It is that time of year again to make the switch from the sweltering heat to the nice fall weather. That means it will be time to lay-up your cooling tower system in the near future. When cooling systems are seasonally taken out of service or put on standby, microbiological growth and corrosion problems can develop and result in:
- Reduced equipment life from corrosion
- Increased operational, production, maintenance, and utility costs
- Down-time at startup
- Decreased efficiency
Here we will walk through these potential issues in-depth as well as provide solutions to prevent them.
The Concerns
- Corrosion in Offline or Standby Systems
Unless continuously replenished, the protective films formed by cooling water corrosion inhibitors tend to degrade over time, leaving chiller condensers, piping, and heat exchangers vulnerable to pitting and accelerated corrosion.
Offline corrosion can cause exfoliation or iron chip scale: flakes or pieces of iron oxide break loose and clog tower distribution deck nozzles, pump strainers, and condenser tubes after spring startup. Iron chip scale tends to occur in partially drained systems where sections of piping have water and air exposure but can occur in idle systems containing water. If there is significant pre-existing corrosion in the piping, there may not be an easy solution.
- Microbiological Growth in Offline or Standby Systems
Idled systems with no water circulation or flow provide ideal conditions for problem-causing anaerobic, sulfate reducing, and iron related bacteria to grow and cause corrosion and fouling concerns. Slime-forming bacteria can also cause severe fouling in unprotected offline systems. The problems can lead to high condenser head pressures, high electricity costs, and/or chiller shutdown when the systems are back in service.
- Concerns with Enhanced Tubes
Enhanced chiller tubes have spiral grooves or “rifling” to increase surface area, which permits greater heat transfer. They are particularly vulnerable to pitting damage and tube fouling from biofilms. Improper lay-up can significantly shorten their life.
The Solutions
- Corrosion Mitigation – Chemsearch FE’s Cooling Loop Gator is a Vapor phase Corrosion Inhibitor (VpCI) powder packages in polyvinyl-alcohol (PA) water-soluble bags. Developed for seasonal, short, or long-term lay-up, Cooling Loop Gator protects enclosed spaces for up to 12 months. Once the bag and powder dissolve, the VpCIs adsorb on all metal surfaces – reaching even recessed areas and interior cavities. The VpCIs form a strong molecular layer on the metal that protects in the liquid phase and vapor phase. Get the peace of mind that your system is protected in the off-season. The Loop Gator is also compatible with most water treatment programs.
- Control Microbiological Growth – Proper system layup would not be complete without a bio-dispersant to help clean up biofilms and remove bacteria. Bioexile is an effective additive that helps break the calcium bridge that holds biofilms together. Combined with a standard oxidizing biocide, you can get great results.
Our water treatment professionals at Chemsearch FE can help you create a program to manage your water systems. If you’d like to meet with one of our resource management experts, please click here and we will get someone in touch with you soon!
