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

• In the inlet duct between the filter house and the Inlet Guide Vane (IGV’s)
• In the exhaust duct between the GT and the HRSG during turbine overhauls and ice blasting
• In the HRSG outlet duct just before the entrance to the exhaust stack
• In the bell mouth of the GT
• In front of a closed damper in the by-pass stack
• In the HRSG Exhaust Stack at the CEMS platform level
• In the GT exhaust duct on a GT running in simple cycle mode

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.

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

Duct and Stack Balloons can be used in conjunction with a dehumidification system to keep the humidity level at or below 35% to keep corrosion levels to a minimum during layups or long term preservation.

Our 1st generation Stack Balloon was introduced in 2004. That design required the operator to install a support rod inside the stack and an access door. Support ropes or cables of varying lengths are attached to the support rod and the top surface of the Stack Balloon so that it tilts downward toward the opening to direct water out through the open access door.   

While this design worked well it could cause corrosion on the outside of the stack

Our 2nd generation Stack Balloon incorporates a sloped top surface that channels rain water towards the center drain hole and then internally conveys it to the perimeter edge when it can be connected to stack drains or a gutter system.  We also added a layer of heavy duty nylon around the perimeter edge to increased durability where it contacts the ID of the stack.

In retrofit applications, the installed access door size should be 36” × 24” (915mm x 610mm) (by others) to insure proper clearance for the inflation tube and external drain connection and allow of ease of installation and removal from the stack. A support cable is now used instead of a support rod to make installation easier. We work closely with HRST, Inc. and we can coordinate the design of the Stack Balloon, access door, support cable and hanger hardware with them to insure that everything you’ll need for your project will arrive at the jobsite as required.