PREPLANNING SPECIAL INDUSTRIAL HAZARDS: METRO-DADE TAKES ON THE DEEP FRYER

PREPLANNING SPECIAL INDUSTRIAL HAZARDS: METRO-DADE TAKES ON THE DEEP FRYER

All fires are different to some extent and, consequently, must be handled in different ways. This is especially true for fires at industrial occupancies, for which fire officers often need technical information to intelligently handle an incident. Fire suppression and hazard mitigation strategies for industrial occupancy emergencies will be more effective if they are devised in advance with technical assistance from the industrial facility. A prefire plan should be developed with input from industry specialists/plant managers, who usually know the best way to handle problems involving their specific products, processes, and hazards.

TARGET HAZARD DRILLS

The Metro-Dade County (FL) Fire and Rescue Department has taken an extra step to ensure the effectiveness of its prefire plans—the implementation of its Target Hazard Drill Program. This program involves writing prefire plans for target hazard occupancies and then testing them by conducting a multiple-company fire scenario at each location. The program, of course, cannot be fully implemented at every occupancy. It takes a lot of persuasion to get permission to stretch hoselines into a factory or residential high-rise building, for example. Drills may have to be conducted late at night so that business or production is not disrupted. Nevertheless, we have found that the benefits of target hazard drills, such as those following, far outweigh the difficulties in arranging them.

• A prefire plan is devised with technical input from plant personnel and addresses the facility’s specific products, processes, and hazards.
• The plan is tested in a realistic scenario.
• Fire department personnel become familiar with the facility’s products, processes, and hazards; fixed fire protection system; and construction and layout.
• Plant managers gain a better understanding of the fire department’s operations, capabilities, and limitations.
• The program fosters an ongoing professional relationship between the fire department and plant management.
• The fire department establishes a better working relationship with emergency response personnel at the plant.

A TARGET HAZARD DRILL SCENARIO

Entenmann’s, one of General Foods’ bakery companies, gave its full support and participation to Metro-Dade’s Target Hazard Drill Program. Entenmann’s commitment to prefire planning and preparedness demonstrates what can be accomplished when private industry and a public fire department work together for their mutual benefit.

The relationship between Entenmann’s and the Metro-Dade Fire Department began under adverse conditions, when firefighters responded to its Miami facility for a stubborn, difficult fire in one of its commercial baking ovens. The ovens, which are more than 100 feet long and 15 feet wide, bake cakes and pies as the products move along an internal conveyor belt. Although fire companies successfully gained control of the fire that extended to the roof by way of the oven’s exhaust system, firefighters knew they needed technical assistance to control the fire inside the oven without unnecessarily damaging this complex piece of equipment. Fire officers conferred with plant engineers to devise an extinguishment plan that resulted in minimal damage to the oven and allowed a speedy resumption of production. The operation ultimately was a success, but it demonstrated the importance of plant management’s working with the fire department to prepare for emergencies.

Officers of the Metro-Dade Fire Department and Entenmann’s safety specialists met on several occasions to revise the fire department’s prefire plan and the facility’s fire emergency plan. Plant engineers instructed fire companies on how to safely control fires in the bakery’s ovens and frying equipment.

A DEEP FRYER THE MOST SIGNIFICANT HAZARD

At the Entenmann’s facility, a deep fryer that cooks 3,100 donuts per hour was identified as the most significant hazard. The fryer, measuring 36 feet long and five feet wide.-contains 400 gallons of liquefied vegetable shortening at a depth of eight inches. Donuts moving on a conveyor are cooked in the oil at 375°F. The fryer is equipped with a carbon-dioxide extinguishing system, but the system has not always been successful in suppressing fryer fires at other Entenmann’s facilities. Handling a fire in a restaurant-size deep fat fryer, which many firefighters may experience, will not adequately prepare a firefighter to handle a fire in a large commercial fryer.

A fire in this Entenmann’s donut fryer will quickly spread across its 180-square-foot liquid surface because the cooking oil is already heated. Fighting a fire involving such a large surface area of cooking oil or grease is difficult and dangerous. Firefighters risk being burned by hot oil that splashes out of its container. Hot vapor and metal surfaces can cause the fire to continually reflash, exhausting limited extinguishing agents.

Burning cooking oil or animal fat behaves quite differently than burning flammable or combustible liquids. As they bum, light hydrocarbon liquids, such as gasoline, boil at temperatures well below the boiling point of water. As a result, any water finding its way into a container of burning gasoline will sink to the bottom and remain a relatively cool liquid. But, when water is introduced into cooking oil at frying temperatures. watch out! The water will flash to steam, expand several hundred times in volume, and forcibly eject hot oil. When oil or fat is on fire, an errant application of water will result in a fireball and running-spill fire when burning oil is forced out of its container.

In view of the hazards and difficulties, fire officers and bakery management agreed that some specialized training would be needed to safely handle a fire in the donut fryer. Entenmann’s conducted this training for firefighters and its own personnel at the conclusion of each of three target hazard drills.

To approximate a fire in the fryer, large semisolid blocks of vegetable shortening were melted down into three 3 ft. x 4 ft. x 6 in.-deep pans. When the pans were laid end to end. their combined surface area produced some very challenging oil fires but still yielded only one-fifth of the actual fryer liquid surface. Accordingly, extinguishing agents were discharged at a proportionately lower application rate. Similar to the donut fryer, the liquid surface w as very close to the top of the containers, making it very difficult to apply an extinguishing agent without splashing burning oil or causing a running-spill fire by overflowing the container with extinguishing agent.

The practice fires initially had to be “stoked” w ith a mixture of gasoline and diesel fuel. But once the shortening became heated, it would ignite on its own with the speed of a flammable liquid. The oil boils as it burns. As burning continues, the boiling becomes more furious, spewing flaming oil over the sides of its container and increasing the size of the flame. The fires were an excellent opportunity to practice various suppression techniques with a variety of extinguishing agents, furnished by Entenmann’s.

PERFORMANCES OF EXTINGUISHING AGENTS

Following is a summary of how extinguishing agents performed and lessons learned through trial and error.

• Carbon dioxide. The fire could be extinguished in its very early stages with two 15-lb. CO: fire extinguishers. Once the fire burns over one minute, however, it becomes a different animal. The fire rapidly gains intensity, fueled by oil boiling at an ever-increasing rate. After a minute, four CO: extinguishers discharging simultane-
• ously could not phase the tire. At this point, CO: is ineffective because of its inability to reduce the heat of the oil and surrounding metal surfaces. Turbulence created by the fire dissipates the CO before it can effectively exclude oxygen.
• Dry chemicals. Predictably, three dry chemical agents, sodium bicarbonate, potassium bicarbonate, and monammonium phosphate, were much more effective than carbon dioxide. The discharge range of a dry chemical fire extinguisher, 25 feet, allowed it to be operated at a safe distance from the fire. Dry chemicals’ ability to extinguish three-dimensional fire was very useful for running-spill fires of overflowing oil. Sodium bicarbonate and, to a lesser extent, potassium bicarbonate have the ability to saponify or react with the hot oil to
• form a frothy, soap-like foam over its surface. When the liquid level of the oil was reduced by fire consumption and unintended splashing, it was possible to apply sufficient sodium bicarbonate to form a one-inch “vapor-securing foam” over its surface. Dry chemicals were not without their limitations. It was very difficult, for example, to apply the agents without splashing burning oil out of its container. Vapor production and hot metal surfaces allowed sustained fires to continually reflash.
• AFFF. Two AFFF fire extinguishers were discharged simultaneously to gently apply foam against an inside wall of the container. The AFFF was not only ineffective; but to the contrary, the fire suddenly gained intensity, formed a fireball, and splashed flaming oil from the container.
• What went wrong? A single AFFF extinguisher is rated to extinguish 20 square feet of flammable liquid. The combined discharge of both extinguishers should have readily extinguished our 36-square-foot cooking oil fire. Why didn’t it? The key to the failure of the AFFF is the temperature of the oil, which is several hundred degrees hotter than the boiling point of water. The AFFF solution is 97 percent water, which forcefully flashes into steam when it contacts the hot oil. Hot metal surfaces further degrade the foam. Clearly, the heat must be reduced before the extinguishing agents can do their job.
• Water. As much as water will create havoc when it is misdirected into burning cooking oil, it can be a very effective heatabsorbing agent when properly applied. The

• key is to deliver the water in finely divided particles over the fire by intermittent, gentle application of a light fog pattern. As water droplets fall into the fire, most flash to steam before they reach the surface of the oil, absorbing a considerable amount of heat. Water that reaches the oil will cause the fire to flare up—but only temporarily. The water fog takes away so much heat from the fire that it becomes an entirely different. tamer animal. Cooling the oil and metal surfaces with water fog prior to applying AFFF, CO.-, or dry chemicals will allow these agents to be much more effective. Flames subside to a point that make close-up, accurate application of AFFF possible. Cooling reduces the conditions that breed a re flash—vapor production and hot surfaces. A blanket of AFFF will last longer when hot oil is first cooled with water fog.

Based on experience with the practice fires, cooling with water fog is now a primary objective in controlling an advanced fire in the donut fryer. The steps necessary to accomplish this objective and ultimately extinguish a fryer fire have become part of the bakery’s new prefire plans, which were practiced during the target hazard drills. The prefire plan is summarized as follows:

1. Bakery personnel shut down the fryer’s gas supply and ventilation system exhaust fans.
2. First-arriving companies deploy their high-rise hose packs from hose outlet cabinets to begin cooling the fryer.
3. Subsequent-arriving companies advance hoselines and utilize dry chemical extinguishers to fight fire that will invariably spread to the roof via vent ductwork and exhaust fans.
4. Ready a 125-gpm AFFF handline and a sufficient (predetermined) amount of concentrate to achieve extinguishment of the fryer fire and maintain a foam blanket.
5. Use AFFF and dry chemical extinguishers on spot fires. Power to the exhaust fans may be restored to help draw dry chemical into vent ductwork to extinguish any residual fire.

Using water to extinguish lire in vent ductwork is a last resort. Water sprayed into ducts from the roof or from the hood above a fryer may fall into hot oil with disastrous results.

The valuable lessons learned from the prefire planning and training sessions have already paid dividends. Firefighters have applied techniques taught by Entenmann’s engineers to successfully extinguish fires in large industrial ovens at three manufacturing plants in Dade County.