Much of what has been written to date on the subject of maintenance strategy refers to three—and only three—types of maintenance: predictive, preventive, and corrective.

Predictive tasks entail checking items or components if something is failing.
Preventive maintenance means overhauling items or replacing components at fixed intervals.

Corrective maintenance means fixing things either when they are found to be failing or when they have failed.

However, there is a whole family of maintenance tasks which falls into none of these categories.

For example, when we periodically activate an alarm, we are not checking if it is failing. We are not overhauling or replacing it, nor are we repairing it. We are simply checking if it still works.

Tasks designed to check whether something still works are known as failure-finding tasks or functional checks. (In order to rhyme with the other three families of tasks, the author and his colleagues also call them detective tasks because they are used to detect whether something has failed.)

Failure finding applies only to hidden or unrevealed failures. This is because, by definition, the failure of an evident function inevitably becomes apparent to the operators, so there is no need to carry out regular checks to find out whether such a failure has occurred. So failure-finding tasks should be considered only if a functional failure will not become evident to the operating crew under normal circumstances or the failure is one that cannot be addressed by a suitable proactive maintenance task.

Hidden failures in turn only affect protective devices. The objective of failure finding is to satisfy us that a protective device will provide the required protection if it is called upon to do so. In other words, we are not checking whether the device looks OK—we are checking whether it still works as it should. (This is why failure-finding tasks are also known as functional checks.)

A failure-finding task must be sure of detecting all the failure modes which are reasonably likely to cause the protective device to fail. This is especially true of complex devices such as electrical circuits. In these cases, the function of the entire system should be checked from sensor to actuator. Ideally, this should be done by simulating the conditions the circuit should respond to, and checking if the actuator gives the right response.

For example, a pressure switch may be designed to shut down a machine if the lubricating oil pressure drops below a certain level. Whenever possible, switches of this type should be checked by dropping the oil pressure to the required level and checking whether the machine shuts down.

Similarly, a fire detection circuit should be checked from smoke detector to fire alarm by blowing smoke at the detector and checking if the alarm sounds.

If reliability centered maintenance is correctly applied to almost any modern, complex industrial system, it is not unusual to find that up to 40 percent of failure modes fall into the hidden category.

Furthermore, up to 80 percent of these hidden failure modes require failure finding, so up to one-third of tasks generated by comprehensive correctly applied maintenance strategy development programs are failure-finding tasks. (Note that these tasks must be done at frequencies that reduce the risk of a multiple failure to a tolerable level.)

A more troubling finding is that at the time they were written, many existing maintenance programs provide for fewer than one-third of protective devices to receive any attention at all (and then usually at inappropriate intervals).

The people who operate and maintain the plant covered by these programs are aware that another third of these devices exist but pay them no attention, while it is not unusual to find that no one even knows that the final third exist.

This lack of awareness and attention means that most of the protective devices in industry—our last line of protection when things go wrong—are maintained poorly or not at all.

This situation is completely untenable.

If industry is serious about safety and environmental integrity, then the whole question of failure finding needs to be given top priority as a matter of urgency. As more and more maintenance professionals become aware of the importance of this neglected area of maintenance, it is likely to become a bigger maintenance strategy issue in the next decade than predictive maintenance has been in the past 10 years. MT

Computer users and programmers working with IBM’s OS/2 Warp operating system for personal computers produced the event. It was a grass roots affair without corporate support. I went there to see a demonstration of a voice-activated and speech-driven computerized maintenance management system from Aviar, Inc. of Pittsburgh, PA. In addition to taking over many of the actions typically executed by the mouse, the voice approach allows the operator to envoke an ad hoc reporting function by simply speaking instructions such as “Look up active work orders” to get the desired screen report or print-out. It worked for my voice without training the system.

The next day I stopped by a computer fair at the local community college and found a bustling bazaar in the gymnasium where one could buy new and used computers, circuit boards, hard drives, peripherals, and software. The prices were good, and there was a steady stream of people lugging boxes out to the parking lot. They knew what they were looking for and could recognize a bargain when they saw it.

The atmosphere at these events triggered some nostalgia. I couldn’t help but remember the first time I tried to land the lunar module by typing in values on a Commodore personal computer and seeing the ASCII character representation of my vehicle crash again and again until I got it right.

However, the image from these two events that stands out the most in my mind is the intensity of the people—both in the booths and in the aisles. The people in the booths were serious about what they were offering and how it could help the attendees. Although the people in the aisles were having a good time, they were equally serious in their search for information, products, and services that would help them get where they wanted to go.

It is time to turn up the intensity on best reliability and maintenance practices. That’s what we plan to do at our event, MAINTECH South ’98. Please join us in Houston on December 1-3 to see how much fun it can be when you get knowledgeable practitioners, experts, and vendors together to share information on successful maintenance practices. MT

Although no single portable computer is best for every application, chances are there is or soon will be a lightweight handheld unit that can fully serve any set of maintenance needs better, faster, and at less cost.

Pen tablet computers allow the technician to collect vibration data and perform trend analysis based on FFTs to find impending problems, evaluate their urgency, uncover root causes, and perform balancing. Photograph courtesy Vibration Specialty Corp., Philadelphia, PA.

In the past, data collectors and service instruments had to be designed for a specific task in order to achieve small size and high performance at a reasonable price. With a low cost but powerful personal computer (PC), a variety of tests could be performed as well or better, with the computer’s function easily altered through software. One PC could replace an entire laboratory of equipment. However, because PCs were heavy and fragile, special portable devices were still needed in the field to make tests or collect data.

Although comparatively light weight, the laptop computer with its mouse, keyboard, and flip-up screen was not ideal for operation by plant personnel. It often quit in harsh environments—it was never intended to operate in a refinery in Texas under the summer sun, at an Arctic pipeline in the winter, in a paper mill’s humidity, in a rolling mill’s dirt and dust, or to survive an accidental drop on a concrete floor.

Handheld pen computers
For industry and the military, the problems with using laptops in the plant or the field are being solved by handheld pen-based computers—a pen tablet or a personal digital assistant (PDA). To date, the pen tablet—almost as powerful as a laptop but smaller and lighter—has been widely deployed with a barcode reader to check inventories, confirm truck deliveries, track rental car returns, or link with utility field-service teams.

While the pen tablet is a full Windows 95-based computer, the PDA runs on the simpler Windows CE or a proprietary operating system, providing limited power. Both are designed for field use, but only pen tablets are available in industrial-strength ruggedized versions. Although widely different in display, storage, and computing power, both use point-and-click “pens” to select menu items for easy operation. Some also include handwriting recognition software although with limited success. For a more detailed comparison of laptops, pen tablets, and PDAs, see the accompanying section “Alternatives to Pen Tablets.”

Two versions of the pen tablet are available—one intended for standalone operation, the other as a remote client for a home-based server. The standalone is a full computer incorporating hard disk storage and fast Pentium processing. The remote client type depends on a remote host server, continuously linked by wireless technology or modem, to provide all storage and processing power. In effect, the client is a stripped-down pen tablet, acting as a remote terminal for display and data entry only. PDAs fitted with wireless communications also can serve as remote clients, although their cramped displays are less than ideal.

In the field
There are three areas of application for portable computers in industrial maintenance:

• As a data collector and/or analyzer for on-site maintenance decisions
• As a field service tool to aid in performing maintenance
• As a management tool for control of maintenance operations

Although the use and type of computer differs for each application, there are a number of advantages for computer-based maintenance.

More reliable data is obtained. Error-prone, hand-written records are replaced by reliable data, automatically gathered, stored, and consistently available throughout the enterprise. Bar codes identify inspection locations reliably, ensuring verifiable route compliance that satisfies even regulatory agencies.
Record keeping costs are reduced. Less paperwork lowers administrative overhead because data is processed more efficiently and disseminated widely without producing redundant copies—or even any printed record at all.

Use of resources is more efficient. One simple device can be programmed to serve multiple purposes. Mobile workers perform better and faster without having to learn multiple devices. Material and equipment can be allocated more effectively. With all necessary information—schematics, design and safety specifications, installation drawings, operating parameters, replacement parts lists, etc.—available on demand on site, downtime is reduced and less time is wasted on repeat visits by the technician.

Decision making is faster and more cost-effective. By integrating real-time field reports with the computerized maintenance management system (CMMS), managers at all levels share complete, up-to-the-minute information, and can react quickly to changing field conditions or emergencies. Condition monitoring tests involving a number of parameters—vibration, heat, oil quality, pressure—can be compared quickly to confirm impending problems before they become catastrophic.

Data collection
Maintenance starts with knowing what is going on—how equipment is operating, what increased stresses are being applied, how conditions have changed. Data must be collected, either by a remote monitoring system or by workers on-site. In the latter case, the handheld computer makes data collection faster, more accurate, and more flexible.

In its simplest mode, local instrument readings are entered manually in a pen tablet or PDA then downloaded to a central server. Downloading usually occurs at the end of the day either directly via hardwire or infrared interface, or remotely via modem or wireless link. Point-of-access data recording has the advantage of allowing the field technician to append pertinent information.

Most pen tablets and some PDAs allow the addition of bar code readers through their serial ports. Bar codes, commonly used to identify parts in inventory, also provide identification of inspection sites where readings are taken. Appended to the actual data, bar codes can be used to verify inspection route compliance in critical facilities such as nuclear power plants.

The U.S. Navy plans to expand the use of their pen tablets, currently under trial for collecting machine vibration data for predictive maintenance, by adding manually entered dial readings of temperature, pressure, etc. Eventually they plan to use the pen tablet for acoustic analysis and to access networks and generate repair orders, increasing technician efficiency and reducing the number of instruments with which he must be supplied.

A commercial system is currently available that uses the power and flexibility of the pen tablet for multi-channel vibration data collection and Fast Fourier Transform (FFT) analysis. Because of the pen tablet’s mass storage, a complete archive of previous data and sophisticated programs is available on-site for trend analysis, alarm, and failure diagnostics.

Handhelds as a service tool
A portable computer also can aid in actual servicing. Its internal storage can provide information on design and operation of the device being worked on, as well as safety codes, standards, installation drawings, and equivalent replacement parts. The small screen and memory of a PDA limits the information that can be displayed. A pen tablet, on the other hand, is ideally suited to store and display complex graphics. Where a machine’s operating or maintenance history is pertinent, it may be downloaded to the pen tablet’s hard drive or solid-state drive either directly from the server before going on location or later on-site via a communications link.

Typical of operations requiring rapid-response maintenance at remote locations are refineries, pipelines, power generating stations, rolling mills, paper plants, auto assembly plants, large machine shops, and utilities. For example, field technicians at Nynex use a pen tablet during servicing for remote control of loop assignment switching as well as to collect and view line data.

Operations which require computer control and read out, such as balancing or alignment, can be programmed into a handheld computer, although they usually require the advanced processing and graphic capabilities found only in a pen tablet.

A pen tablet also can be expanded for use as a number of different test instruments. With the addition of input analog-to-digital conversion, a pen tablet-based system can be programmed to serve not only for balancing and alignment, but also as a digital chart recorder, digital oscilloscope, digital voltmeter, or dual-channel FFT structural analyzer.

Recognizing this potential, the U.S. Navy is developing a multi-channel analog-to-digital (A/D) and signal conditioning card, specifically designed for the pickup of vibration or other dynamic signals, and packaged to plug directly into the PCMCIA card slots available in pen tablet computer. Various PCMCIA A/D cards are also available commercially from a number of manufacturers specializing in plug-in cards.

The computer as a management tool
A pen tablet or PDA with communications capabilities can serve as a link between a CMMS and the field. Timely information from the repair site is available to managers for rapid decision-making to optimize plant utilization. Field personnel are quickly redirected to where they are most needed, while providing all the information they require to maximize their effectiveness such as work orders, availability of resources, spares inventory, and safety standards. A number of CMMS suppliers favor a PDA because of its small size and because its reasonable cost can make it practical in some cases to discard a damaged PDA and replace it with a new one.

Communicating to and from the field
Where sufficient data and programs can be retained at any one time in the PDA, intermittent communication (at the start or end of the work day) via wire modem or local connection to the server is practical. In many cases, however, the PDA does not provide enough storage or processing power. Either a more powerful handheld computer such as a pen tablet must be used, or the PDA must be employed solely as a remote terminal or client in communication with a more powerful server.

Putting all computer power in the server allows the client to be lighter, less expensive and, without the need for a hard disk, more reliable. Only the server needs to be provided with state-of-the-art processing, making periodic upgrades easier. Because data resides on the server, there is less chance of losing data if a client fails in the field. A multi-unit system is more economical with many lower-cost clients and only one expensive server. Disadvantages include limitations in current modem and wireless data transfer rates and, most important, the need to maintain continuous clean links in remote locations where wireless communication is problematical.

Some units can send information back to the server using Cellular Digital Packet Data (CDPD). CDPD transmits digital packets within the unused bandwidth of analog cellular telephone, but works only where a special CDPD network is locally available (at a monthly access charge). Its speed of 19.2 K-bps is sufficient for text, but downloading any but the simplest graphics is prohibitively slow. Also, the addition of CDPD and its dedicated modem seriously tax a PDA’s battery.

In many applications, a PDA is not powerful enough to serve even as a client. Its processing capabilities, screen, and battery are all too weak. Wherever photographs, detailed schematics, layout diagrams, or other graphic-intensive information is needed in the field, a more robust computer is called for. Some manufacturers build their clients around pen tablet-type handhelds with a Windows 95 operating system and a large screen.

Handheld pen-based pen tablets are sufficiently powerful and rugged to perform virtually any computer-based industrial maintenance function in the harshest of environments. Many of these units, complete with typically delicate hard drives, are designed to withstand the shock of dropping 3 feet onto a concrete floor. They also operate at the temperature extremes where humans have difficulty working—from below zero to more than 120 F—and withstand almost 100 percent humidity or driving rain.

As batteries improve and circuitry becomes smaller and less power hungry, the future may see the introduction of such powerful maintenance tools as a high-speed, digital cellular modem (with universal coverage) integrated into a large screen pen tablet, putting the field technician in real-time contact worldwide with his home base and all its data. MT

Richard S. Rothschild has 18 years experience with a major manufacturer of real-time FFT spectrum analyzers and machine vibration predictive maintenance systems. He currently is a consultant in electronic product planning and marketing and may be reached at 175 Knibloe Rd., Sharon CT 06069; (860) 364-1915; email richroth@li.com

The usual goal of benchmarking with other companies is to compare processes and the costs associated with them and to discover new concepts. When you are competing in a national or global economy, competition to reduce costs, improve quality, and increase product output is intense. There are a multitude of competitive benchmarking drivers to deal with: team empowerment, material flow, inventory control, production operation, product design, industrial engineering, utility management, maintenance practices, training, technology, computer support, etc.

But it is difficult to share manufacturing benchmarking data and information without a good analysis of internal activity. The problem is that most companies do not know what they already have internally, good or bad. Nor do they have a process in place to improve common cross-functional weaknesses.

To add to this, it is extremely difficult to find a benchmarking partner whose performance measures and costs can be compared. Even those who have the same equipment and the same process flow will still have different cultural attributes that impact overall performance at all levels of the organization.

Background
About 1992, the Saturn Maintenance Core Council (MCC) sanctioned an effort to develop a process for internal benchmarking relative to world class practices for all of the Saturn maintenance organization. The goal was to compare nine key elements of the Saturn maintenance strategy against perceived world class best maintenance practices. See the accompanying section “Saturn’s World Class Maintenance Strategy.”

The Saturn MCC membership is made up from all the partnered (UAW-represented and nonrepresented) maintenance leadership area module advisors and the three elected UAW skilled trades advisors. The council developed the mission statement and the key support elements for its maintenance strategy. It meets several times each month to review and discuss sitewide maintenance issues.

Assessment process
Several Saturn leaders (UAW-represented and nonrepresented) gathered information from or visited such sources as the Marshall Institute, North American Maintenance Excellence Award, AT Kearney’s Best of Seven, General Motors Corp. facilities, and non-GM manufacturers. As a result, an assessment questionnaire was developed and point values were assigned to each element and question. The assessment totals 1000 points divided across the nine key areas, with Planned Maintenance and Continuous Improvement elements weighted to indicate their higher importance to the company’s growth and development.

The Saturn UAW manufacturing advisor and the vice president of manufacturing sanctioned the maintenance assessment process in 1995.

The 37 Saturn maintenance teams, each consisting of six to 15 skilled trades members, are spread across a wide variety of production processes. These teams cover support for robotics, assembly, paint processing, metal stamping, polymer injection, gear machines, foundry and heat treatment, etc. Each is responsible for running its operations support activities as a business, including planning, absenteeism, continuous improvement, controlling part and tool inventory, performing to budget, etc. Because Saturn has a unique union agreement that allows for partnership at all leadership levels, it was decided that all 37 teams would be assessed, instead of assessment at some higher level in the business structure.

The purpose of the assessment process is to train the maintenance team members as to what world class practices are and help them develop continuous improvement plans as may be appropriate to correct any shortfall the team decides is important. See the accompanying section “Assessment Process—Guidelines.” The process requires that the maintenance team members being assessed develop a team manual with supporting evidence for each of the 67 assessment questions. A group of maintenance peers from other Saturn business units then meets with the team members to review and discuss each of the questions. Originally this took a full day to complete, but today it takes about four hours.

The assessors’ results are averaged and comments combined onto one questionnaire form. Within three to four weeks the maintenance team members are invited to meet again, with the same assessors, to review the results together. Scores are discussed for clarification and future reference, but will not be changed until the next assessment. The questions on the assessment form are subdivided to reduce subjective scoring. In the future Saturn plans to subdivide the questions to a one point (Yes/No) level. This will allow the teams to assess themselves fairly accurately.

It is important to note that the assessors do not share maintenance team scores with other teams within or outside their module or business unit; only with the assessed team’s leadership. The team is asked to put together a continuous improvement plan, due in six weeks, for those items it wants to improve.

It is urged to select items for improvement that the team has the time and resource help to complete. The Saturn maintenance leaders are responsible for their teams’ completion of the process. Team members are asked to help as future assessors for other site teams.

Assessment results
A spider graph is provided to the teams at the feedback session to give them a visual representation of how their assessment score compares to world class for each key element. The MCC has determined that out of the 1000 points only 810 are directly within the teams’ control. The other 190 points deal with the interaction of maintenance support functions like training, indirect materials, operations, maintenance leadership, etc.

As of this writing all of the Saturn maintenance teams have completed the first round of the assessment process and Saturn is about halfway through the second round. Thus far, over 60 assessments have been completed in the past three years.

The MCC has determined that awards will be given to the maintenance teams that score points during the second round assessment in the following ranges:

• Above 700 (Level I): Demonstrated a working knowledge of world class practices
• Above 800 (Level II): Demonstrated and documented progress toward world class
• Above 900 (Level III): Developed, documented, and utilizes world class practices

Benefits
As a result of the first round assessment, various teams have undertaken improvements within their respective areas. From a site perspective several changes have been recommended and started.
For example, team and module preventive and predictive maintenance programs have been reviewed and modified. Saturn indirect materials and Saturn technical resource support functions are currently implementing continuous improvement plans specifically for maintenance. More attention has been given to team norms and point role activities. Several maintenance modules have revised maintenance planner activities. Team manuals prepared for the assessment have become a good foundation for QS-9000 process documentation, and maintenance libraries across the site have been updated. MT

Richard Elliott, P.E., has 36 years experience with General Motors Corp., 14 of them with Saturn Corp., 100 Saturn Pkwy., Spring Hill, TN 37174-1500. He is now Saturn’s sitewide maintenance coordinator responsible for reporting assessment results to the MCC. He can be reached at (931) 486-5796.