluid is injected into the local volume batch-wise.
18. The method according to claim 15 , wherein the functional fluid is injected continuously into the local volume.