Personal safety, training, RCM techniques, and acceptance testing highlight the latest revisions to this key maintenance practice
In today's global economy, the quest for increased productivity is a given for most commercial and industrial facilities. Keeping those facilities running smoothly at maximum efficiency requires a host of programs involving all aspects of the operation, including maintaining the electrical equipment. What should be done and how often are the basic components of any approach, but an effective electrical preventive maintenance (EPM) program goes well beyond that. It must ensure all personnel implementing the procedures are up to speed on what constitutes electrically safe work environments. That's where NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, comes in.
Growing from a four-chapter document serving as an overview on EPM to 31 chapters and 13 annex sections spanning more than 220 pages, the current version of NFPA 70B covers topics from reliability-centered maintenance (RCM) to personnel safety. In addition to the safety and fundamentals of EPM, individual chapters cover topics such as substations and switchgear assemblies, power cables, motor control equipment, electronic equipment, molded-case circuit-breaker power panels, ground-fault protection, fuses, rotating equipment, lighting, wiring devices, testing and test methods, cable tray and busway, uninterruptible power supply (UPS) systems, power quality, grounding, and EPM from commissioning (acceptance testing) through maintenance. The annexes feature an inspection checklist, forms for inspection, testing and repair recommendations, long-term maintenance guidelines, recommended maintenance intervals, and RCM guidelines.
Because the document has been used for more than a third of a century, originally published in 1973, most people are familiar with its value in EPM programs. The rest of this article will focus on the recent revisions and significant additions featured in the 2006 edition. Let's a take a closer look.
Safety. The latest edition of this practice features a new chapter on safety, which is placed up front to provide more complete and updated coverage. It consolidates much of the safety-related information that was originally dispersed throughout the document; though specific references to safety concerns while performing maintenance on individual pieces of equipment remain within those sections.
Minor revisions. Some minor revisions were made to the cleaning procedures for substations, the measurement and testing of bearings, and restoration of rotating equipment. Improvements were also made to the re-lamping process of “luminaires” (which replaced the word “fixtures”). A strong recommendation on not performing hi-pot testing on extruded insulation power cables was included along with new methods of testing, such as partial discharge testing, were added. Other minor changes to the document were the addition of information on low-voltage busways, infrared testing (and replacement) of Belleville spring washers, revised replacement interval for electrolytic capacitors in UPSs, and updated methods of dynamic balancing rotating machinery to reduce vibration.
Major changes. On a somewhat larger scale was the addition of a section on retrofitting equipment. This new section addresses reworking, remanufacturing or retrofitting that involves replacement or refurbishing of major components of electrical equipment or systems. In Annex F, the maintenance and test forms were significantly expanded and updated to reflect the practices of the InterNational Electrical Testing Association (NETA) and U.S. Army Corp of Engineers (USACE).
A new Chapter 7 on “Personnel Safety” relies heavily on NFPA 70E and the appropriate OSHA safety-related documents, which should be followed for the development of programs and procedures associated with maintenance activities. Per 70B-7.1.2, “Personnel safety should be given prime consideration in establishing maintenance practices, and the safety rules should be instituted and practiced to prevent injury to personnel, both persons who are performing tasks and others who might be exposed to the hazard. The principal personnel danger from electricity is that of shock, electrocution, and/or severe burns from the electrical arc or its effects, which can be similar to that of an explosion.”
A key element with regard to personnel safety is first determining what constitutes a qualified person. As noted in 70B-7.1, “Maintenance should be performed only by qualified personnel who are trained in safe maintenance practices and the special considerations necessary to maintain electrical equipment. These individuals should be familiar with the requirements for obtaining safe electrical installations.” Equally important is “the qualified person should determine if the hazard exposure is limited and restricted against those not qualified for the particular task so a person not qualified for a specific task, even though fully qualified in all other ways, should not be exposed to the hazard of that specific task,” as outlined in 70B-126.96.36.199.
Training is another key element in the revised document, as “all employees should be trained in safety-related work practices and required procedures as necessary to provide protection from electrical hazards associated with their respective jobs or task assignments,” as noted in 70B-7.3.
Key steps in establishing an electrically safe work condition are identified in 70B-7.4.2, including:
Determine possible sources of electrical supply to the specific equipment.
After properly interrupting the load current, open the disconnecting device(s) for each source.
Apply lockout/tagout devices in accordance with a documented and established policy.
Use an adequately rated voltage detector to test each phase conductor/circuit part to verify they are de-energized.
Where the possibility of induced voltages or stored electrical energy exists, ground the phase conductors or circuit parts before touching them.
Each job task should be analyzed for what particular safety hazards could be encountered. The arc flash hazard is one of the most important of these. Per 70B-7.6, “Switchboards, panelboards, industrial control panels, and motor control centers that are likely to require examination, adjustment, servicing, or maintenance while energized should be field marked to warn qualified persons of potential electric arc flash hazards.”
The latest revision of 70B also consolidated the section on grounding of equipment to provide protection for electrical maintenance personnel into the “Personnel Safety” chapter.
Another significant addition in the 2006 edition was maintenance procedures for supervisory, control, and data acquisition (SCADA) equipment. As processes become increasingly automated, SCADA systems are at the center of operation. Without such, the programmable logic controller (PLC) and other computer systems can receive incorrect information upon which it decides what action is necessary. Annex I contains maintenance procedures and intervals for SCADA equipment.
A new chapter was added on RCM, along with extensive tables on equipment reliability. As outlined in 70B-30.5.2, “The RCM approach is the process of developing preventive maintenance (PM) programs for electrical and mechanical systems used in facilities based on the reliability characteristics of those systems and economic considerations, while ensuring that safety is not compromised.”
Rather than basing the maintenance on time intervals, the RCM method uses tables of availability data on a specific piece of equipment. This data in Annex K was collected at a large number of statistically diverse facilities over several years in a program funded by the USACE. “Whether or not a given PM task is effective depends on the reliability characteristics of the item in question. Whether or not a task is economical depends on many factors, including how easily the PM tasks can be performed,” as stated in 70B-K-188.8.131.52.
The last major addition recognizes the importance of starting maintenance programs as soon as the equipment is installed (i.e., at the time of commissioning). “Commissioning, also referred to as acceptance testing, integrated system testing, operational tune-up, and start-up testing, is the process by which baseline test results verify the proper operation and sequence of operation of electrical equipment, in addition to developing baseline criteria by which future trend analysis can help to identify equipment deterioration,” states 70B-31.1.1.
Though some of the steps outlined in the procedure may seem more like engineering-level tasks, the maintenance person should be aware of what is involved, see that the required tests are carried out properly, and obtain a copy of the data to use as a comparison for future measurements for benchmarking purposes.
Making the most out of maintenance. Today, an effective maintenance program manager must find ways to spend the limited funds available to him, while maximizing productivity of the facility — whether the work is done by in-house personnel or outsourced. NFPA 70B-2006 provides valuable information on how to do just that for electrical equipment, in a safe and efficient manner. Suggestions on how to improve the document as well as addressing new technologies and methods are always encouraged. Proposals are now being accepted for the 2009 edition, and information on submittals can be found on the NFPA Web site at www.nfpa.org.
Bishop is NFPA 70B committee secretary and technical support specialist for the Electrical Apparatus Service Association, St. Louis.
Sidebar: NFPA 70B Committee Goals
The NFPA 70B committee's primary responsibility is “for documents relating to preventive maintenance of electrical, electronic, and communications systems and equipment used in industrial and commercial type applications” with the view of reducing loss of life and property and improving reliability, performance, and efficiency in a cost-effective manner.
In the last cycle, the committee acted upon 150 proposals before releasing the 2006 edition. Part of the revision process for each edition includes updating references and definitions, as well as some minor changes in procedures to keep current with the latest best practices.