Designing a Preventive Maintenance Program





Valid failure data provide the intelligence for an effective preventive maintenance program. After all, the objective is to prevent those failures from recurring.

A failure reporting system should identify the problem, cause, and corrective action for every call. An action group, prophetically called the Failure Review and Corrective Actions Task Force (FRACAS), can be very effective for involving responsible organizations in both detailed identification of problems and causes and assignment of both short- and long-term corrective action. The following are typical factory and field problems and codes that shorten the computer data entry to four or fewer characters:

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NOOP Not Operable; OTHR Other; BELR Below rate; PM Preventive task; INTR Intermittent; QUAL Quality; LEAK Leak; SAFE Safety; MOD Modification; WEAT Weather; NOIS Noise; NPF No problem found.

The following are typical cause codes:

1. Not applicable

10. Controls 20. Power 21. External input power 22. Main power supply 30. Motors 40. Drivers 50. Transports 60. Program

70. Materials

71. Normal wear 72. Damaged 80. Operator 90. Environment 99. No cause found PM. Preventive maintenance

The typical action codes are as follows: A/A Adjust/align CAL Calibrate CONS Consumables DIAG Diagnose REMV Remove R/R Remove and replace R/RE Remove and reinstall INST Install INSP Inspect REF Refurbish REB Rebuild LUBE Lubricate MOD Modify PM Preventive task RPR Repair TRN Train NC Not complete; NK Not known

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These parameters and their codes should be established to fit the needs of the specific organization. For example, an organization with many pneumatic and optical instruments would have sticky dials and dirty optics that would not concern an electronically oriented organization. Note also that the code letters are the same, whenever possible, as the commonly used words' first letters.

Preventive maintenance activities are recorded simply as PM. The cause codes, which may be more detailed, can use numbers and subsets of major groups, such as all power will be 20s, with external input power = 21, main power supply = 22, and so on.

It is possible, of course, to write out the complete words. However, analysis, whether done by computer or manually, requires standard terms. Short letter and number codes strike a balance that aids short reports and rapid data entry.

Use of the equipment at every failure should also be recorded. A key to condition monitoring preventive maintenance effectiveness is knowing how many hours, miles, gallons, activations, or other kinds of use have occurred before an item failed. This requires hour meters and similar instrumentation on major equipment.

Use on related equipment may often be determined by its relationship to the parent. For example, it may be determined that if a specific production line is operating for 7 hours, then the input feeder operates 5 hours (5/7), the mixer 2 hours (2/7), and the packaging machine 4 hours (4/7).

It is also important to determine the valid relationship between the cause of the problem and the recording measurement. For example, failures of an automotive starter are directly related to the number of times the car engine is started and only indirectly to odometer miles. If startup or a particular activity stresses the equipment differently from normal use, those special activities should be recorded.

ill. 3.1 is a combination work order and completion form. This form is printed by the computer on plain paper with the details of the work order on the top, space in the center for labor and materials for work orders that take a day or less, and a completion blank at the bottom to show when the work was started, when it was completed, the problem/cause/action codes, and meter reading. Labor on work orders that take more than one day is added daily from time reports and accumulated against the work order. ill. 3.2 shows the computer input screen for a simple service call report form that gathers minimum information necessary for field reporting. Those forms may be used as input for a computer system, when a direct-entry system is not available.

IMPROVING EQUIPMENT RELIABILITY

Total Plant Performance Management (TPPM) and similar quality programs promote a holistic approach that includes equipment performance as a major enhancement to productivity. To reinforce the ''five-fingered approach to effective maintenance'' outlined in Section 1, the fundamental thumb is elimination of failures. Uptime of equipment is what counts.

Maintainability and maintenance are most successful if we don't have failures to fix. Successful maintenance organizations spend more time on identification of trends and eliminating problems than they spend fixing repetitive breakdowns.

Computerized maintenance management systems provide a tool to gather data and provide analysis that can lead to improvement.

Improvement Process

ill. 3.3 diagrams a business improvement process. A maintenance organization should start by measuring its own performance. For example, just a breakout of a typical day in the life of a maintenance person will be revealing. Many groups are chagrined to discover that maintenance staff actually work less than 30% of the time. Benchmark comparisons with similar organizations provide a basis for analyzing performance both on metrics and processes. The third step in goal setting is to identify realistic ideal levels of performance. These goals should have the following characteristics:

Written Measurable Understandable Challenging Achievable

The goals will have firm times, dollars, percents, and dates. Everyone who will be challenged to meet the goals should be involved in their establishment. This may seem like a bureaucratic, warm-fuzzy approach, but the time it takes to achieve buy-in is earned back many times during accomplishment. Once the goals are set, any gaps between where performance is now versus where it needs to be can be identified. Then both short-term plans and long-term strategies can be implemented to reach the goals. Frequent measurement and feedback will revise performance to achieve the desired levels of achievement.

ill. 3.1 Combination work order and completion form.

ill. 3.2 Computer input screen for a service call form, which gathers minimum information necessary for field reporting.

ill. 3.3 Business improvement process.

Failures That Can Be Prevented

Simplified Failure Modes and Effects Analysis (SFMEA) provides a method for determining which failures can be prevented. Necessary inputs are the frequency of occurrence for each problem and cause combination and what happens if a failure occurs. Criticality of the failure is considered for establishing priority of effort. SFMEA is a top-down approach that looks at major components in the equipment and asks, ''Will it fail?'' And if so, how and why? Preventive maintenance investigators are, of course, interested in how a component will fail so that the mechanism for failure can be reduced or eliminated. For example, heat is the most common cause of failure for electrical and mechanical components. Friction causes heat in assemblies moving relative to each other, often accompanied by material wear, and leads to many failures.

Any moving component is likely to fail at a relatively high rate and is a fine candidate for preventive maintenance. The following are familiar causes of failure:

Abrasion Abuse Age deterioration Bond separation Consumable depletion Contamination Corrosion Dirt Fatigue Friction Operator negligence Puncture Shock Stress Temperature extremes Vibration Wear.

Maintenance to Prevent Failures

Cleanliness is the watchword of preventive maintenance. Metal filings, fluids in the wrong places, ozone and other gases that deteriorate rubber components-all are capable of damaging equipment and causing it to fail. A machine shop, for example, that contains many electro-mechanical lathes, mills, grinders, and boring machines should have established procedures for ensuring that the equipment is frequently cleaned and properly lubricated. In most plants, the best tactic is to assign responsibility for cleaning and lubrication to the machine's operator.

There should be proper lubricants in grease guns and oil cans and cleaning materials at every workstation. Every operator should be trained in proper operator preventive tasks. A checklist should be kept on the equipment for the operator to initial every time the lubrication is done.

It is especially important that the lubrication be done cleanly. Grease fittings, for example, should be cleaned with waste material both before and after the grease gun is used. Grease attracts and holds particles of dirt. If the fittings are not clean, the grease gun could force contaminants between the moving parts, which is precisely what should be avoided. This is one example of how preventive maintenance done badly can be worse than no maintenance at all.

Personnel

Another tactic for ensuring thorough lubrication is to have an ''oiler'' who can do all of the lubrication at the beginning of each shift. This may be better than having the operators do lubrication if the task is at all complicated or if the operators are not sufficiently skilled.

Whether operators will do their own lubrication, rather than have it done by an oiler, is determined by

1. The complexity of the task.

2. The motivation and ability of the operator

3. The extent of pending failures that might be detected by the oiler but overlooked by operators.

If operators can properly do the lubrication, then it should be made a part of their total responsibility, just as any car driver will make sure that he has adequate gasoline in his vehicle. It is best if the operators are capable of doing their own preventive maintenance. Like many tasks, preventive maintenance should be delegated to the lowest possible level consistent with adequate knowledge and ability. If, however, there is a large risk that operators may cause damage through negligence, willful neglect, or lack of ability, then a maintenance specialist should do lubrication. The tasks should be clearly defined. Operators may be able to do some items, while maintenance personnel will be required for others. Examples of how the work can be packaged will be described later.

Preventive tasks are often assigned to the newest maintenance trainee. In most cases, management is just asking for trouble if it's regarded as low-status, undesirable work. If management believes in preventive maintenance, they should assign well-qualified personnel. Education and experience make a big difference in maintenance. Most organizations have at least one skilled maintenance person who can simply step onto the factory floor and sense-through sight, sound, smell, vibration, and temperature--the conditions in the factory.

This person can tell in an instant ''The feeder on number 2 is hanging up a little this morning, so we'd better look at it.'' This person should be encouraged to take a walk around the factory at the beginning of every shift to sense what is going on and inspect any questionable events. The human senses of an experienced person are the best detection systems available today.

How to Start

The necessary items for establishing an effective preventive maintenance program are:

1. Every equipment uniquely identified by prominent ID number or serial number and product type

2. Accurate equipment history records

3. Failure information by problem/cause/action

4. Experience data from similar equipment

5. Manufacturer's interval and procedure recommendations

6. Service manuals

7. Consumables and replaceable parts

8. Skilled personnel

9. Proper test instruments and tools

10. Clear instructions with a checklist to be signed off 11. User cooperation 12. Management support.

A typical initial challenge is to get proper documentation for all equipment.

When a new building or plant is constructed, the architects and construction engineers should be required to provide complete documentation on all facilities and the equipment installed in them. Any major equipment that's installed after that should have complete documentation. ill. 3.4 is a checklist that should be given to anyone who purchases facilities and equipment that must be maintained.

As can be seen, one of the items on this list is ensuring availability of complete documentation and preventive maintenance recommendations.

Purchasing agents and facilities engineers are usually pleased to have such a checklist and will be cooperative if reminded occasionally about their major influence on life-cycle costs. This brings us back again to the principle of avoiding or minimizing the need for maintenance. Buying the right equipment in the beginning is the way to start. The best maintainability is eliminating the need for maintenance.

If you are in the captive service business or concerned with designing equipment that can be well maintained, you should recognize that the preceding has been aimed more at factory maintenance; but after all, that's an environment in which your equipment will often be used. It helps to view the program from the operator and service person's eyes to ensure that everyone's needs are satisfied.

ill. 3.4 Maintenance considerations checklist for purchasing agents and facilities engineers.

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