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Following an insurance risk assessment in mid-2012, a preparation plant owned by one of the nation's largest coal producers sought a fire suppression system for the plant's motor control center (MCC) and cable spreading rooms. Built in 1978, the West Virginia prep plant is currently fed by two mines and processes a little less than 2 million tons of raw coal per year. The plant's two MCC rooms and two cable spreading rooms are equipped with a detection-only system that requires human intervention to extinguish a fire, leading the auditor to recommend the installation of a pre-action suppression system to "minimize damage and potential business interruption." Water-based sprinklers are a cost-effective fire protection option commonly found in various prep plant areas, but activation of such systems in MCC rooms can cause considerable damage to energized electrical equipment, as well as increase the risk of serious injuries if personnel are present. If a plant's water supply is inadequate, the installation of large water tanks and fire-rated pumps can quickly wipe out the potential cost savings of sprinkler systems, which was the case at this plant. The plant does not have a city water connection, and its pumping system did not have enough volume, pressure and capacity to sup- ply a sprinkler system. Given these hazards and limitations, plant officials asked local contractors to review the application and recommend alternatives for protecting the spaces. Clean agent, dry chemical and hybrid sys- tems were evaluated. Clean agent fire suppression systems are commonly specified for electrical applications because the chemical or gas the system uses does not harm electronic equipment — a considerable advantage over water-based sprinkler systems. Clean agent systems have a few downsides, however, the primary being the requirement for room integrity. For a clean agent system to effectively suppress a fire, the correct concentration of suppressing agent must be maintained in the hazard space. MCC rooms are often not tight enclosures because cable trays and other incoming wiring tend not to be sealed well and could be exposed to the floor below. Conduits running out to the plant also create openings. Sealing MCC rooms to meet specified leak rates can be achieved, but not guaran- teed following subsequent modifications (to run wiring to new equipment or devices, for example). Other disadvantages of clean agent systems vary based on the type of system selected, but include challenges related to pipe size balance, life safety during system activation, and downtime to refill proprietary agents following system discharge. Dry chemical systems were also considered, as they can be more cost effective than clean agent systems, but proper delivery of the agent is a challenge. The powder particles that such systems utilize must be dispensed directly onto the fire. In the MCC rooms, that would require installing discharge nozzles inside the cabinets. Another downside of dry chemical systems is that the chemi- cal often does not provide a cooling effect. If a fire reignites fol- lowing system activation, nothing remains to extinguish the subsequent fire. That left hybrid systems as the only remaining option. Hybrid systems are a relatively new class of fire suppression; Factory Mutual established the FM 5580 category to classify them in 2009. These sys- tems work by deploying a mixture of water and an inert gas to cool the hazard space, reduce the oxygen content, and generate steam. System Selection & Configuration The hybrid system the plant considered — Victaulic Vortex — ade- quately addressed the prep plant's concerns regarding the other types of systems: it is not damaging to electrical equipment, it does not require enclosure integrity to effectively suppress a fire, and proper delivery of the agent is not an issue. Another factor was life safety. Installation of the system would not introduce any hazards to personnel present during system activation. Although the system was more costly than the other fire suppres- sion options considered, the regional vice president made the deci- sion to install Vortex in the MCC and cable spreading rooms, as the system benefits outweighed the costs. Victaulic Vortex, a hybrid inert gas/water mist system, functions by dispensing a high-velocity, low-pressure mixture of water and 46 www.coalage.com March 2014 Vortex control panels installed in MCC Room 1. o p e r a t i n g i d e a s Hybrid Suppression System Overcomes MCC Room Fire Protection Challenges B Y B O B B A L L A R D A N D C H R I S Y O D E R The Vortex emitter atomizes water, forming a dense mist. CA_pg46-47_CA_pg46-47 3/12/14 2:58 PM Page 46