This application required four Duct Balloons for use in controlling fly ash dust during the duct work cleaning process. Large vacuum trucks are brought on site to remove fly ash in the area between the precipitator outlet to the ID fan inlet dampers. In the past, temporary barriers made from 2 x 4 wood frames were built over the existing ID fan dampers  and were then covered with plastic sheeting. While the duct work that surrounds these dampers are square on the sides, the top and bottom areas are sloped making it difficult for a home made barrier to create a good seal.

The existing ID fan dampers are the multi-louver type that measures 4’0” (1.21m) wide x 15’0” (4.57m) long and mounted on an angle as shown here.

Here are the dampers inside the duct in the closed position.

Two 7” (177mm) diameter holes were cut into the duct floor from below. The ID of the hole was cleaned up to remove any burrs or sharp edges.  

Duct tape was applied to the ID of the hole to prevent anything sharp from coming in contact with the 8” (203mm) diameter inflation tube.

Since inflation tubes measure 8” (203mm) in diameter at full inflation pressure, they completely sealed the 7” (177mm) diameter access holes. This prevented any dust from getting below to the clean area where the blowers were located.

That’s a “thumbs up” he is giving to the Duct Balloons compared to the old methods!