Engineering & Mining Journal

APR 2018

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Page 79 of 91

78 E&MJ • APRIL 2018 OPERATING STRATEGIES Let's set the scene. Despite an industri- al safety team's most adept practices to manage a propane storage tank, a leak suddenly erupts from a pipe. In a perfect storm of events, a spark follows. There is ignition. Instantly, there is a fi re. In an ideal scenario, safety team members swiftly respond and take con- trol of this hazard. This team is able to shut off the fuel source and suppress the fi re using the right technique and the right equipment. Among their equip- ment, there is a cartridge-operated por- table fi re extinguisher designed with the high-agent fl ow rate required to take control of that pressurized propane fi re. More specifi cally, it's an extinguisher in compliance with the National Fire Pro- tection Association (NFPA) 10, Standard for Portable Fire Extinguishers, Subsec- tion 5.5, Selection for Specifi c Hazards. This mandate establishes the standard for minimum size and fl ow rate for porta- ble fi re extinguishers used against Class B fi res. Setting Standards to Change Mindsets Prior to 2007, this specifi c NFPA 10 standard did not exist in its current lan- guage. Earlier editions instructed safety professionals to follow manufacturers' recommendations for the best applica- tions of fi re extinguishers. Without an industry-wide standard to follow, incon- sistencies among those recommenda- tions contributed to confusion over what was the best tool for protecting facilities against Class B fi re scenarios. Then, the benchmark was set in 2007. NFPA 10 Subsection 5.5 man- dated "large-capacity dry chemical ex- tinguishers of 10 lb (4.54 kg) or greater and a discharge rate of 1 lb/sec (0.45 kg/sec) or more shall be used" for pres- surized fl ammable liquid and gas fi res. In addition, this exact mandate was also applied to other Class B fi res, specifi cal- ly 3-D and obstacle fi re scenarios. Why High-fl ow Extinguishers for High-risk Environments? "The 2007 NFPA 10 mandate has helped to initiate a change in the mindset of safety teams in high-risk environments," said Dennis D. Brohmer, Johnson Con- trols senior applications specialist. "How- ever, there's defi nitely still more work to do in educating teams about how crucial it is to meet this standard. It's all about what's best for the people who are on the front lines of these fi re hazards, and help- ing to get the right tools in their hands so they have the best opportunity to put out these fi res faster." An important detail of the propane storage tank fi re example is the use of a high-fl ow, cartridge-operated fi re extin- guisher to take control of the situation. Industry professionals might ask why high-fl ow extinguishers like this perform better and are now mandated in high-risk environments with fl ammable liquids or gases. This is a common question, par- ticularly in the misconceptions that exist around UL-ratings. The greater effectiveness of high-fl ow fi re extinguishers comes down to speed and fl ow rate. NFPA 10 addresses and standardizes this essential feature di- rectly — i.e., the requirement for a min- imum 1-lb/sec discharge rate. It is true that stored pressure fi re extinguishers offer a slower fl ow rate and longer dis- charge time of the dry chemical agent. Such fi re extinguishers also receive a higher UL-rating than high-fl ow models. However, the slower fl ow of these stored pressure extinguishers is less effective on Class B pressurized fl ammable liq- uids and gas fi res. Specialized high-fl ow fi re extinguish- ers, on the other hand, meet or exceed the minimum 1-lb/sec fl ow rate required for these fi re scenarios. "These pressure-related fi re hazards are incredibly varied," said Brohmer. "Operators need an extinguisher that de- livers a lot of agent, and delivers it fast. In Choose the Right Extinguisher for Class B Fire Suppression By Sam Boraas The Five Fire Classes According to industry standards, the fi ve kinds of general fi re situations are: Class A - fi res involving ordinary combus- tibles such as wood, paper, cloth, rubber, and many plastics. Class B - fi res involving fl ammable liquids such as gasoline, petroleum greases, tars, oils, oil-based paints, solvents, alcohols. Class B fi res also include fl ammable gas- es such as propane and butane. Class B fi res do not include fi res involving cooking oils and grease. Class C - fi res involving energized electi- cal equipment such as computers, serv- ers, motors, transformers, and applianc- es. Remove the power and the Class C fi re becomes one of the other classes of fi re. Class D - fi res involving combustible met- als such as magnesium, titanium, zirconi- um, sodium, lithium, and potassium. fi res involving cooking oils and greases such as animal and vegetable fats. Some types of fi re extinguishing agents can be used on more than one class of fi re.

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