Patent ID: 8720543
Filing Date: 2014-05-13
Classification: E21B,F16J

Abstract:
1. A sealing system between a relatively rotating element and a stationary element of a dual drill pipe, comprising: at least three sealing elements arranged in series between the rotating element and the stationary element and between a process fluid and an environment; and a barrier fluid arrangement to provide a barrier fluid to spaces formed between the sealing elements, the barrier fluid arrangement comprising at least two compensator devices; wherein a first of the compensator devices is arranged to provide a pressure in the barrier fluid in a first of the spaces that is higher than a pressure in the process fluid, wherein the first of the compensator devices comprises a first piston with a first piston first side and a first piston second side, wherein a cross sectional area of the first piston first side is smaller than a cross sectional area of the first piston second side, and wherein the first piston first side is in communication with the barrier fluid in the first of the spaces and the first piston second side is in communication with the process fluid; wherein a second of the compensator devices comprises a second piston with a second piston first side and a second piston second side, wherein a cross sectional area of the second piston first side is smaller than a cross sectional area of the second piston second side, and wherein the second piston first side is in communication with the process fluid and the second piston second side is in communication with the barrier fluid in a second of the spaces; wherein a difference between cross sectional areas of the first piston first side and first piston second side is different from a difference between the cross sectional areas of the second piston first side and second piston second side.