Abstract: Methods for testing the sealing integrity of seals of joints being added to an underwater pipe string and of each previously laid joint in the pipe string each time a joint is added to the string. The seal testing methods can be accomplished in two ways; dynamically, by pumping the sealed pipe until flow stops if the seal is perfect; or statically, by sealing the pumping unit discharge and measuring the pressure in the sealed pipe.

Abstract: An improved method and apparatus for coupling together conduit sections to form a pipeline while submerged in a fluid medium. During the operation of laying the pipeline while submerged in a fluid meduim, such as the ocean, adjacent pipe sections to be joined are subjected to a reduction in internal fluid pressure with a pump or the like so that during the joining operation, the pressure inside the adjacent pipe sections is lower than the exterior fluid pressure causing the pipes to readily come together and seat properly.