The 4 maintenance strategies are not mutually exclusive. For any given piece of equipment appropriate maintenance strategies should be sought to counteract each identified mode of failure. The strategies are then combined together for the equipment to create what is known as the “Asset Maintenance Plan”.
The selection of a maintenance strategy for any given mode of failure should take into account the failure characteristic, the frequency of failure (mean time to failure) and the lead time to failure.
The “Maintenance Plan” for a site or organisation is produced by co-ordinating the individual unit maintenance plans in order to make the best use of available resources and time. In effect, the unit maintenance plans identify what is to be done, and the site maintenance plan identifies when and how it is to be performed.
There are a number of methodologies which can be used to produce a maintenance plan, including Reliability Centered Maintenance and Review of Equipment Maintenance. Many sites are still operating using a maintenance plan which was generated when the plant was first installed, based on the plant manufacturer’s servicing information.
These plans often do not reflect the current maintenance requirements of the plant as the equipment, production cycle, operating conditions and/or product mix may have changed radically since the plant was commissioned.