16 Nov Case Study: Cooling Tower Basin Repair
The Problem:
Faced with water leakage and a failed installation of a newly built cooling tower basin, a leading specialty chemical company was in need of a quick diagnosis and reliable method of repair to ensure the future structural integrity of this critical utility.
Prior to the installation of the cooling tower on the basin, a proof test was performed where approximately 25,000 gallons of water was introduced into the new basin. The test exposed significant signs of leakage and cracks.
The facility needed a successful repair and startup of the cooling tower to meet their cooling water demands.
Investigation/Root Cause Analysis:
Various tests (nondestructive evaluations (NDE), shear wave ultrasonic tomography and ground penetrating radar) revealed that locations of seepage/leaking were originating along separate concrete placements (lift lines) along the perimeter of the basin walls. In addition, honeycombing and hairline cracks were observed throughout the interior of the basin concentrated along the perimeter walls. The water seepage and leak locations along the basin walls were consistent with concrete consolidation-related issues along lift lines. NDE indicated that these conditions were prevalent along all lift lines, and appear to be both surficial and within the core of the wall. Manifestation of these consolidations-related issues were due to the delayed concrete delivery or placement during construction, inter-layer vibration not adequately achieved, and/or segregation of the concrete after placement.
The Solution:
Based on the nature of the flaws, the repair recommendations varied. Once the voids were initially exposed based on the NDT testing results, a high strength, rapid setting, one component, permanent concrete repair material for vertical basin walls was applied, which developed an integral bond to existing concrete and restored structural integrity within hours of placement.
A hydrophobic urethane grout (1200 to 1500 PSI) was pressure injected to fill wide cracks and voids in the concrete wall due to its quick cure time. When it comes in contact with water, the grout expands and quickly cures to a tough, flexible, closed-cell polyurethane foam that is generally unaffected by common corrosive environments and is not subject to shrinkage due to wet/dry cycles. A layer of primer was sprayed on the basin floor and on the surface of the inside wall to fill pores and to even out the surface.
To expedite the process of healing the cracks in the basin a chemical was required which would react almost instantaneously (rapid curing) and become robust against humidity or moisture concerns. Polyurea was used for this purpose and applied to the basin floor and inside wall surfaces.
Benefit:
Sufficient, on time concrete delivery and proper consolidation of freshly placed concrete with an internal vibrator are crucial parts to concrete placement and key to ensuring homogeneity of the concrete construction. Providing production personnel with the proper vibration equipment and training greatly reduces the quality issues associated with concrete consolidation.
Conclusion:
By breaking down a problem into its components: Listen, Plan, Act and Implement, Chemic was able to deliver engineering solutions to the client. Due to the swift response and steadfast service Chemic helped the client successfully commission the cooling tower with a minimum amount of delays and assisted the client in meeting crucial cooling water requirements.