A pilot installation was designed that simulates a surface treatment tank fitted with a push-pull ventilation system. The installation contained elements for measuring and controlling the operational variables (flow rate and tank temperature) and smoke generating equipment for injecting smoke through the holes of the push unit and from the tank surface. Visual observation and video recording of the flows involved meant it was possible to follow the qualitative behavior of the push flow rate along the tank surface and to identify any emissions not captured by the exhaust system. It was possible to differentiate the initial semifree push curtain, its impact with the tank surface, the wall jet that moved toward the exhaust, and its entrance into the exhaust. The methodology proposed is complemented by a quantitative technique for measuring the efficiency, using sulfur hexafluoride as tracer, which permits the causes and location of losses in the ventilation system to be determined.

A pilot installation was designed that simulates a surface treatment tank fitted with a push-pull ventilation system. The installation contained elements for measuring and controlling the operational variables (flow rate and tank temperature) and smoke generating equipment for injecting smoke through the holes of the push unit and from the tank surface. Visual observation and video recording of the flows involved meant it was possible to follow the qualitative behavior of the push flow rate along the tank surface and to identify any emissions not captured by the exhaust system. It was possible to differentiate the initial semifree push curtain, its impact with the tank surface, the wall jet that moved toward the exhaust, and its entrance into the exhaust. The methodology proposed is complemented by a quantitative technique for measuring the efficiency, using sulfur hexafluoride as tracer, which permits the causes and location of losses in the ventilation system to be determined.

Methodologies are proposed for determining capture efficiencies in the ventilation systems of surface treatment tanks, using test-scale equipment. The equipment, which incorporates a lateral and push-pull ventilation system, can measure and control the variables of interest because it incorporates a tracer gas generator (sulfur hexafluoride, the concentration of which is measured by infrared spectrometer). The experimental methodologies described determine total efficiency (when the tracer is emitted uniformly from the whole surface of the tank) and the so-called transversal linear efficiency (when the tracer is emitted linearly through a perforated tube situated over the tank, parallel to the exhaust hood face). The analytical and graphical relationships that can be are established between the two efficiencies make it possible to detect where the emissions not captured by the ventilation system are produced (i.e., losses to the outside). At the same time, such losses can be quantified. Several experiments, results of which are analyzed by the methods described, are included.

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