OPERATING TEMPERATURE LIMIT
The maximum recommended furnace temperature for the metal “MRH/F” and “MRM/F” tiles is 1800°F (982°C). Depending on the combustion system, it may be acceptable to allow slightly higher furnace operating temperatures. Because of the 4441 Tempest® air staging design, when the burner operates at high fire with cold combustion air, the tile temperature runs cooler than the furnace temperature. If the burner turns down to lower firing rates with on ratio control the tile temperature will increase. If the burner turns down with fuel only control or with a negative fuel ratio bias, the tile will remain cooler relative to the furnace temperature. While 310 Stainless Steel offers excellent resistance to oxidation up to 2,000°F (1093°C). It is important to consider the possibility that the tile longevity will be reduced if the operating temperature exceeds the recommended temperature rating. TILE LENGTH AND SHAPE Because of the way the tiles are made, the tile shape is slightly different than other 4441 Tempest® burners. The tiles are shorter because they lack the straight tile exit “snout” of the classic Tempest® tile. The wall thickness is also thinner than the ceramic tile, so the mounting plates are different for each tile type.
MEDIUM VELOCITY TILES
For many years North American combustion has offered Tempests® with special alternative tile exit sizes, to provide higher or lower tile exit velocities. As an alternative to the standard high velocity tile exit size, the stainless-steel alloy tiles are available with an optional medium velocity exit size. These medium velocity tiles are made with a two size larger tile exit. For example, the 4441-2- MRM/F medium velocity burner has the same tile exit size as the 4441-4-AMRH/F high velocity tile. Burners with high velocity tiles provide great temperature uniformity by creating high amounts of recirculation in the furnace, but medium velocity burners have advantages when high velocity is not needed. Medium velocity burners can be installed in narrower furnaces because lower velocity flames are less likely to impinge the opposite chamber wall, and they generally make less noise than high velocity burners. Tempest® medium velocity (MV) burners do not have as much tile backpressure as high velocity (HV) burners, so the air pressure requirement is lower. A 4441 MV burner with an 8-12 osi air pressure will have the same capacity as a HV burner with a 16 osi air pressure requirement. Many 4441 MV burners provide higher capacities at 16 osi than at 24 osi with the standard HV tile. 4441 MV burners should be sized for 8-12 osi at high fire. 4441 Burners with medium velocity tiles should not be operated over 16 osi (27.7”w.c., or 6.9 kPa) of air pressure. CO EMISSIONS In furnaces with temperatures below 1200°F (650°C) CO emissions can be high at some firing rates when using Tempest burners. To minimize CO, operate the burner between 10% and 100% excess air (11/1 and 20/1 air/fuel ratio) and reduce the capacity to 65-45% of the high fire rate. Once the furnace temperature is above 1200°F (650°C) and the atmosphere remains oxidizing almost all the CO will be consumed, and any appropriate firing rate can be used without high CO emissions.
Alloy Metal Tile
Thin Wall Ceramic Tile
To compensate for the shorter tile, the traditional cast iron tile mounting has been replaced with a flat steel plate. This allows the tile length past the mounting surface to be closer to the familiar nine inch (9”) long tile dimension. See the dimension page for more details.
Sheet 4441-1 page 2
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