Patent ID: 7255515

Claim:
A marine pipelaying system for vertical or near vertical laying of an offshore pipeline, wherein the system comprises: a. a main supporting structure; b. a pivotable structure supported pivotably by the main supporting structure; c. a pipe connecting station, wherein a pipe section is connected to an uppermost end of a previously launched pipeline; d. a static clamp positioned above a mobile clamp adapted for releasably securing the uppermost end of the previously launched pipeline, wherein the static clamp is adapted to support the weight of the previously launched pipeline, wherein the static clamp is located below the pipe connecting station, and the static clamp is arranged on the pivotable structure; e. the mobile clamp positioned below the static clamp adapted for releasably securing the previously launched pipeline at a position essentially below the static clamp, wherein the mobile clamp is adapted to support the weight of the offshore pipeline as the offshore pipeline is released from the static clamp; and f. a mobile clamp hoist comprising a mobile clamp cable connected to the mobile clamp, wherein the mobile clamp comprises pipeline engaging guide members adapted to engage the offshore pipeline and guide the mobile clamp back to the uppermost end, and wherein the mobile clamp hoist is adapted to raise and lower the mobile clamp and the offshore pipeline supported thereby, wherein the path of the mobile clamp cable intersects the pivot axis of the pivotable structure; wherein the offshore pipeline is raised and lowered by releasing the static clamp and engaging the mobile clamp, at which point the mobile clamp hoist raises or lowers the mobile clamp which is engaged to the offshore pipeline; wherein the offshore pipeline is engaged by the mobile clamp in a clamping position while the offshore pipeline is supported by the static clamp, whereafter the static clamp is released, whereafter the mobile clamp and pipeline are lowered to a lower position, wherein at the lower position the static clamp secures the offshore pipeline, and whereafter the mobile clamp is released from the offshore pipeline and the mobile clamp is moved back to the upper position, wherein the upper position is still below that of the static clamp.