Drillingderrick that working many years often has the defect of bending bar.
服役多年的钻机井架常会出现局部杆件弯曲现象。
2
Equipped with suitable derrick and well controlled device in drilling a shallow gas well water drills proved to be able to reduce shallow gas well drilling cost.
通过某浅层气井的施工实例，阐述了水井钻机安装合适的钻塔底座和并控装置，可降低浅层气井建井成本。
3
The fixed set of pulleys (called sheaves) located at the top of the derrick or mast, over which the drilling line is threaded.