Chapter 9 - The “Seven Cause Category Approach” to Root-Cause Failure Analysis

Abstract

Like virtually any other well-thought-out failure analysis method, the Seven Root-Cause Category Approach is aimed at uncovering the sometimes elusive failure sequence, and thus root cause, of the events leading up to the equipment failure. It assumes that all failures belong to one or more of the seven cause categories. These categories are: faulty design; material defects; fabrication or processing errors; assembly or installation defects; off-design or unintended service conditions; maintenance deficiencies; and improper operation. Using this classification, a straightforward approach for identifying the root cause of an equipment failure is outlined. The approach is illustrated by examining six failures in greater detail: bearing failures caused by faulty design; thrust bearing failures in a mining slurry pump caused by mistakes in documentation, fabrication, and processing; vibration and deterioration of grease-lubricated sleeve bearings in large seawater intake pumps traced to operator error; loss of life in a US Gulf Coast plant caused by maintenance oversight; reduced life and catastrophic failure of electric motor bearings due to fabrication and assembly errors; and damage to the twin screws of a large rotary positive-displacement compressor during restart caused by improper operation/off-design or unintended service conditions.