Arc flashes in electric equipment are hazardous to workers and can result in fatalities, costly damage to equipment and delays in production until repairs are made. Arc-flash labels on electrical equipment are required by federal law; OSHA regulations requiring these labels have existed since approximately 2000.
Unlabeled equipment is a safety violation, and if facilities managers have not hired people to label their electrical equipment, they risk increased insurance costs.
The labels contain an orange warning as a minimum, and list the level of personal protective equipment (PPE) an electrician must wear to work on the live equipment. The PPE protects against burns, blinding and other injuries that the graded levels of incident energy can cause. There are four severity levels, requiring four sets of protective gear, ranging from hard hats, goggles and gloves, to full fireproof garments and welding hoods.
Also included on the labels is the incident energy at a working distance, and the safe clearance around the equipment where unprotected persons are excluded.
There is resistance in the industry to complying with the OSHA requirements. Most large organizations have complied, but many companies have put off labeling. The reasons generally fall within budget constraints, work overload or unwanted focus on National Electrical Code violations in the facilities (or the fear of violations being revealed).
Many employers believe code requirements are advisory, as stated in the code’s beginning, and not mandatory. This is false, as the vast majority of local governments have adopted the code as part of their building codes. Also, because electrical failures and injuries are not common, some employers feel the risk of a violation, a possible fine or insurance premium increase is justified.
The standard labeling procedure is to conduct a lengthy survey of the premises and compile details of the electrical system. The system is analyzed, calculating bolted fault currents, arc-fault currents and incident energies at each of the panel boards, motor control centers, switchboards, transformers and medium-voltage equipment on the premises. From the compiled calculated values the labels are prepared, and then applied to the equipment.
This analysis requires engineering-level workers. Electricians apply the labels and the typical number of labels at an average-sized workplace can range from 100 to 300. A large refinery can require as many as 3,000 labels.
Simplified Labeling Method
Half of this procedure is no longer necessary. A simplified labeling method has evolved, whereby an electrician familiar with the premises surveys the system. Based on transformer sizes, nameplates and circuit breaker or fuse information, the electrician can look at a table and find the label information. He then prepares the labels using a portable printer or customized, pre-printed labels, and applies them at the same time.
The tables are based on a detailed analysis of electrical distribution systems. Because electrical equipment is highly hazardous in shock and arcing, and because of its high capital cost, electrical equipment is standardized in both manufacture and installation. All the equipment sizes and their combinations have been calculated for the label requirements. The analytical results have been compiled in the tables.
Voltages from 208 V to 15 kV are included, with sizes from 30 kVA to 98 MVA. This range covers all but the smallest to the largest commercial and industrial facility.
Author Robert E. Henry, PE, is the president of R. E. Henry PE LLC. He received his B.S. in electrical engineering from the University of Florida and his masters in industrial management at the Polytechnic Institute of New York.