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A Study on the Stem Coefficient of Friction of Motor- operated Gate/Globe halves  

Jeoung, Rae-Hyuck (Korea Electric Power Research Institute)
Park, Sung-Keun (Korea Electric Power Research Institute)
Lee, Do-Hwan (Korea Electric Power Research Institute)
Kim, Yang-Seok (Korea Electric Power Research Institute)
Publication Information
Nuclear Engineering and Technology / v.35, no.2, 2003 , pp. 133-143 More about this Journal
Abstract
Stem-stem nut coefficient of friction(COF) in motor-operated gate/globe valves is one of the important factors which determine the performance of the valve/actuators. The COF is affected greatly by the type and condition of the stem-stem nut lubricants, environmental parameters, surface condition of the stem/stem-nuts, and the number of strokes after the lubrication. In this paper, the measured data of the COFs at stem threads of some safety-related motor-operated gate/globe valves in domestic nuclear power plants are presented. In addition, the performance of the lubricants is evaluated by comparing the COFs among those valves. The results show that the measured COF at torque switch trip are higher than the unwedging COF and conservatively applicable to the unwedging COF. It is also shown that the lubricating performance based on the measured COFs varies with the lubricants.
Keywords
motor-operated valve; stem coefficient of friction; probability density function; thread pressure; stem factor; cumulative distribution function; unwedging; torque switch trip;
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