When someone talks about his/her predictive maintenance (PdM) program, we commonly hear about great saves and machinery problems that have been resolved. This would lead most of us to believe that these programs are thriving and well-funded with well-trained, happy personnel. Unfortunately, more often than not, this simply isn’t the case.

Today many PdM programs are dying on the vine—with staff either retiring or returning to the shop floor to perform their previous jobs as tradesmen. In some cases, this exodus seems to be associated with plant management not responding to machinery trouble calls generated by the program. As a result, frustration percolates within the PdM program staff over a perceived lack of appreciation by maintenance or plant management for the usefulness of the PdM program and the value of the results it produces. Interestingly, one of the main contributors to this situation is the type of reports that the typical PdM program produces.

Who wants to know and how? Technical reports can range from simple raw data output to complex documents that are so detailed they defy understanding. Seldom do the authors/providers of these reports consider the needs and capabilities of their readers. It is, therefore, very important to ask the question: "What kind of report will be responded to best?" The first step in answering it is to determine what type of person the reader is and to what that person responds to.

Human behavior shows us that there are four basic personality types* we may encounter. Even though these types may blend together in most people, there typically will be a dominant type that can be used for our purposes. By understanding the type of person you are dealing with, you can create reports that will be better received. Let’s look at these four types and what they want to see in a report.

Driver…

The first and most common type of personality that you may see in management can be described as a "Driver"—a no-nonsense multitasking person that many consider to be a type-A personality. Drivers don’t have time for details! They want to know what’s wrong, what to do, when to do it and why. Time is the big factor here. If you can get more than 10 seconds of a Driver’s attention for your 20-page report, you are lucky. As a result, detailed multi-page reports with pictures and graphs are not the right things for these people. Raw data that has to be examined also will probably go directly into the trash can or, at best, the filing cabinet.

Drivers want simple precise reports that tell them what needs to be done and in what order. Data and long descriptions are not necessary. This does not mean that you don’t need to be prepared to answer questions now and then. When asked, provide the Driver with brief and specific answers. He/she may be testing you to be sure your recommendations can be trusted. Once this person is convinced that you are providing valid information that is helpful to his/her job, you probably will have a strong supporter.

When dealing with a Driver, remember that simple, to-the-point and valid are best. Large print helps as well.

Amiable…

The opposite of the Driver is the type of person we can refer to as "Amiable." These people are easily recognized by their desire for personal contact.

Amiable people like forming relationships with those they work with. They will want you to go over the report with them and take the time to answer questions to their satisfaction. Trust is very important with Amiable types.

A simple report—similar to what is used for the Driver— is fine, but again it is important to be prepared to go over the report with them. Amiables will appreciate the time you spend in making them comfortable with your recommendations. If there is any doubt about the report format, sit down with these people and design the report to their satisfaction. It also is important to show that you care about how they respond to your reports.

Expressive…

The third type of person you may run into can be described to as "Expressive." These people are very active, animated, multitaskers who are interested in the "BIG PICTURE." Colorful reports that include charts and graphs along with the overall department and plant condition are essential. Excessive detail should be avoided, but you should be prepared to provide data and artwork that can be used for presentations and wall hangings. When given the right kind of reports, Expressives will be among your biggest and most vocal supporters.

On the other hand, it is important to keep control of the report process. Expressive managers may ask for more than they need or can digest. Another word of caution is to take special care to establish a process to ensure that the work is done and results are measured as a result of report recommendations. In short, Expressive people sometimes have short attention spans. Enough said.

Analytical…

The fourth and final personality type can be referred to as the "Analytical." Surprisingly, this may be the most difficult type of person for whom you ever will generate reports.

Analyticals like lots of data to study. In many cases, these individuals are successful engineers and technicians who have advanced into management. You may notice that their offices are cluttered with prints, spec. sheets, parts and—unfortunately—reports. They enjoy technology and processes. They always will want more data to examine. Yet, they may not decide what do with your recommendations. This can drive you crazy. As a result, Analytical types may be the hardest to work with.

The reports you provide to Analytical managers should include the basics coupled with some supporting data to back up you recommendations. Let them ask you for more information as needed—then meter out additional details to them sparingly. By doing this, perhaps you can get them to take action. Good luck!

For all types, a simple report generally is best. Too much data challenges the reader to join in the analysis. This can be annoying to a Driver (who typically doesn’t want to waste time); intimidating to an Amiable (who wants you to talk to him/her); confusing for an Expressive (who only wants to see the "BIG PICTURE"); and downright self-destructive for an Analytical (who will immerse himself/herself in the data, never to be heard from again).

In the end

Keep in mind that it is useful to form a "supplier/customer" relationship with those who receive your reports. In essence, your report is the product of your work. To be successful, though, this product must meet the reader’s needs.

Just like a good newspaper or a well-developed Website, a report should communicate the right message to the right people to evoke the desired action—i.e. a response that results in your recommendations being acted on. If this helps create a better running, more efficient and profitable workplace, your PdM program has a good chance of being successful.

Bob Martin is a district manager for Emerson Process Management’s Machinery Health Management Division. He is a CMRP, a category three vibration analyst and holds a level two lubrication certification. He has been supporting predictive maintenance practices for nearly 20 years, primarily working with industries in Detroit and surrounding areas. His experience with spectrum analysis extends back over 30 years, beginning with his work in the US Navy as an anti-submarine warfare systems operator, flying as aircrew on P-3 Orion patrol aircraft.

E-mail: bob.martin@emerson.com

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*Personality Types

Imagine that you are planning a trip. You select a destination and decide upon the route to take. You tune up the car, rotate the tires and send the dog over to stay at your sister’s. You figure your expenses, develop a travel budget and withdraw money from the bank. You ask your neighbor to keep an eye on your house and notify the post office to hold your mail. In other words, you plan your trip to the last detail. Because of this attention and preparation, you are expecting a trouble-free vacation. Not so fast!

If you don’t take the next logical step—and properly schedule the trip—you probably won’t arrive at your destination in a timely and efficient manner. In fact, you might not even get there at all! Most of us know that if we want to have a pleasant and successful journey, we must first decide who else is going with us, who will be driving, when the trip will start and how long it should take. Alas, even the best-planned trip in the world can go awry if it is poorly scheduled.

Many maintenance organizations find themselves in the same situation as many disappointed vacationers. They are planning their work to some extent, but they are not reaping the full benefit of planned maintenance because they are neglecting scheduling, which is one of the most important functions of control available to maintenance managers. It doesn’t matter how well a job is planned if it is assigned to people who do NOT have the necessary skills to complete the work…or if the maintenance team is sent out to perform maintenance or repairs on a machine that is slated to run product that day…or if a crane is required to complete the task and one has not been scheduled.

Uncontested facts
If you are going to succeed as a maintenance manager, you must plan your work—that is an uncontested fact. Furthermore, if you are going to succeed at planning, you must properly schedule that which you have planned. Planning and scheduling are actually two sides of the same coin. It is not possible to do either properly without taking the other into account.

In a sluggish economy, upper management may be hesitant to approve the additional expense associated with adding positions. The answer to that argument is elementary, but it seems that it must be restated again and again—usually every time the economy takes a downward turn. Positions such as planner, scheduler, maintenance clerk and reliability engineer pay for themselves in very short order. As such, they are an investment, not an expense. It isn’t a case of stating that a maintenance department really ought to have these positions staffed. Rather, it is an often documented fact that no maintenance organization can be successful without people filling these roles.

When you schedule work, you ensure that the right people are performing the correct tasks at the proper time in the most expeditious manner. That sounds simple, but it is often the obvious truths that tend to evade us. Once you have received the green light, there are some factors that must be kept in mind as you go about the business of scheduling, particularly if you are new to the task.

A good candidate for the scheduler position will be a person with excellent organizational skills who can envision the big picture. He or she should be familiar with the manufacturing process, but the candidate does not necessarily have to come from the maintenance organization.

Each millwright, multicraft, electrician or other maintenance professional should be scheduled an amount of work equal to 110% of his/her paid time. Thus, if your maintenance personnel work a 40-hour week, they should be scheduled 44 hours of work. It is human nature to tend to slack off once it appears an assigned task will be completed in the allotted time. If, however, there’s always one more job in the queue, you may avoid this loss of efficiency late in the day. Moreover, if the jobs go exceptionally well on a given day, or if the planning times were pessimistic, the maintenance professional will not be faced with having to kill time because there are no more jobs ready to assign.

Work should be scheduled at least a week in advance from a planned backlog no smaller than the number of man-hours available in your full crew during a -to-six week period. In addition, daily adjustments to the schedule will be required as unfinished work is turned back in and newly-discovered issues are written up.

Work should be scheduled from most important (highest priority) to least important. This means that PMs and safety-related work orders take precedence work and must be done first. Then, if time runs out later in the day, the jobs that are left for rescheduling are of a lower criticality.

The cardinal rule of scheduling is that PMs always must be performed before corrective work is commenced. This sounds like an easy rule to follow, but you will be often you are tempted to break it when a previously-undiscovered maintenance issue crops up. Just remember that more than one good maintenance effort has been brought to its knees by not adhering to the PM schedule. A conscientious and well-meaning millwright will encounter a situation that seems to require immediate attention, so the PM he has been assigned will be postponed to allow time for the corrective work to be performed. Then, because the PM was not performed when it was scheduled, another situation is encountered at the next PM interval that again seems to require immediate attention, thus forcing the postponement or cancellation of another PM. Before long, no PMs are being performed because the machine seems to be in a constant failure mode. And, as long as no PMs are performed, the machine will continue to fail. It is a classic case of cause-and-effect.

All work must be scheduled. This means that the correction of any potential mechanical failures that are discovered must be worked into the schedule. It is the scheduler’s responsibility to see that the time for this unexpected work is secured by postponing other, less-important corrective work.

All planned and ready job packets should be filed according to estimated completion time. Thus, the scheduler will have a backlog of one-hour jobs, two-hour jobs, jobs by estimated time allows the scheduler to see at a glance if a particular packet will fit into a millwright’s schedule.

When the schedule isn’t met, there is a reason—and it is the scheduler’s responsibility to determine the cause. As an example, suppose a job was expected to take two hours apiece to complete, but by the time the work was finished, those two millwrights each had four hours on the project, and a third helper had been brought in for the last hour. Consequently, a job that had been estimated at six man-hours came in at nine—adversely affecting the work schedules of three separate individuals. A variety of factors that could explain the time overage are bad time estimates, an incomplete job plan, employee attitude and motivation, wrong parts, undiscovered maintenance issues, inadequate training or improper scheduling of personnel or machinery. Thus, if the scheduler does not determine the cause of the time overage and address or at least make note of it, the job could be 50% over budget the next time it is performed as well.

There are many methodologies that may be employed when it comes down to the actual task of scheduling an individual’s workday. Most of the better CMMS programs have scheduling functions. If you are lucky enough to have access to one of these, for you the job is already half done. Another favorite and time-honored method is the load board, which is a large dry-erase or bulletin board on the wall that allows the scheduler to schedule for and keep track of the entire maintenance crew for a given period of time (an example of a load board can be found at http://www.magnatag.com/page/MF/board/maintenance-schedule-board.asp) Other methods to physically segregate jobs include hanging files, bins, or just piles of work packets arranged by day and employee name. The important thing is not how you separate and schedule the work. The importance and the payoff derive from the fact that you are scheduling your assets for maximum efficiency. Work should be scheduled by the day. Thus, if an individual works a five-day, 40-hour week, he or she will have five separate daily assignments of work packets, each totaling hours (remember the 110% rule).

Work must be prioritized daily. Accordingly, the first work order that the millwright executes on any given day will be the most critical or important job of the day. Generally, or a safety work order. The next work order that the millwright tackles will be the second-most critical of that day’s work. This criticality ranking will continue until the millwright runs out of time or runs out of work.

Work that is not completed on a given day must be rescheduled for the following day, ideally with a higher priority so that the project is not likely to be continuously rescheduling is a permanent and unavoidable requirement of a successful maintenance organization, it is recommended that the scheduler work slightly different hours than the millwrights. The scheduler should either stay later than the maintenance workers or start earlier—so that there is time to reschedule the workloads on a daily basis according to unfinished jobs or newly-discovered maintenance issues. One advantage to staying a little later is that the scheduler can preview the following day’s work with the millwrights so that those individuals can began to think about the jobs they will be performing during their next work shifts.

Scheduling success
For scheduling to be successful in your organization, it must become part of your maintenance culture. Your maintenance professionals must come to understand its function, its purpose and its importance. They must realize it is the company’s expectation that the daily workload they have been given is to be done in the assigned order of priority—in a timely manner and correctly. This enculturation cannot occur if it appears that scheduling is only occurring when it is convenient for management. So, the scheduler cannot be pulled away from his or her duties for days or weeks at a time and assigned other tasks. Scheduling will fail under these conditions.

Remember, scheduling is actually asset control. It is the company deciding what work will be done by whom, when. What company can afford to neglect this important function? Ray Atkins, CPMM, CMRP, is a veteran maintenance professional with 14 years experience in the lumber industry. He is based in Rome, GA, where he spent the last five years as maintenance superintendent at Temple-Inland’s Rome Lumber facility. He can be reached at raymondlatkins@aol.com or throughout his Web site, www.raymondlatkins.com

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If one of your loved ones needed surgery, would you entrust his/her health and safety to a handy, but virtually untrained doctor? If you needed to make a trip by air, would you place your future in the hands of an individual who had good intentions, but no pilot's license? The next time tax season rolls around, are you going to hire an accountant who has done taxes his whole life without really understanding the nuances of the tax code? The answer to these questions is, of course, a resounding no.

We would be foolish, indeed, to engage the services of unprepared professionals such as those described in the opening paragraph. Yet, that's exactly what we, as maintenance managers, do when we send untrained craftspersons out into our processes to perform tasks for which they have been poorly prepared.

At this point in history, the average manufacturing facility routinely operates with technology more sophisticated than what first put men on the moon. In light of ever-increasing complexities on the plant floor, the days of the self-trained millwright are drawing to a close.

We all know the craftspersons I am referring to—they are the backbone of a maintenance organization. They are intelligent, quick-witted and good with their hands. They are hard-working, conscientious and accountable. And they are having a harder time each year keeping the plant running because the highly technological nature of today's manufacturing machinery precludes their reliance on intuition, common sense and the ways in which a task always has been performed before.

Nowadays, millwrights and multicrafts must be trained if they—and your company—are to succeed. Wanting to, working longer and harder and just being lucky are no longer sufficient strategies.

Beginning a new training program for a maintenance department— or improving an existing one—is a large and unwieldy undertaking, especially if you attempt it all at once. It can be a thankless, expensive proposition that often is difficult to justify to upper management. The key to succeeding is to prioritize, to tackle what you can when the opportunity arises and to attempt no more at any one time than you can successfully accomplish. Remember the old joke that asks about the best way to eat an elephant; the answer is "one bite at a time." That's the methodology you must employ when initiating a training regimen.

As you consider the following suggestions and techniques, keep in mind that it is better to perform one or two of these methods well than it is to execute all of them poorly. A journey of 10,000 miles begins with the first step. The following list reflects steps in the right direction. Give some serious thought to them. 

Evaluations. In order to be able to decide where and how you want to go, you will need to determine where you are now. To do that, you must assess the skill level of your maintenance staff before you determine your training priorities.

Please note that this is a hands-on assessment. The idea is to determine what your craftspersons can actually do as opposed to what they think they know. This will take some time, since each individual will need to demonstrate his or her level of competence based on criteria that you have determined to be important to your plant. If employee "A" does not need to weld, then evaluating for welding skill is a waste of time. If employee "B" is not rated for electrical repairs, then there is no point in having him or her demonstrate the wiring of a motor.

Take care to assure all of your maintenance professionals that the evaluation process is for training purposes only. A loss of the workforce's trust will doom any further efforts to failure. It is best to engage an independent assessor—such as a local technical college or an independent contractor—to avoid conflicts of interest, whether real or perceived. 

Mentoring. Nationwide, the maintenance workforce is aging, and one by one, the technicians, millwrights and journeymen who have kept industrial America running for the past four decades are signing up for their pensions and heading for their favorite fishing spots. The next time you have a maintenance meeting, take a look around the room and ask yourself how many of the faces you see will be there in 10 years. Then imagine how well your operations will run when the knowledge that those people possess retires with them.

Now is the time to put a stop to the brain drain. If your facility is like most, your maintenance personnel work in pairs for safety. One of the most important steps that you as a manager can take is to team the veterans with the rookies, so that the hard-won know-how that the senior millwrights possess can be passed on to the next generation.

Some very useful information on the mentoring process can be found at: www.managementhelp.org/guiding/ mentrng/mentrng.htm#anchor4294744861

Apprenticeships. In reality, an apprenticeship is a more formalized form of mentoring. For generations, it was the preferred method of training millwrights and craftspersons. The primary difference between the mentoring and apprenticing approaches is that in an apprenticeship program, promotions and pay raises are often linked to achievement of competencies.

Apprentice programs are an excellent training method, but it is important to have a third-party independent assessment when the time for a skills demonstration rolls around. Otherwise, a strain in the Master-Apprentice relationship can result, particularly if mastery has not been achieved on a training module.

More information on the establishment of an apprenticeship program can be found at: www.doleta.gov/ jobseekers/apprent.cfm

Technical College Affiliations. The average maintenance employee generally has some idle time during the course of the work week. One positive alternative to having another coat of paint applied to the handrails is to send the tradesperson to school in a formal setting.

Many technical colleges now have programs of study that are designed to train the new generation of maintenance professionals. The ideal programs are those that combine theoretical "book learning" with hands-on experience. In order for this type of educational experience to work, it must be mandatory—and the maintenance technician should be paid to attend and successfully complete the classes. Thus, you need to be sure that the courses you require are conducted during the employee's normal work week.

If you have a large number of employees to train, many technical colleges will agree to provide on-site instruction. Contact the community relations officer at your local institution for more information on this type of training opportunity. 

Trainers. For years, maintenance organizations have taken their best millwrights and technicians and promoted them to supervisory, planning and scheduling positions. An alternative to this practice is to create the position of "Trainer."

Similar in function to mentoring, this approach provides one mentor for the entire crew. It is an ideal strategy for smaller organizations whose maintenance professionals do not work in teams in that it still allows for the transfer of knowledge from those that have it to those that need it. 

Factory or Field Representatives. An inexpensive source of knowledge is available to your organization in the form of factory or vendor field representatives. Quite simply, the suppliers of your parts are more than happy to send someone to your organization to instruct your people on the proper installation of those parts. There is generally a commercial announcement or two during these programs, but the training quality is usually quite high.

It is best to schedule these supplier-led sessions when most or all of your employees can be at the presentation. Some examples of representatives who are happy to come out and instruct your people include bearing suppliers, cylinder manufacturers, belting and hose vendors and fastener providers. 

Hi-Tech Avenues. Simply sitting your maintenance personnel down in front of a video, CD or computer module does not make a training program. Still, the presentation of information in this manner can have its place in your overall educational agenda.

There are several excellent video courses of study available that cover general topics such as hydraulics, pneumatics, bearing installation, lubrication and the like. The key to this type of knowledge transfer is to always couple it with a session of hands-on training. In other words, after you show the video on how to make a hydraulic hose, take everyone out and have them make a hose to your specifications.

The various branches of the military train their personnel endlessly, but they also conduct maneuvers on a regular basis. This way, the theoretical knowledge that the service members receive can be reinforced by hands-on application of that knowledge. The same type of strategy offers value for your plant. 

Reference Libraries. Every maintenance organization should have a reference library dealing with—at a minimum—the trades and crafts involved in the upkeep and repair of the manufacturing process, as well as the manuals and specification books for the machinery in that process. 

Specialization. Regardless of how your maintenance organization is compartmentalized, you should have two types of employees if you wish to be successful.

First, all of your personnel need to be good generalists in their fields. Secondly, each person needs to have a specialty on top of their general base of knowledge. Translation: all of your millwrights need to be able to diagnose and repair pneumatic issues, but one of them needs to be a fully-trained, factory-certified pneumatic expert, someone who can step in when an unusual situation occurs that requires a deeper level of understanding.

The same is true for the many other specialties or applications in your process, from hydraulics to welding to pipefitting to PLCs. Most manufacturers of industrial components offer formal schooling to their customers, and the enrollment of selected candidates at these factorysponsored facilities is money well spent. 

Making it happen
There are two factors to keep in mind when you undertake the building of an effective training program.

The first is achieving employee buy-in. It is critical that you have the support of your hourly professionals if you wish to change your maintenance reality. They must realize the value of the educational enterprise if it is to be a successful venture.

As you consider the best ways to begin or enhance your training efforts, keep the intended recipients of this education in the loop. If possible, they should participate in the construction of the course of study. If you let them provide input at the development stage, they will have a vested interest in the success and value of the outcome.

The second factor is gaining the support of upper management if you want a more skilled workforce. Training is not a program. It is a process—one that doesn't expire at the end of the quarter or the current fiscal year and doesn't get suspended when economic times get hard.

Remember, the price of continued improvement of your process is commitment to training by all concerned parties, from the newly-hired maintenance trainee to the president of the company. Moreover, the ultimate goal of excellence in your process can only be attained if that price is paid year-in and year-out.

Ray Atkins, CPMM, CMRP, is a veteran maintenance professional with 14 years experience in the lumber industry. He is based in Rome, GA, where he spent the last five years as maintenance superintendent at Temple-Inland's Rome Lumber facility. He can be reached at raymondlatkins@aol. com or through his Website, www.raymondlatkins.com

Installation and mounting errors are responsible for 27% of all bearing failures, second only to lubrication problems (see Fig. 1). Most installation errors can be avoided through proper training, correct procedures and selection of products with design features that are compatible with operating conditions of the application.

The most common mounting and installation causes of bearing failure along with some recommended approaches for avoiding these problems are detailed here:

• Insufficient Tightness—When installing a bearing, it must be correctly forced up its tapered adapter sleeve. Improperly tightened bearings and adapter assemblies may slip or turn on the shaft. Over-tightening can reduce a bearing's internal clearance and cause it to run hot.

  Historically, in adapter-mounted bearings the point at which the installer reaches a sufficient amount of locknut tightness has been difficult, if not somewhat cumbersome, to achieve. An installer would either use feeler gauges to measure the amount of clearance reduction in the bearing when tightening the locknut, or tighten a locknut a fixed amount after it had been snugged tight with a spanner wrench to take out the clearance between the mounting components.

  Using feeler gauges to measure the clearance reduction in a bearing while mounting is time consuming and can be inaccurate if the gauges are not properly read. The problem with tightening the locknut a fixed amount after it has been snugged tight is that when snugging up the locknut the amount of snug tightness varies from one installation to the next, depending on the installer. If the feeler gauges are not properly read or the amount of locknut snug fit is not just right, the mounting can be left too loose or too tight.

  To overcome these problems, bearings that actually help an installer determine when they are properly tightened are available (see Sidebar 1).

• Incorrect Shaft Diameters—Typically, commercially available shafting is used in most applications due to cost. These shafts usually have a fairly wide range of under-nominal size diameters.

  The proper shaft mounting option is crucial when selecting a bearing. Bearings that use spring and eccentric cam locking collars (see Fig 2 and Fig 3) are subject to excessive fret or possible fracture of the inner ring when the shaft is undersized by more than one to two thousandths of an inch depending on the size.

  Bearings that use tapered adapter sleeves usually can mount to commercial grade shafting without hindering the service life of the bearing. These bearings are provided with housings, and the housing seat diameters are properly sized before they leave the factory. Prior to bearing selection (and installation), the shaft should be inspected and measured with micrometers. This will ensure that the proper bearing mounting type is utilized to avoid service issues as a result of the mounting.

• Defective Shaft—Shafts should be clean, round, straight and smooth before mounting. New shafts can be damaged during handling and should be checked for nicks, gouges and deep scratches. These areas should be made smooth with a fine file and/or emery paper. Areas where shaft material has been raised also will need to be made smooth. The shaft should be checked for straightness, something that typically can be done by using a straight edge or framing square.

  In the case of a worn shaft where there may be fret wear, the bearing seat should be sanded with emery paper and any ridges or burrs made smooth. The worn bearing seat must be measured for proper size. Use a micrometer to check the size of the shaft and verify that it is within specification for the bearing that is to be mounted.

• Misalignment—Misalignment of the shaft with the bearing's housing can be caused by an imprecise mounting frame, shaft and/or housing support deflections or housing-to-shaft squareness. This misalignment is ideally compensated for by dynamically aligning rolling element bearings.

  Installation should be as accurate as possible, even when dynamically aligning bearings are used. Misalignment beyond the bearings' limits can cause damage to the internal components and possibly the seals.

  During installation it is usually most effective to measure the ends of the shaft from a common reference (typically the mounting frame) for a vertical alignment and between the housing feet for a horizontal alignment. There are more accurate methods to measure the alignment of the shaft to the bearings (using laser sights, for example). The most basic signs that a bearing is out of specified alignment are that it usually will vibrate excessively, run hot and/or make an objectionable noise.

• Improper Bearing Support Surfaces—The surface of the machine's frame where the bearing is to be attached must be flat and smooth. An out-of-flat or excessively rough mounting surface can cause stress concentrations to occur in the bearing's housing. Over time the housing may become subject to structural fatigue failure, especially if the load through the bearing is directed away from the housing's base.
• Lack of Expansion Provisions—During the operation of equipment, the heat flow through the shaft will cause it to expand. The amount of expansion that is realized must be compensated for by an allowance of axial clearance. If the expansion of the shaft is not taken into account in the bearing selection, the internal clearance in the bearing may be reduced to zero and the bearing will fail prematurely. The internal axial clearance of the bearing may be enough if the shaft's temperature increase is low. A general rule-of-thumb is that if the bearings are less than 36" apart, the shaft and mounting frame are both steel, and there are no external heat sources or elevated levels of ambient surrounding temperature, then two fixed bearings can be used. Otherwise, a floating bearing should be used that can move axially relative to the position of the housing.
• Abusive Handling—During bearing preparation and installation, it is extremely important to maintain cleanliness. Keep dirt, water and metal chips off all parts. Hammer blows, external heat sources (torches) or the improper use of force can damage the bearing's precision parts. Always refer to the bearings service instructions on how to properly install or remove bearings. Bearings that operate over long periods of time can develop deposits of lubricant and hard residues that may affect bearing performance detrimentally. A periodic cleaning of the bearing surfaces assures that accumulation of such substances will not hinder performance or service life. Always lock out/tag out the electrical service in the off position to any rotating equipment before servicing its bearings. Handling the bearing's internal components with bare hands can be harmful to the exposed metal surfaces. The acidic moisture on bare hands will corrode the bearing's exposed metal surfaces. Bearings should never be spun without being internally lubricated. In some cases, bearing units are shipped to customers with preservative only where the customer intends to use a special lubricant. Metal surface preservatives work best when the metal components are wrapped in protective paper or vacuum sealed. Sudden relative motions and long-term storage in housed units where humidity is present can cause surface damage. In addition, if bearings are stored for long periods of time, it is a good idea to lubricate the bearing and rotate the bearing by hand to distribute the lubricant.

In conclusion
A little care during the installation and mounting process can go a long way toward extending bearing life. A small error can be magnified in downtime, replacement costs and possible damage to equipment or other products. Don't let your operations fall victim to such errors.

Marlon Casey is manager of Advanced Technology & Product Design with the Rexnord Bearings Division in Indianapolis, IN.

Bearing Installation Simplified: Tighten ‘Em Just Right

One manufacturer has designed a bearing that addresses the problem of determining when a bearing is properly tightened. The Rexnord® ZAF6000 series SHURLOK® spherical roller bearings are solid-housed, shaft-ready units that are a drop-in to replace traditional SAF units. They are greased and the clearance is preset, so they can be taken out of the box and mounted immediately to the shaft. These new bearings incorporate a patented Spyglass® Optical Strain Sensor (OSS) that provides instant feedback when the locknut has been strained enough to achieve optimal shaft grip. This device tells the installer when the locknut is sufficiently tight, thus eliminating damage to the shaft and bearing caused by improper tightening during installation. As a full-field strain indicator, the new Spyglass OSS incorporates materials that respond to strain in the locknut by changing reflected light wavelengths. As ambient white light is reflected through the sensor, it appears clear when the locknut is in an unstrained state. The sensor will isolate the specific color band wavelengths within the white light, depending on the direction and magnitude of strain within a tightened locknut. The sensor is calibrated so that the window stays clear until there is enough strain on the locknut to provide sufficient mounting tightness. At that point, a specific color can be seen in the window showing that the minimum threshold of load has been reached. A positive locking system also has been incorporated into the mounting design of units in the ZAF6000 line to maintain mounting tightness during operation. The inner ring is keyed to the adapter sleeve and the adapter sleeve is locked to the locknut with radial set screws that provide a superior spring locking shaft grip. Along with a positive locking system, the tapered sleeve is flanged, making it easy to remove the bearings from the shaft without causing damage, saving both time and repair costs.

Klein Tools has introduced a new line of highperformance specialty chemicals including, among other things:

• Multi-Purpose Penetrant Lubricant – For use on screws, tools, motors, hinges, bearings, gears, relays, starters and generators, it penetrates through rust and corrosion and quickly loosens frozen nuts and bolts to ensure free and easy movement. Its residual anti-corrosive film leaves treated surfaces protected, while moisture is displaced in wet electrical systems to create a waterproof film that inhibits corrosion and electrical discharge. The all-purpose, non-flammable, non-conductive, and non-chlorinated spray features a 39,000 volt dielectric strength, and is safe around most plastic and paint.
• Dielectric Silicone Grease – This translucent white, grease-like silicone paste maintains flexibility of natural and synthetic rubbers, vinyls, plastics, rubber or plastic O-rings. Its moisture-proof seal suits aircraft, automotive and marine ignition systems and spark plug connections, waterproof electrical connections, electrical assemblies and terminals. The automatic dispensing can and nozzle allow for even and uniform application to eliminate waste, mess and lumps.
• Clear RTV Silicone Adhesive – Available in a low-odor and a general-purpose formulation, this clear RTV silicone adhesive is packaged in an automatic dispensing can with nozzle. The adhesive's gel-like, single component material cures to a rubbery solid when exposed to moisture in the air. Resistant to ultraviolet light, it will not sag, slump or run off, and adheres to metal, glass, most types of oily wood, vulcanized silicone rubber, silicone resins, natural and synthetic fibers, ceramic, paper and many painted or plastic surfaces.
• Electrical Cable and Equipment Cleaner – Effective on circuit boards, controls, switches and relays, this nonflammable, non-conductive, non-carcinogenic cleaner evaporates quickly without leaving residue. For use in cleaning oxidation, dust and light oils from electrical equipment, it won't corrode metals or degrade plastics.
• Firestop Caulk – Its cured red silicone rubber composition provides excellent performance stability and a pressure- tight seal that prevents the spread of fire, smoke and toxic gases through service penetrations. A patented char composite contains graphite, which expands when exposed to temperatures in excess of 300 F (150 C). The cartridge fits manual or air-operated caulking guns and is suitable for AB/PVC, flexible foam insulated copper pipe, PEX process and supply tubing penetrations, metallic pipe and electrical cable penetrations.

Klein Tools
Lincolnshire, IL

New Wrench Kit Helps Save Time And Knuckles

Lowell Corporation's new 511X Wrench Kit gives workers greater freedom and leverage in tight spots while reducing the risk of injuries. Designed for rugged applications typically found in plant maintenance, repair, operation and production as well as construction and pipeline work, this new kit incorporates Lowell's Model 51QR ratchet handle and five, hexagonal deep well sockets (7/8", 15/16", 1 1/16", 1 1/8" and 1 1/4"). All components are packaged in a heavy-duty molded plastic case.

Each socket is 3 1/2" long, giving workers an extended reach so that the wrench handle is able to clear many common obstacles. This extra clearance not only reduces the risk of injury, but also gives workers a wider swing. For additional flexibility and utility, the wrench handle incorporates Lowell's unique Bolt-Thru design. This feature allows bolts to pass entirely through the arm head so that nuts can be secured on any threaded length.

These tools are built for hard use in a variety of applications, including those associated with mechanical joints, restraints, couplings, sleeves, repair clamps, saddles and flange bolts, among others. While the sockets are held securely in the handle with a sure-locking dead bolt, their quick-release feature allows users to quickly change them out with just the flick of a thumb.

Like all of the company's products, the machined steel sockets and cast iron handle in the 511X Kit are guaranteed against defects in material and workmanship for a period of one year from date of delivery.

Lowell Corporation
Worcester, MA

Molded Fiber Glass Tray Company high-strength fiber-reinforced polymer (FRP) composite metalparts wash-boxes cost approximately 1/3 the price of traditional stainless steel models. Designed to handle heavy payloads (150 lb. capacity), they are engineered to withstand small-part washing system chemicals and provide continuous operation at temperatures to 350 F. By minimizing the “dumps” from high-speed conveyor-to-container, use of these lighter-weight units requires less labor and reduces part damage/scrap.

Molded Fiber Glass Tray Company
Linesville, PA

Steel Bearing Alternatives

SKF’s MRC® hybrid ceramic ball bearings combine traditional steel rings with nonconductive silicon nitride balls. This combination facilitates insulating properties to prevent electrical arcing and associated surface damage. Bearings provide ideal “drop-in” replacement solutions within existing design envelopes. According to the company, these ceramic components are lighter, harder and more durable than all-steel bearings, and can run at higher speeds and lower operating temperatures.

SKF
Kulpsville, PA

What’s your definition of maintenance?

One of the most frequent remarks we hear from students taking maintenance crafts classes is: “Managers don’t want it done right. They just want to get it running again.” Such comments indicate that the students and their managers don’t truly understand the definitions of maintenance. Even in our current enlightened age of machine reliability, this misunderstanding is prevalent throughout industry. Unfortunately, before we really can progress in achieving the reliability required of our machinery, this dilemma must be solved.

A case in point
Suppose a craftsperson attends a class on drive-belt installation. In the class, the craftsperson is taught that the proper way to install belts is to reduce the shafts’ center-to-center distances and then place the belts on the pulleys. He/she is instructed to never roll the belts onto the pulleys.

Upon returning to the plant, the craftsperson receives a call from operations stating that a set of belts is smoking and must be replaced. There are only two hours left in the shift, after which, the plant will be down for eight hours. Remembering what was taught in the belt installation class, the craftsperson decides to follow the standard learned in class. Arriving at the machine he/she notices that the motor mounting bolts are rusted and cannot be easily loosened. In fact, they may have to be replaced, too.

To follow the class standard would add over an hour to replacing the belts, as opposed to cutting off the old ones and rolling on the new ones. The production manager is hovering over the craftsperson, urging that he/she get the drive up and running again. What is this individual to do? What is the proper thing to do?

In order to please the operations manager, the craftsperson decides to cut off the old belts and roll on the new. The machine is soon up and running again and the production manager pats the craftsperson on the back—congratulations for a job well done. But, the craftsperson doesn’t feel good about what has just happened, and even worries that the belts may fail because cords could have been broken in the process of rolling them onto the pulleys.

Implications
Let’s consider all the implications of performing the belt installation in the previously described manner.

• The craftsperson performed substandard work.
• The new belts probably were damaged and could fail again, leading to more downtime.
• The job probably will have to be performed again.
• The operating crew saw the craftsperson performing substandard work.
• The premature failure of the new belts could place the craftsperson in jeopardy for not performing the job to the standard for which he/she was trained.
• The sign hanging in the work area encourages personnel to “Do it right the first time,” something that was not done here. The craftsperson’s morale falls another notch.

Solutions
People are constantly faced with such dilemmas because of a basic misunderstanding that permeates industry. In order to arrive at the proper solution, let’s revisit the belt replacement and consider some additional information.

The craftsperson arrives at the machine and surveys the situation. There is much to be said for the slogan, “Do it right the first time,” and this individual considers doing maintenance on the machine by installing the belts according to the standard learned in the training class. He/she notes that there are only two hours left in the shift after which the mill will be down for eight hours. The belt failure has the production line down and the cost of lost production is $5000/hr. The cost of new belts is $400. Labor costs also will be incurred.

The craftsperson is knowledgeable of all costs and considers them. It is likely that the belts would be damaged in the process of rolling them onto the pulleys, resulting in rework. That would mean another set of belts at a cost of $400 plus labor. Not doing the job right the first time would likely double the cost of replacing the drive belts, making the total costs approximately $1000. There also is the risk of premature failure due to possible belt damage during the installation.

Having this information and knowing that the primary goal is to make profit for the company, the craftsperson weighs the costs and the risks. He/she decides NOT to perform maintenance work. Maintenance work is always performed to a standard of precision—and it requires time. The craftsperson makes this good faith decision based on the information at hand and decides to perform stopgap measures in order to resume production. He/she announces to the operating crew that maintenance will not be performed on the drive at this time, but that the belts will be rolled onto the pulley so production can start up again. Reasons for this decision are discussed with the production manager and agreement is sought.

After the production line is up and running, the craftsperson notes in the work order why the decision was made to do substandard work. He/she also initiates a follow-up work order detailing the work required to bring the machine up to plant standards.

Understanding
There clearly is confusion in industry over the true definition of “maintenance.” When we see a craftsperson using the tools of his/her trade to perform tasks on machinery, we automatically assume that maintenance work is being performed. Frequently this is not the case. He/she simply may be attempting to resume production.

Craftspeople and managers both need to know the difference between performing maintenance work and performing tasks directed at resuming operations. Only by having adequate information and knowledge can we make informed decisions that will result in the company goal of making profit. Training, coupled with improved communications, will help to erase The Great Misunderstanding.

Bill Hillman brings 30 years of experience in the steel industry and 6 years in the wood products industry to his current position as a managing partner of Asset Management Specialists Co. His entire career has been spent in working in the field of equipment asset management, including over 20 years in the area of predictive maintenance. Chairman of the Board of the International Council for Machinery Lubrication, Hillman is a Certified Maintenance and Reliability Professional, certified by the Society of Tribologist and Lubrication Engineers and a Certified Infrared Thermographer, among other things. Telephone: (903) 407-9488; e-mail: billcmrp@yahoo.com

Ouch! Holding on to Excess, often unwanted and obsolete parts really eats into your bottom line.

A storeroom is, by definition, a waste of capital. It is a bucket of money set aside for contingencies associated with the unpredictable nature of the manufacturing process.

In a perfect world, storerooms would not even be necessary. Your world-class preventive maintenance efforts would ensure that machinery seldom wore out. Parts would arrive from suppliers 10 minutes before they were scheduled for replacement based on recommendations from the predictive maintenance side of the house. Since there would be no emergencies, the need for a selection of replacement components to be kept on site would be eliminated.

In the real world, production facilities don’t operate in ideal settings; some level of spare parts availability must be maintained. Each maintenance organization must determine the minimum number of extra components necessary to sustain production and then strive to reduce excess supply with a minimum of waste.

Changing the scenario
Sometimes, storerooms seem to be stocked with the philosophy that the plant should be completely rebuildable from parts on hand. That philosophy might have merit if holding costs associated with the yearly maintenance of parts inventories did not range from 18 to 30% of the inventory’s value. On a million-dollar storeroom inventory, this translates into between $180,000 and $300,000 per year. As a result, the cost of your parts supply doubles every three to five years.

Pretty shocking, isn’t it. This is real money, too—not just an on-paper figure that the accounting department has circulated. The components of this expense include the opportunity cost of not spending the money on something else, interest, the cost of the storage facility, handling, spoilage, taxes, employees and loss.

If this picture describes your maintenance stores reality and you wish to change the scenario, you must first determine the scope of the problem. Your CMMS will be one of your most useful tools as you undertake this task, because it will allow you to identify slow-moving and non-moving inventory, overstocks and components that have become obsolete due to a change in your process. Once these superfluous parts have been identified, a systematic program of reduction and elimination must be undertaken.

Each maintenance manager must look at the available personnel in the department and assign a single person to spearhead the campaign to reduce surplus stores. The planner or storeroom coordinator would be excellent candidates for this role if some of their current duties could be shifted to free up the hour or two per day—every day—that this project will require. The designated individual should then be assigned the task of reducing inventory via the following methodology:

• Analyze suggested spare parts and stocking levels for any new equipment that is being purchased. There is a reason that this action is first. The use of suggested stocking levels provided by the manufacturers of the equipment in your plant is one of the reasons that your storeroom inventory is at unacceptable levels.
  
  From the machine manufacturer’s point of view, promoting a healthy spare parts list has the benefit of increasing their bottom line, as well as the secondary benefit of keeping breakdown times shorter. If they can convince you to purchase what amounts to most of a spare machine, they have, in effect, sold you two, and the one out on the plant floor can be repaired more quickly if it breaks down.
• Work with your machine suppliers during the design stage of new equipment so that you can take advantage of existing stocks of spare parts. This is called standardization—and it is one of the most important and cost-effective steps you can take to control storeroom inventory.
  
  If you have 17 machine centers on your manufacturing line and each is powered by a small- to medium-horsepower motor just slightly different in some manner from each of the others, you will have to stock 17 replacement motors in the storeroom. But, if some care and thought is put into standardization during the design stages, you may be able to stock only a few—and might even be able to lower the inventory to one.
• Most CMMS programs allow for automatic reordering of parts after a stores issue has occurred. This function is based on minimum and maximum inventory parameters that have been pre-programmed into the system. These reorder points and stocking levels are generally based on the manufacturer’s suggestions and should be analyzed for validity. Since the best time to reduce inventory levels is before you purchase the new part, these reorders must be scrutinized by an individual with the authority to override the system.

As an example, if you have a bearing come up for reorder because one was issued the previous day, several factors must be considered before the requisition is transmitted to your supplier. How many identical bearings are still in stock? Has a cross-reference been run to determine if any other in-stock bearings will work in the application? When was the last time one of these bearings failed? Why did this one fail? Was the issued part actually used? What is the delivery time on a new bearing? What is the criticality of the affected machine? If you normally stock two of these bearings, but you have only used one in the last three years, and the re-order time is two days, then most likely you do not need to re-order this component at present. If it turns out that temporary loss of the machine’s functionality will not cause an interruption in production, then you do not need to reorder next time, either.

It is very important to remember that reorder points and stocking levels must be formally changed in your CMMS or stores program if you decide that you can operate your process with lower levels of spares. Otherwise, the orders will just keep on coming.

• Depending on the nature of your business and geographic proximity to your suppliers, it may be possible to negotiate the staging of larger, more expensive replacements such as motors, gearboxes and pumps at the supplier’s regional sourcing areas for quick dispatch to the plant site. As an example, assume that your process includes several of a certain model speed reducer, and that it takes three hours to replace one if it fails. If your supplier is only an hour away and will agree to keep one of the gearboxes on hand, then there is no need for you to duplicate the action.
• Another method to reduce inventory costs is to share between plants on big-ticket items when such an option is geographically practical. These spares can be centrally housed and their expense shared among the locations.
• If you have a situation in which you are using a predictable quantity of a certain component in your process, this is a good candidate for consignment from your supplier. A consignment arrangement is merely an agreement to pay for an item when it is issued from the storeroom rather that when it is placed into the storeroom. Most vendors are agreeable to these types of arrangements on components that tend to move quickly. Typically, the plant must buy the parts from the supplier if they have not been used within a year.
• The actions discussed so far have dealt with delaying the procurement of spares or reducing the size of the purchase. But what should you do about the excess inventory you already own? Very simply, you must get rid of it as quickly as possible.
  
  The most preferable way to do this is to sell the parts back to the supplier you bought them from in the first place. Most vendors are agreeable to this idea provided that the part is in its original wrapping or package and not obsolete. Sometimes there may be a restocking fee assessed, but rarely will it be higher than the 18 to 30% “holding cost fee” you already are paying.
  
  To your supplier, your surplus part is an item of commerce, and if you don’t need it, one of their other customers might. Additionally, if you have held the item in inventory for several years and sell it back for its original purchase price, it often is a bargain for the supplier—who may be paying a good deal more to the manufacturers due to the impact of inflation over time.

• If your supplier does not want to repurchase, there are other avenues you can try. If your company has multiple plants, chances are that one of them may need the part you don’t need. Another option might be to offer the excess to other manufacturers and competitors in your area. Depending on your company’s policies, sales to the public or to employees also might be considered. In light of liability concerns, however, you MUST be certain to check with your legal department regarding all outside sales or disposals of excess inventory.
• The Internet can be a great resource in reducing storeroom inventories, particularly for electronic or electrical components that are easily shipped. Internet auction sites such as eBay are a possibility, as are surplus and salvage dealers who specialize in the reduction of storeroom inventories. Charitable donations to trade schools and technical colleges are yet another option to explore. Again, due to liability concerns, check with your legal department before proceeding.
• Once you have sold as much excess inventory as you can—and adjusted all of your stocking levels and reordering intervals to reflect your actual needs—you still will be left with merchandise that nobody seems to want. At this point, your choices have become limited. On the one hand, there is that very real holding cost if you keep the inventory—and it is a penalty that re-assesses every year. On the other hand, if you write off the inventory and dispose of it, the company, in effect, has spent money but received no value.
  
  A better approach might be to use these excess—unwanted—parts as tools in your maintenance training program. If you are stuck with obsolete bearings, you have an opportunity for all of your millwrights to practice bearing installation. If you have an obsolete motor, all of your multicrafts can practice wiring the motor to a switch or a breaker.

Getting it done
Keep in mind that your storeroom inventory level did not get where it is overnight. It climbed slowly but steadily over time. Consequently, its reduction also must proceed at a measured pace—if you want to avoid unnecessary waste while eliminating undesirable surplus materials.

One of the key elements in painless storeroom inventory reduction is to have one person responsible for the process, and to have that individual work at the project on a daily basis. Even if he/she can spare only an hour per day for the task of inventory reduction, the time will be well spent. TF

Ray Atkins, CPMM, CMRP, is a veteran maintenance professional with 14 years experience in the lumber industry. He is based in Rome, GA, where he spent the last five years as maintenance superintendent at Temple-Inland’s Rome Lumber facility. He can be reached at raymondlatkins@aol.com

Current limitation improves safety and reduces downtime. Dramatic improvements are possible simply by upgrading circuit protection during routine maintenance.

Any maintenance worker will tell you that he/she would rather deal with circuit breakers than fuses. In their view, finding and resetting a breaker is faster than replacing a blown fuse, increasing the time they can devote to more pressing maintenance work.

In reality, current-limiting fuses can actually reduce downtime and increase reliability. For example, a short-circuit that stops one machine can be selectively coordinated so it has no effect on the rest of the plant, and maintenance personnel can concentrate on finding the single fault rather than checking every circuit.

Current-limiting fuses and breakers also improve reliability by limiting the potential energy of an Arc-Flash and increasing short-circuit current ratings (SCCR) of industrial control panels. Electricity can be amazingly destructive, leading to explosion, fire, melted wires and shattered components. If equipment is damaged from a destructive fault or Arc-Flash, significant downtime may follow until the equipment is repaired or replaced. Moreover, if there is a serious electrical accident, a manufacturing plant can remain closed for days, or even months, before normal operations can resume.

Current-limiting devices are easily retrofitted into existing electrical systems. The job can be handled as part of normal maintenance or when a fault must be cleared, and it may be as easy as upgrading the fuse. Although current-limiting circuit breakers exist, they are more expensive and not as readily available as the current-limiting fuses on which this article focuses.

Current limitation defined
According to Article 240.2 of the National Electrical Code (NEC), a current-limiting overcurrent protective device reduces the current flowing in a faulted circuit to a level significantly less than the current that could flow if the device were not present. This essentially means that the current-limiting device opens and clears the fault (shortcircuit) within the first half cycle of a fault. UL Listed current-limiting fuses must open and clear a fault within 8.3 msec after fault initiation.

The effect of a current-limiting fuse in a circuit is illustrated in Fig. 1. With no current-limiting device in the circuit, the instantaneous peak current during the first half cycle after a fault can be as high as 2.3 times the available rms bolted fault current available at the equipment. For example, if the available rms fault current at an industrial control panel is 100,000 A, the maximum possible instantaneous peak current could be as high as 233,000A. However, with a current-limiting fuse in the circuit, the instantaneous peak current reaches only a small fraction of the maximum possible current at the equipment. A current-limiting fuse not only reduces peak current, it also clears the circuit in 8.3 msec or less.

The area under the curve, or I²t, is the energy released during a fault. The lower the I²t, the lower the destructive forces. Therefore, by minimizing both fault duration and energy released, current-limiting fuses greatly minimize Arc-Flash and Arc-Blast hazards. In addition, currentlimiting fuses significantly reduce Let-Thru energy in the circuit. (Let-Thru energy produces heating and magnetic effects associated with short circuits.)

UL Listed current-limiting fuses must pass a series of short-circuit tests and limit the I²t energy to the maximum values shown in Fig. 2. UL class RK1 fuses have much lower I²t values than UL class RK5. UL class J fuses have even lower maximum values and are sized differently so that they cannot be interchanged with something less current limiting. It is important to note that although these are maximum limits imposed by UL, actual I²t values and Peak Let-Thru currents are generally much lower and vary from one manufacturer to another.

Selective coordination
Another advantage of current-limiting fuses is that they can provide selective coordination of the electrical system. In a selectively coordinated system, like the simple one illustrated in Fig. 3, only the fuse immediately on the line side of an overcurrent opens, keeping all upstream fuses closed. This makes it relatively easy to find the faulted circuit so it can be brought back on line quickly. It also helps eliminate blackouts, unplanned work stoppages and safety hazards. With selective coordination, the least amount of I2t flows to the faulted circuit, reducing Arc-Flash incident energy and PPE required for higher Hazard Risk Categories.

The 2005 NEC requires selectivity coordinated electrical systems for emergency systems (700.27), standby systems (701.18), elevator circuits (620.62) and healthcare facilities (517.26), but selective coordination is best practice for any critical circuit. It is easy to selectively coordinate fuses by maintaining a minimum ratio between the upstream (Line) fuse and downstream (Load) fuse. Circuit breakers can be used in selectively coordinated electrical systems, but coordination is more difficult to achieve, because at high fault current, the breaker trip curves overlap.

Increasing short-circuit current rating
Article 409 of the NEC provides safe installation and construction requirements for industrial control panels for applications such as machine, lighting, conveyor and air-conditioning controls, as well as other panels that control utilization equipment. Article 409.110 requires industrial control panels to be clearly marked with several ratings, including the Short-Circuit Current Rating (SCCR). This is the maximum symmetrical rms current that the device or panel can withstand for a minimum of 3 AC cycles (50 msec) or until a fuse or circuit breaker clears the circuit.

According to UL508A Supplement SB, if a panel contains no current-limiting devices, its SCCR depends on the “weakest” or lowest rated component or combination within the panel. However, Supplement SB also states that if current-limiting fuses are used in the feeder circuit, and if the highest instantaneous current reached during the first half cycle of a fault is less than or equal to the lowest rated SCCR in any branch circuit, the SCCR of the currentlimiting fuse can be applied to the combination.

Supplement SB states that the SCCR of a panel cannot be greater than the interrupting rating of any overcurrent protective device in branch circuits or in the primary of the control circuit. Some manufacturers use fuses or supplementary protectors with low interrupting ratings to protect control circuits. Therefore, simply replacing these devices with current-limiting fuses having higher interrupt ratings can greatly increase the SCCR of many panels. Also, some states or authorities having jurisdiction may allow manufacturers to establish SCCR based on the apparent rms current of the current-limiting fuse.

NEC 110.9 requires overcurrent protective devices and the equipment and wiring they protect to withstand the maximum available fault current to protect workers and equipment from excessive damage if a short circuit occurs. OSHA 1910.132(d) also requires employers to identify electrical hazards in the workplace, inform and train workers on how to avoid the hazards, and provide employees with personal protective equipment.

Therefore, fault current studies must be performed regularly, and the SCCR should be verified to make sure that industrial control panels can survive catastrophic short circuits. This is particularly important when panels are installed, moved or modified, or when Arc-Flash and Electrical Hazard Assessments are performed to meet OSHA and NFPA regulations and standards.

Why SCCR is important
When the SCCR is clearly labeled, installers and inspectors can compare fault current studies at the facility where the panel is to be installed to the SCCR of the control panel to minimize potential hazards. The whole point of overcurrent protection is to prevent electrical components from damage. If the SCCR of an industrial panel is too low, then the reliability of its components is in jeopardy. What’s more, it means worse injuries if there is an electrical accident.

Reducing Arc-Flash incident energy
Reliability extends beyond machinery and equipment to include a reliable electrical supply. The electrical system needs protection against overcurrents, of course, but also against Arc-Flash hazards—a particularly destructive event that is a leading cause of workplace fatalities among qualified electrical workers. According to IEEE and NFPA, a critical factor in controlling the level of possible Arc-Flash energy is the clearing time of an overcurrent protective device. Most standard non-current-limiting circuit breakers can take up to 6 AC cycles (0.1 sec) to open under short circuit conditions. Although this is relatively fast, it is at least 12 times longer than a typical current-limiting fuse, and can expose a worker to a potential Arc-Flash hazard for a longer period of time.

Fuses generally open much quicker than circuit breakers. By opening faster, fuses reduce the fault current and in turn limit the Arc-Flash hazard. In addition, according to IEEE1584, the clearing time for Class RK1 current-limiting fuses actually decreases at higher available fault currents, thus producing lower incident energy at higher fault currents. This is in contrast to electromechanical circuit breakers that reach a fixed minimum opening time as the available fault current increases.

Another important consideration is the fact that low available fault currents (below the current limiting range of the fuse) may produce the greatest hazard. A fuse or circuit breaker takes longer to open at lower fault currents, and a difference of 0.5 sec in clearing time can make a big difference in the amount of Arc-Flash energy produced during an accident. Therefore, when estimating Arc-Flash hazards, consider both maximum and minimum available fault currents.

Conclusion
Current-limiting fuses can be an important addition to plant electrical circuits to reduce downtime, improve reliability and increase safety. Current-limiting fuses require no maintenance, are fail-safe, and generally limit the destructive energy if an Arc-Flash or short-circuit occurs. What’s more, these devices can be installed during regular maintenance to improve circuit protection.

Ken Cybart is a senior technical engineer with Littelfuse, Inc., headquartered in Chicago, IL. His 20 years in industry includes teaching and training engineers, managers and electrical workers on safe electrical design, electrical safety, NFPA and OSHA regulations, and working closely with Federal and State OSHA investigators and compliance officers, Underwriters Laboratories and the OSHA National Training Institute. Cybart holds a B.S. in Electrical Engineering from the University of Illinois and is a member of NFPA, NEMA and IEEE. E-mail: KCybart@Littelfuse.com

If you fail to correctly determine the cause(s) of your downtime, you’re setting the stage for your next breakdown.

All maintenance professionals know the hollow feeling in the pit of the stomach that accompanies sudden and unexpected silence out in the plant. Sooner or later, the process will roll to a stop. When it does, how will you view the subsequent diagnosis and repair? Will the breakdown be a problem, or will it provide an opportunity?

If you see the cessation of production simply as another in a seemingly unending series of maintenance crises, you probably will repair or replace the failed component as quickly as possible and your follow-up will be minimal. In this mindset, you are the fireman and the quicker you put out the fire, the happier everyone will be. This type of rapid response historically has been the yardstick by which maintenance organizations are measured. But, if you don’t take the time to correctly determine the causes of the downtime so that a failure analysis can be performed, you are by default setting up your next breakdown. When a machine or component fails, it is pointing out a weakness in your process. If you take the time to investigate the clues, you have the opportunity to improve your maintenance reality.

Notes on the concept of blame
Unfortunately, some organizations consider an interruption of the process to be the signal to begin the search for the guilty. If you find yourself in such a culture, you likely will have limited success in gathering the factual input required to positively impact your maintenance reality.

A majority of process failures involve human error at some level. Consequently, if employees—hourly or salaried—do not feel the level of trust that is required for total honesty, the process interruption investigation will not get to the root cause of the failure. Even worse, you may follow bad data up the wrong road and end up changing some other part of your process that was sufficient as it was. This could lead to subsequent process interruptions—from issues at the original failure site that have not been resolved, as well as from the new weakness in the process you have inadvertently created. In technical maintenance terms, this is called “chasing the rabbit.”

Step #1: Acquiring and interpreting facts
A successful process interruption investigation is, in its simplest form, the unbiased acquisition and interpretation of a set of facts. Since the interruption of a manufacturing process is a complex affair, however, the gathering of the data surrounding it is by no means a simple matter.

An incident must be looked at from several angles so that no important clue is neglected. And, while a good deal of information must be gathered, the plant cannot be down indefinitely. When production ceases, the business is not making money. That’s a condition that does not need to continue any longer than absolutely necessary. As your process interruption protocols develop and evolve, hourly and salaried employees who have been trained in the acquisition of pertinent data will gain speed at their tasks, and downtimes due to data collection can be held to a minimum. 

The following activities should be part of your investigative approach to process interruptions. It is important to note that the production or maintenance supervisor on the scene is a poor choice to gather all of the necessary facts. Such individuals should be supervising during the upset condition. Other qualified employees must be assigned to gather the bulk of the information.

Think safety first.
A breakdown is an upset condition, so the potential for an injury is much greater than usual. The work area must be assessed for safety concerns by a competent person (or persons) prior to the gathering of data or the start of repairs. This is a very important step. Although the plant is down and everyone is in a hurry to get it back up, if a deliberate decision is not made to carefully evaluate the situation for potential and actual hazards, an injury could easily occur. Members of the Safety Committee are excellent candidates for this role.

Take photographs.
Every maintenance department needs to have access to a goodquality digital camera. As a tool, it is as valuable as a set of wrenches or a welder, and it costs less than either. A complete photographic record should be made of the point of failure. Be certain to take shots from all angles, and get as many close-ups as possible. If your particular product or one of your raw materials were involved in the breakdown due to a misfeed or some other reason, capture images of the widget or substance in question before it is removed from the machine.

Retrieve computer printouts.
If your process is under computer control, any printouts that are available to you should be retrieved. Some examples of the types of information that might be obtainable include piece number, piece size, piece composition, date, time, production speed, ambient temperature, previous interruptions, upstream and downstream upsets and operator number. If you have a condition monitoring system, you may be able to access and record bearing temperatures, lubrication flow rates, lubricant temperatures, electrical spikes and other anomalies. The point is to gather all the data available. It is better to have facts you don’t need than to be missing a key piece of information that you could have obtained—but didn’t.

Make video records.
Many organizations have invested in video monitoring as one way of controlling their processes. If you have access to video data, it should be someone’s assigned task during a cessation of production to recover the video data. During downtime, operators often find themselves with idle time. One of these hourly professionals could be assigned the task of burning the DVD or recording the videotape.

Recover the failed part.
This reminder seems obvious, but you would be surprised at how often the failed component is misplaced or thrown away. More than one replaced part has been found in the dumpster, on the catwalk or on the back of the maintenance truck. Failed components more often than not contain their own record of why they failed. It is imperative that the failed part be recovered, preserved and tagged so that it can be analyzed, either by your personnel or by factory reps or consultants.

Interview production.
The machine operator should be interviewed while the incident is fresh in everyone’s mind. Has the machine been running smoothly? Was it in automatic or manual? Have there been feed problems? Is the operator the primary or a back-up? Has the operator been newly trained, or is he/she a veteran?

Interview maintenance.
The run-time maintenance personnel will need to be interviewed concerning any mechanical calls made to the area prior to the failure. Did offsets or adjustments have to be made? Were any unusual sounds or odors detected? Was there a new vibration? The personnel dispatched to perform the repair should be interviewed after the work is completed. They can provide information about machine condition and unexpected repair issues, and they can provide a summary of the necessary follow-up.

Assess recent corrective work orders.
The corrective work and emergency work maintenance files for the failed machine or component should be assessed. If corrective work has been performed in the near past on or around the affected area, this is an important piece of information. Was the correct part installed? Was the part installed correctly? Was there an SMP? Why was the corrective work being performed in the first place? The answers to these questions may provide clues.

Review PM and PdM work orders.
The preventive maintenance (PM) and predictive maintenance (PdM) files for the failed machine or component should be reviewed. Are the PMs current? Has a different maintenance professional been assigned to the machine? Has a changing condition been detected or monitored?

Compare.
If there are similar machines in other parts of your plant or company, their history should be checked to ensure that the breakdown you have experienced is not part of a much larger issue. If you are a single-site operation, vendors, colleagues or factory reps are possible options for consultation. Online message boards are another possibility, as are individual vendor Websites.

Record the data.
This cannot be overstated: If your facts do not exist in some tangible form, your facts simply do not exist. Memories fade very quickly, and nothing can corrupt data faster than word-ofmouth transfers of information. But even while urging you to write “it” down, I must warn you against the very real danger of having the medium become the message. If the breakdown report or whatever you choose to call it becomes the point of the exercise, you have wasted your time and your company’s money. The only purpose for the gathering of these facts is so a competent team of professionals can analyze them.

Think outside the box.
A quick and informal brainstorming session at the conclusion of the information collection period may provide further clues. Is it colder or hotter than usual? Has a new parts vendor been added? Could the failure in question be the result of another recent failure?

Step #2: Evaluating the data
Once you have gathered the facts concerning the process interruption, the next step is to evaluate the data. This portion of the process may be several days or weeks removed from the actual breakdown, depending on how long it has taken to examine the failed parts. If you have one, your reliability engineer should lead the team, as he/she has been trained in the proper issue resolution methodology. The team also should include a machine operator, at least one of the maintenance technicians who performed the repairs and the planner. While you may choose to have additional members, keep in mind that groups with more than six participants sometimes lose effectiveness.

The team will conduct a RCFA (Root Cause Failure Analysis). As was the case with an FMEA (Failure Modes and Effects Analysis), performing an RCFA can be a daunting task—but don’t let it scare you. The idea is to try to determine the ultimate circumstance or set of circumstances that led to the interruption of the process, so that the disruption can be avoided in the future. (By the way, a good source on the subject of RCFA development is http://www.bill-wilson.net/b35. html)

The time and trouble required to properly quantify and analyze a process interruption is well worth the effort. Just remember that your perceived maintenance reality (i.e., what you think is happening) has a way of becoming your actual reality, especially when it has been committed to paper. Thus, it is vital for everyone on the team to set aside agendas and preconceived ideas and try to get to the real root of the matter. Your process and your business depend on it.

Ray Atkins, CPMM, CMRP, is a veteran maintenance professional with 14 years experience in the lumber industry. He is based in Rome, GA, where he spent the last five years as maintenance superintendent at Temple- Inland’s Rome Lumber facility. He can be reached at raymondlatkins@aol.com

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