Duct Balloon

 Inflatable Isolation Barriers

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The locations where a Duct Balloon has been used are as follows:

To reduce the intrusion of outside air from entering the inlet duct work, a Duct Balloon can be installed in duct work that runs horizontally or vertically. The blower is typically placed outside the duct work and the inflation tube is fed through an existing man way.  While only one balloon is required for this type of installation, this artist rendering shows how it could be installed in either vertical or horizontal duct work.

Another installation point can be in the exhaust ductwork of the HRSG just before the entrance in to exhaust stack. These Duct Balloons balloons are typically 7’ (2.13m) to 9’ (2.74m) wide and can be as tall as 50’ (15.2m) or more depending on the size of the unit. Either of these locations will permit temporary installation of Duct Balloons without any modifications to the plant. Your choice depends on several factors including which direction the outside air is entering or if certain areas are experiencing off line corrosion.

Due to plant cycling, weekend shut downs may occur many times during one year. If the plant will be down for a few days, a Stack Balloon can be inserted inside the exhaust stack after a 24 hour period to keep the residual heat “bottled up” inside the HRSG’s. Some plants use a combination of one Duct Balloon in the inlet duct in front of the IGV’s and one in the HRSG Exhaust Stack. The quantity and location on where to use them are based on the operating cycles of the plant, corrosion prevention goals, personal resources and time constraints for removal prior to restarting the unit.

*HRSG’s that sit idle for extended periods of time are at risk of gas side corrosion from the humidity in ambient air. In North America, HRSG’s tend to sit idle more frequently in the fall and spring, which also coincide with wetter weather, increasing potential for damage unless preventative action is taken. Rain water and humidity entering through an open stack helps drive the corrosion process. Another driver is the change in ambient temperatures between day time and night time, where tube metal temperatures lag behind the daily high ambient temperature. When humid air contacts the cool tubes, condensation can occur, causing corrosion. This can be considered another form of “dew point corrosion”, except that entire sections of the HRGS’s typically are affected, not just a few rows of preheater tubes receiving cool feed water. *Excerpt taken from the HRSG Users Handbook, 2nd Edition (Chapter 9.1), distributed by the HRSG User's Grou

To see how a Stack Balloon is installed inside a HRSG Exhaust Stack, click here

Copyright © 2017 by  G.R. Werth & Associates, Inc. - All rights reserved - Duct Balloon is a trademark by  G.R. Werth & Associates, Inc.