Field evaluation of methods for determining the obstructed section of branches of industrial ventilation systems

This study proposes and evaluates the effectiveness of three methods in determining the location of obstructions and alterations in the branches of industrial ventilation systems. Three branch-screening methods (reference ratio, static pressure ratio, and power loss coefficient methods) were adapted to determine if obstructions lay in four distinct areas of a branch. The areas were the hood, middle, and end sections, with the middle and end sections combined to form the fourth area. These methods were evaluated for their ability to detect obstructions in each specific section and also for their ability to detect obstructions in sections after the branch was surveyed for obstructions using a screening method. The results of this study indicate that each method is very useful in determining the presence and location of an obstruction in every section of the branch except the hood section. Each method performed poorly when determining obstructions in the hood section. However, because of the ability of the methods to detect obstructions in the other three sections, the process of elimination can be used with confidence to determine obstructions in the hood.