Prognosis and Health Management
Prognosis and Health Management
Basic approaches:
- corrective maintenance,
- scheduled maintenance, and
- preventive maintenance
The way these basic approaches are applied, five basic maintenance policies:
- failure-based maintenance,
- design-out maintenance,
- use-based maintenance,
- condition-based maintenance, and
- detection-based maintenance.
The evolution of maintenance strategies:
- breakdown maintenance (BM)
- also known as reactive maintenance or corrective maintenance.
- run-it-till-it-breaks mode, run-to-failure mode
- to restore the functional capabilities of failed or malfunctioned equipment or systems.
- preventive maintenance (PM)
- also known as time-based maintenance or periodic preventive maintenance
- time-based mode, time-directed mode
- assuming the mean time between failures (MTBF)
- schedule based maintenance
- to overhaul the equipment overhaul or replace item.
- to prevent the failure, to detect the onset of failure, and to discover the hidden failure.
- predictive maintenance (PdM)
- also known as on-condition maintenance, condition-based maintenance (CBM), or condition-directed maintenance
- to monitor the equipment for changes that could be destructive in the future,
- to correct them before the destruction starts
- to identify production equipment needing maintenance attention before product quality is reduced or an unplanned shutdown occurs
- actual condition based maintenance
- to detect the onset of a failure/fault and applied to critical equipment where a failure would interrupt a continuous process or impact quality.
PHM
The concept and framework of PHM have been developed based on the well-known maintenance methodologies and diagnostics techniques, such as preventative maintenance (PM), reliability-centered maintenance (RCM), and condition-based maintenance (CBM).
CBM consists of data acquisition and data processing (condition monitoring), resulting in actionable condition information on which maintenance decision making can be based, thus avoiding unnecessary maintenance tasks. Currently, more and more research effort has shifted toward prognostics and health management which focuses more on incipient failure detection, current health assessment, and remaining useful life prediction.