Maintenance strategies and associated costs.

Abstract

Choosing the correct maintenance strategy can be challenging for the decision maker as there are many approaches to the same problem; equipment wear out and break down. In this thesis three simulations on maintenance strategies are done using Vensim. The first, second and third strategy focuses on preventive maintenance, corrective maintenance and condition-based maintenance respectively. The author has 3 years of offshore experience as a drilling and maintenance operator, therefore the selected system to be simulated are the mud pumps in the drilling facility. The thesis does not include the drilling operation and the results are not limited to the oil industry, the focus is on the maintenance strategies.

The main aim for the thesis is to estimate the cost of maintenance and operation in terms of downtime hours and maintenance hours used in the operational phase of the equipment over a 10-year period. Methods used in thesis are interviewing, literature review and simulations.

The simulation consists of a system divided into sub-systems, where each sub-system is built up by several components. Equipment wear down over time and has its condition restored by maintenance events. Each maintenance event is counted and assigned a duration which is then accumulated to get a total amount of maintenance hours used. The equipment has a chance of a random breakdown which causes downtime. The corrective maintenance scenario will let equipment run to failure, thus allowing for more downtime to occur. The total amount of downtime is also accumulated.

The preventive maintenance scenario came out as the best scenario in terms of lowest amount of downtime hours but at the cost of the highest amount of maintenance hours used. The condition-based maintenance scenario has 11% less hours used in maintenance than the preventive maintenance scenario but has 10% more downtime. The corrective maintenance scenario has 30% less hours used in maintenance than the preventive maintenance scenario but has 160% more downtime. Parts that are critical to either the operation, safety or environment should have condition monitoring implemented and follow a condition-based maintenance program. Parts that are not critical and inexpensive should follow a corrective maintenance approach, whereas the rest should be maintained on a scheduled basis, following a preventive maintenance program.