Safety is just as important during maintenance operations as it is during construction. In fact, the maintenance and repair of existing electrical installations can be more dangerous than for new construction because work is often carried out in a functioning and occupied facility. Safety considerations should not only include workers, but also those around whom the maintenance work is being performed.
Regulations, standards, and recommended practices
Regulations, standards, and recommended practices that address safety during electrical maintenance operations include Occupational Safety and Health Administration (OSHA) Regulations, NFPA 70E, and NFPA 70B.
OSHA regulations apply to maintenance and construction activities. They are intended to protect those performing maintenance work and those in the vicinity. The electrical contracting firm should be specifically aware of several OSHA regulations concerning electrical maintenance operations. OSHA Part 1910.147 is entitled “The Control Of Hazardous Energy” and deals specifically with lockout and tagout requirements and procedures during maintenance.
Subpart S of OSHA 29 CFR 1910 addresses electrical safety specifically, which includes OSHA Parts 1910.331 through 1910.335. These five sections address personnel training requirements, selection, and use of work practices, use of equipment, and safeguards for personnel protection.
NFPA 70E is published by the National Fire Protection Association (NFPA) as part of the Fire Code and entitled Standard for Electrical Safety for Employee Workplaces. NFPA developed this standard to complement NFPA 70, which is the National Electrical Code (NEC), and to meet OSHA’s need for a safety standard that addresses electrical safety for employees.
The 2000 edition of NFPA 70E includes four parts. Part I covers the general requirements for electrical installations, which are applicable excerpts from the NEC. Safety-related work practices are covered in Part II, which applies to maintenance and includes general requirements for electrical work practices, protective equipment and its use, and lockout/tagout procedures.
Part III builds on the work practices covered in Part II and directly addresses safety-related maintenance requirements. Part IV covers the safety requirements for specific types of equipment such as electrolytic cells, batteries and battery rooms, lasers, power electronic equipment, and more.
NFPA 70B is the 1998 edition of the Recommended Practice for Electrical Equipment Maintenance. Like NFPA 70E, NFPA 70B complements the NEC and focuses on providing maintenance methods and tests for specific electrical systems and equipment. However, safety in maintenance operations is addressed throughout NFPA 70B and in particular sections of this article.
Electrical maintenance safety procedure
A basic electrical maintenance safety procedure can be summarized in four steps.
Step 1: De-energize the circuit.
Circuits and equipment must be de-energized before work begins. If the circuit is properly de-energized, there is no electrical danger. However, this basic rule of electrical safety is sometimes ignored for 120- and 277-volt circuits, which can cause shock and, under the right circumstances, electrocution. A shock may not be fatal or even serious, but other injuries that result from the person’s reaction may. Take for instance the electrician working on a fluorescent lighting fixture that is left energized. He received a shock that knocked him off his ladder and through the ceiling grid, nearly slicing off his left thumb and then breaking his right arm in the fall.
NFPA 70E requires that circuits and equipment be de-energized before maintenance unless de-energization will result in an increased hazard; for example, with the shut down of hazardous location ventilation equipment. In addition, circuits and equipment often need to remain energized for testing and troubleshooting. When work on energized circuits and equipment is necessary, precautions must be taken to protect the electrician and others in the vicinity from possible shock or flash burn. This is accomplished by using barriers, protective clothing, insulated tools, and rubber blankets, among other items.
Detailed information and requirements for protective clothing and other personal protective equipment is provided in Chapter 3 of NFPA 70E Part II. Personal protective equipment covered includes head, eye, and face protection; insulating gloves and sleeves; and footwear; among other equipment.
Table 3-3.9.1 of NFPA 70E provides a detailed listing of common work tasks such as racking circuit breakers in medium-voltage metal clad switchgear. It assigns a hazard/risk category to each activity, which can then be used to determine the type of protective clothing and personal protective equipment required for the activity using the matrix provided in NFPA 70E Table 3-3.9.2 and the characteristics of the protective clothing in NFPA 70E Table 3-3.9.3.
Step 2: Ensure that the circuit is de-energized.
Opening the switch or circuit breaker should de-energize the circuit. However, there is no guarantee that movement of the switch handle or tripping the breaker will open the circuit. Sometimes, the mechanical and electrical disconnecting mechanisms malfunction, and one or more phases remain energized. Another unexpected power source may be connected on the load side of the switch or circuit breaker. Always verify that the circuit or equipment is actually de-energized prior to starting work.
It only takes a minute to check the voltage on the load side of the switch or circuit breaker to ensure that the circuit or equipment it feeds is de-energized. If an inspection window is provided on a switch, verify that all blades have opened prior to opening the switch cabinet or cubicle. Use a properly rated voltage detector or meter to check for voltage between phases and between each phase and ground. Ensure that any energy storage devices, such as capacitors, are either discharged or disconnected before starting work.
Step 3: Guard against accidental re-energization. This usually takes the form of tagging and locking out the switch or circuit breaker feeding the circuit or equipment being maintained. Lockout and tagout procedures are provided in OSHA 29 CFR 1910.147, entitled The Control of Hazardous Energy and Chapter 5 of NFPA 70E Part II, entitled Lockout/Tagout Practices and Devices.
OSHA requires an established procedure for using lockout and tagout devices and that service personnel be trained in the procedure. Appendix A of OSHA 29 CFR 1910.147 entitled Typical Minimal Lockout Procedures provides a sample procedure that the electrical contracting firm can use to develop its own lockout/tagout procedure.
Similarly, Appendix E of Part II of NFPA 70E provides a sample lockout/tagout procedure. OSHA defines lockout as the placement of a device, such as a key or combination lock, on a switch or circuit breaker that will physically prevent that switch or circuit breaker from being closed until service personnel removes the lockout device.
Tagout is defined as placing a prominent warning device, such as a tag on a switch or circuit breaker, to indicate that the switch or circuit breaker should not be closed until the tagout device is removed. OSHA 29 CFR 1910.147(c)(2) requires a lockout device to be used, unless it can be demonstrated that tagout provides an equivalent level of protection for service personnel.
Step 4: Install a safety ground if warranted.
Where ever the circuit could become energized during maintenance, a safety ground should be installed. Safety grounds need to meet the following minimum performance criteria:
• Be capable of carrying the available fault current until the protective device protecting the conductors or equipment, which the safety ground is connected across, can safely interrupt the fault current.
• Have a sufficiently low impedance to prevent a dangerous buildup of voltage if the circuit or equipment is energized, and permit sufficient current flow to allow quick detection and operation by the protective device.
All safety ground components should be suitable for the application and meet the requirements of ASTM F 855 entitled Specifications for Temporary Grounding Systems to Be Used on De-Energized Electric Power Lines and Equipment. In addition, safety grounds should be as short as possible to minimize impedance and prevent injury from the violent movement of the cables caused by the magnetic forces when the circuit is reengerized.
Chapter 20 of NFPA 70B is entitled De-Energizing and Grounding of Equipment to Provide Protection for Electrical Maintenance Personnel and provides detailed information on the use of safety grounding.
Be safe: Plan your work
Electrical maintenance isn’t dangerous if time is taken to plan the safe performance of the maintenance work, and ensure that all the necessary safety equipment is available and in good repair. It is important that industry regulations, standards, and recommended practices are understood and followed.
As always, safety starts with planning and awareness and ends with the deliberate and careful execution of the work plan. The old saying “plan your work and work your plan” is as applicable to electrical maintenance as it is to electrical construction, and it is the key to safe and effective maintenance activities.
This article is the result of ongoing research into the development of service contracting business by electrical contracting firms sponsored by the Electrical Contracting Foundation, Inc. The author would like to thank the foundation for its continuing support.
GLAVINICH is Chair and Associate Professor of Architectural Engineering at The University of Kansas. He can be reached at (785) 864-3435 or firstname.lastname@example.org.