Maintenance and Asset Integrity is a broad and diverse subject covering multiple types of equipment and structures. Maintenance regimes typically require support from various companies and sources of manpower as well as original equipment manufacturers (OEM). The Maintenance Strategy adopted by the Company sets the type of maintenance carried out. The strategy is the central document that sets the path to find the optimum balance of various factors in achieving the business objectives. Included in this it must consider:
- Maximize production (or increase facilities availability) at the lowest cost consistent with the required quality and safety requirements,
- Reduce downtime, breakdowns, failure and emergency shutdowns,
- Optimise equipment life, resources and spares stock utilization,
- Improve equipment efficiency, minimizing energy usage and reducing scrap rate,
- Provide reliable cost and budgetary control,
- Identify and implement improvements,
A useful way to understand the failure of equipment and structures is using the principle of the "bath tub curve". The principle holds that in the early stages of the lifecycle of equipment or structures failure rates are declining as "infant mortality failure" is overcome ("red line"). After overcoming this a constant rate of failure is witnessed as contributed by a declining "infant mortality failure", a constant random failure ("green line") and a increasing wear and tear failure rate ("yellow line"). Towards the end of the lifecycle failure begins to increase as wear and tear increase the failure rate sharply. What is witnessed is the bath tub of reliability as shown by the blue line.
Over time there has been a gradual developmentof applied scientific approaches to maintenance. Essentially based on more understanding of the typical causes of failure and statistical data. There are three basic approaches to maintenance and asset integrity each with its own pro's and cons. These are summarized below:
In reality most regimes are made up of a mixture of different approaches to maintenance and asset integrity based upon the characteristics of the equipment or structure in question. Below is a quick reference guide showing some of the factors that may contribute to the selection of a maintenance regime.
In addition to these factors critical equipment should be considered in more depth as the consequences of getting the strategy wrong is likely to be significant. On one hand underestimating the requirement may lead to costly emergency repairs and large production losses, whilst over estimating ties up significant amounts of capital in inventory, storage, warehousing and preservation. As such an appropriate economic balance must be struck.
To be most effective in the maintenance and integrity of assets and equipment maintenance and reliability must be considered from day one - during design. Maintenance should be considered in depth during the design of assets and equipment with the view to ensuring the most cost effective solution is identified.