Out with the old
An annual or semiannual plant shutdown gives maintenance staff time to repair equipment, retool for a new production run or even wax and seal the floors. Plant facilities are upgraded or equipment is overhauled during these planned shutdowns. The key word is "planned," especially when it comes to the electrical distribution system.
An annual or semiannual plant shutdown gives maintenance staff time to repair equipment, retool for a new production run or even wax and seal the floors. Plant facilities are upgraded or equipment is overhauled during these planned shutdowns.
The key word is “planned,” especially when it comes to the electrical distribution system.
“A maintenance shutdown is an excellent time to consider what other work needs to be done on the distribution system, avoiding the necessity of performing energized work during the rest of the year, and avoiding the risk of an arc flash accident,” said Joseph Weigel, product manager of Square D Services Marketing at Schneider Electric in Nashville, TN.
The issues to consider when faced with a challenge of this magnitude include the age of your electrical system and its components, safety, cost, reliability and the feasibility of modernization.
“Do your research to determine the best fit for your system and personnel skills,” said Jim Closson, ABB’s national sales manager of aftermarket products and services in the Circuit Breaker Technology Solutions Div. in Florence, SC. “Determine whether your system is marginal for increased fault duty. Turn to plant maintenance personnel to determine shortcomings with existing equipment and what solutions they would recommend.”
Identify the scope of work
The scope of work depends on how much time you have to perform it. Other considerations are budget, available manpower and other resources, training level and access to outsourced services. Planning the scope of work also depends on knowing the systems and equipment that require service, overhaul or replacement.
When identifying the work, don’t limit its scope without first identifying all the work that needs to be done. Good planning and skillful project management will enable your plant to get more work done than you may first think. Even if you put off a project, identifying all the work in the beginning stages gives you a jump-start on the next big project, shutdown or overhaul.
Upgrading an electrical system requires investigating the integrity of the entire system. Components to inspect or investigate include poles and other electrical cable support structures, low and medium-voltage breakers, fused disconnects, low and medium-voltage switchgear (Fig. 1), transformers, motor starters and MCCs, as well as the machines and equipment they power and the conductors that interconnect them (See “Equipment to inspect”).
Examine repair records and equipment history. Focus on the electrical systems or equipment that cost the most to maintain and operate, or have the most work orders charged to them.
Identify what is to be repaired, replaced or placed on the future work list well in advance of the actual shutdown. Some work can be performed ahead of time. Parts, equipment and services can be procured in time for the work to start.
Another way to identify problematic electrical equipment is by using infrared thermography. IR scans can identify loose or corroded connections or defective equipment that may not be detected by normal visual inspection (Fig. 2). Prepare electrical equipment and systems for safe energized access during the scans, and provide appropriate personal protective equipment. The level of PPE can be minimized, or even eliminated, by using an IR port built into panels and cabinets. If your equipment does not have this feature, this may be a good time to investigate including it. List all the connections and equipment to be scanned. Schedule IR scanning for times when electrical loads are near their peak to allow the worst problems to show up.
According to Frank Gerdts, director of marketing and business development, industrial services at Siemens Energy & Automation, Inc., in Alpharetta, GA, the typical age of electrical power systems installed in the U.S. is around 30 years. “Electrical power systems are typically forgotten. It is very difficult to justify the replacement or retrofit costs. The obvious solution is to replace or upgrade the equipment before it fails. Understanding and predicting the failure is the challenge.”
If equipment is working — or appears to be working — how can a company justify replacing it, or even refurbishing it? Consider it the cost of doing business right.
Making sure the electrical documentation is accurate is the first step to determine what in the plant may be obsolete. The plant’s one-line diagram and its supporting drawings and documents make up your plant electrical system documentation.
NFPA-70E says that electrical documentation, including the one-line diagram, should accurately reflect the plant electrical system. The National Electrical Code requires that power be removed before maintenance is performed (except when using the “Energized Work Permit”). Knowing how your plant is wired helps identify alternate feeds such as tie-breakers. Equipment may have been rewired, modified, reconfigured or rerouted without the changes ever being documented.
“An updated and accurate electrical one-line diagram is an essential ingredient for electrical safety,” said Chet Davis, president of ESA, Inc. in Clackamas, OR. “If workers do not have an accurate map of the system, they can be exposed to potential back-feeds from alternate sources — energized capacitors, undocumented switching conditions and unknown voltages — in addition to the problem of not being able to accurately perform lockout/tagout procedures.”
Davis said that this is one of the most neglected aspects of electrical safety in industry. “Very few of the facilities I have reviewed in the past 20 years maintain accurate electrical one-line diagrams.”
“The focus and enforcement on arc flash safety is raising the bar with respect to maintenance of these records. They may likely become evidence in an injury litigation,” said Weigel.
“The electrical system impedance characteristics have no doubt changed over the years,” added Closson. “Fault and coordination studies, coupled with an up-to-date one-line diagram, are measures that must be taken in order to safely install and set new trip units for low-voltage equipment, and to ensure that both low and medium-voltage equipment are within the safety ranges of fault current availability.”
The weakest link
You may not have the time, money or resources to upgrade everything at once or your system may not need very much upgrading. Sometimes it is prudent to focus on the weakest link.
Weigel said that in most U.S. manufacturing plants, “the weakest link is the circuit breaker — both low and medium voltage — if they are obsolete or past their intended service life. Slow-operating devices can greatly increase the incident energy from an arcing fault, and might not even open for a bolted fault condition. Westinghouse did a study back in the 1980s that indicated a low-voltage ANSI power circuit breaker (open iron frame ACB) that did not have maintenance for a period of five years would have only a 60% likelihood of operating properly during a fault.”
“Low-voltage circuit breakers are the sentinels that stand guard over each main and feeder within a plant,” said Closson. “If they are tired, worn out or haven’t been properly maintained with new, reliable parts, they cannot function reliably to interrupt faults. Circuit breakers that do not open when called upon to do so, or perform this function too slowly can lead to catastrophic system damage or serious personnel injury.”
Repair or replace?
The decision of whether to repair or replace parts of your electrical system is a large part of the planning process. Factors to consider include:
Availability of parts for existing equipment
Ongoing maintenance costs associated with keeping your existing equipment
Cost of replacing existing equipment
Reduced maintenance requirements of new units
Need to increase the fault current rating of specific switchgear without replacing the entire unit.
“The refurbish vs. replace decision comes down to a cost-benefit analysis for the given facility,” said Closson. “Most original breaker manufacturers — if they are even still in business — do not provide support for legacy models past a certain age. Refurbishment and remanufacturing shops have moved in to fill the void left by the original manufacturers. But in some cases, there can be quality concerns with breakers not meeting the demands now being placed upon them.
“Typically, when the cost for refurbishing approaches 60% of replacement, replacement should be strongly considered — particularly when availability of parts, modern technology and increased fault duties are factored in.”
Components, such as protective relays, switches and meters that don’t experience mechanical wear and tear or are not exposed to electrical fault extremes, can be maintained reliably. Breakers do not meet this criterion. “Some breakers are called upon to perform as motor starters or have been exposed to severe duty cycles,” said Closson.
“Replacements should be done at or before the end of the manufacturer’s recommended service life,” added Weigel. “This seldom happens in general industry, as the habit seems to be run to failure. Repair costs — especially for obsolete equipment — become much more expensive than replacing the device with a new, more reliable one. Consider the age of the equipment and availability of replacements and/or parts to keep it functioning properly.”
“The life of mechanical operators can easily be prolonged with proper lubrication and maintenance,” said Gerdts. “Electrical insulation materials can be properly maintained by simply keeping them clean and dry. Many good predictive technologies are available to identify the remaining useful life of insulation materials. It is definitely prudent to identify deteriorating insulation systems prior to their failure.”
“Even circuit breakers that have been properly maintained should be considered for replacement due to technological advances such as modern, reliable microprocessor-based trip units (as compared to older electro-mechanical units), breakers designed for reduced arc incident energy, greatly reduced maintenance requirements and higher system fault level capability,” added James McWhirt, P.E., product marketing specialist with Schneider Electric in Nashville, TN.
Many larger facilities do not have the personnel to manage and execute a project of this scope within the allotted shutdown time. However, several companies that specialize in electrical equipment also have service divisions that can bring qualified technicians onsite en masse, to manage the project and work. Services are also available to reconstruct your one-line diagram, as well as perform other studies — including arc flash analysis.
Identify future work
“After the system upgrade is done, any subsequent changes to the system should be updated in the one-line diagram, and the other electrical system studies should be revalidated,” explained Weigel. “These documents are required when producing an accurate arc flash analysis (which is required), and an accurate one-line diagram is essential in future lockout/tagout procedures. Following the maintenance upgrade, facilities should diligently follow the equipment manufacturer’s recommended maintenance intervals for electrical equipment.”
You should inspect, identify and prioritize the work to be done — especially if you choose to upgrade extensively during a shutdown — to determine what is critical, what is costing you the most money and what can wait. If you have investigated your entire plant electrical system, updated your documentation and identified current and future work, planning, project management and hard work will enable you to execute a plant electrical system upgrade.
The Bottom Line…
Identify all the work that needs to be done, regardless of how extensive it seems initially
Most low and medium-voltage switchgear in service is 30 to 40 years old
NFPA-70E says that electrical documentation, including the one-line diagram, shall accurately reflect the plant electrical system
In most U.S. manufacturing plants, the weakest link is the circuit breaker.
Equipment to inspect
If you are planning for a shutdown that involves upgrading your plant’s electrical system, you should investigate the integrity of the entire system — even if some equipment won’t be repaired or replaced until the next shutdown or maintenance project. Equipment and systems to check include:
Incoming power connection from utility: switch yard, secondary unit substations, etc. — If your plant has aerial cable supports, poles or suspensions, inspect them periodically for mechanical damage or evidence of vibration or deterioration.
Circuit breakers: main, feeder, MV, LV etc. — Inspect low and medium-voltage breaker and fuse disconnect enclosures for dust, dirt, critters, corrosion and tracking. If equipped with a counter, record the number of operations.
Transformers: power, step down, distribution — Check and record transformer primary and secondary voltage and current. If the current exceeds cooled levels, check the transformer cooling equipment (pumps or fans) for proper operation. Transformer voltages must be within
Transformer oil — Check transformer oil level and temperatures. Inspect transformer tanks, fittings, cooling tubes and bushings for leaks (other than those that occur during initial startup). Also inspect transformers for dents, scratches, paint loss and corrosion.
Switchgear — Primary switch, MV, LV, switchboards, panelboards. Using an accurate DMM, test low-voltage switchgear voltage by checking phase-to-phase and phase-to-neutral. Phase-to-phase voltage should be within 1%. Readings should be
MCCs — MV and LV MCCs are typically the oldest components in the plant. Check for work mechanisms, pitted contacts and evidence of arcing.
Busway, conductors and connections — Use IR scanning to determine the integrity of conductors and connections.
Adapted from Cooper Bussmann
NEMA releases revised polyethylene conduit standard
The National Electrical Manufacturers Association has released TC 7-2005, “Smooth-Wall Coilable Electrical Polyethylene Conduit,” which has been revised for the first time since 2000. This standard covers the following types of electrical high-density polyethylene (HDPE) conduit designed for applications below ground, either concrete encased applications or direct burial: EPEC-A, EPEC-B, EPEC-40, and EPEC-80.
Members of the Plastic Pipe Institute worked with NEMA members to harmonize NEMA TC-7 – for electrical, communication, and signaling applications – with ASTM F2160, “Solid Wall High Density Polyethylene (HDPE) Conduit Based on Controlled Outside Diameter.”
“NEMA TC-7 is used by utility and communication companies when specifying HDPE raceways,” says David Kendall , director of industry affairs for Carlon, Lamson & Sessions, and chairman of NEMA’s Polymer Raceway Section. “This standard is vital because it includes technical information supplied to the members by users and inspectors to ensure that the HDPE Raceway is safe and durable.” For more information, visit Jack Smith
States adopting new revision of National Electrical Code
Jurisdictions throughout the United States are moving quickly to adopt the 2005 edition of NFPA 70, National Electrical Code . Since the 50th edition of the code was issued by NFPA late last year, it has been adopted and used in 14 states.
Previous editions of the NEC have been used throughout the U.S. and around the world as the blueprint for electrical safety. Many state and local governments update their electrical code adoptions in conjunction with the three-year NEC revision cycle.
“The quality of the 2005 NEC is what led us to make this decision,” said Don Offerdahl , executive director of North Dakota’s Electrical Board. “We know that the added provisions in the 2005 NEC have strengthened public safety in our state.”
“Our focus is on providing the safest electrical requirements possible,” said Bill Laidler of the Massachusetts Board of Fire Prevention Regulations. “The fact is the 2005 NEC provides the best set of safety requirements ever found in an electrical code.” Joining North Dakota and Massachusetts in using the 2005 NEC are the following states: Colorado, Idaho, Nebraska, New Hampshire, North Carolina, Ohio, Oklahoma, Oregon, South Carolina, Texas, Washington and Wyoming. Many other states have already started the process of updating their current NEC adoption to include the 2005 edition.
Topics in the 2005 NEC include:
Stronger protection against electric shock
Greater protections against fire
New safeguards for electrical workers
Increased reliability of emergency systems.
The NEC has long been the world’s most widely adopted safety code. The 2005 edition of the code offers additional safety requirements to protect people and property against fire and shock hazards associated with the use of electricity. — Jack Smith
Looking for resources?
For more information on the ANSI, NFPA and OSHA standards governing electrical equipment maintenance, go to