Targeting five years of AFD operation without interruption

Total process reliability is of prime importance to most refining industry operators or anyone in a continuous process industry environment. Typically, even momentary interruptions of critical equipment can shutdown an entire process and cost millions of dollars in lost production. Toward this end, a large Midwestern US refinery sought to purchase an AFD (adjustable frequency drive) system that could operate continuously for five years, without any interruption of any kind. Reliability and risk assessment studies were conducted as well as economic cost justification. The selected AFD systems offered unique features including component bypass and redundancy, redundant cooling capability, and a process tolerant protection system. Together, the manufacturer and user have further modified each unit to maximize fault tolerance through a thorough joint design review. Communications and diagnostics were integrated into the plant control system to provide the operators with full system status information to enable smart system operating decisions to improve process availability further. The system studies and decision making are reviewed. Features are described. Additional system modifications derived from a user design review are presented