High-Accuracy Calibration of the Wheel Spindle Tilt Angle for Grinding Hydrostatic Seal Rings Used in Reactor Coolant Pumps

Abstract

The hydrostatic seal rings are one of the most important components used in reactor coolant pumps. They are generally made of hard materials such as silicon nitride, alumina, silicon carbide and tungsten carbide. Meanwhile, the form error should be within the length of one to two helium light bands and the surface roughness should be in the scale of nanometers, which make them difficult to machining. In order to solve this problem, a high accuracy grinding method using a large cup wheel had been proposed and the tilt angle of the cup wheel spindle become a crucial factor affecting the ground form errors. This paper addresses a novel method for high-accuracy calibrating the tilt angle of the cup wheel spindle to fit the extremely shallow taper angle of the seal ring conical surface, and the mathematical model is established incorporating a standard optical flat with a high-accuracy laser displacement sensor. The practicability of this method is verified by grinding a seal ring sample with the outer diameter is 200 mm and the taper angle is 700 μrad. It is found that the taper angle error is only 1.72 μrad and the radical profile error of the conical surface is about 0.22 μm.