ALT Model Development and Implementation for High Pressure Rotary Valves

Abstract

Liquid Chromatography (LC) systems generally include at least one rotary type valve. The designs of these valves vary from one another in terms of materials of construction, fluidic geometry, and assembly based on the application. Evaluation of new valve designs or new applications for an existing valve is often required to support development engineering activities. Valve testing consumes time and resources, which may detract from the Reliability team’s ability to support competing efforts and increases time spent optimizing a valve design. The time, effort and costs associated with valve testing may be reduced by applying an accurate acceleration model. The intent of this paper is to summarize the results of an Accelerated Life Test (ALT) performed on LC rotary valves using temperature as the accelerating stress. The goal of which is to develop and verify a model of valve life as a function of ambient temperature. Such a model would increase the efficiency of valve evaluations by estimating use condition life from data collected at elevated stresses over a shorter test time. Along with the rigors of developing and verifying this model, the direct application of such a tool while maintaining production provides challenges to Reliability Engineers. This paper will also discuss issues faced when attempting to implement this model to verify design changes and what hidden information ALT may reveal about supplier, process, and part variability as it relates to predicted life. Accurate identification of these parameters not only ensures success in reducing evaluation time to demonstrate confidence in an adequate design life but also creates a more stable product and enables related functions, such as quality, to perform at a higher level.