Why: Use data to solve problem by attacking root causes to reduce failures and make reliability grow. Fixing failures requires data-not opinions-to use the data acquisition system in a closed loop to record, analyze, correct, and verify improvements have been achieved. First data reported is usually a symptom of a failure and with a failure investigation, the symptom can be converted into a root cause which requires the system to be editable to correctly report failes.
When: The maintenance repair order system usually generates evidence of a failure. Failures with significant costs (repair costs + collateral damage + lost margin from the failure + other appropriate business costs) must be investigated and evaluated to reduce failures and to reduce failure costs. Little is to be gained by spending big money to investigate trivial failures.
Where: This is an engineering tool requiring clerical effort to input the data and build the Pareto distributions for identifying significant events requiring corrective action and thus it also becomes a management tool for controlling costs.
These definitions are written by H. Paul Barringer and are also posted on his web site at www.barringer1.com