INDUSTRIAL & UTILITY
Chimney and Smokestack Repair With FRP
Dry layup FRP is faster on large and vertical structures, including chimneys over 500 ft tall. QuakeWrap® wet and dry layup systems strengthen chimneys and smokestacks.
- Chimneys over 500 ft tall
- Dry layup for vertical structures
- Carbon & glass FRP
MATCHING PRODUCTS
QuakeWrap® Systems for Chimneys & Smokestacks
Not sure which system fits?
Tell us about the structure and conditions. Our team will recommend the right QuakeWrap® system.
WHY CHIMNEYS NEED STRENGTHENING
Why Chimneys and Smokestacks Need Strengthening
-
Corrosive flue gases
The chemicals and gases leaving a chimney attack the concrete and corrode the reinforcing steel quickly.
-
New openings for emission controls
Selective Catalytic Reduction (SCR) and scrubber ductwork needs large openings in the chimney wall, which cut out reinforcing steel and concentrate stress around the hole.
-
General deterioration
Without a proactive inspection and maintenance plan, the concrete near the top of a chimney can spall, crack and open up cavities.
HOW IT WORKS
How FRP Strengthens a Chimney
Thin FRP sheets, about 0.05 in. (1.3 mm) thick, are bonded to the chimney shell much like wallpaper. They add significant strength while adding very little weight to a tall structure.
Around a new opening, carbon FRP placed around the perimeter of the hole replaces the reinforcing steel that was cut out and resists the stress concentrations the hole creates. Where the concrete has decayed, the damaged areas are patched first and the FRP then confines the shell and protects it against corrosion.
Wet layup and dry layup are both used. Dry layup, developed by QuakeWrap®, places dry fabric on a tack coat and saturates it in place, which is faster on large vertical surfaces. The number and orientation of the fiber layers are set for each chimney. Our team will recommend the right QuakeWrap® system and provide specifications for your engineer of record.
- Installs during scheduled shutdowns
- Little added weight
- Carbon and glass fabric systems
- Specifications for your engineer of record
- typical FRP sheet thickness (1.3 mm)
- 0.05 in.
- working height on a restored chimney in Kazakhstan
- 690 ft
- of carbon fabric on one power plant smokestack
- 10,900+ sq ft
CASE STUDY
Strengthening a Smokestack Around an SCR Opening: Alabama Power, Bucks, Alabama
Federal rules requiring tighter control of NOx and SO2 emissions meant new SCR equipment for this coal-fired plant’s smokestack. The ductwork needed an opening of roughly 15 ft by 75 ft in the concrete wall, which removed large amounts of vertical and horizontal reinforcing steel and changed the stresses around the hole.
Carbon FRP was installed around the perimeter of the opening during the plant’s shutdown maintenance period. A 12 ft wide band of CFRP about 1/8 in. thick replaced the strength of No. 8 bars at 12 in. vertically and No. 4 bars at 12 in. horizontally. The project used more than 10,900 sq ft of QuakeWrap® carbon fabric and was completed in March 2008.
- Opening of about 15 ft by 75 ft
- Installed during the unit shutdown
- About 5,000 lb of CFRP in place of more than 100,000 lb of steel or concrete
CASE STUDY
Restoring the Top of a 690 ft Chimney: Tengiz, Kazakhstan
This reinforced concrete chimney was commissioned in 1984 in a climate that ranges from more than 53 °C in summer to minus 58 °C in winter. An inspection found the uppermost 5 m of the concrete windshield porous and spalled, with cavities through the wall at three elevations.
The damaged concrete was patched, a tack coat about 1 mm thick was troweled on, and biaxial glass fabric was bonded to the windshield. Installed properly, the fabric provides tensile force equal to 10 mm bars at 200 mm in both directions. High winds ruled out saturating the fabric at the top, so 1.2 m by 6 m pieces were saturated on a table at the base and carried up rolled on PVC tubes.
A crew of four worked nonstop for four days at 690 ft. An acid-resistant, heat-tolerant coating then restored the chimney’s original color. The project paper notes that the FRP system is not expected to require any maintenance during its service life.
- Top 5 m of the windshield restored
- Biaxial glass FRP, wet layup
- Work carried out while the chimney stayed on stream
ADVANTAGES
Why Owners Choose FRP for Chimneys
-
Savings in time and materials
Conventional materials lead to expensive, time-consuming repairs.
-
Fits a shutdown window
The Alabama Power retrofit went in during scheduled maintenance.
-
Works around openings
Fabric is cut and trimmed around openings and complex shapes.
-
Low weight
Strength without adding meaningful load to a tall shell.
Planning an SCR opening or a chimney repair?
Tell us about the chimney, its height, the opening or damage and your shutdown window. Our team will recommend the right QuakeWrap® system and provide specifications for your engineer.
Chimney Papers and Project Sheets
- CICIND REPORT, 2011 FRP Repair to a Reinforced Concrete Chimney Ehsani, Kelly, Smith and Kelly: inspection, repair scheme and installation at 690 ft.
- PROJECT SHEET Carbon FRP Strengthening of Smokestack Alabama Power, Bucks, Alabama, 2008.
- PHOTO SUMMARY Chimney Retrofits With FRP Alabama Power and Tengiz, Kazakhstan, step by step.
Chimneys & Smokestacks FAQs
Can FRP replace the steel cut out for an SCR opening?
Yes. At Alabama Power, carbon FRP placed in a 12 ft wide band around a roughly 15 ft by 75 ft opening replaced the strength of the reinforcing bars that were removed and resisted the stress concentrations around the hole.
Does the chimney have to be taken out of service?
Not always. The Alabama Power work was done during the plant’s shutdown maintenance period. In Kazakhstan the repair was carried out on stream to a safe distance from the top, with one flue liner off line and a temporary heat shield on the other.
Should a chimney be strengthened with carbon or glass FRP?
Both are used. The Alabama Power smokestack used carbon fabric around its opening. The Kazakhstan chimney used biaxial glass fabric, which reinforces in two directions and intercepts cracks either way.
Can you provide specifications and design details for our engineer?
Yes. Our team will recommend the right QuakeWrap® system and provide product data sheets, specifications and sample design details for your engineer of record.
Related FRP Repair Applications
Have a Project That Needs Repair?
Tell us about your structure. Our team will recommend the right QuakeWrap® system and provide specifications for your engineer.