Productivity and Reliability-Based Maintenance Management, Second Edition

By Matthew P. Stephens

Productivity and Reliability-Based Maintenance Management, Second Edition is intended to provide a strong yet practical foundation for understanding the concepts and practices of total productive maintenance (TPM) management—a proactive asset and resource management strategy that is based on enhancing equipment reliability and overall enterprise productivity. The book is intended to serve as a fundamental yet comprehensive educational and practical guide for departing from the wait-failure-emergency repair cycle that has plagued too many industries, instead advancing a proactive and productive maintenance strategy. It is not intended to be a how-to-fix-it manual, but rather emphasizes the concept of a world-class maintenance management philosophy to avoid the failure in the first place. Universities, junior and community colleges, and technical institutes as well as professional, corporate, and industrial training programs can benefit by incorporating these fundamental concepts in their technical and managerial curricula. The book can serve as a powerful educational tool for students as well as for maintenance professionals and managers.

In addition to updating the previous historical and statistical data and tables, the second edition expands on and adds to case studies based on current maintenance-related events. Several numerical examples and explanations are revised in order to enhance the clarity of the methodology. The second edition introduces the readers to the state-of-the-art concepts of the Internet of Things (IoT), smart sensors, and their application to maintenance and TPM.

• Language: English
• Publisher: Purdue University Press
• Release date: Jul 15, 2022
• ISBN: 9781612497501

Matthew P. Stephens

Dr. Matthew P. Stephens is a professor in the School of Engineering Technology at Purdue University, where he conducts his research and teaches courses in total productive maintenance (TPM) management, facilities planning, statistical quality control, and design of experiments (DOE). Stephens holds undergraduate and graduate degrees from Southern Illinois University and the University of Arkansas, with specialization in operations management and statistics. Prior to joining academe, Stephens spent nine years with several manufacturing and business enterprises, including flatbed trailer and washer and dryer manufacturers. He also has been extensively involved as a consultant with a number of major manufacturing companies. Stephens has numerous publications to his credit in the areas of productivity, quality improvements, and lean production systems. He is the author of Manufacturing Facilities Design and Material Handling, Sixth Edition (Purdue University Press, 2019). Stephens has served various professional organizations including the Association of Technology, Management, and Applied Engineering (ATMAE), and the American Society for Quality, where he attained his training in CQE and Six Sigma.

Book preview

1

Introduction

OVERVIEW

1.1 Introduction to Maintenance Management

1.1.1 Definition of Maintenance

1.2 Maintenance Objectives

1.2.1 Primary Goals

1.2.2 Secondary Goals

1.3 Management and Structure of the Maintenance Function

1.3.1 Planning

1.3.2 Scheduling

1.4 Total Productive Maintenance (TPM)

1.4.1 Definition

1.4.2 Operator Responsibility

1.4.3 Obstacles to Achieving Full Equipment Effectiveness

1.5 Types of Maintenance Activities

1.5.1 Reactive or Corrective Maintenance

1.5.2 Preventive Maintenance (PM)

1.5.3 Predictive Maintenance (PDM)

1.6 Maintenance Department Organization

1.6.1 Centralized Maintenance Department

1.6.2 Decentralized Maintenance Organizations

1.6.3 Combined System

1.7 Maintenance in Service Industries

1.8 Changing Maintenance Strategies

OBJECTIVES

At the completion of the chapter, students should be able to

Define maintenance.

Develop a basic understanding of the role of maintenance in profitability and productivity.

Understand the primary and secondary goals of maintenance.

Identify the three types of maintenance activities.

Develop a basic understanding of TPM.

Explain the different ways to organize the maintenance department effectively.

1.1 INTRODUCTION TO MAINTENANCE MANAGEMENT

In today’s global economy with fierce competition to attain and maintain the competitive edge in productivity and quality, a key factor often is neglected. The planning and managing of productive maintenance activities in industrial and manufacturing organizations rarely are given the attention they deserve. Whereas industrial managers and corporate leaders fully realize the importance of investment in the latest technologies for quality and productivity improvements, the maintenance of the equipment and technologies does not seem to enjoy the same level of attention and priority. It is ironic that the increased complexity and automation of plant equipment highlights the need for highly skilled maintenance personnel and specialized planning, training, and development of programs for maintenance activities.

Such planning aims at minimizing downtime and provides for the most efficient and effective use of the facilities and equipment at the lowest cost. The mind-set of equating maintenance activities, especially planned preventive and predictive maintenance, with expenditures must be changed. The maintenance department should be considered a profit center rather than a cost center. Consider the most basic definition of profit:

Profit = Income − Expense

Any unnecessary expenditures that can be avoided by implementing a sound maintenance program, such as downtime, idle equipment and personnel due to equipment breakdown, missed delivery dates, and subsequent loss of customers, will result in reduction of expense, hence an increase in profit. A utility company that is responsible for supplying power to 13 counties in Florida shuts down one of its power-generating units for one to three weeks per year for planned maintenance work. Furthermore, each unit undergoes an exhaustive inspection and overhaul that takes nearly eight weeks once every three years. The maintenance activities entail the performance of several thousand repair and preventive tasks. These planned shutdowns can cost the company an additional $50,000 to $60,000 per day. However, additional costs associated with an unplanned outage could cost from $250,000 to $500,000 per day. This simple example clearly underscores how planned maintenance activities can and do reduce real costs.

1.1.1 Definition of Maintenance

Maintenance can be defined as all activities necessary to keep a system and all of its components in working order. The objectives of any maintenance program should be to maintain the capability of the system while controlling the cost. The components of the cost can be further defined as follows:

The cost of maintenance labor and material

The cost of production loss due to an inadequate and ineffective maintenance program

Any deviation or change in a product or a system from its satisfactory working condition to a condition that is below the acceptable or set operating standards for the system can be defined as failure. Although all failures do not necessarily result in catastrophes, most are disruptive, inconvenient, wasteful, expensive, and at the very least annoying. Maintenance programs are aimed at eliminating or reducing the number of these failures and the costs associated with them. Widespread automation and mechanization adds to the complexity and the necessity of prudent maintenance programs. Millions of dollars spent on state-of-the-art technologies and equipment, along with elaborate training programs, innovative approaches for improved customer service, quality and productivity improvements, inventory management and control techniques, are quickly nullified by unplanned equipment failures and unexpected plant shutdowns.

The severity of these failures and associated costs can give an invaluable indication of the level and the extent to which a maintenance program is required and can be justified. A certain level of maintenance is almost always needed because of natural wear and tear on equipment, tools, and facilities in general, but the maintenance cost must be in line with the savings resulting from such maintenance programs. Figure 1–1 compares the cost of a preventive maintenance program (fix it before it breaks) with the overall cost of failures and the associated repairs. As expected, the cost of a maintenance program increases at higher levels of prevention. Planned shutdowns; inspection of systems and components; statistical, mechanical, chemical, and other required analyses; and replacement of parts and components before they are completely worn out all constitute a substantial cost. As this level of prevention increases, however, the costs associated with failures decrease. The question then becomes, At what point is the ounce of prevention no longer worth the pound of cure? The optimum prevention level is the point at which the total costs (the cost associated with prevention maintenance plus the cost of repairing failed equipment) are at the minimum. The maintenance manager must therefore determine the cost and the benefits associated with the unique circumstances of a specific company or department and decide on the appropriate maintenance program.

It is imperative to realize that Figure 1–1 does not represent a universal relationship between the cost of repairs and preventive maintenance for all situations. Although the cost of breakdowns is expected to dramatically decline with the implementation of an effective preventive maintenance program, the curve depicting the increase in the cost of preventive maintenance may assume varying slopes. A variety of factors such as the type and the age of equipment, type of industry, as well as the training and the commitment level of the operating personnel can affect the slope of the curve. Figure 1–2 shows how the slope of the PM cost curve can and does influence the optimal level. Furthermore, we cannot assume that the relationship between the preventive maintenance commitment and the cost always will be linear. Beyond a certain point of maintenance commitment, the curve, and hence the cost, may increase exponentially due to demand for specialized training or special monitoring equipment, as shown in Figure 1–3. Conversely, as an organization matures in its skills to apply and perform preventive and predictive strategies, the cost of such practices may actually decrease over time. Experience with one’s own industry and benchmarking against the best in class (discussed in more detail in Chapter 7) are usually good starting points for determining the initial level for preventive maintenance commitment. Once organizations discover the benefits of their preventative maintenance program, the level of commitment gradually increases.

FIGURE 1–1 Comparison of costs at different levels of maintenance

1.2 MAINTENANCE OBJECTIVES

As stated earlier, the overall objectives of a maintenance program should be to maintain the capability of a system while controlling the cost. Within a manufacturing facility, these objectives or goals can be divided into two main categories: primary and secondary goals.

FIGURE 1–2 Maintenance costs comparisons with varying slopes for PM

FIGURE 1–3 Maintenance costs comparisons with nonlinear PM

1.2.1 Primary Goals

Primary goals may include the following:

Maintaining existing equipment. The timely and appropriate response to equipment failure, reduction of equipment downtime, and an increase in equipment availability can be accomplished by establishing adequate preventive and predictive maintenance programs.

Equipment inspection, cleaning, and lubrication. This goal may include development of a comprehensive program for operators to perform routine tasks to detect problems before they occur and a comprehensive schedule for regular and routine cleaning and lubrication and equipment.

Equipment modification, alteration, and installation. These are nonroutine activities and therefore can be schedule during nonpeak or slack periods to increase the efficiency and utilization of the maintenance personnel.

Utility generation, distribution, and management. This covers maintenance and efficient operation of steam, electricity, and so on.

Maintaining existing building and grounds. This may include building repairs, painting, and a variety of other similar tasks.

Building modification and alteration. Plant expansions and changes in processes may necessitate other related changes. These tasks, as with equipment installation and modification, often can be scheduled as filler work for slack periods.

1.2.2 Secondary Goals

Secondary functions of the maintenance department may include the following:

Plant protection and security

Salvage of obsolete equipment and waste disposal

Pollution and noise control

ADA, EPA, OSHA, and other regulatory compliance

Any other function that may be deemed appropriate by the plant manager

1.3 MANAGEMENT AND STRUCTURE OF THE MAINTENANCE FUNCTION

The nature and the size of the industry determines the structure and the organization of maintenance department; therefore, no single model can serve as the definitive maintenance organization. The processes handed in a plant, whether they are primarily chemical, manufacturing, or other types of activities, determine the need for specific skilled technicians. The size of the facilities and the number of production employees, as well as the degree of automation, can influence the size of the maintenance crew.

Regardless of the organizational structure, maintenance management must include two important functions: planning and scheduling.

1.3.1 Planning

Planning the maintenance activities is necessary to set goals and objectives and to establish the procedures for accomplishing these goals. An important aspect of planning is setting priority for various tasks, estimating the amount of time required for completing each task, and determining the type of equipment, tools, and labor needed to accomplish the task. The planning process must address such issues as the amount of maintenance needed and the size and the skills of the maintenance crew needed to achieve the maintenance objectives. Planning also is concerned with upgrading and updating the skills of the maintenance personnel, providing for training, and involving the production employees in routine and basic maintenance tasks such a routine cleaning, inspection, and lubrication. Plans must specify which, if any, maintenance functions will be performed by outside contractors and clearly identify these agents.

Planning also establishes limits and tolerances for deviations from set goals. Therefore, a system should be developed to measure the performance of the maintenance department and to compare the actual performance against the objectives and determine the causes of deviation. Based on the feedback, plans should be devised for corrective actions and procedures to implement these corrective actions.

1.3.2 Scheduling

Scheduling is the other important function of a successful maintenance program. Scheduling involves the actual execution of the planned (and sometimes unplanned) maintenance activities. The primary concern is setting the sequence of the outstanding work orders. The scheduler must consider priority, availability of maintenance personnel, and material and maintenance equipment availability. In general, a work order should not be scheduled until all resources are available.

Scheduling requires the prudent use of the resources available and a careful management of the maintenance backlog. Successful scheduling requires a keen knowledge of the time requirements (work measurement) for each task and scheduling techniques such as critical path methods (CPM) and analysis, which are covered in more detail in Chapter 8.

Determining and maintaining a desired level of backlog is critical in the efficient operation of the maintenance department. The level of backlog determines the responsiveness of the maintenance department on one hand and the idleness of the maintenance crew on the other, and provides alternatives for the scheduler. Too much backlog, or a backlog that is continuously growing, can significantly slow the response time and increase the equipment downtime. Too little or no backlog can decrease the productivity of the maintenance crew and increase the cost. As a rule of thumb, an average backlog of two to three weeks is recommended. The optimal crew size can be determined based on the desired level of backlog.

Equation: Crew Size

Crew size = (Scheduled labor-hours per week) / (Backlog × Hours per week)

Example: If the schedule requires 1,400 labor-hours of maintenance work during a 40-hour week, and we want to maintain a backlog of three weeks, then:

Crew size (number of employees) = 1400 / (3 × 40) = 11.67 or 12

The equation also can be rearranged to determine the backlog as a function of the crew size, available hours, and scheduled number of hours.

Equation: Backlog

Backlog = (Scheduled hours per week) / (Crew size × Hours per week)

Modern maintenance management planning and control incorporates the use on computerized maintenance management systems (CMMS) and employs various statistical analysis and techniques. Computer simulation and waiting-line theory (queuing theory) are used to determine resource allocation requirements, such as staffing, and for effective planning and scheduling of events. The ability to track and control the backlog, as well as creating and tracking equipment history and work orders, all are important factors in effective management of the maintenance function.

1.4 TOTAL PRODUCTIVE MAINTENANCE (TPM)

1.4.1 Definition

The objective of TPM is to provide a continuous and overall improvement in equipment effectiveness through the active involvement and participation of all employees. TPM is not merely a maintenance program; it is an equipment management program. It combines and promotes the concepts of continuous, total quality improvement and employee empowerment. TPM aims to achieve zero breakdowns and zero defects by making the operator a partner in the maintenance and equipment management efforts.

1.4.2 Operator Responsibility

The operator is the key participant in the TPM environment. The maintenance department takes the role of the advisory group by providing training, setting standards, and performing major repairs.

Instead of relying exclusively on the maintenance department to perform all maintenance tasks, TPM utilizes all available resources including the operators, maintenance personnel, engineers, and the vendors to improve and maintain the equipment at its highest level of performance. Autonomous group of operators are empowered and take ownership of the equipment and assume responsibility for basic and routine maintenance activities, which include the following:

Housekeeping: Proper organization of the work environment and appropriate locations for all tools, materials, and parts.

Equipment cleaning: The simplest yet most important step in equipment maintenance and improvement, and at the same time the most neglected step. Equipment cleanliness is the first and most critical step in inspecting and detecting any equipment malfunction. The operator can perform this task on a routine basis with a minimal amount of effort.

Protection from dirt: Covering machinery and equipment after each use, whenever possible, protects it from dirt and the environment.

Lubrication: The equipment operator can perform most lubrication on a routine schedule.

Inspection: Routine inspection can detect vibration, loose bolts, or other obvious abnormalities that are probably more evident to the operator who knows the equipment than anyone else.

Routine adjustments: The operators can perform routine adjustments to keep equipment operating efficiently.

1.4.3 Obstacles to Achieving Full Equipment Effectiveness

TPM programs strive to reduce and eliminate six significant obstacles to achieving full equipment effectiveness:

Equipment failure. Direct involvement of the operator as the first line of defense can reduce equipment breakdown.

Setup and routine adjustments. The machine operator can increase equipment utilization by reducing setup times and performing routine adjustments.

Idling and stoppage. A trained operator can detect and remedy routine causes of abnormalities and slowdowns due to sensors, blockages, and so on.

Reduced speed. Trained operators will be able to detect deviations between the expected and the actual speed and take appropriate action.

Defects. Scrap and defects due to out-of-control conditions can be easily recognized and corrected.

Startup problems. Problems associated with achieving a stable process are identified and rectified.

1.5 TYPES OF MAINTENANCE ACTIVITIES

Maintenance activities can be grouped into three categories: (1) reactive or corrective maintenance, (2) preventive maintenance (PM), and (3) predictive maintenance (PDM).

1.5.1 Reactive or Corrective Maintenance

As implied by the title, reactive or corrective maintenance is the repair work required after the equipment failure has occurred. Seldom, if ever, does an equipment breakdown occur at a convenient or an opportune time. Even if such failures do not create serious damage to other components and/or injury to people, they cause shutdowns, delay production, and necessitate unexpected and unplanned repairs, and therefore are the most expensive and costly type of maintenance activity. The aim of a proactive maintenance management program should be to reduce the need for this type of maintenance through establishment of PM and PDM whenever feasible. Depending on the nature of the failure, scheduling these repairs often constitutes a high priority and will likely interfere with other planned activities. In some cases when material, equipment, or skilled maintenance personnel are not available, the problem takes on an added dimension of cost.

1.5.2 Preventive Maintenance (PM)

Contrary to reactive maintenance, preventive maintenance takes steps to prevent and fix problems before failures occur. These steps may include proper design and installation of equipment; keeping an accurate history of equipment performance and repairs; scheduled routine inspections and performing necessary upkeep and service; and scheduled cleaning, lubrication, and overhaul. Since these activities are planned, shutdowns, when necessary, will not cause undue burden on the production activity, and availability of materials and personnel is ascertained. Most operators with a minimal amount of training can perform most PM activities.

1.5.3 Predictive Maintenance (PDM)

Statistical tools and various instruments and tests, such as vibration analysis, chemical analyses of lubricants, thermography, optical tools, and audio gages, are used to predict possible equipment failure. Appropriate preventive maintenance steps can be scheduled and performed based on the data gathered and the analyses performed.

Successful PM and PDM programs require proper identification of all equipment and designation of the required level of PM and PDM. A well-defined inspection schedule and the development of appropriate checklists are necessary, along with trained operators and inspectors, to carry out more sophisticated PDM procedures. A committed budget for this type of maintenance is also necessary.

PDM is necessary to develop an efficient and reliable production system. The returns on such investments are direct and significant; they include quality improvements, long and reliable equipment life, improved safety, and better customer service. PDM will result in increased employee morale due to reduced breakdowns and fewer downtimes, less idle time, reduced needs for spare parts, and reduced overall maintenance costs. PM and PDM and will be discussed in greater detail in subsequent chapters.

Tables 1–1 through 1–3 show the status of maintenance programs and activities for various manufacturing and process industries in North America. These tables contrast the actual percentage of each type of maintenance activity for a given industry with that of the ideal level found in world-class organizations. Tables 1–1, 1–2, and 1–3 compare reactive, preventive, and predictive maintenance activities respectively.

Although the level of various maintenance activities substantially varies for any given enterprise, Table 1–1 shows that currently the overall amount of reactive maintenance in each category is substantially higher than for what could be considered a world-class maintenance operation. Consistent with the data in Table 1–1, Tables 1–2 and 1–3 indicate that in each area of the manufacturing industry, the efforts spent in the areas of preventive and predictive maintenance need to dramatically improve for a maintenance organization to achieve a world-class status.

1.6 MAINTENANCE DEPARTMENT ORGANIZATION

The organization of the maintenance department varies depending on the size and the nature of the enterprise. It may have no formal organization and consist of only one or two individuals who report to the production supervisor and perform the required functions on an as-needed basis. In large plants that require a large crew with varied skills and trades, the maintenance organization becomes more formal and may require its own group of supervisors, planners, and schedulers. In general, the maintenance organization may be a centralized or a decentralized system; each method has its own set of advantages and disadvantages. Experts will agree to disagree on the benefits and pitfalls of each type of system.

1.6.1 Centralized Maintenance Department

A large maintenance organization requiring special material and equipment may lend itself to this type of system, in which crew members may be assigned to performed various tasks in any area of the plant but report to the maintenance department head. This arrangement allows for better utilization of human and equipment resources. Crew members can receive better and more specialized training, and since the overall backlog can be controlled through more effective planning and scheduling, fluctuation in the number of maintenance personnel can be kept to a minimum. This system allows for efficient control of the inventory of special equipment and material. Centralized maintenance organization provides for better accountability for maintenance activities and the maintenance budget.

Disadvantages of centralization

There are a few disadvantages associated with a centralized department. Since the maintenance crew is dispatched from a fixed location, a substantial amount of time is lost traveling among various locations, reducing the productivity of the maintenance crew. In a large organization, scheduling can become cumbersome and the response time may increase to unacceptable levels. Transportation of tools and equipment from location to location increases material handling and may require special material handling equipment. Supervision of the maintenance crew also may pose a problem.

1.6.2 Decentralized Maintenance Organizations

This approach to the maintenance organization allows various areas, units, or departments to have their own maintenance departments. Obviously, this system allows for a faster response to maintenance needs, reduces travel time and material handling problems, and allows better supervision of the maintenance crew. Furthermore, since the same crew work on the same equipment, they can develop a better understanding of the equipment and its eccentricity or special characteristics. The disadvantages of this system can include duplication of personnel, special maintenance equipment, and material requirements across the plant that add to inefficiency and cost.

1.6.3 Combined System

A blend of the two systems works well for many organizations. A centralized system may handle specialized maintenance operations and have responsibility for the special maintenance equipment and material inventory. Major equipment overall, modification, and rebuilds that require long-term planning and scheduling may be performed by the central maintenance staff. Hiring and retaining specialized maintenance engineers and staffs who serve the entire plant can be easily justified. The central maintenance department also may handle specialized predictive maintenance activities for the entire plant.