Archive | June, 1998

228

3:42 am
June 2, 1998
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Magic Circle

bob_baldwinKaizen means continuous improvement. It was one of the few Japanese words I understood, until I had an opportunity to spend some time with Masaaki Imai, chairman of the Kaizen Institute and author of Gemba Kaizen (McGraw-Hill, 1997). I found out there is more to kaizen than I had thought, and I learned a few more Japanese words.

Imai says there are two approaches to problem solving. The first involves innovation, which typically means the application of technology, often at considerable cost. The second, kaizen, uses common sense tools and techniques that do not cost much money.

Kaizen is a philosophy to be practiced by everyone at the plant. The major components of kaizen are total quality management, total productive maintenance (TPM), just-in-time (JIT) management, quality circles, and suggestion systems. I was fortunate to see Imai’s American consultants facilitating work of three kaizen teams in a light manufacturing plant near here. One team was installing TPM, the other two were addressing JIT issues.

The two new Japanese words I learned are muda and gemba. Muda means waste, and includes any activity that does not add value. The elimination of muda is one of three ground rules for kaizen. The other two are housekeeping and standardization.

Gemba is the most important word I learned. It means “real place” or that place where value is added. In manufacturing, it usually refers to the shop floor. Within Japanese industry, the word gemba is almost as popular as kaizen.

Because gemba is the place where value is added, it is at the center of what is right or wrong with plant production processes. It follows that the practice of kaizen in gemba can improve plant performance.

In his book, Imai tells the story of the importance of gemba to Taiichi Ohno, who is credited with having developed the Toyota production system. When Ohno noticed a supervisor out of touch with the realities of gemba, he would take the supervisor to the plant, draw a circle, and have the supervisor stand in it until he gained awareness. Ohno urged managers, too, to visit gemba. He would say, “Go to gemba every day.”

Think how much you could get done in your plant if some of the managers would come to gemba occasionally and stand in that magic circle until they were slightly aware of what is going on. Come to think of it, most of us could benefit from an extra turn in the gemba circle studying maintenance and reliability activity with our associates and other plant personnel. MT

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231

3:41 am
June 2, 1998
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The Fuzzy Side Of Equipment Reliability

In nearly all of the 250 or so equipment-intensive plants and facilities I have visited, taught, and worked in over the past 30 years, I have observed the relationship between the skills of employees and the reliability of the equipment. These observations may provide helpful insights for plant and facility managers who are troubled with unreliable equipment and high maintenance costs.

Observation 1: There is a direct correlation between the way plant-floor people are treated and the reliability of the equipment for which they are responsible. Clean and reliable equipment usually means that employeesî needs are regularly addressed. The people are listened to. The same applies to the equipment–its needs are also regularly addressed, its needs are “listened to.” Responding in a proactive manner to people typically results in proactive maintenance of the equipment. A work culture of “equipment ownership” develops.

Observation 2: The highest levels of equipment reliability exist where skilled maintenance people operate the equipment. Likewise, the lowest levels of equipment reliability exist where unskilled or semi-skilled people operate the equipment. There is a direct correlation between equipment reliability and the equipment-specific skills and knowledge of equipment operators.

The conclusions from these first two observations? Equipment-specific skills and knowledge improve equipment reliability. The positive attitudes of employees lead to more reliable equipment. So why don’t all managers and supervisors, all levels of decision-makers and leaders in a business, emphasize the well being of their people and equipment alike? This is a real mystery to me.

Observation 3: In the United States we are firmly in an era where there is a shortage of skilled employees in manufacturing and maintenance. Fewer young people are being encouraged to undertake this kind of work. There is also a trend of having operators perform routine maintenance on their equipment. This trend makes sense, but only if handled properly–the right tasks, the right training, the right people, for the right reasons. However, overall productivity can suffer if downsizing maintenance results in more operator-performed maintenance that takes time away from their “operating” job roles and responsibilities. There must be a careful balance.

Observation 4: We are in another cyclical era of improving performance by cutting costs. Often, cost-cutting programs have a negative impact on employees’ workloads and attitudes, which can be directly linked to more equipment reliability problems. This in turn increases costs and reduces operating efficiency, or throughput. It appears easier to look at overall cost reductions rather than finding ways to reduce the cost per unit produced by improving equipment reliability and work processes.

A vision of the future. Reliable equipment reduces overall operating costs by producing more first-pass quality production during the scheduled time available. People waiting for equipment to be fixed, people waiting for product at the next stages in the process, in-process inventory buffers, and customers waiting for orders add up to significant losses. These losses are exponentially higher than the cost of an emergency, reactive repair.

Unreliable equipment is not necessarily a positive motivator of people either. If left unchanged, unreliable equipment leads to more unreliable equipment and then the “escalating costs must be cut!” Remember that there is a direct correlation between the reliability of the equipment and the way the plant-floor people are treated.

Henry Ford said it best when describing the “Ford principles of management” in his 1926 book, Today and Tomorrow: “Put all machinery in the best possible condition, keep it that way, and insist on absolute cleanliness everywhere in order that a man may learn to respect his tools, his surroundings, and himself.” This was one of the many concepts from Ford Motor Co. that led to the development of the Toyota Production System, Total Productive Maintenance, and Just-in-Time manufacturing from the early 1900s through the 1970s in Japan.

The future of equipment-intensive businesses will always depend on the people who operate and maintain the equipment, and their on-going dialogue with those who design, build, and manufacture the equipment. There is no way around it. People, the work processes they use, and the equipment they work on are the roots of productivity in the workplace of the 1920s –and the workplace of the future. MT
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716

7:10 pm
June 1, 1998
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A Management Guide to Balancing

Mass balancing of rotating machinery can reduce noise, allow higher speeds, increase bearing life, and more. Here is an overview of the process and instrumentation.

Mass balancing compensates for less-than-perfect manufacturing. There would be no need for balancing if materials had uniform density, if holes could be bored exactly in the center, if perfectly round or symmetrical shapes could be machined, and if all assembled parts had exactly the same weight and were placed at the same radius.

Prior to 1880, machinists did limited balancing by trial and error without instruments. The technology of balancing was driven by higher speeds in the electric power generation industry and has leap-frogged the development of bearings. Better balancing required better bearings, and better bearings demanded better balancing to function to their full potential.

Mass balancing is routine for rotating machines, some reciprocating machines, and vehicles. Mass balancing is necessary if an operation or product requires quiet operation, high speeds, long bearing life, operator comfort, controls free of malfunctioning, or a “quality” feel.

Balancing machines
There are three basic types of balancing machines: static balancing stands, hard bearing machines, and soft bearing machines. Static balancing stands do not require spinning up and can correct for static or single-plane unbalance only. They are sensitive enough for grinding wheels. They feature low cost and safe operation.

Hard bearing balancing machines have stiff work supports, lower sensitivity, and more sophisticated electronics. They require a massive, stiff foundation where they are permanently set and calibrated in place. Background vibration from adjacent machines or activity can affect balancing results. They are used mostly in manufacturing production operations where fast cycle time is required.

Soft bearing balancing machines have flexible work supports, high sensitivity, and simple electronics. They can be placed anywhere, and can be moved without affecting calibration. Their flexible work supports provide natural isolation so nearby shop activity can continue while the machine still achieves fine balance levels. A belt-driven soft bearing balancing machine can always achieve finer balance results than a hard bearing machine. Every repair facility should have a soft bearing balancing machine and perhaps a static balancing stand.

A balancing machine is not difficult to make. The rotor must be supported and driven, and the motion measured. A fan wheel can be balanced by attaching it to a motor shaft and measuring the motion with portable vibration instruments while the motor is operated on a rubber mat. This homemade balancing machine can achieve results as well as a commercial machine, but without calibration benefits. And the balancing procedure will take longer.

The mechanical parts of soft bearing balancing machines have not changed significantly in more than 60 years. With few changes, the velocity pickups of 50 years ago are still the preferred sensors on balancing machines. The major changes have occurred in the electronics and computerization. A cost-effective solution to balancing is to purchase an old soft bearing machine and upgrade it with modern digital electronics.

Shop versus field balancing
Mass balancing can be done in a shop with the part mounted on a balancing machine. Or, it can be performed in-place in the field with the rotor mounted in its own bearings and driven normally.

Shop balancing is performed during the manufacturing process after the rotor is fully fabricated and prior to final assembly into its housing. It corrects for manufacturing variability so it spins up smoothly. Shop balancing also is done in repair facilities as one of the last steps in re-manufacturing.

Field balancing is done mostly for convenience to the equipment user because the rotor does not need to be removed. It is less convenient for the person doing the balancing because the instrument must be transported to the job site. Field balancing usually results in lower vibration because the balancing is done at final speed, with the machine’s own bearings and drive system, and some site factors, such as aerodynamics, misalignment, and structural effects, can be accommodated. There are hazards such as loose balancing weights being thrown from a high-speed rotor.

In-house versus service contractor
Shop balancing can be performed in-house for quality control and for throughput in production operations. Balancing is a highly technical skill and requires specialized knowledge and expensive machines and instruments. If an operation cannot or chooses not to acquire and maintain the necessary skills and tools, then there are other alternatives.

Electric motor repair shops have balancing machines. If a rotor can be transported there and it fits on a machine, it can be balanced. Instruments are portable and they can be detached from the balancing machine for field balancing at a facility if there is access to the rotor so weight can be added or removed.

Field balance times average 4 hours and rates range from $60 to $200 per hour. Every field balance job is a time-and-materials task because of the unknowns of access, pre-existing faults, coordinating starts and stops, possible resonance, and how much balancing reduction is required.

Tooling up for balancing
It is possible to balance with no instruments, but it takes a long time and only gross improvements in balancing result. The two main types of field balancing instruments are tunable filters and digital analyzers.

Tunable filter instruments are easy to learn, easy to use, field proven, affordable, and capable of measuring to fine levels. Digital analyzers (FFT spectrum analyzers or other types) are more complicated, prone to operator setup errors, and usually more expensive.

Digital analyzers generally use a photoelectric sensor for phase measurement that is safer because the operator can stand back and close the door. Tunable filter instruments use a strobe light for phase measurement that requires visual access to the rotor in subdued light.

Tunable filter instruments make it easy to grasp the physics of the situation by simple and direct measurements, and balancing proceeds rapidly. But the instrument only takes measurements; the balance calculations must be done separately. The digital analyzer combines measurement and calculation, but physical relevance is lost, especially in two-plane problems. Balancing must proceed “by the numbers” with digital analyzers. The instrument used is the least significant factor to achieving good results. It is the instrument operator who interprets the measured data and responds.

There are various balancing methods-single-plane vector, four-run without phase, two-plane influence coefficient, static-couple, seven-run without phase, flexible rotor, and trial-and-error. The operator chooses the appropriate method initially based on original readings, then may switch to a better method if things are not going well. Balancers need additional training beyond reading the owner’s manual. They especially need to be able to recognize a nonbalance problem and abandon the balance job in favor of some other solution.

Other accessories are required to conduct field balancing: an assortment of balance weights, a scale for weighing to 0.1 gram, a calculator, some wrenches and screwdrivers to disassemble panels, a flashlight, a padlock and safety tags, marker pens, and a battery powered hand drill. Shop balancing requires additional tools also: master calibration rotor, tapered arbors, and ANSI S2.19 specifications.

The down side
It is risky to work on a sick machine that is partially dismantled and being operated in a start-and-stop mode. Risks include failing to reposition a damper, leaving a tool inside, not securing a test weight sufficiently, or some other inadvertent slip that may cause a crash. The danger is to everyone standing by observing, especially if a test weight should fly off.

Balancing may not always work in the field to reduce vibration as well as it does on a balancing machine. There are a number of reasons: the influence coefficient method uses equations which are not entirely independent, the structural system may be nonlinear with resonance, other root causes of vibration exist, the system may be unstable, bearings may be worn, shafts may be distorted, or test weights may be ill-placed.

Balancing instruments are capable of measuring what is required and have reached a mature level. The methods of balancing have room for improvement. A self-balancing rotor is a wonderful idea, and some day they will be affordable for all common machines. But until manufacturing reaches a level of precision where balancing is not required, those involved in balancing will enjoy plenty of satisfaction from machines that are running smoothly after they perform their job successfully. MT


Victor Wowk, P.E., is the president of Machine Dynamics, Inc., 3540B Pan American Fwy, NE, Albuquerque, NM 87107, and the author of Machinery Vibration: Balancing ISBN 0-07-071938-1 published by McGraw-Hill. He can be reached at (505) 898-2094.

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327

5:24 pm
June 1, 1998
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Controlling Maintenance Inventory

Solid management process supported by CMMS can ensure that parts and materials are available and costs are documented.

A plant’s maintenance storeroom is set up to provide maintenance personnel with the parts and materials needed to keep the plantîs facilities and production machinery running efficiently. A well-managed inventory system helps alleviate workersî downtime and improve their productivity.

A comprehensive management process applied to the maintenance storeroom will ensure that the parts are there when needed, redundant items are not being purchased, items will be automatically re-ordered as needed, obsolete items are reported upon for depletion, cost-effective methods are being used for purchasing lot type items, and item usage costs are being documented and reported to plant management.

A plant’s maintenance storeroom when integrated with a computerized maintenance management system (CMMS) should improve maintenance productivity, identify maintenance material costs, identify equipment spare parts and usage, and identify equipment with problems.

Maintenance productivity
What is the importance of a well-managed maintenance inventory operation and how does it affect overall maintenance productivity? To answer this question, look at how maintenance personnel spend their workdays.

On-the-job working time does not allow for such necessary activities as travel to and from a job, interdepartmental communications, personal time, break times, etc. These activities are inherent in all work environments and must be provided for with an additional allowance factor. Industry studies have shown that these per-shift time periods could typically be 10 min for personal time, 25 min for communications, 20 min for morning and afternoon breaks, and 30 min for traveling to and from breaks.

In an average sized plant under normal working conditions, an allowance of 85 minutes or 18 percent would be subtracted from the normal craftsmanîs workday for these activities. This allows 82 percent of the craftsmanîs time to be spent working on the job each day. It is this time that could be improved by effective planning, scheduling, and maintenance inventory control.

In the available working time, a craftsman is expected to be:
• Working. The efforts of the craftsman are productive. For example, he is traveling with tools, parts, or equipment as specified in the work order job plan; reading an operations/maintenance manual; pulling wire through a conduit; or aligning a motor.
Traveling loaded with tools, parts, or equipment not specified in the work order job plan.
• Traveling empty to and from the job at an unspecified break time without tools or parts.
• Waiting on or off the job at unspecified times for instructions, parts, tools, etc.
• Idle, when the craftsmanîs time does not fall into any of the above categories.

Major causes of lost maintenance productivity include:

1. Waiting time
• Job is not set up properly
• Equipment is not available
• Permits are not ready
• Crafts are not scheduled in the proper sequence
• Work request is not clear
• Parts are not readily available

2. Traveling empty
• Parts or materials are not centrally located or described in a work order job plan
• Special tools are not indicated on a work order job plan or not available
• Work request or job plan is not clear
• Maintenance personnel are deployed to jobs without specified tools

3. Idle time
• Excessive break times
• Early quits and late starts
• Work order manpower estimates are too high or too low
• There is not enough work on the schedule

Maintenance inventory management plays a large part in the craftsman’s idle time but what about that of the maintenance planner, purchasing agent, and storekeeper? How much of their time is unnecessarily wasted looking for and purchasing parts, tools, and supplies for maintenance work?

CMMS selection
If you have some sort of computerized inventory system, you may know the cost of your inventory usage but do you know where the maintenance dollars are being spent?

A well-designed CMMS will track work order costs back to equipment, recording not only the labor cost but material cost as well.

Most CMMS systems will provide for equipment spare parts cross referencing. Does the system also have the ability to identify the total number of an inventory item required to maintain equipment?

A well-designed CMMS not only will display inventory by equipment for work order planning but also will identify potential plant requirements as well as historical usage for helping determine stocking levels.

A well-designed CMMS will contain reports identifying inventory by high volume usage as well as high cost usage. Both reports typically identify equipment with problems.

When purchasing a CMMS, you also should consider the system’s capability to:
• Identify equipment spare parts from the equipment and job plan records
• Identify all pieces of equipment that a part could be used in at the inventory record level
• Commit inventory to job plans
• Record material cost to equipment maintenance
• Automatically reorder maintenance stock
• Provide sorting categories for quick location of inventory parts and for printing catalogs
• Produce maintenance usage reports sorted by item and equipment MT


Ronald J. Hemming is president and managing partner and Daniel L. Davis is a senior maintenance management consultant at Maintenance Technologies International, LLC, a plant maintenance management consulting and engineering firm in Milford, CT, with an affiliated office in Niagara Falls, NY. Hemming may be contacted at (203) 877-3217; Davis at (716) 284-4705. Continue Reading →

611

5:06 pm
June 1, 1998
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Up the Reliability Ladder to World Class

Visual representation of steps necessary to reach top levels of maintenance and reliability performance.

One issue that all companies deal with is what steps are needed to achieve world-class performance in their maintenance departments. HSB Reliability Technologies developed the Reliability Ladder to communicate the steps and changes needed to reach this high level of performance and qualify for certification as such under the company’s World Class Maintenance. The Reliability Ladder shown in the accompanying illustration provides corporate and plant personnel with a visual representation of the individual steps and the integration necessary to reach top levels of performance. These steps were developed using a database encompassing a variety of industries. Best practices derived from the database define each “rung.” The rungs and ladder, viewed systemically, illustrate the interdependency of various maintenance processes.

steps_to_world_class_maintenanceThe steps do not necessarily have to follow the sequence depicted. For individual organizations, the sequence may vary slightly. In addition, until a comprehensive benchmark is completed and changes are implemented, some rungs may be strong, weak, broken, or not in place. For example, an excellent computerized maintenance management system (CMMS) may be installed but not used (broken rung), or used only partially (weakened rung).

The ladder may be considered to have several major extensions, each supporting those above. The first of these is the maintenance basics section (red rungs) of the ladder. This is followed by the computer and reliability section (yellow rungs), and the advanced reliability technology section (green rungs) in which maintenance requirements are engineered out to a high degree and more technical reliability studies are justified in support of these efforts.

Maintenance basics phase
Maintenance basics are the support structure upon which the more-advanced practices rest. One of the major problems identified in benchmarking plants is that companies initiate advanced reliability technologies without first having a firm basic infrastructure in place. This probably stems from management’s technical orientation. Hence, technical solutions are sought for what often are behavioral problems in how work is performed. Therefore, excellent predictive maintenance tools such as vibration analysis, oil particle analysis, infrared thermography, and eddy current inspection are employed without fully achieving expected gains. The full benefits of the technology can accrue only to those who have the basic infrastructure (red rungs) in place and in use.

As an example, consider a situation in which vibration analysis identifies an impending failure, and the basic maintenance system has not identified, planned, scheduled, prioritized work, and ordered parts for nonemergency items that should be completed when the equipment is down. In this case, opportunities to reduce costs and improve reliability will be lost. Work may not be performed; resources may be wasted on last-minute rushing to get parts; or, worse yet, start-up is delayed because equipment or parts are not available. Clearly, the investment in the technology, even though preventing consequential damages, does not provide full benefits in reducing downtime.

Similar problems occur in attempts to employ Reliability Centered Maintenance. These concepts assume the availability of proper information in useful form. Equipment histories, mean time between failure, and the other data that good maintenance basics provide are necessary for proper analysis and decision making. This is particularly important in repair vs. replace decisions and in evaluating the total cost of equipment across expected life cycle.

Computer and reliability phase
Once the maintenance basics are in place, the steps upward on the ladder become easier. A good set of performance assurance metrics, equipment histories, and a failure analysis discipline are prerequisites to move into the computer and reliability phase.

In this “yellow rung” area, we consistently find that organizations have acquired a powerful CMMS that is used to only a fraction of its potential. The causes: lack of the maintenance basics, failure to establish disciplines in computer use, and inadequate hands-on training. There is a tendency to assume that the CMMS will be a panacea not requiring attention to all of the basics. The result is that many CMMS systems fall into disuse. In fact, most are not being used to their potential as powerful tools in reliability improvement. The majority of plants can profit greatly by an assessment of their CMMS utilization and a plan to improve the processes to take advantage of the tool.

Another step up the ladder is operator-performed maintenance. In most industries, studies indicate approximately 30 percent of operator time can be used to perform minor maintenance. In addition, companies often struggle in negotiations to obtain labor agreements permitting multi-skilling and operator-performed maintenance.

Once they obtain agreements, they have difficulty implementing the concepts. They never get the benefits because they attempt to move directly to operator-performed maintenance without going through three logical and required steps:

1. The first step is to achieve operator-driven maintenance, which is independent of labor contract restrictions and is available to almost every organization. It involves having the equipment operators take “ownership” of their equipment. This includes such things as writing accurate, meaningful work orders; having equipment clean and ready to work on when maintenance people arrive; and communicating with mechanics as to equipment symptoms and condition.

2. The next step is operator-involved maintenance, where operators provide job set-up help and good equipment performance information, and assist in simple maintenance work.

3. The third step is operator-performed maintenance or the autonomous feature of Total Productive Maintenance (TPM), which requires steps 1 and 2. It also requires a training program in maintenance procedures for operators. In short, operator-performed maintenance means establishing a team of operators and maintenance people with the common goal of keeping the equipment running at rated speed, at top quality, and at maximum uptime. These are the three elements of overall equipment effectiveness (OEE), a performance measure with roots in TPM.

Advanced reliability technology phase
As an organization moves further up the ladder, a reallocation of maintenance resources occurs. With the shift away from reactive maintenance to more preventive/predictive maintenance, there will be a reduction in the overall amount of maintenance to be done. The pie charts that accompany the Reliability Ladder illustration show the mix of reactive, preventive, and predictive maintenance that typically exists in the three phases of the climb up the ladder. The pie is considerably larger at the lower end of the ladder where reactive “fix it when it breaks” maintenance prevails because the total cost of maintenance (driven by reactive practices) is greater. The pie also gets larger at the top of the ladder where multiple redundancies and high levels of engineering are required by the safety needs of industries such as aerospace.

At higher positions on the ladder, a greater amount of process de-bottlenecking will occur with maintenance being avoided through engineered process improvements, condition monitoring, system redundancies, etc. For any industrial facility, there is a point at which risk and cost factors establish a practical limit. It is important to know where you are on the ladder. A good set of metrics is essential.

Where industries stand
Average positions of various industries are shown along the ladder. These are relative rankings. Obviously there are companies within industries that perform at the high and low ends of a bell shaped curve peaking approximately where their industry is shown.

Corporations or plants can use the ladder as a model for comparison of their reliability and maintenance practices. Take a realistic look at your maintenance/reliability practices in comparison to the steps shown. Typically, such a look shows the strong, weak, missing, and broken rungs that exist. What does your ladder look like? If it were a real ladder in your garage, would you use it to paint your house? Would it give an OSHA inspector fits?

The comparison will provide an initial assessment of the strengths upon which to build and the improvement opportunities that exist. Through a detailed benchmarking study and implementation of the changes recommended, corporations and plants can make each rung as strong as required for their operations; they can climb up the ladder to world-class performance; and they can optimize production, reliability, and flexibility to meet strategic goals. MT


Robert R. Viosca is a consultant at HSB Reliability Technologies, Three Kingwood Place, Suite 180, Kingwood, TX 77339; (281) 358-1477; Internet www.hsbrt.com.

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