Archive | February, 2004

1940

2:44 am
February 2, 2004
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The Dangers of Arc Flash Incidents

Regulations require safety programs and hazard analysist o address expensive and potentially deadly occurrences.

The flash is instantaneous, almost too fast for the eye to comprehend. But the end result of this incident could be more than $15 million in direct and indirect costs to a company.

So companies cannot afford to ignore the safety issues surrounding arc flash explosions, as the Occupational Safety & Health Administration (OSHA) enforces new standards for employee safety protection in potential arc flash situations.

0204arcblastWhat is arc flash?
An arc flash is a short circuit through the air, explained George Gregory, industry standards manager at Square D/Schneider Electric, Palatine, IL. When insulation or isolation between electrified conductors is breached or can no longer withstand the applied voltage, an arc flash occurs. As employees work on or near energized conductors or circuits, movement near or contact with the equipment, or a failure of the equipment, may cause a phase-to-ground and/or a phase-to-phase fault.

The temperature of an arc can reach more than 5000 F as it creates a brilliant flash of light and a loud noise. An enormous amount of concentrated radiant energy explodes outward from the electrical equipment, spreading hot gases, melting metal, causing death or severe radiation burns, and creating pressure waves that can damage hearing or brain function and a flash that can damage eyesight. The fast-moving pressure wave also can send loose material such as pieces of equipment, metal tools, and other objects flying, injuring anyone standing nearby.

Regulations require the calculation of the “flash protection boundary” inside which qualified workers must be protected when working. Gregory said this boundary is an imaginary sphere surrounding the potential arc point, “within which a person could receive a second-degree burn if an electrical arc flash were to occur,” according to the National Fire Protection Association (NFPA) 70E standard. This standard also defines incident energy as “the amount of energy impressed on a surface, a certain distance from the source, generated during an electrical arc event.” That surface could be a person.

Incident energy is expressed in calories per cubic centimeter squared (cal/cm2). The flash protection boundary is the point at which the energy number is 1.2 cal/cm2, equating to a second-degree burn. As workers get closer to the energized equipment, that energy figure rises. This boundary is different for different types of equipment and depends in part on the voltages involved. Typically, the higher the voltages, the larger the danger zone. A 10,000 A arc at 480 V is equivalent to 8 MW or approximately eight sticks of dynamite, noted John Lane, electrical safety engineer at AVO Training Institute, Dallas, TX. The photograph shows a side view of an equipment rack during an arc flash explosion. (Photograph provided by Square D/Schneider Electric.)

Medical costs high
Between five and 10 times a day, an arc flash explosion occurs in electric equipment somewhere in the United States that sends a burn victim to a special burn center, according to statistics compiled by CapSchell, Inc., a Chicago-based research and consulting firm that specializes in preventing workplace injuries and deaths.

That number does not include cases sent to regular hospitals and clinics, or unreported cases and “near misses,” estimated to be many times that number. There are one or two deaths a day from these multi-trauma events, noted Dr. Mary Capelli-Schellpfeffer, principal investigator.

The costs of these incidents are staggering. According to a 1999 Electric Power Research Institute (EPRI) study cited by CapSchell, a utility company’s total spending estimate for electrical incidents over a two-year period was $15.75 million per case when related indirect costs were considered along with the direct expenses.

One manufacturer, as reported by the Institute of Electrical and Electronics Engineers (IEEE), reported it has experienced an average of 2.2 arc flash injuries per year over the past 10 years.

Development of standards
Serious study of arc flash began in the early 1980s, with publication of an IEEE paper by Ralph Lee, a former consultant from DuPont. His work on blast burns convinced companies, especially in the petrochemical industry, to take steps to establish the first set of practices to protect employees working on electrical equipment.

Since then, work has evolved with OSHA, the NFPA, the IEEE, and other organizations to compile a set of regulations specifically to address arc flash (see accompanying section “Standards Relating to Arc Flash Incidents and Safety”).

Now companies must perform a hazard analysis to determine flash protection boundaries and appropriate protection for employees, and electrical equipment with potential for arc flash must be marked with a warning label. Companies must have electrical safety programs in place.

Safety programs are key
OSHA, in enforcing worker safety procedures, cites the NFPA 70E guide as the “how to” source for compliance. One basic requirement there is that an electrical safety program must be established for each facility with specific elements included. See accompanying section “Requirements for Safety Program Under NFPA 70E.”

The safest way to address maintenance and repair situations with electrical equipment is to work only when equipment is de-energized and verification has been made that de-energization has occurred. But with facilities operating 24/7 and systems often required to operate continuously, that is not always possible. So the safety program must stipulate procedures to address the hazards of working on energized equipment.

Proper protective equipment must be worn when any of this work is conducted within the established flash protection boundary for that equipment.

The goal of an electrical safety program is to remove the worker from the danger zone or remove or eliminate the intensity of the arc flash. Thus the plan should consider use of long-handled tools to put the worker further from the electrical circuit, infrared windows to allow inspection with cabinets and doors closed, remote racking, current-limiting circuit breakers, and other options.

Hazard analysis provides facts
But the specifics of the plan need to follow the completion of the hazard analysis; “you have to know the facts before you make decisions,” as Gregory put it. This analysis determines the flash protection boundary distance and the type of personal protective equipment (PPE) required for working in various situations.

0204flash1

An arc flash test used a circuit adjusted to deliver 20,000 amperes at 480 V, 3 phase. The bright light is the arc developing (top), indicating the energy in the arc that is radiating outward as heat. As the arc develops (second from top), it melts and vaporizes the metal of the electrodes and the box. This vaporizing metal (third from top) expands outward with the pressure wave, and the test stand is enveloped in the arc flash explosion (bottom) as smoke and debris spread from the test stand. The duration of the arc was about 0.045 sec. The test was set up at the Square D High Power Lab in Cedar Rapids, IA.

0204flash2
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0204flash4

IEEE 1584 standard establishes nine key steps in the analysis process:

  • Collect system and installation data
  • Determine system modes of operation
  • Determine bolted fault current
  • Find protective device characteristics and arc duration
  • Document system voltages and equipment class
  • Determine arc fault current
  • Select the working distances
  • Calculate the incident energy
  • Calculate flash protection boundary

As Lane explained, an arc flash hazard analysis “starts with gathering up-to-date equipment information, then performing a detailed analysis comprised of a load-flow study, short circuit study, and protective device coordination study as well as an equipment evaluation to determine that the current withstand rating is acceptable. For facilities with generators and large motors (100 hp or larger), a motor starting and fault contribution analysis also should be performed.”

At the end of this analysis procedure, companies will have incident energy calculations and arc flash boundaries for each location in their power systems. Warning labels and safety programs then can follow.

Regulations do not dictate any specific method of analysis. Tables and guidelines for a simple approach to calculating incident energy are available in NFPA 70E, although more detailed calculations are explained in IEEE 1584 as well as a number of shortcuts for low voltage circuit breakers.

There are also consulting services available to handle analysis as well as published values from manufacturers and commercial software.

“ The more accurate the analysis, the more likely that proper preventive measures can be taken,” Gregory said.

And incident energy figures can vary widely. Daniel R. Doan and Ronald A. Sweigart in an IEEE technical paper studied 33 plants with 4892 buses or switching points under 600 V. The median incident energy was 2.1 cal/cm2, but that energy figure varied dramatically: 24 percent of buses were over 8 cal/cm2, 10 percent over 50, 5 percent over 85, and 1 percent over 205. Employers cannot assume that similar equipment will have similar flash protection boundaries.

In those cases where incident energy is over the 40 cal/cm2 that is considered safe for work with PPE, no work should be done with equipment energized; engineering or operating changes may be needed, noted Craig Wellman and Bruce McClung in an article “Performing Arc Flash Hazard Calculations” in Electrical Contracting & Engineering News magazine (March 2003). Wellman is an electrical consultant and project engineer with DuPont Co. and McClung is vice-chair of IEEE 1584 Working Group.

Engineering options, according to their article, might include replacing switchgear with arc resistant switchgear, adding a secondary main relay that can trip a primary circuit breaker, or changing fuses. Operating changes might include adding a provision for remote racking and remote operation, and changing the sequence of switching operations to reduce the time when exposure is high.

Accurate incident energy levels are vital in setting the level of PPE required for work inside the flash protection boundary. PPE categories range from 0 (untreated cotton clothing) to 4 (cotton underwear plus fire resistant shirt and pants plus double layer switching coat and pants).

Companies are reluctant
“ Economics is constraining safety” in many companies, Dr. Capelli-Schellpfeffer said. In this global economy, other countries have lower safety standards and it is difficult to compete. “Arc flash is a low probability/high cost event. Therefore, it is difficult to argue for prevention dollars.”

Wellman stressed that there must be a “culture for safety” throughout the entire company. “Management must promote safety first all the time, and safety excellence must be everyone’s job.” He added, too, that companies “do not recognize (the arc flash) hazard to business and the potential costs of it.”

“ Electrical workers are working on the basis of decisions made by others, for better or worse,” said Palmer Hickman, director of safety, training, and curriculum development of the National Joint Apprenticeship and Training Committee (NJATC). “A company should not expect to get work done energized.”

A comparison was made to police bomb squads. These specialized workers do not go into an “energized” situation without careful planning, proper protection, and training. Employees facing work on electrical equipment should be similarly prepared.

Standards Relating to Arc Flash Incidents and Safety

Four separate industry standards establish procedures for preventing arc flash incidents and ensuring employee safety:

OSHA 29 Code of Federal Regulations (CFR) Part 1910, Subpart S
This regulation states, in part, “Safety related work practices shall be employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts… .”
OSHA also addresses the qualification of workers exposed to electrical shock hazards and the provision for protective equipment appropriate for the work to be performed.
OSHA enforces safety practices and cites to the NFPA requirements.

NFPA 70-2002, National Electrical Code
Section 110.16 requires that companies place a warning label on equipment likely to cause arc flash conditions. This field marking can be generic or very specific, whichever the company selects. Future revisions of the NEC standard may require more detailed information on this label.

NFPA 70E-2000, Standard for Electrical Safety Requirements for Employee Workplaces
NFPA 70E can be considered the “how to” standard behind OSHA enforcement. It provides the detailed actions companies must take to be in federal compliance. Specifically:

  • Safety program with defined responsibilities
  • Calculations for the degree of arc flash hazard
  • Personal protective equipment (PPE) for workers
  • Training for workers
  • Tools for safe work
  • Warning labels on equipment

IEEE Standard 1584-2002, Guide for Arc Flash Hazard Analysis
In order for the warning labels to carry enough information to show the danger zone for arc flash conditions, companies must determine that area within which only qualified workers should enter—the flash protection boundary. IEEE 1584 provides a method to calculate the incident energy in order to specify the level of PPE required for workers.

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Requirements for Safety Program Under NFPA 70E

OSHA and NFPA 70E require equipment be in an electrically safe work condition before employees work on or near it. Equipment, therefore, should be de-energized before any work is done. In some cases, however, work cannot be done on de-energized systems, such as in a hospital or a 24 hr continuous operation.
There are specific steps NFPA 70E dictates to ensure an electrically safe working condition exists:

  • Determine all possible sources of supply
  • Open disconnecting device(s) for each source
  • Where possible, visually verify device is open
  • Apply lockout/tagout devices
  • Test voltage on each conductor to verify that it is de-energized
  • Apply grounding devices where stored energy or induced voltage could exist or where de-energized conductors could contact live parts.
  • Establishing these safety procedures is part of the company safety plan that must be in effect for each facility:
  • Employers must formalize procedures and practices such as the qualification of employees to work in hazardous areas, tasks they may perform, steps needed to secure management approval for work to be done, and audits.
  • Employers must provide training for employees in the skills and techniques needed to work with electrical equipment, equipment details, and emergency procedures.
  • Employees must implement the practices according to the training.
  • Companies must perform a flash hazard analysis before work is done on any energized equipment.

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190

2:42 am
February 2, 2004
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Selecting the Right Maintenance Information System

Using proven guidelines for evaluation and selection, finding a suitable EAM/CMMS need not become an overwhelming or difficult task.

The old maintenance system has gasped from sheer exhaustion. There are no more patches or upgrades available or perhaps the company has decided to take the predictive maintenance route. Whatever the reason, it is time for a new system. The question now becomes, what makes a good maintenance management system?

The first essential characteristic of a good enterprise asset management/ computerized maintenance management system (EAM/CMMS) is obvious: It should work. If it does not provide true and accurate reports regarding the cost, planning, and scheduling of maintenance, it does not work.

A good CMMS is based on currently accepted programming practices. In the past decade, users have demanded more integration among software packages. The software selected should be able to export data in a format understandable by current spreadsheet and document programs.

Another feature to look for is ease of implementation. Moving from an older system to a newer one can be a complicated process. The biggest cause of worry is the change in database structure. There should be some mechanism to import or export data from a variety of widely known formats. Keep in mind, the age of the current software will be a factor. Tables that are part of a DOS-based application in use since 1983 may require special handling.

Research is important
Research must be conducted. Even though the word causes many people to stifle yawns, it does not need to be a boring or time-consuming process. The Internet is a great tool and can make light work of the task. A good place to start would be the list provided by Maintenance Technology.

There are three important questions that must be considered before buying a maintenance program. First, what are the features the software must have? Define the needs carefully. Divide the essential features from the features that would be nice to have. Write a list of criteria and order them by importance. A typical item would be something similar to: The application must run off the network server.

Next, ask what additional features would be nice to have. For example, assume the current system has several custom availability, reliability, and utilization reports written in Access. Software that can export data directly into Access would save the time and expense of having those reports rewritten. This is a feature that serves a useful purpose. A word of caution: There may also be additional features that are of no practical value and add to the cost of the software. The main thing to avoid is paying for added features that are not necessary or beneficial.

Finally, the most important question: What is the budget for this software? Be on the lookout for hidden and unexpected costs that lurk beneath the surface. A few of those are detailed in the next sections.

Ranking the software
With the list of criteria, select those EAM/CMMS software programs that fit the requirements. List each package by name with a column for price on a separate sheet. Now, go through the list one by one and determine the answer to each of the following questions:

What are the computer system requirements? How much is the software license? Will the employees need training?

System requirements
If cost is a driving factor, the goal is to find a system that works and is compatible with the current hardware and operating system. Learn the hardware configuration and operating system of the computers where the software will reside. The company information technology department can help.

Avoid expensive hardware upgrades if possible. If a program requires 1024 MB of RAM and your installation PC has 512 MB, then the purchase of additional memory will need to be added to the price column for the software. Take a hard look at which operating systems will run the software, how much memory is required, how much hard drive space is required, and if there is a processor speed limit.

Licensing expenses
Software is rarely sold to the general public. What most people buy is a software license. Purchasers are not buying the software program itself and do not own it. They own only the license to use that piece of software. The benefit of a license is that it makes users’ rights and the software supplier’s rights clear to both parties. However, it also imposes certain obligations and limitations.

A license agreement will state how the software can be used. Read this carefully. It will outline what the user may or may not do with the program. For instance, some software can be used only in certain countries. Make sure to understand the terms. Licensing questions to consider include how many users or computers will need to be licensed, how often the license will need to be renewed, and what the license scheme will cost.

Remember that buying a software license grants only the legal right to use a piece of software. Often there will be maintenance programs available for annual purchase. These programs provide bug fixes, updates, and technical support. While the prices vary, typical annual fees fall between 15 and 20 percent of the cost of the software license.

Employee training
If the software is easy to use, employees will be able to learn the program on their own with minimal time and effort. If this is not the case, training may need to be outsourced. Although outsourcing costs more in the short term, employee productivity and satisfaction will far outweigh the expense over time.

If possible, download a trial version of the software and give it a test run. For larger systems, call the company and ask for a presentation. Always view the software in action before committing to it. Set realistic goals and timelines for the implementation. A complicated software package will always take longer for employees to understand and use.

The final decision
Add all additional costs that were discovered during the evaluation—for example, any expenses such as hardware or software upgrades and licensing fees. Automatically cross off any software that is more than 10 percent over budget. Now, compare the features against cost to determine which software will be best.

Using this technique will alleviate some of the difficulty involved in selecting the EAM/CMMS package to fit your specific needs. Of course, there is not always an ideal solution. If no commercial software seems to fit the requirements, consider approaching the vendor of the software closest to your needs. The company may be willing to adapt the software for a price. Hiring a firm to write a complete custom package is also an option, but this can be expensive.

It may not be easy to discover what is actually needed or to distinguish between wants and needs or to determine the priority of the requirements, but determining specific software needs is the key to successfully finding and implementing an EAM/CMMS package. MT


Carla Fair-Wright is a service maintenance planner for the Maintenance Technology Services department at Cooper Cameron Corp., Cooper Energy Services, 11800 Charles St., Houston, TX 77077; (713) 856-1615

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9521

1:25 am
February 2, 2004
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Maintaining and Troubleshooting Solenoid Valves

Decisions depend on valve design and application.

As with any mechanical apparatus, proper and proactive maintenance and care of solenoid valves can extend their lives and ensure predictable operation. This article will address how maintenance of such a small component can be worthwhile and the difference upkeep can make to the system; when to repair vs replace; whether maintenance can prove more or less time- and resource-consuming than replacement; and how to troubleshoot these valves.

When to maintain To determine when best to service a solenoid valve, consider these questions:

• What is the opportunity cost of valve failure at an inopportune time?

• Is there the risk of safety hazards in the event of a failure?

• What is the financial cost of a valve failure in terms of productivity and scrapped work?

• What is the cost for service in terms of time and manpower?

Generally speaking, if the machinery is being taken apart for other service, that may be the best time to complete the valve maintenance procedure. A proactive approach can result in the best possible performance of the valve and the overall system, as well as extended product life.

The frequency at which a solenoid valve should be serviced is very much design- and application-dependant. Certain applications are particularly damaging to the valve’s internal and external components and will require more frequent attention. For example, without lubrication, components wear quickly. In this case, it would not be unusual to replace components at 100,000 cycles or less. However, media that are lubricated or provide lubricity can offer component life up to millions of cycles.

For standard valves, controlling media as common as air and water can be a challenge. Some of the most damaging applications are those that involve dry air and rapid cycling. The lack of lubrication and the pounding of the internal parts can cause valves to deform and deteriorate. Valves controlling water can experience mineral buildup, especially when water sits idle in the valve for extended periods of time.

If one considers a solenoid valve’s small clearances between moving parts and small orifices through which media travel, it stands to reason that unfiltered, corrosive, or viscous (adhering to the inner components) media can substantially increase the likelihood of premature failure. In these situations, building a maintenance regime into the valve’s use can extend life as well as maintain the consistency of the overall application’s functionality.

Repair or replace In order to make the repair vs replace decision, consider again the valve itself as well as the overall application. As with other products, there are varying levels of durability built into different solenoid valves.

Certain types are so simple in design and construction that low replacement cost makes this the most simple and cost-effective choice. However, high-end designs exist where the interaction of components is so critical that servicing the valve in the field is not recommended for fear that the original function may not be attained. Likewise, the replacement cost may be significantly greater in comparison to a maintenance scenario, especially in cases with custom designs or exotic materials.

Maintenance generally implies solely the replacement of the rubber parts and springs. If the remaining parts show wear or are damaged, it is time for replacement. On the other hand, if the valve’s connections have sweat fittings or its location makes its removal difficult or dangerous, it may be wiser to leave the valve body in place and rebuild its components regularly. The caution here is to verify that the valve seat is not nicked or worn, which may result in seat leakage even with new seals.

Where cost is the determining factor, replacement is most often the best choice. Generally, solenoid valves are inexpensive in comparison to service labor cost. The time and manpower it takes to disassemble the valve, replace the parts, reassemble, install, and check for proper performance often outweighs the cost of labor simply to install a new valve.

Valve maintenance Replacement part kits for solenoid valves can be purchased from the manufacturer. These typically will contain replacement O-rings, springs, a plunger, and possibly diaphragms, pistons, and a host of related components. Of course, be sure that the replacement kit is appropriate for the particular valve. Here are the steps of the maintenance regimen:

• Safety. Before repairing a valve, always disconnect the power source and depressurize the system. Consideration should be given to safe handling of the unit based on the fluid controlled therein.

• Coil. Inspect the coil for cracks in the encapsulation. In wet or humid environments, these can lead to moisture penetrating the coil, resulting in valve failure. Connections to the coil should be checked for damage or corrosion. Never power up an ac coil without ensuring that the coil is properly installed on the valve’s sleeve or stem. The resulting high inrush of current will likely result in a coil burn-out.

• Pressure vessel. When the coil is removed, the resulting unit is the pressure vessel. The sleeve will have a feature to accept a sleeve removal tool, usually a wrench. Care should be taken to never remove the sleeve by clamping onto the sleeve tube, as this may cause the tube to dent or bend.

Removal of the sleeve from the valve body will expose the internal components of the valve operator. These include the plunger with a seal, the plunger return spring, an O-ring, the sleeve, and the operator body. These should be examined for damage or wear and replaced as needed.

The seals may exhibit swelling, cracking, or general deterioration. The spring should be inspected for worn or broken coils. The body orifice may be nicked or the crest may be worn. When the plunger lifts, it normally makes contact with the sides and stop of the sleeve. As a result, the top of the plunger and the inside of the sleeve may show wear as well.

For more complex solenoid valve types using diaphragms, pistons, spools, and levers, specific manufacturers’ instructions must always be followed.

• Reassembly. Once all necessary parts are replaced and the valve cleaned of buildup and grime, reassemble the pressure vessel according to the manufacturer’s directions and reattach the coil. Then reinstall the newly assembled valve back into the application. Power to the valve should not be reengaged until you are positive that the parts are installed correctly.

Valve troubleshooting At this point, you might have done all of the right things to maintain an application’s solenoid valve, yet you still experience problems. There could be any number of malfunctions with the valve:

• It does not energize when power is applied.

• There is internal or external leakage.

• It makes a chattering noise when energized.

• It is sluggish or sticks in position.

• There is reduced flow output.

The accompanying section “Troubleshooting Guide for Solenoid Valves” covers the most common problems and corresponding actions.

For problems and questions beyond these, always contact your solenoid valve manufacturer. The manufacturer is your best source of information on its particular valve and can help you address any special needs you have based on the application or complex valve design. MT


Michael D’Amato is technical sales and service manager for Parker Fluid Control Division, 95 Edgewood Ave., New Britain, CT 06051; (860) 827-2300

Troubleshooting Guide for Solenoid Valves

PROBLEM

PROCEDURE

Valve fails to operate

1. Check electrical supply with voltmeter. Voltage must agree with nameplate rating.
2. Check coil with ohmmeter for shorted or opened coil.
3. Make sure that pressure complies with nameplate rating.

Valve is sluggish or inoperative—electrical supply and pressure check out.

1. Disassemble valve; clean out extraneous matter. The plunger must be free to move without binding.
2. If a diaphragm design, check the diaphragm for tears and/or clogged or obstructed bleed hole or pilot orifice. Torn diaphragm must be replaced.
3. Check all springs. If broken, replace.

External leakage at sleeve flange or joint between body and cover

Check that the sleeve and/or cover screws are torqued to specifications. If leakage persists, replacement of diaphragm assembly or flange O-ring may be required and/or bodies or covers with damaged sealing surfaces may have to be replaced.

External leakage at speed control device

Check O-rings for damage and replace if necessary.

Internal leakage

1. Disassemble valve, remove extraneous matter, and clean parts in a mild soap and water solution.
2. Examine diaphragm sealing surface for dirt. Remove all foreign particles. Examine orifice for nicks. Damaged parts must be repaired or replaced.
3. Check plunger return spring. Replace if broken.

Chatter or buzz sound when energized

1. Remove power from the coil.
2. Inspect the plunger and sleeve forexcessive wear or contamination.

 

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183

6:19 pm
February 1, 2004
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Don’t Forget Your Team

bob_baldwin

Robert C. Baldwin, CMRP, Editor

I rediscovered The Team Memory Jogger, a book published by Oriel, Inc., as I straightened my bookcase recently. The 3 x 5-in. book, designed as a pocket guide for team members, had fallen behind larger volumes.

I thumbed through it before placing it on a stack of other small books and happened to scan the chapter on Getting a Good Start, which had a section on identifying stakeholders—the people and groups inside and outside the organization who will affect and be affected by the team’s work. Four examples were given: managers, customers, coworkers, and suppliers.

The page on suppliers provided some bullet points of what that group often cares about:

  • What they are expected to provide to you
  • If you are getting your needs met
  • If you will still want to do business with them
  • If they will be expected to make changes

It offered the following tips for team members:

  • Be clear about what you expect of suppliers
  • Most suppliers will be eager to work with you if changes are needed
  • If possible, invite a key supplier or two to a team meeting or arrange a visit to their site.

The last item about face-to-face meetings with suppliers is a worthy exercise. It helps both sides but it may be hard to accomplish early in a project when a number of different suppliers are being considered.

An alternate approach might be to meet several of those suppliers on neutral ground such as the Maintenance & Reliability Technology Summit (MARTS) scheduled for May 24-27, 2004 in Rosemont (Chicago), IL. The event, produced by MAINTENANCETECHNOLOGY and Reliabilityweb.com, promises to provide significant opportunities to meet with a variety of suppliers of maintenance and reliability products and services.

The Technology Track at the MARTS conference is designed to provide opportunities to hear about the latest offerings from suppliers in a series of concurrent technical and commercial innovation sessions where suppliers will explain their technology and answer questions from practitioners. Extended conference breaks for refreshments and lunch are being planned for the MARTS exhibit hall to provide further opportunities for conversation.

Get you and your team involved with MARTS, where there will be opportunities to learn from consultants and practitioners, as well as suppliers. We look forward to seeing you there along with your team. MT

rcb

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241

6:17 pm
February 1, 2004
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Shopping for Computerized Maintenance Management Systems Online

In the past few months, this column has covered computerized maintenance management systems (CMMS) and enterprise asset management (EAM) resources available on the web. We also have covered an open source code CMMS and freeware CMMS. At last count, there were more than 400 CMMS products available. You will need a great deal of time to investigate even a small percentage of them.

One solution is to run with the crowd and select SAP-Plant Maintenance (if your company runs SAP, this decision may be in your future), MRO Software or Datastream. Our research shows that these three vendors cover just over 50 percent of the CMMS/EAM market.

That leaves at least 397 maintenance software packages uncovered. If you are like many companies, you may decide to bring in an expert to assist in your CMMS selection process.

Consultants can be an excellent resource for ensuring a good software selection process. You must seek one willing to fully understand your requirements and partner with you for the long-term success of your CMMS project. These types of CMMS consultants are available if you look hard enough. You should also make sure that the consultant is not affiliated with any specific software vendor, lest the results be skewed in its favor.

Online knowledge base
An alternative for CMMS selection is available for those who want to do it themselves. Cmmscity.com, which is affiliated with the writer’s Reliabilityweb.com, has just completed a project with Technology Evaluation Centers Inc. to launch an online knowledge base of CMMS and EAM software. This system allows a CMMS shopper to be armed with powerful information that should make the initial vendor selection process more productive.

The CMMS knowledge base contains more than 2700 criteria for CMMS vendor evaluation and selection. The data supplied by each CMMS vendor has been vetted by leading CMMS subject matter experts to create an impressive man/machine information system.

The Cmmscity.com knowledge base, allows users to describe the type of work environment, specific work requirements, number of users, the type of computer operating system, budget ranges, and hundreds of other optional information elements. The knowledge base displays all the possible CMMS choices with summarized information and allows the user to select up to five vendors for a detailed side-by-side comparison. Original criteria may be adjusted on a what-if basis to see how different factors affect different vendors. Once the reports display the information as the user wants, cost justifications and business case reports may be prepared to begin the real world evaluation process.

The Cmmscity.com knowledge base is available at no cost for up to 7 days. If someone wants to take more time to evaluate CMMS options, a small service fee applies. Even with the fee, it is a fraction of the cost of hiring a CMMS consultant.

This is another example of the Internet changing the way things are done and we are always in favor when the power of information shifts into the hands of the buyer. In the past, CMMS buyers sometimes did not know what they did not know until the final software decision was made.

Cmmcity.com also offers an alternative manual CMMS shopping system that allows users to supply basic system requirements. These requirements are sent to various CMMS vendors who each reply to the shopper with their best offers including software, implementation services, support, and training.

With almost 60 percent of CMMS implementations failing to generate the expected return on investment, it is important to have every advantage available to make sure you end up with the right software for your maintenance operation. Try the Cmmscity.com knowledge base and see how your decision-making process can be markedly improved with the power of detailed information and side-by-side CMMS comparisons. MT

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218

6:16 pm
February 1, 2004
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Why Can’t Maintenance Be a Strategic Initiative, Too?

Maintenance suffers from a deficiency of understanding and respect. It is probably fair to say that most people (even management) think the role of maintenance is to “fix things when they break.” That could hardly be further from the truth. When things break down, maintenance has failed. The maintenance job is to maintain it so that it never breaks.

A typical manufacturing plant has hundreds, even thousands, of equipment components that can create problems in myriad ways. Plant managers and production managers often do not understand the reasons behind these chronic problems and thus miss one of the biggest strategic opportunities available to make improvements in capacity, throughput, and profits—performance improvement through better maintenance and reliability.

In many of these companies, maintenance practices are highly informal, not well-organized, and not based on “best practice” approaches. Good systems of work control are either inadequate or not present at all. Breakdowns are frequent and the majority of maintenance activity is reactive. In the pressure of time, maintenance may be subjected to a “quick fix” mentality, an approach that actually exacerbates the situation—not exactly the formula for world class status.

The challenge for maintenance managers today is to gain recognition, at all levels, in all departments, that maintenance is a strategic tool, too—recognized as an integral part of the plant production strategy, an integral component of the overall plan by which the plant meets its marketplace.

What can you do to move to world class status in maintenance and reliability? The following steps provide a useful framework for constructing the “vision” and organizing the effort for making the journey to maintenance excellence.

Step 1. Get your act together
Maintenance improvement must start with good management processes. To make maintenance resources more productive requires the implementation of appropriate planning methods, organizational structures, work control systems, material control techniques, information management systems (CMMS), and measurement and control techniques so as to optimally manage and control the maintenance resources—labor, materials, and capital.

Step 2. Get beyond the boundaries
Maintenance cannot do it alone. Both production and maintenance share a number of basic responsibilities that each must exercise diligently in concert with each other to get what they all want.

As a minimum, production should work with maintenance to reduce dependency on “stand-by” shift mechanics and “just-in-case” maintenance. Furthermore, production should develop performance measures which reflect the maintenance contribution in terms of the overall production objectives, not as a cost but as a necessary value-added resource to best meet production objectives.

Step 3. Fix the process, not just the problems
By this step, zero breakdown maintenance is the goal, and it is actually achievable using such techniques as total productive maintenance (TPM), reliability centered maintenance (RCM), and PM optimization (PMO).

TPM. TPM is a process to improve machine reliability and efficiency by involving all employees in the care, purchase, and improvement of equipment. It fully engages the entire organization (especially maintenance and production) in eliminating every possible thing that gets in the way of overall equipment effectiveness (OEE = Availability x Production Rate x Quality Rate).

RCM. Reliability centered maintenance (RCM) is a systematic, highly structured, disciplined approach to maximize safety and function of equipment assets. RCM uses a rigorous framework for identifying and eliminating all the potential ways an asset can fail to perform its intended function and/or the consequences of that failure.

PM Optimization. PM Optimization uses RCM principles to optimize current maintenance strategies with the result that downtime is reduced, performance is increased, maintenance costs are reduced, and the resulting maintenance procedures are actually more effective.

It is time that enhanced asset reliability is recognized as a critical element in manufacturing performance and market competitiveness (maybe even survival) in today’s manufacturing environment. It is time that maintenance is recognized as a cost to be optimized, not as a necessary evil to be minimized. MT


Dale R. Blann, PE, is principal and CEO of Marshall Institute, Inc., a management consulting firm providing professional consulting and training services to maintenance and operations personnel throughout the world for more than 25 years. Continue Reading →

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4:39 pm
February 1, 2004
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The Discipline of Maintenance Excellence

Management, planners, maintenance, and operations need to know their roles to achieve excellence goal.

Many companies have the desire to achieve maintenance excellence but lack the discipline to make it happen. Once the mechanisms are in place for maintenance excellence, maintenance and operations personnel often still do not understand what must happen to achieve the goal. Simply buying a computerized maintenance management system (CMMS) and turning it on will do only a portion of what is needed to improve the maintenance process.

Maintenance personnel, planners, and maintenance and operations managers, with no training on their roles and responsibilities, can be confused about the overall objective. The following elements of discipline must be put in place when heading down the road to maintenance excellence.

Management discipline
Management, especially upper management, must set the tone for what is usually a significant culture change in the entire organization. A few important questions must be asked:

• How will jobs change from this point forward?

• How will we drive this effort in the right direction?

• What is the first step?

The answers to these questions may vary, but a good first step is to identify the goals of this effort. All parties involved must agree on the metrics that will be used to measure progress. These metrics must be just as important as Safety, Quality, and Output standards. (See accompanying section “Performance Metrics.”) Attention must be given to these new metrics, which in the end support all of the company’s standard measurements of performance.

When managers and supervisors are held accountable for their performance against these new measurements, an important message is sent. This message will quickly filter down to even the lowest level. People tend to do what makes their bosses happy. Management must clearly identify what those things are and the expected behavior.

The focus must change from how many widgets did we make today to how reliable was our equipment today? What delays are eating our lunch? Do we have preventive and/or predictive maintenance tasks in place for this equipment? What percentage of our PMs are we able to complete? Which equipment needs to be restored so that we can maintain it? Management must demand detailed action plans that will eliminate recurring equipment problems.

How effectively are we planning our maintenance? What is our backlog of work? What percentage of our maintenance is reactive? The answers to these questions will provide management with the important information needed to manage the organization toward the ultimate goal of maintenance excellence.

Planning discipline
Management also must have the discipline to dedicate personnel to the planning function and provide them with a tool—a CMMS—and the support to utilize it to its full potential. This step is critical to achieving the goal of maintenance excellence. Once this mechanism is put in place, planners must take on an important role in the organization.

In order to fulfill this role, their position must be defined and guidelines developed on how equipment information will be collected, work will be planned, history will be captured, and performance will be measured. There must be a disciplined approach to planning work. Planning must provide the maintenance department with detailed information, material, tools, and equipment requirements to perform the work. Accurate man-hour estimates are needed to efficiently schedule the day or week’s activities.

Close coordination with operations is key to getting their cooperation and equipment access for PMs or repairs. Planners must facilitate meetings with operations and maintenance to negotiate the scheduling of activities. Everyone in the organization must have the discipline to attend these important meetings. Management must stay focused on maintenance excellence in order to drive this needed teamwork.

Another important facet of disciplined planning is the manner in which work order feedback data is collected. Entering feedback information into the CMMS is critical so that equipment data is readily available and accurate. All worker time must be reported against work orders. This data will be needed to answer the new questions that management will be asking about failures and overall performance.

Planner performance must be evaluated. Are jobs being estimated accurately? Are assignments of PM development being completed? Is completion information on work orders being entered properly? Are periodic PM audits being performed and frequencies adjusted as needed? A combination of audits and metrics can be used to measure planner effectiveness: For example, planned vs actual, number of PMs created per week, or completion code accuracy.

Process discipline
In order to clearly identify how people should function in their assigned roles, the maintenance process must be mapped out. Once again, all parties involved need to be part of this effort. With the business process identified, there will be no question or excuse for noncompliance.

Maintenance then can adopt the position that no work is performed without a work order. This can be clearly defined in the maintenance process flow chart. Setting this discipline in place from the very beginning will eliminate confusion and excuses. The work order review and approval cycle also should be identified in the process flow, as well as planning, execution, and feedback flows. It is best to start with a high-level flow chart and then develop subprocess flow charts where necessary (Fig. 1).

These flow charts provide the basis on how the business of maintenance will operate in the facility. This is a key step and will provide everyone with a clear map toward maintenance excellence.

Maintenance discipline
The maintenance group may feel as if it is being driven down a road of endless red tape and paperwork. Some may struggle with the concept of work orders. This area will require the highest degree of discipline. Switching from what is often a list of jobs in a notebook to a formal work order system can be a daunting task for some longtime maintenance supervisors.

Progress in this area often can be gained by teaming up the maintenance manager and the planner to decide which jobs need to be planned and to jointly work on creating the schedule for the coming week. Once the jobs are planned and scheduled, the primary concern of the maintenance manager is execution and feedback.

It is important that every work order be issued to the maintenance technicians and that every work order be returned and filled out with completion or status information. An area or bin should be provided for these returning documents so there can be no excuse as to why they were not returned. The maintenance manager should review the returned work orders and demand accuracy and completeness from the maintenance technicians.

The completed work orders then must be returned to the planner for review and the entering of closing information and time reporting. The technician or supervisor can enter this information into the CMMS, but standardization of data entry is often at risk.

Properly entered failure codes are needed for equipment failure analysis. Failure in receiving and entering work order information will lead to an incomplete or broken feedback loop (Fig. 2). Planners can help in this area by providing worthwhile information on the work orders so the maintenance technicians will realize the work orders have value and will treat them accordingly. Maintaining the discipline to complete this loop will form the basis for a fully utilized system.

Operations discipline
Operations personnel must now enter a work order to request maintenance on the equipment in their area. It will be difficult at first but must be accepted as the method in which to get work done by the maintenance department.

The work to be done must be clearly defined so planners are not tied up investigating every job for minor details. It should be understood that the better the information, the more efficient the maintenance department can be in addressing the request in a timely manner. The operator can gain twofold by cooperating with maintenance: The equipment will be well maintained and the operator can monitor the progress of the request by using the CMMS.

Another operations responsibility is to work with maintenance to identify and maintain an accurate priority list. Taking the time to communicate and keep this list accurate will ensure that maintenance is working on the right things, not just the request of the day. The CMMS can be used to show if discipline is lacking in this area.

Turnaround/outage planning discipline
When planning a plant turnaround or equipment outage, the team members who are developing the plan and schedule must be willing to spend the time required to develop realistic estimates and expectations. Too often these plans are put together with the intention of giving management something that looks good, with little intention of following the plan once the outage has begun. Often, financial decisions are being made based on these plans.

It is important that the same discipline that is used to complete the work be in place to plan the work accurately. Lacking this kind of discipline will likely cause cost overruns and disappointing results. Management must realize the importance of this effort and allocate resources and time to achieve this important part of the turnaround or outage.

The road to maintenance excellence can be rough and winding, but with the right discipline at the wheel, your final destination is well within reach. MT


Randy Heisler senior consultant, maintenance strategies, at Life Cycle Engineering, Inc., 4360 Corporate Rd., Suite 100, North Charleston, SC 29405; (843) 744-7110

PERFORMANCE METRICS

Safety
• Lost time accidents
• Accident frequency

Quality
• Percent diversion
• Percent rejects

Output
• Tons/hr
• Cost/ton

Maintenance
• Percent unscheduled
• Percent PM completion
• Backlog
• Percent delay

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Maintenance Process Flow Chart

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Fig. 1. Diagramming the maintenance process provides the basis for how the business of maintenance will operate in a facility. Planning subprocess flow will eliminate confusion and excuses.

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Feedback Loop

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Fig. 2. For this feedback loop to be successful, it is vital that work order information be received and entered.

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2:44 pm
February 1, 2004
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Achieving Precise Alignment

Without proper preparation, standards and tolerances, and precision procedures, machines may have significant residual misalignment even though the alignment computer is reading zeros.

When asked which alignment methods are employed at a plant, the staff will often proudly display the latest laser alignment technology tool. When used properly, laser tools can provide accurate alignments for a variety of machine configurations.

Based on observations in the field, however, it is apparent that many companies are actually misaligning their machinery precisely with these tools. The consistent and precision approach outlined below will maximize the effectiveness of any alignment tool—whether dial or laser—and help achieve the best possible alignment.

Gather information
Before the first wrench is turned, gather all of the information required for the alignment job.

  • Identify the alignment specifications for the shaft-to-shaft alignment and the base. Refer to the machine manufacturer’s documentation as well as historical records. In the absence of specifications, 0.001 in. (1 mil) offset at the coupling with no more than 0.002 in. (2 mils) offset at any foot plane will provide a precision alignment. Be aware that some high-speed or high-precision machinery may actually require a tighter specification. Do not rely on the coupling tolerances or rules of thumb based on shaft speed and shaft diameter, as these will often provide insufficient precision.
  • Determine the thermal growth offsets for the machine. If well-documented thermal growth values are not available, a thermal growth study using any of a variety of methods may be necessary. Most thermal growth values provided by manufacturers are recommended starting points, and the actual growth must be determined from the installed condition. Offsets based on horsepower, for example, are not accurate and may actually worsen the condition.
  • Verify the as-left readings from the previous alignment records. A significant change from the as-left readings and the current or as-found readings may indicate a base problem such as corrosion, distortion, cracking, or loose or damaged anchor bolts.
  • Check bolt torque requirements.
  • Review the work order for completeness and reconcile any questions or problems before continuing with the job.

Assemble tools and supplies
No matter how well calibrated the technician’s forearm is, it is no replacement for a proper torque wrench. When bolts are torqued unevenly, the machine will move unpredictably. Use the right tools for the job, which include properly sized and safe wrenches, crow’s feet, sockets, torque wrenches, etc.

If the shafts are difficult to turn manually, use an approved and appropriate turning tool, such as a strap wrench, to ensure that pipe wrenches or other tools that could damage the shaft or coupling components are not used. Check out a shim kit with the properly sized shims for the feet and the hold-down bolts.

Select the alignment system to be used for the job. Reverse dial and laser systems provide accuracy to within the thinnest shim that can be used, which is typically 0.001 in. (1 mil). Some machines may require rim-and-face fixtures if one of the shafts cannot be turned depending on the capabilities and available fixtures for the laser system the company may have.

Inspect the machine
Whether realigning an existing machine or setting up new equipment, perform a thorough inspection of the machine and base before starting the job. Look for any degradation of the base due to corrosion or concrete damage. Check for cracks in bases or frames and check any anchor bolts.

If the machine is still operating, hand-feel all joints and interfaces to determine the presence of relative motion, which may indicate looseness or other problems. Check the condition of all shims on the driver and driven machines. If any of the machine components are bolted directly to the frame or base without shims, suspect soft foot. If spacer plates are used, ensure that they are installed correctly and that they are not damaged, bent, or corroded.

Verify that the hold-down bolts are correct for the application and that they are not damaged. Hardened washers should be present under all bolts. If the washers are cupped or damaged, they should be replaced. Check for horizontal and vertical jacking screws and verify that they are free to move and that they are not providing any binding force. If jacking screws are not present, fabricate new ones, as this will speed the alignment process and ease machine movement.

On existing machinery, collect a set of as-found readings when the machine has reached ambient conditions, and compare with previous results. If there is a significant discrepancy, re-evaluate the base, foundation, piping, etc., to determine the cause of the movement.

A difference may be due to errors with the previous alignment or because offsets were used during the alignment that were not recorded. Tactfully review the previous alignment with the lead technician if available. Ask about the alignment method that was used and if there were any difficulties encountered while aligning the machine the last time.

Perform a step-by-step alignment
Every plant has slightly different work procedure rules based on safety requirements, machine types, and the labor structure. The fundamental alignment procedures necessary for consistent precision are easily adapted to any work environment. There are many benefits when using a procedure, but the most important are that it assures that every machine will be aligned with the same attention to detail and it helps to overcome many of the bad habits that may have become engrained with the workforce.

The largest portion of an alignment typically involves preparing the machine for the actual alignment moves. When the machine is on solid footing with minimal strain from attachments and the shafts and bearings are within specifications, it is much easier to move a machine consistently and quickly into the desired position.

The following provides an overview of the typical steps required prior to actual alignment. Although these steps appear to be quite basic, they are often skipped in the interest of time or due to lack of precision training and focus.

• Properly secure the machine using your company’s lockout/tagout procedures. Divert flow to fans or pumps that could cause a shaft to rotate unexpectedly.

• Eliminate soft foot in the driver and driven machines. Soft foot will have an adverse affect on the machine components due to strain and distortion. During the final alignment, soft foot often creates inconsistent readings from move to move. Generally, the maximum gap under any foot of the machine should be no more than 0.001 in. (1 mil).

Be aware that a laser system cannot determine the actual gap at a foot—it only measures the effect of the soft foot at the shaft. Always measure the gap with feeler gauges and make the appropriate parallel and angle corrections.

Before making the soft foot corrections, it is advisable to place the driver and driven machines at the center or midpoint of their horizontal movement limits. This can save time later and may avoid the necessity of making bolt-bound corrections.

• Minimize pipe, duct, and conduit strain on all of the machine components in the machine train. Measure shaft movement horizontally and vertically at the coupling as each flange is attached. Movement greater than 0.002 in. (2 mils) indicates corrective action is necessary. Some mechanical seals may have requirements that are more stringent. Refer to the seal manufacturer’s specifications for the recommended values.

• Inspect all shafts and bearings to ensure that axial and radial runout and play are within tolerance. Before rotating any shaft, however, be sure that the bearings are properly lubricated. A dry rolling element bearing can be damaged simply by rotating the shaft during an alignment. Circulating oil systems may need to be energized to provide an oil film.

A machine with a severely bent shaft can be aligned with a laser or reverse dial system because the rotation occurs at the centerline of the shaft’s two bearings. The effective shaft centerlines can be aligned, but the actual offset at the coupling may exceed its capabilities, and it is likely that the machine also will exhibit evidence of unbalance.

• Inspect the coupling and all components. Missing components or incorrect key length can create unbalance. Worn parts on gears, spiders, grids, etc., can cause the coupling to lock axially and may produce thrust-related bearing problems. If the coupling is lubricated, remove the covers and hand-pack the coupling with the correct type and quantity of grease.

• Inspect all bolts and shims to ensure that the proper types are being used and that they are not damaged. Replace any suspect parts. Ensure that hardened washers are used under all hold-down bolts or nuts. Plates may have to be fabricated to provide a smooth bolting surface so that proper clamping force can be obtained and to minimize horizontal shifting of the machine when the bolts are tightened. Make sure that the hardware is not bottoming out and that there is no binding.

If possible, limit the number of shims under each foot to three. This avoids uneven shim compression and a soft foot–like condition and makes the machine movements more consistent. Make sure that all shims are of high quality precut stainless and are sized for the bolts and for the machine footprint.

• Verify soft foot condition one last time before beginning the alignment.

The order in which these steps are performed will vary from plant to plant. For example, some may prefer to inspect the shafts first. If the shafts are not within specifications, the alignment should stop until the shaft has been repaired or the machine replaced.

At this point, the final alignment can be performed. What may seem to be an inordinate amount of preparation time actually speeds the entire alignment process because it insures that the machine will move predictably in the horizontal and vertical planes. When problems are encountered, check for the following conditions:

• Base- or bolt-bound component

• Pipe strain

• Soft foot

• Improper shims

• Failure to use a torque wrench and tightening sequence

• Lack of vertical and horizontal jacking screws

• Bent shaft, excessive bearing clearance, inconsistent oiling of plain bearings

• Locked coupling or uncorrected coupling backlash, shaft end-float

• Setup and/or interpretation of alignment system results. For example, bar sag or parallax errors, laser interference, loose or slipping fixtures, incorrect dimensions, etc.

Standard practice should include a reading repeatability check. If the readings do not repeat, a setup problem must be addressed. When in doubt, go back to the preliminary steps and then take a new set of readings.

Misalignment example
In some cases, a visual inspection will reveal a misalignment condition—even when the dials or laser read zeros when the job had been completed. Improper shimming, cupped washers, etc., all reveal an inadequate alignment and the likely presence of soft foot, case strain, and even altered dynamic characteristics.

Figure 1 shows that plates were installed under the motor feet on both sides to raise the motor’s shaft centerline up to the level of the lube oil pump. Notice that the plate does not match the footprint of the motor, which could compromise the stiffness or rigidity of the motor. It may have simply been installed backwards or upside down. Notice also that the plate is made of what appears to be mild steel. The uneven surface of the plate due to corrosion and apparent field flattening will make a precision vertical alignment of this machine difficult.

Figure 2 shows the typical condition of the hold-down bolts and washers found on the motor. Notice that the soft washer has been ground to accommodate the radius of the foot but that the washer was installed backwards. The cupped condition of the washer would make this machine very difficult to align horizontally as it would tend to locate around the washer.

The shims shown in Fig. 3 under one of the lube oil pump’s feet are grossly oversized. The slot in the shim is nearly as large as the foot. Tightening the hold-down bolt will actually pull the foot down into the shim slot, which will compromise the stiffness of the foot and make the vertical misalignment change dramatically depending on the bolt torque.

Laser alignment of this machine alone will not correct its misalignment problems. The precision-minded technician must identify the corrections necessary to bring this machine back on-line at 100 percent (or better) of its design condition.

A quality and precision alignment is possible on virtually any basic horizontally mounted machine when a step-by-step approach is followed. When the integrity of all machine components is verified and the machine is resting on a solid foundation, the alignment moves will be predictable and the final results will be confirmed with a smooth, long-running machine.

None of these steps can correct inadequate time to do the job correctly or a “close enough, let’s start it up” attitude. These are management and reliability issues that must be in place before a maintenance staff can realistically begin performing true precision alignments. MT


Gary Patrick is supervisor, proactive reliability maintenance skills and training, at SKF Reliability Maintenance Institute, Norristown, PA ZIP; (303) 979-0506

Fig. 1
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Fig. 2
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Fig. 3
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Misalignment conditions are not always corrected by laser alignment. Visual inspections can identify machine installation problems (Figs. 1 and 2) and incorrect shimming (Fig. 3) that need to be addressed before proper alignment can be achieved. (Photographs courtesy of SKF Reliability Maintenance Institute.)

 

 

 

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