Reliability is a measure of a refiner’s ability to keep the equipment available for use by maintaining mechanical integrity. In general this means minimizing the time that process units are out of service, especially from unplanned outages.

The primary measures of reliability are:

Mechanical availability – This is a measure of the proportion of time that a process unit is mechanically capable of running (irrespective of whether it actually is running). Generally this is measured as a percent of unit capacity.

Unplanned downtime – This is a measure of either the frequency or duration of unit outages. For example, 3 times per year or 20% of the time.