Two-Phased Repair of a Cooling Tower Basin
- A cooling tower that houses 15 mechanical draft cells needed major repairs to its deteriorating concrete basin.
- Phase I of the repairs was completed while the cooling tower remained online.
- The ICCP system successfully extended the life of two existing walls of the basin, and was then used on the two remaining walls, as well as the newly built section of the basin.
- STRUCTURAL TECHNOLOGIES
Product Design and Supplier
Owned by one of the largest chemical and refining licensees, this plant is located in the southern United States. Comprising approximately 2,000 acres, it employs over 300 people, and produces ethylene, propylene, and other petrochemical products. The plant has been in service for over 20 years and has a major economic impact on the surrounding area. A crucial part of the plant is the multi-cell cooling tower that houses 15 mechanical draft cells. The cooling tower basin showed significant signs of leakage, cracks, delaminated concrete and corrosion. In addition, because the tower processes seawater as part of its cooling media, there was extensive embedded metal corrosion throughout the entire structure.
A Unique Repair Approach
STRUCTURAL was contracted to perform concrete repairs of the deteriorating cooling tower concrete basin while it remained online. Performing an online basin repair is a unique approach in the industry, but was possible due to the unusually thick cooling tower basin walls. The thickness allowed STRUCTURAL crews to perform all repairs from the outside without breaching the containment for the cooling waters.
Starting with the cooling tower basin walls, STRUCTURAL crews excavated any unsound concrete behind the reinforcing steel and then prepared the walls for concrete placement. Mechanical anchors were installed to integrate the new repair materials with the existing wall.
Due to the amount of chlorides and corrosion activity present, a galvanic cathodic protection system was insufficient for providing corrosion protection; instead, an impressed current cathodic protection (ICCP) system designed and manufactured by Structural Technologies was used.
The south and north walls of the cooling tower basin were left without an ICCP system during Phase I of this project due to a planned extension of the structure.
Seven years after Phase I was completed, STRUCTURAL was contracted to aid in the extension of the cooling tower basin and repair both the south and north walls, which showed significant signs of delamination, surface cracking, adhesion failure, and coating failure due to corrosion. In contrast, the east and west walls, which had received an ICCP system during Phase I, showed no signs of corrosion or physical deterioration.
After experiencing the benefits of having a cathodic protection system extend the life of the east and west walls of the existing structure, it became clear that an ICCP system was necessary for the remaining repairs to the south and west walls of the basin, as well as for the newly built section of the basin. STRUCTURAL TECHNOLOGIES designed the ICCP system for Phase II of the repair and the newly built section. The integration of the control and operating equipment into the Phase 1 system control system resulted in the ability to control both the existing and new sections of the ICCP system from a single main control unit.
Throughout this phase of the project, all repair work was performed during a planned outage. STRUCTURAL TECHNOLOGIES’ on-site technicians supervised the installation and performed testing and commissioning of the ICCP system, as well as closeout documentation. Quarterly performance tests were performed to confirm continued functionality of the ICCP system.