Abstract: A method and apparatus for achieving a fluid tight seal of a fluid coupling having an axis, wherein a spring interposed between a coupling nut and an inner member of a first coupling element is compressed when the coupling nut is engaged with a second coupling element and rotated in a tightening direction such that complementary sealing surfaces between the first and second coupling elements are axially pre-loaded to achieve a fluid tight seal. A fluid tight seal is dependent on the axial compression of the spring, indicated by the axial location of the coupling nut with respect to the inner member and second coupling element, and is visually indicated by the rotational relationship of the coupling nut and the second coupling element.

Abstract: A redundant locking fluid coupling has a first coupling element including a coupling nut and a second coupling element including an outer ring biased towards the sealing end, such as by a coil spring. The coupling nut and outer ring include circumferential ends that are engaged when the coupling nut is tightened on the second coupling element inner member. Rotation of the coupling nut in a loosening direction is prevented by ratcheting teeth, or, in an alternative embodiment, complimentary sawtooth teeth, in the circumferential surfaces of the coupling nut and outer ring. Loosening of the coupling nut may be accomplished by sides of a wrench engaging a wrench lead in chamfer forcing axial movement of the outer ring to disengage the ratcheting teeth, or in the alternative embodiment, loosening torque being sufficient to overcome the thread torque and the increased frictional force across the complementary sawtooth teeth.