Blowing $ up the Stack? An Exhaust Primer
An introduction to semiconductor exhaust ventilation by local ventilation expert Gary Knutson, of Knutson Ventilation, and Mike Sherman, FSI International.
Gerry discussed costs for ventilation systems including operating and capital costs. He provided specific examples to improve ventilation system efficiency including selecting the correct size fan and reducing drag in the duct system. Next Gerry provided calculations of horsepower costs and replacement air costs (heating and cooling). Through these calculations he made the point that small changes when extrapolated over longer time periods can be significant. Variable speed drives are one example of how to take advantage of variable needs related to work shifts.
Gerry then discussed method for calculating theoretical concentrations above a spill in an exhausted system (i.e. wet bench) and outside of an exhausted system. Dilution by exhaust volumes and air exchange rates were evaluated for several scenarios of spill location and chemical hazard (flammables vs toxics).
Mike discussed how an OEM determines exhaust specifications. He emphasized that purchasers should request specific information about conditions (i.e. chemical inputs) used to determine the exhaust specification.
Next Mike used several examples from the Honeywell Plymouth facility to describe a process for determining exhaust requirements in an open system (i.e. wet bench). Mike provided some useful references to assist in making calculations of face velocities for open systems. Then he discussed, and had examples of, tools to qualitatively (foggers) and quantitatively (velometers and pitot tubes) measure air flow in these systems.
The next meeting will be in the fall with a topic to be determined.