To replace the drilling line wrapped around the crownblock and traveling block.
为更换缠绕在天车和游动滑车周围的钻井钢丝绳用。
2
The drilling line is reeled over the crownblock and traveling block to gain mechanical advantage in a "block and tackle" or "pulley" fashion.
钻井用钢丝绳通过天车和游动滑车以滑轮组的形式获得机械上效益。
3
The text detailedly introduced crownblock, running system, availability work period of bridge girder erection equipment and improve case for precast beams install.