Planning is the heart of good inspection and preventive maintenance. As described earlier, the first thing to establish is what items must be maintained and what the best procedure is for performing that task. Establishing good procedures requires a good deal of time and talent. This can be a good activity for a new graduate engineer, perhaps as part of a training process that rotates him or her through various disciplines in a plant or field organization. This experience can be excellent training for a future design engineer.
Writing ability is an important qualification, along with pragmatic experience in maintenance practices. The language used should be clear and concise, with short sentences. Who, what, when, where, why, and how should be clearly described. A typical preventive maintenance procedure is illustrated in ill. 4.1. The following points should be noted from this typical procedure:
1. Every procedure has an identifying number and title.
2. The purpose is outlined.
3. Tools, reference documents, and any parts are listed.
4. Safety and operating cautions are prominently displayed.
5. A location is clearly provided for the maintenance mechanic to indicate performance as either satisfactory or deficient. If it's deficient, details are written in the space provided at the bottom for planning further work.
The procedure may be printed on a reusable, plastic-covered card that can be pulled from the file, marked, and returned when the work order is complete; on a standard preprinted form; or on a form that's uniquely printed by computer each time a related work order is prepared.
Whatever the medium of the form, it should be given to the preventive maintenance craftsperson together with the work order so that he has all the necessary information at his fingertips. The computer version has the advantage of single-point control that may be uniformly distributed to many locations. This makes it easy for an engineer at headquarters to prepare a new procedure or to make any changes directly on the computer and have them instantly available to any user in the latest version.
Two slightly different philosophies exist for accomplishing the unscheduled actions that are necessary to repair defects found during inspection and preventive maintenance. One is to fix them on the spot. The other is to identify them clearly for later corrective action. This logic is outlined in ill. 4.2. If a ''priority one'' defect that could hurt a person or cause severe damage is observed, the equipment should be immediately stopped and ''red tagged'' so that it will not be used until repairs are made. Maintenance management should establish a guideline such as, ''Fix anything that can be corrected within 10 minutes, but if it will take longer, write a separate work request.'' The policy time limit should be set, based on:
1. Travel time to that work location
2. Effect on production
3. Need to keep the craftsperson on a precise time schedule.
The inspector who finds them can affect many small repairs most quickly. This avoids the need for someone else to travel to that location, identify the problem, and correct it. And it provides immediate customer satisfaction. More time-consuming repairs would disrupt the inspector's plans, which could cause other, even more serious problems to go undetected. The inspector is like a general practitioner who performs a physical exam and may give advice on proper diet and exercise but who refers any problems he may find to a specialist.
The inspection or preventive maintenance procedure form should have space where any additional action required can be indicated. When the procedure is completed and turned in to maintenance control, the planner or scheduler should note any additional work required and see that it gets done according to priority.
Since inspection or preventive maintenance is a standardized procedure with little variation, the tasks and time required can be accurately estimated. Methods of developing time estimates include consideration of such resources as the following:
1. Equipment manufacturers' recommendations
2. National standards such as Chilton's on automotive or Means' for facilities
3. Industrial engineering time-and-motion studies
4. Historical experience.
Experience is the best teacher, but it must be carefully critiqued to make sure that the ''one best way'' is being used and that the pace of work is reasonable.
The challenge in estimating is to plan a large percentage of the work (preferably at least 90%) so that the time constraints are challenging but achievable without a compromise in high quality. The tradeoff between reasonable time and quality requires continuous surveillance by experienced supervisors. Naturally, if a maintenance mechanic knows that his work is being time studied, he will follow every procedure specifically and will methodically check off each step of the procedure. When the industrial engineer goes away, the mechanic will do what he feels are necessary items in an order that may or may not be satisfactory. As has been discussed in earlier, regarding motivation, an experienced preventive maintenance inspector mechanic can vary performance as much as 50% either way from standard, without most maintenance supervisors recognizing a problem or opportunity for improvement. Periodic checking against national or time-and motion standards, as well as trend analysis of repetitive tasks, will help keep preventive task times at a high level of effectiveness.
ESTIMATING LABOR COST
Cost estimates follow from time estimates simply by multiplying the hours required by the required labor rates. Beware of coordination problems where multiple crafts are involved. For example, one ''Fortune 100'' company has trade jurisdictions that require the following personnel in order to remove an electric motor: a tinsmith to remove the cover, an electrician to disconnect the electrical supply, a millwright to unbolt the mounts, and one or more laborers to remove the motor from its mount. That situation is fraught with inefficiency and high labor costs, since all four trades must be scheduled together, with at least three people watching while the fourth is at work. The cost will be at least four times what it could be and is often greater if one of the trades does not show up on time. The best a scheduler can hope for is, if he has the latitude, to schedule the cover removal at say, 8:00 a.m. , and the other functions at reasonable time intervals thereafter: electrician at 9:00 , millwright at 10:00 , and laborers at 11:00 .
It is recommended that estimates be prepared on ''pure'' time. In other words, the exact hours and minutes that would be required under perfect scheduling conditions should be used. Likewise, it should be assumed that equipment would be available from production immediately. Delay time should be reported and scheduling problems should be identified so that they can be addressed separately from the hands-on procedure times. Note that people think in hours and minutes, so 1 hour and 10 minutes is easier to understand than 1.17 hours.
Most parts and materials that are used for preventive maintenance are well known and can be identified in advance. The quantity of each item planned should be multiplied by the cost of the item in inventory. The sum of those extended costs will be the material cost estimate. Consumables such as transmission oil should be enumerated as direct costs, but grease and other supplies used from bulk should be included in overhead costs.
Feedback from Actual
The time and cost required for every work order should be reported and analyzed to provide guidance for more accurate planning in future. It is important to determine what causes the task and times to change. Blindly assuming that the future will be like the past, or even that the past was done perfectly, may be an error. Comparisons should certainly be made between different individuals doing the same tasks to evaluate results in the amount of time required, what was accomplished during that time, quality of workmanship, and equipment performance as a result of their efforts.
Some people will argue that setting time standards for preventive maintenance is counterproductive. They feel that the mechanic should be given as much time as he desires to ensure high-quality work. This is generally not true. In fact, the required tasks will generally expand or contract to fit the available time. Preventive maintenance inspection and lubrication can in fact be treated as a production operation with incentives for both time performance and equipment uptime capability. The standard maintenance estimating and scheduling techniques of time slotting, use of ranges, and calculations based on the log-normal distribution may be followed as reliable data and analytical competence are established. Since preventive maintenance time and costs will typically comprise 30-60% of the maintenance budget, accurate planning, estimating, and scheduling are crucial to holding costs and improving profits.
Scheduling is, of course, one of the advantages to doing preventive maintenance over waiting until equipment fails and then doing emergency repairs. Like many other activities, the watchword should be ''PADA,'' which stands for ''Plan-a-Day Ahead.'' In fact, the planning for inspections and preventive activities can be done days, weeks, and even months in advance to assure that the most convenient time for production is chosen, that maintenance parts and materials are available, and that the maintenance workload is relatively uniform.
Scheduling is primarily concerned with balancing demand and supply. Demand comes from the equipment's need for preventive maintenance. Supply is the availability of the equipment, craftspeople, and materials that are necessary to do the work. Establishing the demand has been partially covered in the sections on on-condition, condition monitoring, and fixed interval preventive maintenance tasks. Those techniques identify individual equipment as candidates for preventive maintenance.
When the individual pieces of equipment have been identified for preventive maintenance, there must be a procedure for identifying the order in which they are to be done. Not everything can be done first. First In-First Out (FIFO) is one way of scheduling demand. Using FIFO means that the next preventive task picked off the work request list, or the next card pulled from the file, is the next preventive maintenance work order. The problem with this ''first come, first served'' method is that the more desirable work in friendly locations tends to get done while other equipment somehow never gets its preventive maintenance. The improved method is Priority = Need Urgency Customer Rank Equipment Criticality. The acronym NUCREC will help in remembering the crucial factors.
NUCREC improves on the Ranking Index for Maintenance Expenditures (RIME) in several ways:
1. The customer rank is added.
2. The most important item is given the number-one rating.
3. The number of ratings in the scale may be varied according to the needs of the particular organization.
4. Part essentiality may be considered.
A rating system of numbers 1 through 4 is recommended. Since most humans think of number 1 as the first priority to get done, the NUCREC system does number 1 first.
Need urgency ratings include:
1. Emergency; safety hazard with potential further damage if not corrected immediately; call back for unsatisfactory prior work.
2. Downtime; facility or equipment is not producing revenue.
3. Routine and preventive maintenance.
4. As convenient, cosmetic.
The customer ranks are usually as follows:
1. Top management
2. Production line with direct revenue implications
3. Middle management, research and development facilities, frequent customers
4. All others.
The equipment criticality ratings are as follows:
1. Utilities and safety systems with large area effect
2. Key equipment or facility with no backup
3. Most impact on morale and productivity
4. Low, little use or effect on output.
The product of the ratings gives the total priority. That number will range from 1 (which is 1 1 1) to 64 (4 4 4). The lowest number work will be first priority. A ''1'' priority is a first-class emergency. When several work requests have the same priority, labor and materials availability, locations, and scheduling fit may guide which is to be done first.
The priorities should be set in a formal meeting of production and maintenance management at which the equipment criticality number is assigned to every piece of equipment. Similarly, a rank number should be applied to every customer and the need urgency should be agreed on. With these predetermined evaluations, it's easy to establish the priority for a work order either manually by taking the numbers from the equipment card and the customer list and multiplying them by the urgency or by having the computer do so automatically. Naturally, there may be a few situations in which the planner's judgment should override and establish a different number, usually a lower number so that the work gets done faster.
Ratings may rise with time. A good way to ensure that preventive maintenance gets done is to increase the need urgency every week. In a computer system that starts with preventive maintenance at 3, a preventive task that's to be done every month or less frequently can be elevated after one week to a 2, and finally to a 1 rating. Those increases should ensure that the preventive task is done within a reasonable amount of time. If preventive maintenance is required more often, the incrementing could be done more rapidly.
Dispatch of the preventive maintenance work orders should be based on the demand ordered by priority, consistent with availability of labor and materials.
As discussed earlier, predictive maintenance provides a good buffer activity in service work, since time within a few days is not normally critical. The NUCREC priority system helps ensure that the most important items are done first.
Some pressure will be encountered from production people who want a particular work request filled right away instead of at the proper time in the priority sequence. It can be helpful to limit the ''criticality 1'' equipment and ''rank 1'' customers to 10%, since, according to Pareto's Principle of the Critical Few, they will probably account for the majority of activity. If rank 2 is the next 20%, rank 3 is 30%, and the balance is 40% for rank 4, the workload should be reasonably balanced. If temporary work needs exist for selected equipment or a customer needs to be given a higher priority, then equipment should be moved to a lower criticality for each equipment that's moved higher. After all, one objective of prioritization is to ensure that work gets done in proper sequence.
A preventive maintenance action that's done on time should ensure that equipment keeps operating and that emergency work is not necessary.
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Truck 3500 Mile Oil Change
PURPOSE: List cautions and steps required for changing oil.
REFERENCE: Driver's manual for vehicle.
Ensure vehicle is blocked securely before going under it.
CAUTIONS: Hot oil from a recently operating motor can burn.
Ensure adequate ventilation when running gas or diesel engine.
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ill. 4.1 A typical preventive maintenance procedure.
ill. 4.2 Logic for inspection findings.
Coordination with Production
Equipment is not always available for preventive maintenance just when the maintenance schedulers would like it to be. An overriding influence on coordination should be a cooperative attitude between production and maintenance.
This is best achieved by a meeting between the maintenance manager and production management, including the foreman level, so that what will be done to prevent failures, how this will be accomplished, and what production should expect to gain in uptime may all be explained.
The cooperation of the individual machine operators is of prime importance.
They are on the spot and most able to detect unusual events that may indicate equipment malfunctions. Once an attitude of general cooperation is established, coordination should be refined to monthly, weekly, daily, and possibly even hourly schedules. Major shutdowns and holidays should be carefully planned so any work that requires ''cold'' shutdown can be done during those periods.
Maintenance will often find that they must do this kind of work on weekends and holidays, when other persons are on vacation. Normal maintenance should be coordinated according to the following considerations:
1. Maintenance should publish a list of all equipment that's needed for inspections, preventive maintenance, and modifications and the amount of cycle time that such equipment will be required from production.
2. A maintenance planner should negotiate the schedule with production planning so that a balanced workload is available each week.
3. By Wednesday of each week, the schedule for the following week should be negotiated and posted where it's available to all concerned; it should be broken down by days.
4. By the end of the day before the preventive activity is scheduled, the maintenance person who will do the preventive maintenance should have seen the first-line production supervisor in charge of the equipment to establish a specific time for the preventive task.
5. The craftsperson should make every effort to do the job according to schedule.
6. As soon as the work is complete, the maintenance person should notify the production supervisor so that the equipment may be put back into use.
Overdue work should be tracked and brought up to date. Preventive maintenance scheduling should make sure that the interval is maintained between preventive actions. For example, if a preventive task for May is done on the 30th of the month, the next monthly task should be done during the last week of June. It is foolish to do a preventive maintenance task on May 30 and another June 1, just to be able to say one was done each month. In the case of preventive maintenance, the important thing is not the score but how the game was played.
Opportunity Preventive Maintenance Activities
It is often helpful to do preventive maintenance when equipment suddenly becomes available, which may not be on a regular schedule. One method called Techniques of Routine Interim Maintenance (TRIM) was covered in the preceding section. TRIM means generally that specified cleaning, inspection, lubrication, and adjustments are done at every service call. TRIM can be very effective.
Another variation is to convert (or expand) a repair call to include preventive activities. A good work order or service call system will quickly show any preventive maintenance, modification, or other work due when equipment work is requested. The system should also check parts availability and print pick lists. Parts required for preventive maintenance replacement can then be taken to the site and all work done at one time. Unless production is in a hurry to use the equipment again as soon as possible, doing all work on a piece of equipment during the single access is much more efficient than having to gain access several times to perform a few tasks each time.
A formal record is desirable for every inspection and preventive maintenance job. If the work is at all detailed, a checklist should be used. The completed checklist should be returned to the maintenance office on completion of the work. Any open preventive maintenance work orders should be kept on report until the supervisor has checked the results for quality assurance and signed off approval. Modern computer technology with handheld computers and pen-based electronic assistants permit paperless checklists and verification. In many situations, a paper work order form is still the most practical medium for the field technician. The collected data should then be entered into a computer system for tracking.