Flanged coupling device with a static ball-and-socket joint

A flanged coupling device having a static ball-and-socket joint, the device comprising:

• a first coupling member having a cylindrical-surface seat and a sealing surface;
• a second coupling member having a concave sealing surface that is substantially spherical in shape between a minimum diameter and a maximum diameter;
• a two-barrier metal gasket placed between the sealing surfaces of the first and second coupling members, said gasket comprising:
• two fine and resilient lips each of which is terminated by a toroidal bead in leakproof contact with the sealing surfaces;
• an annular end having an inner surface co-operating with the cylindrical-surface seat;
• and
• a structural ring having an inner surface in leakproof contact with the sealing surface of the first coupling member, and an outer surface of spherical shape in leakproof contact with the concave sealing surface of spherical shape of the second coupling member;
• leak monitoring means;
• assembly means for assembling together the first and second coupling members so as to hold the gasket between their respective sealing surfaces;
• and
• means allowing a certain amount of angular deflection between the axes of the coupling members;
• wherein the radius of curvature Rc of the spherical surface of the second coupling member is such that the tilt angle β relative to the axis of the first coupling member of the tangent T to the spherical surface common to the gasket and the second coupling member at the point where the diameter of the second coupling member is at its maximum, lies in the range 27° to 33°;
• the means allowing a certain amount of angular deflection between the axes of the coupling members are provided first by a gap A between facing front faces of the two coupling members and by radial clearance δ due to the difference between the diameters of each of the holes in the flange of the first coupling member and each of the assembly means, the angle α between the axes of the coupling members is given by the following relationship:
• tan α>A/Rc·cos β
• where:
• A in mm is the axial gap between the face of the first coupling member and the facing face of the second coupling member when the assembled coupling members are in alignment;
• Rc in mm is the radius of curvature of the spherical surface common to the second coupling member and the gasket;
• β is the tilt angle relative to the axis of the first coupling member of the tangent T to the spherical surface common to the gasket and to the second coupling member at the point where its outside diameter is at a maximum, where β lies in the range 27° to 33°;
• and
• the length of the radial clearance δ due to the difference in diameter between each hole in the first coupling member and each assembling means satisfies the relationship:
• δ≦(A+H)·tan α
• where H in mm is the thickness of the flange of the first coupling member, the two-barrier metal gasket placed between the sealing surfaces of the first and second coupling members is held by a retaining ring and the metal gasket is made of a refractory nickel alloy made by powder metallurgy, suitable for withstanding hydrogen, and having a uniform fine-grain structure with isotropic properties and coated in sealing layers.