Back Ground
Al-Bilal Group for GE and MGH
Baghdad, Iraq
Al-Bilal Group for General Contracting is an Iraqi infrastructure and energy contractor, best known for building the country’s first large-scale solar plant, a 300 MW facility in Karbala. On this project it worked for GE and Mass Group Holding (MGH), whose gas-fired power plants in Baghdad supply Iraq’s national grid.
Challenge
Three GE gas turbines at a Baghdad power plant were going into an extended shutdown. For all that time, each turbine’s two largest openings would be exposed to the elements. At one end was the inlet air duct between the filter house and the compressor. At the other was the exhaust duct between the diffuser and the silencer.
Open ducts let in wind-blown dust and humid air, which together cause internal corrosion. If corrosion took hold during the shutdown, the plant would face costly repairs and delays before it could return to service.
The exhaust ducts were the bigger challenge. They measure 4 m square, and their walls are rougher than the smooth inlet ducts. Any seal there had to hold for a long time, with no one on hand to watch it.
Steel blanking covers were the usual answer, but they need cranes to lift into place and take weeks to fit. They can also scratch the duct linings they are meant to protect. Al-Bilal Group also needed the equipment quickly, so it wanted a lighter, faster option that would not damage the ducts.
Specialized Solution
Giant Inflatables Industrial designed six sealed-air inflatable duct plugs, one for the exhaust duct and one for the inlet duct of each turbine.
Exhaust duct plugs. Each plug measures 4 m × 4 m and is 1.8 m deep, filling the duct completely. It is built as two separate air chambers inside a protective outer skin for redundancy, with stainless steel tie points at the corners.
Each exhaust plug is paired with two 230 V intelligent inflator/monitors for safety. They check the internal pressure continuously and top it back up from 1.1 psi to 1.5 psi if it falls, so a small leak never becomes a failed seal. A remote pressure monitor on each duct lets staff check the plug from outside, and an auxiliary inflation port allows the plug to be inflated without the pumps.
Inlet duct plugs. These measure just over 3 m × almost 2.1 m and are 1.5 m deep, with tie points and lifting points. Each comes with its own inflation pump. Crews inflate the plug until it is firm, close the ball valve and switch off the pump. The plug then holds its pressure as a sealed unit with no power supply.
Every inflatable duct plug is UV-stable and flame-retardant, with welded seams and a 2 psi over-pressure valve to prevent over-inflation. Giant Inflatables Industrial also supplied a hygro-thermometer for manual humidity checks, a portable hydrogen gas detector, an extended warranty and illustrated setup instructions for each plug type.
Results
A closer look
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Inflatable insulated isolation barriers
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Duct Balloons are widely used worldwide in the mining and power generation sectors to isolate duct sections or stacks and facilitate maintenance.
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