Muab kev txhawb nqa ruaj khov: Ib hydraulic prop hauv cranes, cov khoom siv me me thiab kev hloov kho cov khoom siv kom ntseeg tau tias qhov sib npaug ntawm cov khoom siv thaum lub sijhawm ua haujlwm.
Tsis siv neeg kho thiab tswj: hauv kev tsim tsheb tsim kev lag luam, tib lub cev muaj kev lag luam kom haum rau cov txheej txheem sib txawv thiab cov qauv yuav tsum tau ua.
