New information about the cause of electrical accidents has led to revised safety requirements.

As irrigation systems in the 1960s and 1970s were electrified, the number of electrocutions from irrigation systems increased. Individuals and companies too numerous to mention, including the Irrigation Association, worked together and determined the lack of electrical grounding practices supplying irrigation systems was a major factor. At the time, new electrical grounding requirements and standards were developed, and the National Electrical Code even designated a specific section for the irrigation machine in the code. Irrigation equipment manufacturers incorporated the codes and standards into their designs and manuals, and safety increased across the industry.  

In recent years, changes in both Occupational Safety and Health Administration and electrical industry safety rules and procedures have brought a relative new term to the forefront of any industry using electric-powered equipment: arc flash safety.  

Prior to 1980, most electrical professionals believed electrical accidents were primarily from human contact with live and/or short-circuited portions of equipment (electrocution). Forensic analysis of electrical accidents brought new information to light indicating that many fatalities and injuries were actually from the accompanying arc flash (explosion) rather than an electrocution.  

What is an arc flash?

An arc flash happens when an electrical short or fault in a power system creates an electrical arc through the air to other conductive items. They are a safety concern because anyone in the direct area can be exposed to burns from intense heat, hit by shrapnel of exploding metal parts, blinded by intense light, deafened by the shock wave, asphyxiated by toxic gas, or thrown off scaffolding or ladders.  In recent years numerous codes and safety standards have begun to address this issue and include new safety rules and requirements related to arc flash safety when working on or around certain pieces of electrically powered equipment.

An arc flash happens when an electrical short or fault in a power system creates an electrical arc through the air to other conductive items.

As the NEC and OSHA have added provisions for arc flash safety, the additions have increased awareness in all industries, not just irrigation. As people in the irrigation industry become aware of the new safety requirements, the general questions of what arc flash safety is and how does an employer comply have become important. OSHA has indicated it will judge an employer’s arc flash safety program using the rules in NFPA 70E, the Standard for Electrical Safety in the Workplace published by the National Fire Protection Association, to determine compliance.  

According to NFPA 70E, the general arc flash safety analysis of an irrigation system involves several steps:

1. An employer is required to conduct an arc flash safety analysis of certain types of electric equipment operating at more than 240 volts, three phase to ground (many irrigation machines operate at 480 volts). The arc flash study determines the worst-case arc flash hazard (how big the arc flash could be), and therefore the level of arc flash protection equipment people working on or near the system need to use to be safe. The employer is required to conduct an arc flash safety analysis every five years or earlier if major changes have been made to the electrical equipment or service.For a typical irrigation system, the most common equipment requiring the arc flash analysis would be any electrical disconnect someone would use to turn off power to the system operating over 240 volts, three phase to ground. This could be the main electrical service, a pump panel, an irrigation machine control panel and other ancillary equipment disconnect panels for fertigation or other uses.

2. 

   Based on the results of the arc flash analysis, the employer is required to apply arc flash warning labels to alert employees where arc flash hazards exist. The arc flash warning label can include several things, but in general, it should include the required level of arc flash protection safety (1 through 4 shown in fig. 1) necessary to work safely around the equipment, as well as the minimum approach distance for unprotected workers. For example, the arc flash warning label shown in fig. 2 would require use of arc flash hazard category 2 equipment for anyone performing work closer than 18 inches to the specific piece of energized equipment. Anyone not wearing arc flash protective equipment must keep at least 18 inches away from the piece of equipment with the label when it is energized. Anyone wanting to shut off the disconnecting switch to remove power to the panel must wear arc flash hazard category 2 equipment to protect from the switch failing and the accompanying arc flash when operating the switch, should it fail.

3. Train employees that operate or work on the equipment on the dangers of arc flash and how to read an arc flash label on a piece of equipment and determine the necessary level of personal protective equipment required to work safely around it. After the training, document the arc flash safety training for the employees.

Equipment labeling

A common question often heard is, “Why don’t equipment manufacturers (like those selling irrigation systems) include arc flash labels on the equipment when they sell it?”  The level of arc flash energy a piece of equipment can produce is determined by several factors, including the short-circuit voltage of the electrical utility system provider and transformer supplying it, the operating time of the fuses, the breakers protecting it and the environment around it. Because of these factors, specifically that the short-circuit current of the electrical power provider’s system varies so much from one installation to the next, accurate arc flash energy levels can only be determined after the equipment has been installed in the field under its actual operating conditions.

There are numerous companies that can provide arc flash hazard analysis for equipment to determine the arc flash hazard level. Some companies will make the labels for you and install them, or you can find templates to make your own labels. The final step is to make sure your employees are trained to understand what the labels say; provide them the necessary personal protective equipment if needed and document the training.  

Greg Stark, PE, is an assistant professor of practice in the Texas A&M University Biological and Agricultural Engineering Department.