Making the Grade

Updates at Bowater Inc.'s newsprint plant at Grenada, Miss., have strengthened workers' protection against arc flash while easing heat stress concerns.

• By Mike Longman
• Jul 01, 2007

IN 2005, Bowater Inc., a leading producer of coated and specialty papers and newsprint, stood by its commitment to ensure the safety of its workers at a Grenada, Miss. facility that is Mississippi’s only newsprint manufacturer. Bowater looked to our Electrical Services and Systems district office in Pelham, Ala. to implement its arc flash training, perform an Arc Flash Hazard Analysis to assess its safety needs and concerns, and to coordinate its power systems.

An arc flash is produced by a flow of electrical current through ionized air after an initial flashover or short circuit. An arc flash event releases a tremendous amount of energy in the form of thermal heat, toxic fumes, pressure waves, blinding light, sound waves, and explosions that can result in serious injuries that include critical burns, collapsed lungs, loss of vision, ruptured eardrums, and puncture wounds. Some are fatal.

Accidents, unintentional contact with electrical systems, equipment failure, improperly designed equipment, and/or work procedures can cause an arc flash explosion. According to the National Fire Protection Association, an arc flash occurs “when an electric current passes through air between ungrounded conductors or between ungrounded conductors and grounded conductors.” NFPA 70E, Standard for Electrical Safety in the Workplace, sets forth basic requirements for electrical safety at work sites and requirements for arc flash hazards, in particular.

An arc flash releases dangerous levels of radiant heat energy that can cause fatal or severe burns. Fatal burns can occur to workers up to 5 feet or more from the arc, and severe burns can happen up to 10 feet away during a high-energy arc flash. An arc flash produces some of the highest temperatures on earth—up to 35,000 degrees Fahrenheit. These excessive temperatures cause the air and metal in the path of the arc to expand and explode, creating an arc blast.

Protective Clothing Strikes a Balance
Based upon the initial systems study findings, Bowater and our team devised a strategy to reduce arc flash danger significantly at the Grenada facility. Bowater immediately called upon our power systems expertise to coordinate its existing electrical protective measures, devices, and monitoring, as well as conduct the arc flash analysis. An integrated systems approach for Bowater served to identify potential arc flash hazard areas within the electrical system and offer a variety of possible solutions.

Employee safety was the primary concern of Gary Fant, Bowater’s maintenance manager. Because of generally hot and humid conditions at the facility, Fant wanted to create an environment in which the employees could wear sufficient personal protective clothing to prevent the potentially fatal or severe effects of arc flash, yet not so much that employees would be exposed to the danger of extreme heat stress.

Installation of new switch units offered the primary line of defense. These innovative protective devices, installed in the company’s power circuit breakers, lower arc flash incident energy levels by temporarily lowering trip settings while workers are performing work on the energized electrical system.

Bowater’s commitment to employee safety and arc flash incident prevention was emblematic of its historical efforts to prevent workplace accidents. The company’s meticulous recordkeeping and data collection removed a major hurdle faced with many industrial clients; implementation could be expedited because Bowater had helped lay the groundwork. Still, there were several key challenges during the safety solutions implementation.

No Downtime Allowed
Bowater, one of the world’s largest newsprint producers, could not afford lengthy downtime. This led to a tight timeframe to upgrade and install the units onto the company’s circuit breakers. Bowater’s production schedule allowed only a threeday window for operation shutdown, during which the retrofitting and testing of 96 circuit breakers in almost 30 locations had to take place, while simultaneously performing testing and maintenance at all levels of the power system.

Several workstations were set up to retrofit the units onto the circuit breakers and test them. Switchgear specialists were brought in from Alabama and Louisiana to oversee the project. In the meantime, additional, specific information was being collected about the connected loads and operating parameters for each breaker, and an on-site system study was under way to verify proper settings for each individual breaker. While the installation took place, key parts of the Bowater mill remained open and functional so other necessary maintenance work could be done.

The work was completed in June 2006, resulting in a state-of-the-art safety system and maximum peace of mind for electrical maintenance employees and managers.

Heat Stress Concerns Eased
By installing the units, Bowater was able to offer its electrical workers three key safetyand reliability-related benefits:

1. The change lowered arc flash incident energy levels in work locations.

2. Less arc flash PPE is required, which reduces heat stress. For example, MCC 51- 05 before the retrofit was a category 3 arc flash hazard at 8.3 cal/cm², requiring a flame resistant (FR) shirt and pants, plus FR coveralls over them. After the retrofit, MCC 51-05 was reduced to a category 1 arc flash hazard at 1.9 cal/cm², requiring only an FR shirt and pants.

3. For system reliability, replacing the older analog breaker trip units with microprocessor- based true RMS trip units gives more flexibility to the power systems engineer in making settings for system coordination. Also, the true RMS units are less susceptible to nuisance tripping from harmonic signals on the line generated by Bowater’s paper mill drives.

Bowater is currently implementing an electrical safety program that includes all aspects of NFPA 70E. It is implementing procedures to take the arc flash safety improvements within its electrical system a step beyond. As the company develops and implements its ongoing electrical safety program, informational sharing sessions will increase employees’ awareness of their evolving role in the overall safety program.

With a safety initiative of this magnitude, there is no downtime.

This article originally appeared in the July 2007 issue of Occupational Health & Safety.