Aerotech Fans
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Engineering answers to the most common questions about industrial ventilation, air handling, and pollution control systems.
A Barometric Relief Damper is a gravity-operated pressure valve used in tightly sealed buildings. When the HVAC system brings in high volumes of fresh outside air, internal pressure rises. The barometric damper automatically swings open to relieve this excess static pressure, preventing doors from becoming stuck.
Opposed Blade Dampers (OBD) feature adjacent blades that rotate in opposite directions. Unlike parallel blade dampers which throw air to one side of the duct, OBDs maintain a straight, laminar airflow profile even when partially closed, making them mandatory for precise volumetric balancing in AHUs.
Commercial kitchen balancing requires the Make-Up Air (FAU) to supply roughly 80% to 90% of the air volume extracted by the exhaust fan. The remaining 10% to 20% deficit creates a slight negative pressure, ensuring food odors are kept inside the kitchen rather than drifting into the dining room.
While 304 stainless steel resists general oxidation, it is highly susceptible to chloride pitting in salt-spray environments. 316L Stainless Steel contains molybdenum, which drastically increases its resistance to chloride corrosion, making it mandatory for marine and offshore ventilation systems.
A Variable Frequency Drive (VFD) slows down the motor electrically to reduce airflow. Inlet Guide Vanes (IGV) are mechanical louvers installed at the blower's intake. IGVs pre-spin the air in the direction of impeller rotation, physically altering the aerodynamic performance curve without changing the motor RPM.
Standard carbon steel impellers begin to lose their structural yield strength at approximately 300°C (572°F). For continuous operation above this threshold, the impeller must be fabricated from specialized high-temperature alloys like Corten steel or Inconel to prevent high-RPM centrifugal creep and catastrophic failure.
A bleed-in (or dilution) damper is an automated safety valve installed upstream of a high-temperature baghouse. If the exhaust gas temperature spikes dangerously close to the melting point of the filter bags, the damper rapidly opens to draw in cool ambient air, quenching the gas stream instantly.
For highly acidic environments where FRP (Fiberglass Reinforced Plastic) lacks the necessary structural integrity, steel impellers and casings must be coated with baked Phenolic epoxy, PTFE (Teflon), or Halar (ECTFE). These coatings create a seamless, impermeable barrier against aggressive chemical vapors.
In sub-zero climates, drawing 100% outside air can instantly freeze and burst hydronic cooling coils. FAUs require a pre-heat coil (electric or hot water) installed upstream, or the chilled water system must be dosed with a precise concentration of Propylene Glycol to lower the fluid's freezing point.
Silica dust acts as a highly abrasive sandblasting agent. To prevent the lower cone of the cyclone from eroding, the internal apex and impact zones are often lined with replaceable cast basalt tiles or vulcanized rubber, which absorb the kinetic energy and extend the cyclone's lifespan indefinitely.
Aerodynamic surge occurs when system resistance pushes the blower beyond its stall point, causing violent, oscillating airflow reversals. It is prevented by ensuring the system operates to the right of the surge curve, or by installing an automated bleed-off bypass damper to artificially maintain minimum flow.
Bridging occurs when hygroscopic or interlocking dust forms an arch over the rotary airlock, blocking discharge. It is prevented by designing the hopper with a steep 60-degree angle of repose, and installing pneumatic fluidizers or mechanical vibrators to continuously agitate the dust cake.
