Duct Balloon

 Inflatable Isolation Barriers

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The following are some installation notes and photos on a recent project for installing a Stack Balloon inside the HRSG exhaust stack at the CEMS platform level on a 7FA Gas Turbine with HRSG

The plant has two GE Frame 7FA Gas Turbines. The exhaust stack is 17’6” (5.3m) diameter x 125’0” (38.1m) high. The CEMS platform level is at a 60’ (18.2m) elevation.

An access door was installed about half way up the stack which measures 2’6” x 2’6” (762mm x 762mm). Note the 2” (50mm) diameter stainless steel support rod above the door opening which spans the 17’6” (5.3m) diameter stack. The support rod was installed to stay permanently in place inside the stack after the balloon is removed. This installation location was chosen as it is below the existing CEMS equipment.

“Quick Link” type oval rings are attached to the support rod that will attach to the carbineers

Nylon rope is attached between the stack balloon anchor points which are sewn into the top of the balloon and also to the carabineers.

The Stack Balloon is now hanging inside the stack and ready for inflation.

As the balloon starts to inflate, it expands off the ID of the stack near the access door and moves outward along the support rod. Inflation time is less than 3 minutes. Removal time from the stack takes about 5 minutes.

The 120V high pressure blower must remain on continuously to keep the Stack Balloon fully inflated. The Stack Balloon is typically installed inside the stack on a slight angle to permit water runoff towards the access door. If snow accumulates on the top of the Stack Balloon, it will quickly melt due to the residual heat from the HRSG rising from below. Even though the blower is rated for outside use, it was eventually moved inside the HRSG building. A temporary shelter may be required over the blower in high moisture conditions.

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