* at work, the wind is not greater than 6.
* The working site is flat and solid, and the ground slope is not higher than 3%.
* The safety factor of chain hoist shall be not less than 5.
* The hard pipes and connecting parts used can withstand three times the pressure of the hydraulic circuit 1min, without rupture and abnormality.
* The structure can bear the overload weight of 1.33 times the rated pressure without deformation and damage.
* overload 10%, portal system and hydraulic system should not have leakage and other anomalies.