Archive | May

105

6:00 am
May 1, 2007
Print Friendly

Solution Spotlight: Circuit Breaker Replacement & Retrofilling For Industrial Facilities

Electrical distribution is pretty simple in an industrial facility, at least for those who aren’t involved in MRO activities. As long as the lights are on and machinery is humming, everyone is generally happy. On the other hand, if the constant flow of electricity is interrupted for an extended period, it could lead to grave consequences like missed deadlines, lost sales and a tarnished reputation.

0507_solspotlight01

Circuit breakers are the linchpin of a facility’s electrical distribution system, so it’s probably not surprising that several warning signs of an aging system relate to these devices. That includes a steadily increasing amount of breaker nuisance tripping or failure of a main breaker. When these warning signs occur, it’s a message that breakers may need to be upgraded to help the power distribution system meet current and future needs.

Replacing and retrofilling
When an electrical distribution system is new, it doesn’t require a great deal of attention outside of routine maintenance. But loads increase over time, through expansion and other factors, and equipment ages, including circuit breakers. Nuisance tripping and minor outages become more common, translating to increased maintenance costs that strain budgets.

More ominous is the possibility of a massive power outage that could occur at any time. Suddenly, an entire system upgrade—including brand-new equipment purchases, short circuit coordination and revision of the facility’s single-line diagram, along with downtime and all the related labor issues—is required, costing thousands of dollars and potentially weeks to complete.

Replacing or retrofilling existing decades-old circuit breakers with the benefits of today’s devices can go a long way in modernizing a system and avoiding the problems associated with removing old switchgear and replacing it with new equipment. For example, fused switches and circuit breakers have provided arc flash protection in the past, but breakers have been introduced to the market that provide high interrupting ratings without fuses, up to 200,000A at 508Vac. Such breakers eliminate problems common to fused switches and breakers, including hazards associated with changing fuses and the need to stock/replace fuses, as well as dependence on related mechanical hardware that requires maintenance or replacement. Plus, they are built to trip faster in order to protect both equipment and workers nearby, and typically feature a smaller footprint than fused breakers.

Replacement and retrofilling options don’t require a major time commitment, either. For example, replacing a breaker may require a short 15- to 20-minute outage that can be done during off-hours. A retrofill process is a bit more extensive; it might take 8 to 10 hours per breaker section—but, that’s certainly more desirable than a complete system upgrade.

Consider the following information as a primer regarding replacement and retrofill processes for LV and MV circuit breakers.

Replacement circuit breaker
A replacement LV or MV power circuit breaker is a new breaker that uses a modern modular drawout assembly, designed and tested to interface with components inside the existing switchgear’s breaker compartment. An MV replacement breaker is simply a like-for-like replacement that requires no interface to rack into the existing cubicle. With the LV upgrade option, a new cradle interface is inserted into the existing breaker compartment. The cradle design typically includes a new racking mechanism, safety interlocks, primary and secondary disconnecting devices, truck operated contact (TOC) mechanisms, a new breaker compartment door and other provisions.

A replacement LV or MV power circuit breaker matches the original breaker in form, fit and function and is designed and tested in accordance with ANSI C37.59 and C37.09 standards. Because a number of breakers manufactured more than 50 years ago are still in operation but no longer supported, the replacement breaker provides facilities utilizing older switchgear with a viable alternative for increasing performance and reliability.

Another key benefit of LV breaker replacements is that they allow maintenance personnel to exchange older, existing breakers for one common breaker that is interchangeable throughout a facility’s power distribution system. Another advantage is that they allow for equipment upgrades without having to schedule a bus outage.

Circuit breaker retrofill
An LV or MV circuit breaker retrofill entails the replacement of the old breaker and related compartment components, such as the stationary primary and secondary disconnects, cell interlocks and racking mechanisms, with a drawout circuit breaker and cradle of a modern, previously qualified design.

During the retrofill design and installation, the existing switchgear cell is modified and equipped with a new drawout cradle assembly. Significant changes are made to the structural components of the existing circuit breaker compartment as well as to the line and load bus structure and bus bracing. New isolating barriers are installed to conform to the latest electrical switchgear industry standard requirements.

LV or MV circuit breaker retrofills are employed when and where a facility can afford modifications that require extended switchgear shutdown (minimum 8-10 hours). When the available fault current is higher than the withstand capabilities of the existing circuit breaker, a retrofill or replacement can upgrade the capacity of the existing system. In such cases, the entire switchgear bus structure and bus bracing must be evaluated and upgraded, which requires the switchgear to be de-energized during modifications.

Heed the warning signs
Confronted with the warning signs of an aging power distribution system, a maintenance organization should consider commissioning a facilities audit. Such a study includes evaluation of the entire electrical infrastructure, and can indicate if replacement or retrofill options are appropriate or if a more extensive upgrade is recommended.

The bottom line, however, is to do something if the warning signs are present. Doing nothing runs the risk of extended downtime and higher costs.

Joseph Weigel is a product manager for Square D Services marketing. He has been strongly involved in the development of the Arc Flash Safety program for Schneider Electric to educate customers on emerging arc flash safety standards.

Continue Reading →

1096

6:00 am
May 1, 2007
Print Friendly

Problem Solvers

High-Speed Vision Sensors

0507_probsolvers_cognexCognex Corporation now offers the In- Sight® 5600 series of vision sensors. This new line features the same design as the In-Sight 5400 series, but has double the processing speed and memory. Included in the product line is the standard (640×480) resolution
as well as the two-megapixel (1600×1200) models for performance in high-speed applications. All sensors have an IP67 (NEMA 4) rating and advanced vision software for inspection, identifi cation, measurement and alignment tasks.

Cognex Corporation
Natick, MA

 

Better Safety Instrumentation Monitoring

0507_probsolvers_honeywellHoneywell says that its new SIS-Health Monitoring technology helps reduce maintenance and failures in safety instrumented systems. It includes the SIS-Health Monitoring Local Reliability Database module that stores all inventory information regarding a site’s safety instrumentation. The SIS-Health Monitoring Analysis Toolset lets operators analyze, validate and optimize these systems’ reliability and Safety Integrity Level (SIL). Operating as standalone units or together as an integrated system, the two modules can be used with any type or brand of safety instrumentation.

Honeywell
Phoenix, AZ

 

Lockout/Tagout Solutions0507_probsolvers_panduit

A new Lockout/Tagout and Safety Solutions Catalog, SA-IDCB33, is now available from Panduit Corp. The smallsized catalog covers the company’s lockout/tagout products, safety and facility identifi cation products and training materials. A convenient reference section on industry standards also is included. The free catalog can be requested through customer service or downloaded from the company’s Web site.

Panduit Corp.
Tinley Park, IL

 

 

 

 

0507_probsolvers_commtestState-of-the-Art Vibration Analysis

With the popularity of its vb3000™ portable vibration analysis tool in mind, Commtest has engineered its all-new vb7™ instrument’s electronics from the ground up. Designed by and for predictive maintenance professionals, the vb7 incorporates stateof- the-art components, sculpted into an especially comfortable, lightweight unit. The manufacturer notes that the all-in-one tool is suitable for every level of vibration analyst, from novice through expert. Its Ascent® software contains the collective experience of over 25 years of  expert in-depth machine fault analysis.

Commtest
Knoxville, TN

 

Centralized Mist Removal In A Box

0507_probsolvers_cecoAcid and other chemical mist can be removed with a minimal 99.5% effi ciency, using CECO Filters’ Mist Collector Systems (CMC). Mist cleaning is confi ned to a single room with this “boxed solution” design that can collect effl uent from several operations. According to the manufacturer, its fi ber bed fi lters provide up to 10 years of service life. Standard CMC units come in 18 sizes, with ACFM capacities ranging from 2,400 to 36,000.

CECO Environmental Corp.
Cincinnati, OH

 

Extreme Condition Computers

0507_problemsolvers6Glacier Computers notes that products in its new Everest series for harsh environments are ideal for both forklift and fi xed-mounted applications. These computers have passed thermal and reliability testing, have been HALT tested and have an MTBF of 40,000 hours. Screens are available in 10.4” and 12.1”. They also come with multiple processor options, a 6V to 60V isolated internal power supply and the ability operate in Linux and numerous Windows formats.

Glacier Computer
Amherst, NH

Continue Reading →

147

6:00 am
May 1, 2007
Print Friendly

Viewpoint: Top Management Culture Change

My grandmother used to say “Nice words are seldom true and true words are seldom nice.” I do not sell engineering services, hardware or computer systems, so I do not need to be nice. In my role as an adviser and consultant, I must be honest. This means that I often must tell organizations what they need to hear and not what they want to hear—although I really try to do it in an as nice way as possible. Here are some true words to top management.

Anyone who has been involved in reliability and maintenance improvement initiatives for any length of time has heard that a culture change in work practices is necessary to deliver sustainable results. This is true—and these needed changes are the same as they were 30 years ago. So, why don’t all companies succeed with these types of improvement initiatives?

The culture change that is so talked about must first occur at the top level of the organization. If the president of a company tells the vice president of Manufacturing that he or she must cut the cost of manufacturing, this message will trickle down in the organization and the focus will be on cutting costs instead of doing something about measures that can drive down the cost. As many other contributors to this publication have noted, short-term savings followed by long-term losses will be the result of this culture. If a plant needs to save energy, no doubt heat recovery systems, better insulation, more efficient processes etc. will be considered and investments in these solutions will be made. Such investments, in turn, will drive down the use of energy. The only difference when it comes to maintenance cost reductions is that many of these do not require capital investments at all. It is more a matter of doing better with what you already have.

The resistance to accomplish more cost-effective maintenance is seldom in the Maintenance organization. Many Maintenance managers are in veritable “budget jails” built by management cultures that prioritize short-term savings ahead of long-term gains that can generate savings 10 to 50 times higher than the costs of deferring maintenance. To temporarily survive, these Maintenance managers will focus on cutting costs until such measures result in reduced reliability. As a consequence, he or she will be fired.

What a shame. We can’t afford not to implement measures that improve reliability, which, in turn, will drive down maintenance costs. It is, perhaps, the last significant improvement initiative we can make to stay competitive. The rest of the world buys modern equipment. With automation, it is easier than ever for anyone to learn how to operate this equipment. The real challenge lies in how well the equipment can be maintained and how reliable it will be.

Oh, yes, I generally get agreement from top management when I have the opportunity to talk with them. Agreeing with an idea and eagerly championing it, however, don’t necessarily go hand in hand. All too often, I hear the following: “We agree with you. Better reliability is our greatest improvement potential. But, we must first cut costs.”

The opinions expressed in this Viewpoint section are those of the author, and don’t necessarily reflect those of the staff and management of MAINTENANCE TECHNOLOGY magazine.

Continue Reading →

175

6:00 am
May 1, 2007
Print Friendly

The Rise & Decline Of U.S. Auto Manufacturing

bob_williamson

Bob Williamson, Contributing Editor

While the U.S. automotive industry is enduring one of the most challenging eras in its history, foreign nameplate auto manufacturers in the U.S. appear to be flourishing. This reminds me of a similar situation: the rise and decline of the British automotive industry.

In the years following World War II (the very early ‘50s), the British automotive industry was the second largest in the world, and the largest exporter of automobiles and commercial vehicles. It exported more than the U.S. and was second only to the U.S. in auto manufacturing output. In fact, it out-produced any other country in Europe and any other industrialized country, save the U.S. Yet, by the late 1960s, it had embarked upon a precipitous decline, followed by “nationalization” in 1975.

In 2005, the last of the BIG British-owned auto plants, MG Rover, closed its doors, idling some 6,000 auto workers and severely undercutting another 20,000 supplier employees in the midlands of England. This sad event was punctuated with union leaders blaming mismanagement and the lack of government support—nevertheless, the doors still closed.

My lifelong fascination with British motorcars (especially the MG) sparked my interest in another story that made the news on March 28, 2007: The “First MGs Roll off Nanjing Automobile’s Production Lines.” Nanjing? As in China? Yes, China, the second largest, fastest growing automobile market in the world according to some sources…

Founded in 1947, Nanjing Automobile Group (NAG) is the oldest auto manufacturer in China. Today, it has 16,000 employees making cars, trucks and buses. The company clearly has big plans for its new acquisition, as evidenced by the fact that it produced its first MGs less than two years after purchasing the Brits’ ailing MG Rover firm and moving it to China!

NAG’s production goals include 200,000 MG cars plus engines and gearboxes in the High-Level New Technology Economic Development Zone located in a new $452 million manufacturing facility. The company has begun producing three models, among them the “MG-TF” reminiscent (by name only) of my own restored 1954 MGTF. While the original “MG” stood for “Morris Garage,” the new Chinese version stands for “Modern Gentleman,” which is meant to appeal to China’s rapidly emerging elite class. What’s even more interesting—especially for those of us in this country—concerns some other changes in the works. Apparently, NAG is planning to open an assembly plant in Ardmore, OK, USA.

Tough numbers Since the late ‘60s, in light of many historical labor, management and capitalization challenges, British auto-industry labor productivity had shrunk to only one-fourth that of the U.S. auto industry. Then, the reorganizing, nationalizing and dismantling began. Ford bought Aston Martin (recently sold), Daimler, Lanchester, Rover, Jaguar, Land Rover and Vanden Plas. BMW bought Riley, Standard, Dawson, Triumph, Autovia, MG Rover and Mini. Nanjing then bought Wolseley, Austin, Morris, Vanden Plas, MG Rover, American Austin, Princess and Sterling. What a list! Many of these names represent very strong brands, some them dating back to the late 1800s and early 1900s.

Speaking of past strength, for years, the MG Rover Longbridge plant was one of the most important factories in Europe, as well as one of the largest British-owned auto plants, employing over 22,000 workers in the mid ‘70s. In 1995, however, only 16,000 worked at the Longbridge plant. Ten years later, plant rolls had fallen to 6,000. Bankruptcy finally claimed MG Rover on April 7, 2005—just two years before NAG began rolling out MGs. Not too much left of the traditional British auto industry today…

Improving numbers
These days, a largely renewed British automobile industry is producing huge volumes of quality cars and trucks. In 2005, over 1.5 million cars and 200,000 commercial vehicles were produced with export sales of 74% and 63%, respectively. The Top Five auto makers in England today include: Nissan (The “Most productive car plant” in Europe for seven years running), Toyota, BMW (Mini), GM-UK and Honda.

  • GM and Ford are numbers one and two in commercial vehicle production.
  • Ford (including Land Rover) is the largest engine producer in the UK, more than double that of number two, Toyota.
  • Ford manufactures the largest number of cars and trucks sold in England ahead of Vauxhall (a GM company).

All of this proves that the auto workers in the UK today are capable of performing and producing at world-class levels, despite the decline and destruction of their traditional auto industry. We’ve been noticing similar trends on this side of the pond, too, for more than a decade.

I’ve seen it for myself, during a visit to the BMW plant in South Carolina, where two separate production lines (the BMW X-5 Sport Activity Vehicle [SAV] and the BMW Z4 sports car) recently were combined into a single line. In less than six weeks (over the Christmas/New Years break), the company literally gutted over a million square feet of this 11-year-old manufacturing facility and re-fitted an entirely new “single-line” process. Over the next 12 weeks, it ramped up to its current rate of 650 vehicles per day.

BMW undertook this radical modification to optimize production of the increasingly popular X5 SAV and adapt to changing seasonal demands for its Z4 model. Accordingly, I saw three to four X5s coming down the assembly line for every Z4. Almost every vehicle was different, too—different colors, wheels, interior and exterior trims, diesel or gas, basic or high-performance, domestic or export, left- or right-hand drive, coupe or convertible, etc. The combined line reflects an astonishing engineering and construction feat, as well as a significant logistical and workforce training success. This BMW plant is living proof that the U.S. workforce and leadership can do anything they put their minds to…certainly making us the most productive nation in the world. Refer to the following points to see how it works.

0507_uptime_img11U.S. productivity… Auto plant productivity is measured in a variety of ways across three operations: stamping, power-train and assembly. Let’s look at “hours per vehicle,” which includes ALL employees in the facility being measured—hourly, salary, direct and indirect.

In 2006 Nissan’s overall productivity per vehicle led the North American industry at 28.46 total labor hours/vehicle (HPV). Toyota’s was 29.40 HPV; Honda’s was 32.51; Chrysler Group’s was 33.71; GM’s was 33.19; and Ford’s overall productivity was 35.82 HPV. These types of statistics tell us that our auto industry can be competitive. Unfortunately, the cultures of some of our more traditional U.S. auto manufacturers significantly reduce their competitive edge.

0507_uptime2The most productive U.S. auto assembly plant (not including power-train and stamping) was Ford’s Atlanta operation, which turned out the Taurus and Mercury Sable (15.37 hours per vehicle). Ford, though, recently announced the closing of this plant. The second most productive plant was GM’s Oshawa #2 (16.08 hours per vehicle). But, like Ford, GM has announced plans to close this plant. The lesson here is that while “productivity” is essential, business success involves much MORE.

Additional factors pertaining to sustainable competitiveness include product sales volumes, operating costs, labor cost/hour, profit margins/ vehicle, production flexibility, future growth potential, labor relations, flexible work practices and distance from suppliers. Consider, too, the issues of “capacity utilization” and “profitability.”

Capacity utilization…
In 2005, in their North American operations, Toyota, Nissan and Chrysler were near full capacity (94%-100%), while Ford plants were only producing at 79% capacity.

Profitability…
Likewise, in 2005, Nissan, Toyota and Honda earned more that $1,200 pre-tax profit on every vehicle sold in North America, while Chrysler Group earned only $223. During the same period, though, Ford lost $590 and GM lost $2,496.

The rise and decline of the British automotive industry and the woes of the “Big Three” U.S. auto makers should provide some “lessons learned” for ALL U.S. manufacturers:

  • Market forces—Paying attention to customers and markets is as important as paying attention to the competition.
  • Business strategy—Manufacturing competitiveness demands that from time to time we fundamentally re-think how we perform work. (Design, build, work methods, marketing, sales, etc.)
  • Measures of success—Productivity, efficiency and quality are important, but are only part of a complex formula for business success. (Sales Revenue – Cost = Profit)
  • Hidden capacity—Capital asset utilization, or tapping the “hidden capacity” in a plant’s critical processes, must be a high priority. (Focus: Overall Equipment Effectiveness, MTBF, MTTR)
  • Equipment reliability—Poorly maintained, unreliable equipment can undermine almost all improvement initiatives in a capital-intensive business. (Higher costs, delayed shipments, interrupted flow, etc.)
  • Labor & management—Labor/management communications across and throughout the organization must be open, honest, continuous, and focused on business success, not individual or organizational agendas. (“We’re going to win or lose together.”)
  • Work methods—Restrictive work practices, outdated work rules and past practice can stifle creativity and innovation and lead to signifi- cant and irreversible losses. (“If you always do what you’ve always done, then you’ll always get what you’ve always got.”)
  • Standardized work—Consistent work procedures provide the basis for training and qualifying the workforce and drive out human variation shift-to-shift and crew-tocrew. (Drives out variation, improves efficiency, reduces errors, lowers cost, etc.)

Better numbers ahead
Historically, the auto industry has set the stage for manufacturing strategies across many other non-auto businesses. History repeats itself and history often tells us why things are the way they are today. Status quo, complacency and ignorance can kill a once thriving business. We can, and we should learn from history to avoid common pitfalls that have hurt businesses and their workforces. Successful businesses and workforces help communities and nations thrive. Let’s do our part in our businesses, plants, departments and crews to remain competitive and prosperous.

bwilliamson@atpnetwork.com

References

  1. The Rise and Decline of the British Motor Industry, 1995. Roy Church
  2. The Machine that Changed the World, (Chapter 2: “The Rise and Fall of Mass Production”), 1990. Womack, Jones, & Roos
  3. The Harbour Report 2006, Harbour Consulting
  4. The Society of Motor Manufacturers & Traders Limited (SMMT), the UK/England

Continue Reading →

176

6:00 am
May 1, 2007
Print Friendly

Soution Spotlight: Zooming Technology

Municipal supervisors are increasingly turning to zooming, a pipeline inspection technique that delivers quick, comprehensive information about pipe condition using inexpensive equipment and few personnel. The goal of zooming is to rapidly classify infrastructure as either satisfactory or in need of maintenance, mapping, rehab or additional CCTV inspection. These classifications allow a supervisor to prioritize maintenance activities confidently, committing precious maintenance resources—inspection crawlers, cleaning trucks, cutters/rodders, GPS surveyors and grouting and relining crews—exactly where they’re needed most.

Very often, time, budget and resources keep a municipality from maintaining comprehensive, up-to-date information on the condition of pipeline infrastructure. Without a complete picture of infrastructure condition, however, it is difficult to prioritize and schedule maintenance activities. As a result, a vicious cycle of emergencies, including backups, collapses and overflows, can erupt unexpectedly. When this happens, these emergencies must be dealt with on a triage basis—often at great expense. Unfortunately, these incidents can detract from the inspection work that is meant to prevent them in the first place.

Zooming complements other inspection techniques, it doesn’t replace them. Inspection crawlers cannot be matched for their detailed, 360° inspection of pipe, but they move slower, require substantial investment and demand considerable manpower and overhead.

By contrast, zooming allows a single operator to make a rapid visual assessment of pipe using an inexpensive, ultra-portable zoom inspection camera. Such a camera identifies satisfactory regions of pipe, and also finds problem areas where detailed crawler inspection or other action must be taken.

Zooming’s simplicity is its power. A typical zoom inspection system consists of a camera, lamps, a positioning pole and a video display. Grasping the pole, an operator at street level lowers the camera into a manhole and orients it to look down an adjoining pipe. Starting with a wide-angle view, the operator slowly increases zoom so the camera’s view advances down the pipe. In this manner, an operator inspects the entire length of the pipe for anomalies, and then classifies its condition accordingly. With zooming, you don’t have to squander time and resources crawling every foot of pipe—you can deploy your crawler only where conditions warrant.

Sewer Technologies of Port Perry, ON—one of Canada’s leading trenchless sewer rehabilitation companies—finds that zooming with Envirosight’s QuickView and having the ability to conduct on-the-spot inspections affords it an edge on bid jobs with City of Toronto departments and agencies. The company’s estimates are much more accurate and it can assess job parameters very quickly. “We’ve used zooming technology to accurately assess infrastructure conditions without pulling in the big CCTV unit,” says Brent Giles, VP of sales and marketing at Sewer Technologies. “It allows us to rapidly assess the condition of the sewer lines in the contract and price them accordingly. The zoom camera is responsible for the increased growth of both our municipal and construction projects.”

Woolpert, Inc., a Dayton, OH-based engineering, geospatial and architectural consulting services firm, uses zoom cameras to keep abreast of manhole conditions. Zooming allows this company to capture unlimited digital images with greater magnification and illumination than a traditional camera. Woolpert also uses the QuickView to measures focal length, which is a helpful and accurate way to estimate the distance of a pipe defect from the camera. This ultimately allows crews to better estimate the location of needed repairs. Upon completion of the inspection, the operator classifies the pipe as “satisfactory,” or in need of additional CCTV inspection, new mapping, cleaning or rehabilitation.

Can it work for you?
Any operation with water systems to inspect can benefit from zooming technology. Although crawlers will always be essential to pipeline inspection, zooming simply helps you use your crawling capability more effectively and gives you an affordable option for maintaining a thorough, upto- date assessment of infrastructure condition. Savings in equipment costs, time, labor and resource allocation are all important factors for any organization, large or small. MT

Envirosight LLC
Randolph, NJ

Continue Reading →

517

6:00 am
May 1, 2007
Print Friendly

Field Balancing

0507_field_balancing1For sure. It’s not good for every situation. When it is and when it’s done right, downtime can be reduced and dollars can be saved.

Today’s business environment, with its emphasis on maximizing plant output and efficiency, demands that machinery downtime be minimized. Excessive vibration adversely impacts the health of the affected machine and can shorten repair intervals, thus increasing downtime. The increased vibration also can lead to catastrophic failure, posing a threat to people and surrounding equipment. Unbalance is one cause of this vibration.

Most people observe the effects of unbalance in common rotating machinery like washing machines and ceiling fans. In these situations, restoring the proper balance may be as simple as rearranging a load of clothes or cleaning fan blades. Reducing or eliminating the unbalance in rotating plant equipment is usually more complex, however. Still, it often can be accomplished on site with the proper tools and techniques.

Is balancing the answer?
Attempting to balance a machine that has other problems may lead to unpredictable, possibly catastrophic results. Before attempting to balance a machine in the field, you need to determine the following:

  • Is unbalance the cause of the high vibration?
  • Is an in-place balance going to be sufficient, or does the rotor need to be removed for shop balancing, rebuilding or replacement?

A thorough inspection of the machine should be conducted and other causes of increased vibration should be corrected before balancing is undertaken. If the other defects are not corrected, satisfactory balancing may not be possible, or the correction may be short-lived. Some of the most common causes of increased vibration include:

  • Machinery support problems such as soft foot
  • Defects of mechanical transmission, such as loose or broken couplings, gear or pulley wobbles or cracked gear teeth
  • Bearing defects, including increased bearing clearances, non-uniform lubrication or non-uniform wear of friction surfaces
  • Shaft-line issues, such as misalignment or rubs (As we’ll discuss later, it is important to ensure the machine has reached thermal stability before measuring the effects of balance corrections.)
  • Rotor problems (Increased vibration can be the result of a shaft crack, machine fouling, or a broken or loose rotating component [i.e. blades, vanes, buckets, etc.].)

The best solution for conditions like these is to correct the root cause, rather than attempting to compensate for their effects by balancing.

Balancing the machine
Correcting unbalance is conceptually easy—place a corrective weight on the rotor to counter the effect of an excessive radial mass. Accomplishing this in the field, however, is usually less straightforward.

There are several software packages available to assist in developing balance solutions. They are particularly useful in solving complex, multi-plane balance problems or when the machine needs to be balanced for multiple operating speeds. Solving complex balance problems, though, is best left to properly trained and experienced technicians and is beyond the scope of this article.

Preparation…
Before the actual balancing begins, you must understand the machine’s normal mode of operation. The relationship of the machine’s normal operating speed to its “critical speed” is crucial to understanding the machine’s response to the unbalanced condition. Since we cannot directly identify the rotor’s “heavy spot, ” we must infer its location by observing the point of maximum radial displacement, the “high spot.” If a machine operates below its critical speed—that is, if it doesn’t go through a resonance point while accelerating to normal operating speed—the heavy spot will coincide with the high spot. As the rotor accelerates through the critical speed, the heavy spot and the high spot will separate until they are about 180o out of phase.

Measurements during balancing runs should be taken after the machine has reached thermal stability and when other conditions, such as load or bearing conditions, are as close to normal operation as possible. This minimizes the influence of other sources of vibration, such as a temporarily bowed rotor.

If the machine is to be balanced based on measurements at a single operating speed, the speed must be held steady during the balancing runs as the centrifugal force caused by the unbalance is proportional to the square of the shaft speed. If the machine is equipped with sensors to measure the shaft speed and determine the phase and amplitude of vibration, it is better to collect measurements over a transient event, especially if the operating speed is above the machine’s critical speed. The collection of transient measurements allows for better analysis of the influence of weight changes on the machine, particularly near resonance. (This article focuses on the constant speed method since many 0507_maintenancelog2common smaller machines are not equipped with permanently installed vibration monitoring equipment.)

For machines that lack installed vibration measurement equipment, you will need to measure vibration and shaft speed. Use the measurement points specified by the equipment manufacturer. If not specified, use a point, such as a bearing end cap where the vibrations are transferred from the shaft to the machine casing. A phase reference also will be needed to determine the angular position of maximum displacement.

Before taking measurements, the trial weights and attachments should be prepared. Again, the manufacturer will usually specify the weight placements and may even prepare locations, such as balance holes or dovetailed slots, on the rotor to place balance weights. If the weight placements are not specified, then the weights should be attached on an accessible rotating surface.

0507_maintenancelog3

All weights should be held rigidly in place to prevent them from shifting or flying off during operation. Either of these events will invalidate a balance run. Moreover, if a weight flies off, it may present a hazard to people or nearby equipment.

If you have no reliable prior balancing data, the first trial weight should produce a centrifugal force not greater than 10% of the weight of the rotor. This limit is imposed because the addition of weight to an unfamiliar rotor may cause undesirable vibration during startup, particularly near resonance.

If there is more than one balance plane, a separate trial run must be used for each plane. The required correction weights are calculated independently for each plane. The verification run is performed after all the individual correction weights have been calculated and applied.

Determination of baseline condition…
With the machine at normal operating conditions, measure the vibration. Determine the amplitude and phase of maximum vibration and plot on a polar plot. Furthermore, record the condition of the machine—temperatures, rotor speed, process state, etc. All information recorded during the balancing procedure should be retained to facilitate future balancing procedures.

Calibration or trial run…
Install a calibration weight (Wcal). Record the weight and position. Bring the machine up to normal operating conditions. The more closely you can duplicate the conditions of the baseline run, the better. Measure and record the machine’s vibration response to the weight. Plot the resulting response vector on the polar graph.

Calculation of balance weight…
Calculation of the balance weight is done with vectors. Subtract the baseline response vector O from the trial run response vector TR. The resultant vector C is the response due solely to the calibration weight. The correction weight should be placed to produce a desired response vector – O that is equal in magnitude and opposite in direction from the baseline response.

The size of the correction weight (Wcor) is calculated by multiplying the size of the trial weight by the ratio of the amplitude of the baseline run vector to the trial weight vector. The correction weight is placed at an angle equal to the angular difference of the desired response vector and trial weight vector. If the trial weight was placed at a position other than 0Y, add this angle to the angular difference to determine the correction weight position. Apply the correction weight to the machine (see Fig. 1).

Verification and documentation…
Bring the machine up to normal operating conditions, then measure and record its response to the correction weight. Verify that the vibration has changed as expected and is within tolerance.

One correction may not produce the desired results. There often are small errors in vibration measurements, differences in the parameters (size and placement) of the actual correction weights compared to the calculated ones or other influencing forces. These small variances may require the addition of a trim weight.

The size and position of the trim weight is calculated in the same manner as the correction weight. Another validation run is required after the trim weight has been applied. (Keep in mind that zero or near-zero vibration is not the end goal as achieving this state would usually involve several iterations. In most cases, there are some manufacturer- recommended or ISO-recommended acceptable vibration levels.)

Once the final weights are placed, document the steps of the balancing process. This documentation can serve to reduce the number of runs in future balancing events. In typical balancing events, the majority of time is spent either securing the machine to make the required adjustments or bringing the machine back up to speed and reaching thermal stability and normal operating conditions. Eliminating just one run can shave hours or even days off the balancing job—which means the machine can be returned to profitable operation more quickly.

A quick case study
The importance of having good machine balance data cannot be overstated—even if it’s not for the machine in need of balancing. Consider the following situation involving a gas turbine at an integrated cogeneration plant that powers a combined refinery and chemical complex. Downtime costs in such facilities are enormous, often several million dollars a day.

One of the two gas turbines in this facility began to exhibit high vibration levels. Unbalance was determined to be the most likely source of the problem. Since this machine was fairly new, there was no previous balance information associated with it.

This machine needs a two-plane balancing. With no balancing history, however, a two-plane balance would normally require at least three runs—one trial run for each plane and the correction verification run.

Fortunately, machinery diagnostic engineers and rotor dynamic experts were able to use a database of similar machines and calculate the required correction weights. This allowed the machine to be balanced in just one run. The owner/operator noted that the savings in this case were “…well over a million dollars.” [Ref. 1]

References

  1. Y. Lee and W.C. Foiles, “One-Shot Balancing for a Gas Turbine,” ORBIT Magazine, pgs. 5-13, Vol. 25, No. 1, 2005

Patrick Hamilton is a licensed Professional Engineer with 20 years of experience in plant operational and maintenance management. Prior to joining GE Energy, he spent 12 years in the U.S. Navy, which included service as the Engineer Officer of a nuclear submarine. GE Energy’s optimization and control group includes the Bently Nevada™ Asset Condition Monitoring and Optimization and Control Services product lines. In addition to providing hardware and software solutions, the company has an MDS (Machinery Diagnostic Services) group to assist in solving complex machinery problems.

Continue Reading →

167

6:00 am
May 1, 2007
Print Friendly

The Maintenance/Engineering Partnership

ken_bannister

Ken Bannister, Contributing Editor

Technically, the Engineering department is the closest relative to the Maintenance department. Examining each other’s role in the context of equipment life cycle management portrays a definitive, closely related directive.

Maintenance is charged with the primary role of providing equipment availability, reliability and capacity (throughput) in accordance with the engineering and production design specifications on a day-to-day basis. Engineering is charged with the primary role of designing and developing equipment specification(s) to fit the needs of the Production department, as well as commissioning of equipment or systems capable of delivering on their specified performance.

More recently, great strides have been achieved in amalgamating technical effort through the introduction of the Reliability department— wherein reliability engineers and predictive maintenance technicians dovetail the two departments into a cohesive partnership. The partners focus specifically on increasing equipment reliability and availability of both new and legacy equipment through increased understanding of equipment failure and the incorporation of Reliability Centered Maintenance principles. Companies that have achieved this advanced partnership state have understood and acknowledged that both partners’ roles constantly overlap, requiring mutual exchange of information on a continual basis to realize both mandates and significant increases in equipment availability, reliability (life cycle), and throughput.

As with any successful relationship, both parties must understand and state what they expect from the relationship, then work together on mapping the input and output instruments that will deliver on those expectations, e.g. meetings, work flow, standardized operating procedures or guidelines, informational reports, budgets, tools, skills, etc. Once mapped, both sides must commit to a management action plan and work through the process, adjusting as the relationship progresses.

The following complaints are typical of the kind that must be addressed in this relationship:

Complaint #1
Maintenance:
“The only time Engineering involves us is when they hand us the keys to the new equipment, at which time they believe their job is finished.”
Engineering:
“We’ve tried numerous times to involve Maintenance in the design and commissioning process of new equipment, yet every time they are either too busy, unprepared or unable to specify their needs.”

Solution…
Too many times, the performing of a simple maintenance task is made difficult due to either poor access, or having to shut down and lock out the equipment. This increased maintainability easily can be avoided through effective dialogue between the Maintenance and Engineering departments in the early design stage.

Engineers are schooled from the beginning on all facets of operator ergonomic design, but few are aware of designing for maintenance prevention using a perimeter-based maintenance design (PBM) in which all lube access, filter change points and predictive maintenance (PdM) measurement points are brought to the machine’s perimeter. This allows Maintenance (or Operators, in a Total Productive Maintenance–TPM environment) to perform proactive work while the equipment is running in production mode.

Adopting guard designs that allow access in less than 30 seconds can reduce redundant maintenance work by hours, freeing up precious resource time. If, however, Engineering actively solicits the assistance of Maintenance in the early design process, Maintenance must commit to the process and provide the services of a maintenance planner who is acutely aware of the access and replacement problems.

New equipment acceptance sign-off at the machine builder’s plant and on-site commissioning are great opportunities for Maintenance and Engineering to work together toward common goals. Often a new equipment specification requires the Original Equipment Manufacturer (OEM) to deliver a set of working drawings accompanied by a set of preventive maintenance (PM) job plans.

Unfortunately, most OEM PM plans are too generic, not taking into account the recipient’s work culture or the operating conditions under which the equipment will perform. These stock PM plans can be traded for much more valuable OEM engineering time by inviting the OEM engineer(s) to take part in a Maintenance-department- conducted RCM failure analysis process on the new equipment—PRIOR to receiving the equipment on site. When the equipment is being commissioned, the job plans can be verified while both the reliability engineers and maintainers familiarize themselves with the machine.

Complaint #2
Maintenance: “When specifying new equipment components such as bearings, controls, chains, gearboxes, etc, why does every Engineer have to specify similar, yet different components? Don’t they realize this leads to the stocking of multiple similar parts and unpredictable failure patterns?”
Engineering: “If the Maintenance department is unhappy about the components we specify, why can’t they make the effort to inform us on items they prefer, with a reasonable justification for their choice?”

Solution…
Both parties will receive tremendous benefits from a consolidation and standardization process in which known MRO items that produce consistent reliability are documented. Developing a shared preferred-parts and component-specification listing book in which parts are recognized and listed according to reliability, maintainability and life cycle, is crucial for building and maintaining equipment that can be trusted.

0507_communications1In the parts book, each part is categorized as it would be in the CMMS or EAM maintenance management inventory module, It would include, as a minimum, a photograph of the item, item description, OEM #, corporate inventory identification # (if used), vendor #, and item price. Reliability data used to justify the item listing primarily includes Mean Time Between Failure (MTBF) reports, cost of downtime associated with item failure and item maintenance replacement cost (item cost + total labor cost). This listing book also will benefit both the Purchasing and Inventory departments—which are able to reap cost savings through the setup of preferred vendors and the reduction of MRO inventory requirements. At the same time, this approach promotes familiarity with both maintenance components and component maintenance.

Complaint #3
Maintenance: “When capital budgets get cut, the first system to be eliminated on new equipment is always the lubrication system.”
Engineering: “Maintenance performs manual lubrication throughout the rest of the plant, what’s their problem?”

Solution…
An engineered lubrication approach is crucial to achieving moving equipment reliability. Automated systems deliver up to three times the life cycle of bearings that are manually lubricated. In order to protect and justify an automated lubrication system, the maintenance department must provide lubrication-failure-related data through fault code analysis of lubricationrelated failures tracked and reported within the CMMS program.

Industrial lubrication education is crucial for both Maintenance and Engineering, in order for these departments to be able to better understand and facilitate how to apply a truly efficient failureprevention program.

Concluding thought
The relationships between Maintenance and Engineering have great strengths, whose benefits are multiplied exponentially when harnessed through a team effort.

Ken Bannister is lead partner and principal consultant for Engtech Industries, Inc. Telephone: (519) 469-9173; e-mail: kbannister@engtechindustries.com

Continue Reading →

195

6:00 am
May 1, 2007
Print Friendly

Is Your Electrical PPE Adequate?

0507_electricalsatefy1Despite the great strides that have been made over the years to get workers into safer clothing, researchers still want to know what level of thermal protection is safe enough.

The last 15 years have seen tremendous progress in protecting workers against the heat energy associated with arc fl ash. One major area of improvement has been the steps taken to get workers into safer clothing. The arc rating system developed by ASTM and the development of the predictive equations identifi ed in NFPA70E and IEEE1584 have been instrumental in this effort.

Arc fl ash testing has been at the center of these developments. The arc thermal performance value (ATPV) of electrical personal protective equipment (PPE) relies on arc fl ash tests performed in a high power test lab. The IEEE 1584 equations were developed empirically from arc fl ash tests performed in North American test labs from the late 1990s through 2002.

Recent research into arc fl ash phenomena, however, indicates that workers could be under-protected against the heat generated during an arc fl ash event. Test results presented at IEEE conferences [Ref. 1, 2, 3] and at the 2007 IEEE Electrical Safety Workshop show that different confi gurations of electrodes (conductors) yielded heat energy higher than current predictions due to the directional nature of the arc development. Additionally, initial tests of PPE, when placed within this directional plasma fl ow, did not provide the level of thermal protection predicted by its APTV.

0507_electricalsatefy2Directional nature of arc development
Unrestricted high-current arcs move according to magnetic forces to increase the area of the current loop. Currents fl owing in the opposite direction in parallel conductors give rise to forces that drive the arc away from the source to the end of the conductors where they typically burn off the tips of electrodes (busbars).

The behavior of a 3-phase arcing fault in equipment is very chaotic, involving rapid and irregular changes in arc geometry due to convection, plasma jets and electromagnetic forces. Arc extinction and re-ignition, changes in arc paths due to restriking and reconnection across electrodes and plasma parts and many other effects add to this chaotic nature and make it diffi cult to create equations for accurate predictions of its properties (e.g. impedance). Although it does not capture this chaotic behavior, Fig. 1 demonstrates an arc’s general directional nature. The alternating 3-phase current creates successive attractive and repulsive magnetic forces, dramatically moving the plasma jets which feed an expanding plasma cloud. The cloud is driven outward, away from the tips, creating “plasma dust” as the highly energized molecules in the plasma cool, then recombine into various materials. The molten electrode material ejected off the tips also is in this fl ow.

Arc fl ash hazards
When the arc is being established, current begins passing through ionized air, generating massive quantities of heat. Large volumes of ionized gases, along with metal from the vaporized conductors, are explosively expelled. As the arc runs its course, electrical energy continues to be converted into extremely hazardous energy forms. Hazards include the immense heat of the plasma, radiated heat, large volumes of toxic smoke, molten droplets of conductor material, shrapnel, extremely intense light and a pressure wave from the rapidly expanding gases.

Recent tests have shown that an object in the expanding plasma cloud (refer to the red object in Fig. 1) is directly exposed to the highest heat of the event. Temperatures greater than 15,000 C have been cited for this area. In addition to the convective heat transfer from the plasma, this object is directly exposed to the molten metal ejected from the electrode tips and radiated heat from surrounding plasma.

Objects close to the arc but outside of the plasma jets (refer to the green object in Fig. 1) are not likely subjected to as high a quantity of heat. Exposure is predominately radiant heat, but includes convective fl ow from the thermal expansion of the gases. Objects in line with the electrodes but distant from the plasma jets (refer to the blue object in Fig. 1) receive lower convective heating and less radiant heat and molten metal spray.

The amount of heat absorbed varies with the method of heat transfer and receiving surface properties. For example, the amount of heat transferred from a mass of molten copper to a surface area would be greater if it adhered to the object instead of contacting it for a brief time.

Test setups currently used for standards
Although the overriding principle of electrical safety is to de-energize equipment and place it into an electrically safe condition prior to work, there are numerous cases where companies put workers in PPE to perform tasks on energized equipment. The standards typically utilized to predict the magnitude of heat exposure and the protective ability of fl ame resistant (FR) fabric worn by exposed workers are based upon two unique electrode confi gurations in their test procedures. Heat transferred during tests with these orientations is most likely dominated by radiant heat (see Sidebar page 36).

0507_electricalsatefy3Effects on heat measurements with alternate test confi gurations
Research performed at Ferraz Shawmut’s High Power Test Laboratory has uncovered electrode confi gurations that project signifi cantly more heat energy out of enclosures toward worker locations than currently predicted by the standards. To simulate components found in low-voltage electrical equipment, various setups were created for controlled testing. Heat was measured and compared with results obtained with the standard confi guration shown in the Sidebar fi gure on page 36. Results of these comparisons were published in two recent IEEE papers. [Ref. 2, 3] Confi gurations that forced the arc’s plasma jets outward toward the worker produced heat measurements nearly twice those predicted by current IEEE 1584 equations when studied at typical working distances of 18 inches.

In the barrier confi guration setup, the electrodes are “terminated” into a block of insulating material (barrier) as shown on the left in Fig. 2. This setup represents conductors connected to equipment from the top, such as the component shown on right in Fig. 2.

With the barrier in place, the arc’s downward motion is halted and plasma jets are formed along the plane of the barrier top surface (i.e. perpendicular to the plane of the electrode). This signifi cant fi nding is demonstrated in Fig. 3. The photo on the top shows a side view of arc development along the plane of the barrier in a setup without side panels. This test shows the possibility of higher convective heat transfer toward workers than the open vertical setup, shown from the front, on the bottom in Fig. 3. The barrier confi guration also ejected signifi – cantly more molten electrode material. [Ref. 3]

Chart 1 compares heat measurements (made with copper calorimeters) with the barrier setup to standard predictions. The black line represents predictions of IEEE 1584 equations for switchgear (20” cubic box) for the available fault currents with a fi xed 6-cycle clearing time. Alarmingly, the barrier test results almost always rose above the line—sometimes more than twice the prediction. All tests with the vertical confi guration at this voltage were at or below the prediction.

Another confi guration that deserves serious consideration is the “horizontal electrode confi guration.” This setup simulates equipment where bussing is open-ended, but pointing toward the front of the enclosure, like that in the equipment shown on the left in Fig. 4. The arc development, very similar to that described for Fig. 1, is shown on the right in Fig. 4. Like the barrier confi guration, all tests resulted in heat measurements signifi cantly above the predicted levels.

Continue Reading →

Navigation