Derrick lift system of offshore structure

Abstract

Disclosed herein is a derrick lift system of an offshore structure. The derrick system can improve drilling workability by enabling safe and easy height adjustment of a derrick using an adjustment unit, and can improve structural stability by lowering the center of gravity of the derrick through the height adjustment of the derrick, as occasion demands.

What is claimed is: 
     
         1 . A derrick lift system of an offshore structure, comprising:
 a base plate secured to a drill floor and having a locking groove formed on one side thereof;   a gearbox placed at one inner side of the base plate and coupled to a drive motor;   a relay gear rotably mounted on the base plate to engage with the gearbox;   a pinion rotably mounted on the base plate to engage with the relay gear;   a post supporting a lower end of the derrick to lift or lower the derrick and provided to the other inner side of the base plate to be perpendicularly movable, the post having a rack formed on one surface thereof to engage with the pinion and a locking groove formed on one side thereof;   a stopper mounted on the base plate and selectively inserted into the locking grooves to secure the post at a lifted or lowered location; and   a derrick height adjustment unit placed at one side of the base plate to align the locking grooves through height adjustment of the derrick.   
     
     
         2 . The derrick lift system of an offshore structure according to  claim 1 , wherein the derrick height adjustment unit comprises:
 a mounting bracket secured to the base plate; and   a hydraulic cylinder provided to the mounting bracket and adjusting the height of the derrick.   
     
     
         3 . The derrick lift system of an offshore structure according to  claim 1 , wherein the base plate is provided with a sensor detecting alignment of the locking grooves. 
     
     
         4 . The derrick lift system of an offshore structure according to  claim 1 , wherein the pinion comprises a securing pin engaging with the rack, and the base plate is provided with a safety cylinder coupled to the stopper to selectively lock the stopper. 
     
     
         5 . The derrick lift system of an offshore structure according to  claim 4 , wherein the base plate is provided with a ratchet cylinder, the ratchet cylinder comprising a rod and a pivot latch latched to a latch jaw of the pinion through the rod of the ratchet cylinder. 
     
     
         6 . The derrick lift system of an offshore structure according to  claim 1 , wherein the base plate and the post are arranged to support four lower corners of the derrick. 
     
     
         7 . The derrick lift system of an offshore structure according to  claim 1 , wherein the stopper comprises:
 a guide plate secured to a side surface of the base plate and having a guide rail formed on an upper surface thereof;   a rod horizontally secured above the guide plate;   a cylinder body disposed to receive the rod therein and to be locked into the locking grooves while moving along the rod by hydraulic force, and having safety grooves formed on upper surfaces of both ends thereof; and   a safety cylinder secured to a side surface of the base plate and coupled into the safety grooves to prevent separation of the cylinder body from the locking grooves when the cylinder body is inserted into the locking grooves.   
     
     
         8 . The derrick lift system of an offshore structure according to  claim 7 , wherein the cylinder body is formed with fluid inlet and outlet ports and a hydraulic chamber, and has safety grooves formed on upper surfaces of both ends thereof