Exploration on Maintenance of Hydraulic Hoist Cylinder for Large Gates in HPP

The hydraulic hoist is classified according to the tonnage of the gate. The lifting force of more than 4000T is called super large scale hoist, and the cylinder is its core component. Cylinder maintenance cycle varies from 10 to 15 years, combined with the condition-based maintenance strategy. For the unit hoist, in order not to affect power generation, it is best to carry out the maintenance of the hoist cylinder during the unit maintenance period.

For the power station the paper mentioned, the gate driven by the hoist is installed in 70m below the dam crest with big size and heavy weight which cause the gate lifting out the chamber to be another issue that will not be discussed in the paper. After the maintenance of the cylinder is completed, the gate maintenance inside the chamber is subsequently carried out.

The length of cylinder in this paper is about 19m and the weight is 55T (cylinder with oil). The safety risk in the procedure of overturning and hoisting is high, so it needs special control. After dismantling with the hydraulic system, it is generally transferred to the factory for repair, replacing the easily damaged parts of the piston, evaluating the condition of the inner wall of the cylinder block and the surface of the piston rod, and putting forward the treatment measures. For piston rod, treatment measures are relatively multiple. Generally, if there is no serious wear, light holes can be simply honed, and the piston rod can be reinstalled after reaching the corresponding standards. If there are serious defects and corrosion, the repair welding is necessary, finally along with anti-corrosion coating. If the corrosion is more serious that the dimensional tolerance is unable to meet the requirements after treatment, a new piston rod will be procured. For coatings, generally chromium plating or better effect of ceramic spraying will be adopted, mainly depended on the technical level of the relevant industries in the region or country, anti-corrosion effect and economic considerations.