Swivel seal construction

In a swivel (40) comprising an outer annular wall (41) and an inner annular wall (42) coaxial with the outer wall, the outer and inner walls defining a toroidal chamber (44) and an upper (45) and a lower gap (52), between their peripheral opposing faces, at least one gap (45, 52) having a first section (46) extending axially from the toroidal chamber (44) to an end part, a second section (47) extending from the end part transversely to the first section (46), and a third section (48) extending in an axial direction, two seals (49, 50, 51) in at least one of the second (47) and third (48) section of the gap (45, 52), the seals having two flexible legs (61, 62) arranged in a generally u-shaped or v-shaped orientation, the legs extending in a direction of fluid flow toward the toroidal chamber 44, the gap at the seal position being filled with a sealing fluid during use, a fluid duct (56) extending through the outer or inner annular wall (41, 42) to the gap (45, 52) and having an outlet in the gap section between the seals (49, 50, 51), and means for transporting a flushing fluid under pressure through the duct (56) to the toroidal chamber;

• the improvement wherein a fluid seal (49) is placed in the second or third gap section (47, 48), each seal being placed at an axial distance (H) from the end part of the first gap section (46), closer to the toroidal chamber (44) than the end part, the seal (49) located between the outlet of the fluid duct (56) and the toroidal chamber (44) being an isolation seal allowing the flushing fluid to pass from the duct (56) to the toroidal chamber (44).