Systems and indicators Evident cause(s) Hidden root Fig 4 Root-cause analogy Levels. The three levels of root-cause analysis are physical roots, human roots, and latent roots(Ref 17, 18, 19, 20, 21) Physical roots, or the roots of equipment problems, are where many failure analyses stop These roots may be what comes out of a laboratory investigation or engineering analysis and are often component-level or materials-level findings Human roots (i.e, people issues) involve human factors that caused the failure, an example being an error in human judgment. Latent roots lead us to the causes of the human error and include roots that are organizational or procedural in nature. as well as environmental or other roots that are outside the realm of control These levels or root cause are best defined by the two examples Table 2 Examples of root causes of failure of pressure vessel and bolt root type Pressure vessel fail Bolt failure Physical roots Corrosion damage, wall thinning Fatigue crack; equipment vibration. lack of vibration;isolation Human roots Inadequate inspection performed Improper equipment installed Latent roots nadequate inspector training Inadequate specification verification process How deeply one goes into the root causes depends on the objectives of the RCA. These objectives are typically based on the complexity of the situation and the risk associated with additional failures. In most cases, one desires to identify root causes that are reasonably correctable. An example of the variety of possible root causes of an electric motor driven compressor assembly is provided in Table 3(Ref 22) Table 3 Possible causes of electric motor driven pump or compressor failures System design Component Shipping and Installation Operations and Distress damage or and specification manufacturer's storage responsibility maintenance failed components responsibility responsibility esponsibility responsibilit Application Material of Preparation Foundations Shock Distress damages construction for shipment Undercapacity Settling Thermal Vibration Overcapacity Improper materia//clsystem not Flaw or defect Improper or Mechanical Short/open circuit sufficient Inadequ tartup Failed componentsFig. 4 Root-cause analogy Levels. The three levels of root-cause analysis are physical roots, human roots, and latent roots (Ref 17, 18, 19, 20, 21). Physical roots, or the roots of equipment problems, are where many failure analyses stop. These roots may be what comes out of a laboratory investigation or engineering analysis and are often component-level or materials-level findings. Human roots (i.e., people issues) involve human factors that caused the failure, an example being an error in human judgment. Latent roots lead us to the causes of the human error and include roots that are organizational or procedural in nature, as well as environmental or other roots that are outside the realm of control. These levels or root cause are best defined by the two examples in Table 2. Table 2 Examples of root causes of failure of pressure vessel and bolt Root type Pressure vessel failure Bolt failure Physical roots Corrosion damage, wall thinning Fatigue crack; equipment vibration; lack of vibration; isolation Human roots Inadequate inspection performed Improper equipment installed Latent roots Inadequate inspector training Inadequate specification verification process How deeply one goes into the root causes depends on the objectives of the RCA. These objectives are typically based on the complexity of the situation and the risk associated with additional failures. In most cases, one desires to identify root causes that are reasonably correctable. An example of the variety of possible root causes of an electric motor driven compressor assembly is provided in Table 3 (Ref 22). Table 3 Possible causes of electric motor driven pump or compressor failures System design and specification responsibility Component manufacturer's responsibility Shipping and storage responsibility Installation responsibility Operations and maintenance responsibility Distress damage or failed components Application Undercapacity Overcapacity Incorrect physical Material of construction Flaw or defect Improper material Preparation for shipment Oil system not clean Inadequate Foundations Settling Improper or insufficient grouting Shock Thermal Mechanical Improper startup Distress damages Vibration Short/open circuit Failed components