Derrick-crown positions for repairing Wells are always not provided with safe operating platforms for derrick crowns.

修井作业的井架天车部位，一直没有天车安全操作平台。

youdao

Derrick-crown positions for repairing Wells are always not provided with safe operating platforms for derrick crowns.

修井作业的井架天车部位，一直没有天车安全操作平台。

youdao