Abstract: Pipe connectors particularly useful in securing sections of an underwater marine riser together, including a pin received in a box and bearing against a box shoulder, the pin and box being secured together by coengaging members mounted on the box, and between the pin and box, and forced against a shoulder at the outer portion of the pin over substantially 360.degree. of the shoulder, to correspondingly force the outer end of the pin against the box shoulder, with the contacting pin and box surfaces axially preloaded against each other. The coengaging members can include a plurality of lock dogs mounted in the box and movable radially inwardly against a ring device disposed between the box and pin and engaging the shoulder at the outer portion of the pin, the dogs and pin device having coengaging cam surfaces causing dogs to exert an axial thrust on the ring device which is transmitted from the ring device to the pin shoulder.