Coupling device and combination and assembly thereof with a tube

A coupling device (10) for a tube (12) having a Palladium-based membrane deposited thereon, the tube for use in separation and purification of hydrogen in a hydrogen separator or reactor, the coupling device having an inlet (14) for a gas and configured to couple said tube to the inlet so that the gas can be supplied via the inlet into the tube, the coupling device comprising:

• a body part (5) with a cylindrical opening (6) for receiving the tube, the opening being arranged to receive gas flow to the inlet;
• and
• a nut (1), wherein the body part and the nut being configured such that the nut can be screwed onto the body part at the opening;
• the coupling device further having a stack (16) of at least two sealing rings (3, 4) provided between an end portion (20) of the body part surrounding the opening and an axial end portion (18) of the nut,
• wherein the body part, the nut and the stack of sealing rings are configured such that the tube extends through the axial end portion of the nut, through the stack of sealing rings and into the opening such that, in use, the stack of sealing rings is compressed in an axial direction (8) of the stack as a result of screwing the nut onto the body part so that the sealing rings sealingly engage a circumferential surface (11) of the tube;
• and
• wherein a sealing ring (4) of the stack (16) of sealing rings (3, 4), which sealing ring (4) in use contacts the end portion (20) of the body part (5) surrounding the opening (6), is a square or rectangular shaped O-ring having an axially protruding tapered ridge (22) facing the end portion (20) of the body part, wherein the end portion of the body part has a correspondingly tapered or chamfered portion (24) for receiving therein the ridge (22).