There is little question that the majority of water/wastewater equipment requires some sort of periodic routine maintenance. The reason for maintenance is simply that replacements are costly and each piece of equipment has a rather long life expectancy. Therefore, regular or routine maintenance will keep the component running smoothly until it eventually wears out.
However, every once in a while someone will ask, "Why maintain a piece of equipment that is relatively inexpensive to replace?" Although there is not an easy answer to this question, both sides of the issue should be closely examined before any final decision is reached on whether or not a specific piece of equipment should or should not be maintained. All too often the answer to this question is based on a financial analysis, and not on a philosophy of equipment reliability.
In situations where a piece of equipment is inexpensive, the need for maintenance is often ignored and the component is operated until it fails. From a financial standpoint this might seem to be the best approach because of the savings in maintenance, labor and repair parts. Additionally, it eliminates placing the item on the maintenance schedule and the associated record keeping functions that go along with it. However, is the shortened life and early replacement really a cost-effective procedure?
The cost/maintenance ratio benefit can be determined easily by plotting the purchase and maintenance costs against the equipment life expectancy.
Suppose the original equipment cost was $150.00 and had a life expectancy of three years with no maintenance. If the estimated annual maintenance cost was $30.00 and would at least double the life of the unit, then the cost of maintenance can be justified because it eliminates the three-year replacement costs.
However, there are two financial items that have not been taken into account in this analogy. One is the cost of the actual changing of the unit (labor). The second is the depreciation value of the equipment. Most municipal operations do not consider depreciation, but it is a financial consideration for others. There also has been no anticipated increase in the equipment purchase price.
On the other side of the financial coin is the question of how much cost is really involved to replace the item. What happens if the equipment fails in the middle of the night or on the weekend and a replacement is not available or someone is not around to change it. There also are questions about what effect the failed item has on the process and at what cost. If the failure upsets the process flow and requires changes or adjustments to other elements that are non-automatic, then additional labor costs out of the norm will be incurred.
When considering the operating reliability and life of a piece of equipment, the cost of maintenance becomes a secondary issue. More important is the reliable operation of the plant and process, and the extended operating life of the item. By maintaining the equipment in good operating condition, the reliability of the plant process remains at peak performance.
Additionally, properly maintaining the equipment not only extends its operating life (along with the reduced replacement cost), but its anticipated failure time can be estimated. Being able to predetermine the date of failure allows a plant the flexibility of replacing the item when it is the most advantageous and the least disruptive to the overall plant operations. This includes the proper purchasing and receipt of the item as well as the scheduling of the repair personnel.
My position on the question is to maintain all equipment as part of a regular maintenance schedule. Properly maintaining the equipment tells the owners (private or public) that your operation is responsible and organized. On the other hand, if you ignore maintenance on some items and stress it on others, you are sending mixed signals to the people responsible for maintenance, telling them that maintenance can be ignored if they have other things to do. Keeping the proper focus on maintenance keeps the proper focus for the entire plant operation.