1、Mai ntai nabi I ity new materials, particularly composites; and, most importantly, through human motivation, thought processes, and user demands. A typical automobile, for example, gives more utility at lower relative cost than did cars of even a few years ago; however, it must still be maintained.
2、Computer-related failures are reduced to units of years. The failure-free, never-wearout item has yet to be produced. Perhaps some day it will be, but meanwhile we must replace burned out light bulbs, repair punctured car tires, overhaul jet engines, and correct elusive electronic discrepancies in c
3、omputers. Availability, the probability that equipment will operate properly when called on, requires an efficient balance of reliability, maintainability, and maintenance to provide an effective system Maintainability (a.k.a. serviceability or supportability) is the discipline of designing and prod
4、ucing equipment so that it can be maintained. Maintenance is the performing of all actions necessary to restore equipment to, or keep it in, specified operation condition. A major challenge of the profession is to create awareness among designers of how important maintainability/serviceability is an
5、d what good practices should be followed. Exposure to actual maintenance is the best way to provide insight into examples of good and bad maintainability. Every engineer should spend time at users locations watching operators and maintenance personnel in a working environment. A few days invested in
6、 detailed observation and discussion will payoff handsomely in products that work better, cost less, and gain satisfied users. Maintenance is big business. Gartner estimates that hardware maintenance and support is $120B per year and growing 5.36% annually. The ten largest petrochemical producers to
7、gether spend over $15 billion Overview 3 annually on maintenance, which averages 4.3% of their expected replacement costs. US Bancorp estimates that spare parts spending is $700B in USA alone, which is 8% of gross domestic product. Durable equipment is designed and built once, but it must be maintai
8、ned for years. With design cycles of six months to three years and decreasing, and with product lives ranging from about three years for computers through 40 + years for hospital sterilizers, alarm systems, and even some airplanes, the initial investment (or lack of investment) in maintainability wi
9、ll either bless or haunt the perpetrator for many years. If a company profits by servicing equipment it produced, good design will produce high return on investment in user satisfaction, repeat sales, less burden for the service force, and increased long-term profits. In many corporations, service g
10、enerates as much revenue as does product sales, and the profit from service is usually greater. Products must be designed right the first time. That is where maintainability comes in. The combination of maintainability and maintenance has not been ad dressed in previous texts. The approach of this t
11、ext is that maintainability and maintenance are convenient divisions of the same function, supporting an operating capability that satisfies the user over the desired period of time. The very word “durable“ means that the equipment is intended for long life and must therefore be maintained. The tigh
12、tening military budget, at the same time as increasing operating and support costs and a drive toward high technology equipment, means that less money is available for research, development, and acquisition of new items. A similar situation is occurring in commerce and industry. It is encouraging to
13、 note that business people in both civilian and government enterprises are paying more attention to life cycle costs and are at least talking about making the investment required for front-end reliability and maintainability in order to improve system availability and reduce operating, support, and
14、overall costs. Managing maintainability and maintenance requires, first of all, an ability to relate to people, hardware, software, and support systems. The maintainability function is concerned with creation of the product, while maintenance is involved with the installation, repairs and prevention
15、 of problems. Too often there is little communication between the two groups, even if they exist in the same company. Organizations who design, produce, and support their own equipment, often on lease, have a vested interest in good maintainability. On the other hand, many companies, especially thos
16、e with sophisticated high technology products, have either gone bankrupt or sold out to a larger corporation when they became unable to maintain their creations. Then, of course, there are many organizations such as automobile service centers, TV repair shops, and most factory maintenance department
17、s that have little, if any, say in the design of equipment they will later be called on to support. While the power of these dealers is somewhat limited by their inability to do more than refuse to carry the product line, their complaints generally result in at least modifications and improvements t
18、o the next generation of product. Overview 4 The two main drivers of maintainability and maintenance improvement are economics and emotions. Major gains can be made in relating economic improvements to maintainability efforts. Data has been gathered showing a payoff of 50: 1; that is a benefit of $5
19、0 prevention value for each $1 invested in maintainability. Methods and techniques exist to evaluate the contributions of maintainability and maintenance, and a section of this text is devoted to those analytical tools. The major challenge remains in convincing top executives, program managers, and
20、design engineers to invest in maintainability efforts that are more work and cost for them today and probably will payoff only over the long term. An objective of this book is to provide information that shows the dollar advantages of investing in maintainability. Executives understand financial adv
21、antages. Emotions also play a role. An angry user or a frustrated senior manager has frequently stimulated better maintainability simply by shouting. “If you dont get it working right, then get it out of here!“ Historically, the two main maintenance costs were labor and materials. Labor costs are in
22、creasing. This means that priority efforts must be given to reducing frequency, time, and skill level and thereby the cost of labor. The costs of parts are also increasing. A specific capability probably costs less, but integration of multiple part capabilities into a single part brings high costs a
23、nd more critical need for the replaceable costs. A third leg is becoming important to product development and support: information; generally provided by software on computer and communications systems. Digital electronic and optical technologies are measurably increasing equipment capabilities whil
24、e reducing both costs and failure rates. Achieving that reduction is vital. Results are seen in the fact that a service technician, who a few years ago could support about 100 personal computers, can now support several thousand. There are several approaches to the delivery of maintenance. One appro
25、ach simplifies tasks through initial investment in design for maintainability so that operators or relatively low-skilled service technicians can easily trouble- shoot the failures and make quick repairs to restore full performance. Another approach holds that technicians of the future should all be
26、 college graduates with a high level of intelligence along with diagnostic and repair abilities. Our approach is the former and aims for simplicity of human involvement with exceptions only for one-of-a-kind custom equipment where qualified technicians are readily available, often having built and t
27、ested the equipment themselves, and little savings are to be gained through better design. The concepts of preventive, predictive, and reliability-based total maintenance are emphasized, along with total quality management and continuous improvement. Hopefully, ideas from this book will stimulate br
28、eakthrough improvements that reengineer processes to dramatic success. The preferred rules for modem maintenance are to regard safety as paramount, to emphasize predictive prevention, to repair any defect or malfunction, and, if the system works well, strive to make it work better. Terms and Definit
29、ions 5 Terms and Definitions Access To gain entry in order to contact part of a system. Acquisition Costs Financial and other investments made to obtain goods or services. Advance Exchange Method of quickly obtaining a good part, whereby the supplier immediately provides a good part and the technici
30、an returns the defective core part as soon as it is replaced by the good part. Alignment The placing of a variable setting to a condition within tolerance. Allocation Assignment or distribution for a specific purpose or to particular persons or things. Availability The probability that a system or e
31、quipment will, when used under specified conditions, operate satisfactorily and effectively. Also, the percentage of time or number of occurrences for which a product will operate properly when called upon. Inherent Availability (A) is “pure, as designed,“ and considers only corrective maintenance t
32、ime. Achieved Availability (Aa) includes preventive maintenance time, but with an ideal support environment. Operational Availability (Ao) considers total downtime, which includes administrative and supply times. Backward Compatibility Retrofit or other change in configuration that will work in prev
33、ious versions of equipment. Bar Code Linear array of vertical lines and spaces that holds about 20 data characters and can be rapidly scanned to send data to a computer that processes the data for identification, pricing, and other information. Newer 2D bar codes can store more than 1,000 characters
34、 with redundancy. Built-In Test Equipment (BITE) Diagnostic and checkout devices integrated into equipment to assist operation and service. Calibrate To verify the accuracy of equipment and assure performance within tolerance, usually by comparison to a reference standard that can be traced to a pri
35、mary standard. Capital Durable items with life or value that allow them to be used a long time. An accounting classification, contrasted with expense. Chaining Sequence of part relationships that ties superseded parts to the current configuration and part number. 6 Terms and Definitions Change Impac
36、t Analysis The logic and reasoning process used to predict the outcome of a change in quantifiable terms before the change is attempted. Checkout Determination of the working condition of a system component. Compatibility An item performs the same form, fit, and function so that the item can be used
37、 in the system. Concept Basic idea or generalization. The concept phase is often the first phase in program planning. See also Maintenance Concept. Condition Monitor Techniques used to determine when a family of devices is beginning to incur failures which need attention. The alert system behind con
38、dition-based maintenance. Configuration The arrangement and contour of the physical and functional characteristics of systems, equipment, and related items of hardware or software; the shape of a thing at a given time. The specific parts used to construct a machine. Configuration Control Documentati
39、on and management of part relationships to assure compatible form, fit, and function. Consumables Materials used up during a products operation, as are gasoline and oil in a car. Corrective Maintenance (CM) Unscheduled maintenance or repair actions, performed as a result of failures or deficiencies,
40、 to restore items to a specific condition. See also Unscheduled Maintenance and Repair. Cost Effectiveness A measure of system effectiveness versus life-cycle cost. Critical Describes items especially important to product performance and more vital to operation than non-critical items. Critical Path
41、 Method (CPM) A logical method of planning and control that analyzes events, the time required, and the interactions of the considered activities. Customer Person or organization that purchases a service or commodity, usually frequently and systematically. Depot Central, usually specialized, facilit
42、y for repair, warehousing, and other support activities. Design Review Examination of design against check lists and specifications to determine if the result will be adequate for performance, manufacturability, and supportability. Device Relationship Management (DRM) Monitoring test equipment that
43、can identify when equipment is not operating correctly and automatically request service if it can not correct itself. Diagnostics Tests using software, logic, measurement tools, and sometimes parts, to determine the source of a problem so that corrective action may be applied. Terms and Definitions
44、 7 Direct Costs Any expenses associated with specific products, operations, or services. Disposal The act of getting rid of excess or surplus property under proper authorization. Disposal may be accomplished by such processes as transfer, donation, sale, abandonment, destruction, or recycling. Downl
45、oad Software term for installing new or revised digital data from a master system. Downtime That portion of clock time during which an item or equipment is not in condition to fully perform its intended function. Economic Repair A repair that will restore the product to sound condition at a cost les
46、s than the value of its estimated remaining useful life. Emergency Maintenance (EM) Corrective, unscheduled repairs. End Article or End Item An entity of hardware capable of performing an operational function but not intended to be installed in or part of another piece of equipment. Examples of end
47、items are an automobile, an electric drill, a hammer, and an early-warning radar system. Engineering The profession in which knowledge of the mathematical and natural sciences is applied with judgment to develop ways to economically utilize the materials and forces of nature. Engineering Change Noti
48、ce (ECN) or Engineering Change Order (ECO) Any design change that requires revision to specifications, drawings, documents, hardware, or software configurations. Environment The aggregate of all conditions influencing a product or service, including physical location, operating characteristics of su
49、rrounding or nearby equipment, actions of people, conditions of temperature, humidity, salt spray, acceleration, shock, vibration, radiation, and contaminants in the surrounding area. Equipment All items of a durable nature capable of continuing or repetitive utilization by an individual or organization. Essentiality Importance of an item to the performance of a mission. Expendable Parts that will not be repaired, usually due to complexity or low cost. Expense Cost incurred for items that are directly charged as costs of doing business since they are used over a specific period of time. Ex
