There has been a fair amount of news about battery storage systems being involved in fire and explosion incidents around the world. Do not forget that these are not the only safety issues when dealing with batteries. Battery systems pose unique electrical safety hazards. The system’s output may be able to be placed into an electrically safe work condition (ESWC), however there is essentially no way to place an operating battery or cell into an ESWC. Someone must still work on or maintain the battery system. Working on a battery should always considered energized electrical work. NFPA 70E®, Standard for Electrical Safety in the Workplace®, Chapter 3 covers special electrical equipment in the workplace and modifies the general requirements of Chapter 1. The chapter covers the additional safety-related work practices necessary to practically safeguard employees against the electrical hazards associated with the special equipment.
Working around batteries can expose an employee to both electrical shock and arc flash hazards. A person’s body might react to contact with dc voltage differently than from contact with ac voltage. Batteries can also expose employees to the hazards associated with the chemical electrolyte used in batteries. Battery charging can sometimes generate flammable gases, so it is important for employees to avoid anything that could cause open flames or sparks. Employers must consider exposure to these hazards when developing safe work practices and selecting personal protective equipment (PPE). That is where Article 320, Safety Requirements Related to Batteries and Battery Rooms comes in. Its electrical safety requirements, in addition to the rest of NFPA 70E, are for the practical safeguarding of employees while working with exposed stationary storage batteries that exceed 50 volts.
Article 320 reiterates that the employer must provide safety-related work practices and employee training. The employee must follow the training and work practices. It also requires that each battery room or battery enclosure be accessible only to authorized personnel. Article 320 defines authorized personnel as the person in charge of the premises, or other persons appointed or selected by the person in charge of the premises who perform certain duties associated with stationary storage batteries. All of this means that the employer must specifically understand and document an electrical safety program (ESP) for batteries. NFPA 70E, once again, does not detail who an authorized person is, how to write a procedure for the specific authorized task, what task is to be conducted and the risks to the employee performing that assigned task, or the training necessary to do any of this. It does not need to. The employer is responsible for determining what is specifically necessary to protect an employee from the specific hazards they will be exposed to while conducting the specific task on the specific battery system. I have written many blogs on the employer’s responsibilities.
It is required that, prior to any work being conducted on a battery system, a risk assessment must be performed to identify the chemical, electrical shock, and arc flash hazards and assess the risks associated with the type of tasks to be performed. The procedure for conducting an arc flash risk assessment must be specified in an employer’s ESP. The risk assessment must include the use of the hierarchy of risk controls. The risk associated with batteries could be mitigated starting with the system design. For example, a battery system could be designed to allow the battery to be partitioned into low-voltage segments before work is conducted on it. Other system design mitigation methods might include widely separating the positive and negative conductors and installing insulated covers on battery intercell connector busbars or terminals.
Batteries are somewhat unique in that they present chemical hazards as well as electrical hazards. Electrolyte (chemical) hazards vary depending on the type of battery, so the risks are product-specific and activity-specific. For example, vented lead-acid (VLA) batteries allow access to liquid electrolyte, thereby potentially exposing employees to chemical hazards when performing certain tasks. By contrast, valve-regulated lead-acid (VRLA) and certain lithium batteries are designed with solid or immobilized electrolyte so that employees are only exposed to electrolyte under failure conditions. Most modern density meters expose a worker to a quantity of electrolyte too minute to be considered hazardous, if at all. Such work might not be considered handling electrolyte. However, if specific gravity readings are taken using a bulb hydrometer, the risk of exposure is higher and should be considered as handling electrolyte. The employer must have an electrical safety plan in place if a task is assigned while the battery is not under normal operating conditions. The employer must understand that the safety requirements are dependent on the electrolyte type and assigned task.
There is specific training necessary for employees who will be working with batteries. Proper procedures, tools, personal protective equipment (PPE) and ventilation might be specific to a battery installation. A qualified employee trained to establish an ESWC on a motor is not qualified to deal with energized batteries. Additional training is necessary for that “qualified employee” to be qualified to enter a battery room to conduct a specific task. What they are trained for is no different than other training requirements. The employer must know, document and train the employee for the assigned task and exposed risks.
It is a requirement to have all the documentation in place prior to authorized personnel entering a battery room to perform a specific work task on a battery system under normal operating conditions. However, it is likely the employee will need to enter the battery room to deal with a battery system that is not operating normally. Is it possible that there are substantially different risks for performing that same task in this case? The employer must have procedures, risk assessments, and training for this condition as well. Sending an employee who is trained only for the normal operating conditions into a battery room under thermal runaway, for example, is knowingly exposing an unqualified person to risk of injury.
The employer is responsible for protecting their employees from known or recognized hazards in the workplace. NFPA 70E provides the basis and guidelines for an employer to develop an electrical safety program regardless of the type of electrical equipment. Remember this whenever an employee is required to interact with electrical equipment at your facility.
Want to keep track of what is happening with the National Electrical Code® (NEC®)? Subscribe to the NFPA Network to stay informed of new content. The newsletter also includes NFPA 70E information such as my blogs.