Researchers at Purdue University have...
The life of any treatment plant, pumping station, or other water or wastewater system structure is determined in part by such factors as the materials of construction, the design engineer, the contract specifications, and the facilitys location and cost. But the major contributor to an effective life span is more often than not a well developed and implemented maintenance program that keeps equipment running and buildings and structures sound. Without proper maintenance, the usable life of any piece of equipment is much shorter than its design life, sometimes by 30 percent.
All plants probably have some kind of maintenance program in place. In many instances, however, maintenance amounts to repairing equipment that has broken down, or abandoning it and replacing it with new equipment. Breakdown maintenance is far removed from what is considered good maintenance practice.
A treatment plant often lacks a maintenance program because management has the notion that establishing one requires very special knowledge, or that a typical program is too complex to be handled without specialized personnel or equipment. Nothing is further from the truth. Developing an effective program is easily accomplished if a few basic rules are followed.
A good maintenance program will extend equipment life and reduce breakdowns. But regardless of how intensive such a program is, sooner or later a piece of equipment will break down. If preventive maintenance is planned and carried out, however, such occasional breakdowns will be few and far between.
There are important benefits, other than the prevention of breakdowns, that a maintenance program will generate. In many instances, these hidden results are not necessarily associated with maintenance, but are recognized for improving general operations. A good program will ensure
Some of these seemingly trivial consequences that result from an organized maintenance plan, such as the efficient use of lubricants or the spare parts purchasing function, help to illustrate the effectiveness of such a program. If personnel are sent frequently to a local supply house to purchase parts, money is being spent unnecessarily on higher-priced over-the-counter goods, with a simultaneous waste of manhours.
The bottom line of any maintenance program is that it can be one of the most economical tools available for achieving a cost-effective operation. Maintenance is often viewed as overhead, but it keeps costs down when implemented properly.
A maintenance program (based on either computer software or some alternative system) can be self-generated or purchased. No two operations are alike, and each program will be site specific. Purchased programs must be flexible, user friendly, and adaptable to accommodate the local application.
A thorough inventory of each operation and its related equipment is the simplest way to organize what must be maintained. Items that should be a part of the inventory are shown in Figure 1. Secondary equipment (e.g., HVAC, compressors, landscaping hardware) must not be overlooked. All such items require maintenance, either by in-house personnel or contracted help.
A second part of the inventory should be a listing of support capabilities (Fig 2). The inclusion of personnel is important. If too few personnel are on the staff to maintain the equipment at a desired level, steps must be taken to acquire more help from outside contractors or suppliers. Situations like this have to be considered when managers are establishing the maintenance budget.
After all items have been accounted for, the maintenance list should be prioritized according to the intensity of maintenance required. This procedure provides the foundation for the development of a program based on need. It also keeps the program in perspective as it relates to staffing requirements.
Many managers of water or wastewater treatment plants have the attitude that developing a maintenance program is beyond their capabilities or that they do not have the time. This is not necessarily true, and a predesigned computer package or other purchased maintenance program could help accomplish the task. But there are disadvantages that go along with the advantages.
A package will provide basic procedures, charts, and other paperwork needed to get started. Its format must be followed, and it may not be flexible enough to be modified or adapted to an operation even though it may be user friendly. And in many cases, the program allows only limited space for each item of maintenance.
Also, two features of computer programs should be considered. First, they generate large amounts of paper (some of which is useful for permanent records and storing inventory data, and some of which is simply redundant). Second, certain computer programs may be so complex that they require a full-time operator.
It is advisable to develop part of a maintenance program before any commercial software system is investigated. This will indicate what a computer package should be able to do, and the data collected in the exercise is available for insertion in the computer program. This data collection and insertion is required by any purchased program.
Developing a maintenance program is not as complex as it may appear, because plant personnel already have knowledge of the facilitys equipment. All that is required to get this information into a usable form is to organize and schedule work activities. This organization is based on the inventory priority list and should be accomplished as three separate tasks:
The frequency at which a piece of equipment or machine should be maintained is governed by its type, location, the hours it runs, and the type or level of maintenance to be accomplished. Two types of maintenance have to be considered-routine and scheduled.
Routine maintenance comprises the periodic inspections and tests performed on equipment at regular intervals. Included are daily, weekly, monthly, quarterly, semi-annual, etc., inspections during which minor routine maintenance tasks are carried out. Lubrication, vibration tests, packing adjustments, and other activities are part of this program.
While routine maintenance is underway, housekeeping chores (including landscaping if applicable) can become a part of the routine and is helpful is the plant covers a large area. Bringing all operating logs/records up to date can be done at this time. These items should be incorporated in the program and put down on paper rather than left to the discretion of the maintenance staff. If it is not on paper as a maintenance item, it may never be carried out.
Routine maintenance can be organized in several ways: by types of equipment, location, time required to complete the work, maintenance frequency, available personnel, etc. If most of the equipment is located in a general area, the easiest way to schedule maintenance is by equipment type. Tasks will be similar or repetitive, encouraging work continuity and efficient time utilization. This approach presumes that one person will do the same task for all equipment
On the other hand, if the work sites are scattered, then grouping the work tasks for several different pieces of equipment situated relatively close to each other is probably more effective. In this case, several different tasks may be scheduled for the same period. For example, some 30- or 90-day checks might be done along with hourly or daily checks.
Time for even routine maintenance has a cost, and the more efficiently the tasks are organized, the better the program will be--and the potential for breakdowns will be less.
A maintenance frequency schedule based on time can be changed depending on how the life cycle of the equipment progresses. For example, if electronic maintenance tests are performed at 30-day intervals, perhaps these could be extended to 45 or 60 days if the equipment has demonstrated satisfactory performance without any apparent need for the 30-day checks. Extending frequency intervals can produce significant cost savings. But if the need for maintenance should increase due to some new condition, the schedule can be readjusted.
Scheduled maintenance also is carried out on a time basis, but not a daily, weekly, or other timed schedule. Instead, it can be defined as the systematic and periodic removal from service of a piece of equipment for the replacement of parts, or for reconditioning and overhaul. The time cycle is based on wear and the expected life cycle of the equipment's individual components.
For example, if a centrifugal pump ran 24 hours a day without being shut off, it would accumulate more than 17,000 hours in two years. If the expected or normal bearing life is 15,000 running hours, a decision has to be made when to take the pump out of service for bearing replacement. Proper maintenance standards would say that when the bearings are being replaced, the pump impellers, wear rings, seals and casing should be inspected. Items that appear to have wear should be replaced. In addition, the drive motor, couplings, and electrical gear also should be included in any overhaul project. It is advisable-and sensible-to have all parts on hand before work is started.
Many plant personnel believe it may be cheaper to wait until a piece of equipment breaks down before it is repaired. This is false economy. Scheduled overhaul is less expensive because only parts showing normal wear are replaced, and the time required to accomplish the work can be managed by scheduling around other activities. Planning such activities avoids emergency overtime, or having to recall personnel from other routine work. Another advantage of scheduled maintenance is that equipment can be removed from service during off-peak operations when it is not needed, and more time can be devoted to thorough inspection.
A preventive maintenance program requires a variety of records and forms. They should be developed locally to suit the specific organization. Experience has shown that the better the records, the more up to date and effective the maintenance program will be. Predesigned maintenance programs usually come with forms included.
Work order forms should be developed to assist in scheduling and completing maintenance tasks. A side benefit of the work order is that it provides a place for the notation of equipment and building discrepancies or additional work required. This, in turn, can be added to future routine work orders or handled separately as scheduled maintenance.
Additionally, a work order serves as a check on the maintenance activity, the time required to complete the task, and as a reference for work accomplished and materials used.
Task analysis sheets should be completed for every maintenance activity. This task is time consuming and may not be necessary for some plants to perform. But if there is a large staff, or one prone to turnover, the need to perform each maintenance task properly and in the same manner each time requires documentation. The description of the work to be done does not have to be elaborate, but should be concise and clear. It should also include any tools needed to complete the task. They can be included on the work order.
Log books can be kept at each location if buildings are separated, or beside any piece of equipment. This log can be used by maintenance or operating personnel to record any repair work or machine adjustments made. A log provides other persons with a historical record and aids in decision making.
Inventory records are helpful, especially if parts are kept at different locations or if large numbers of spare parts are required. This record need not be too detailed, but should include where the parts are stored and to what piece of equipment they belong. (Stored parts also should carry this identification.) If possible, for future reference, the parts inventory also should show where the parts were purchased.
A preventive maintenance program is a product of careful thought and contains much detail. Every water or wastewater treatment facility is different and requires a site-specific approach to how maintenance should be undertaken. The skill level of the maintenance personnel, the complexity of the equipment, and many other factors all influence the development of a program and its ultimate success.