Keywords: Maintenance procedures, Safety in fertilizer plants, Condition monitoring, Risk-based inspection.

Since the beginning of time (at least since the beginning of the time of Homo sapiens) maintenance has been a necessary tool to sustain survival, whether the maintenance has concerned hunting tools, windmills or private property. Later on, the industrial revolution required more focus on unexpected and unwanted breakdowns mostly due to pressure from the lack in production capacity.

Basically, nothing has changed. Nowadays industrial maintenance is similarly first of all focused on economic survival. However the increase in personal and environmental safety has also become a crucial factor in all maintenance.

This paper has been written to explain some of the activities involved in a complete maintenance system, and is not specific to any particular industry. The paper will also establish a connection between specific maintenance activities, aiming to give a general overview.

Since the core business in all maintenance is inspection and the associated maintenance tasks, a treatment of non-destructive examination methods will also be considered.

Obviously, this paper will not turn the reader into a maintenance expert, but hopefully it will give a valuable overview of the overall maintenance system and thus provide a better foundation for making sensible and carefully considered maintenance decisions.

It is claimed above that maintenance goals consist of different interests. Based on this it would be appropriate initially to divide maintenance costs into two main areas:
- The purely financial part.
- The overall safety part.

The latter will not be discussed specifically in this paper, as increased safety should always be considered as an individual issue, independent of the overall maintenance costs. However, as it will be stated, improvements in safety will also inevitably result in improved economy.

This paper will therefore focus on maintenance questions related to financial matters. In addition, exposure of the financial matters will reveal various maintenance-related subjects, e.g. good-will, employees’ motivation etc.

The main points in this paper will be:
- Overall maintenance activities.
- Administrative activities (managing activities).
- Technical activities.
- Example of condition based monitoring in relation to corrosion progression.

Lars Nøhr-Nielsen B. Sc. Chem. Eng. FORCE Institute, Brøndby, Denmark.

19 Pages, 5 Figures, 5 Refs.