Abstract: In the cylindrical water distributor of a hydro turbine, eccentric pins are usually used to compensate manufacture deviations and worn surfaces, but their influence on the opening of wicket gates is often ignored. First, this paper develops an ideal model for the gate opening and derives a motion relationship among the assembled parts to realize the gate opening mechanism for the case without eccentric pins. Then, using this model, we examine two types of eccentric pins and use Matlab to calculate and depict curves representing the influence of the pins on the angle of the fully opened gates. The analysis shows that two dominant factors are the eccentricity of the pins and those parts that are locked to the pins, and the latter factor is more significant and should be emphasized. In design and installation, a reasonable eccentricity and appropriate locked parts should be considered and selected, and the same eccentric direction should be guaranteed for the eccentric pins locked to the regulating ring.

Key words: eccentric pin, opening of wicket gate, deviation in opening, eccentric value, eccentric pin-locked object