Granular Activated Charcoal (GAC) tanks are notoriously abrasive, which has a negative impact on coatings. With how expensive coating systems are, it’s important to prolong the lifespan as much as possible, yet many incorrectly specified coating systems can fail within 10 years.
When the coating system on a GAC tank lasts longer than 30 years, it’s a notable accomplishment. This article looks into a specific case where a group of tanks have not needed to be reconditioned since they were new in 1988, and how they’ve managed to maintain the coating system so well.
New Brighton, Minnesota, a suburb of the Twin Cities, built their GAC tank in 1988, which provides water treatment services to over 22,000 residents. In the summer these tanks process 300,000 gallons per day, while this number increases up to 2,000,000 gallons per day in the winter. With such a high demand, it is crucial for their GAC tanks to work smoothly. After over 30 years of service, New Brighton’s tanks have withstood the test of time gracefully thanks to professional engineering (by Barr Engineering) and inspections (by KLM Engineering), proper preparation and maintenance.
KLM Engineering, Inc. has monitored their tanks for over 20 years and has recorded a mere ~1 mm yearly loss in their interior coating system. Given that a GAC tank is a very abrasive environment, this is considered a minimal loss.
A vital part to this nominal wear started when the coating was applied in 1988. Proper application and inspection ensured it was applied correctly according to well-written specifications to last through its expected lifespan. These tanks used a Carboline Plasite 4110 coating system, which can be difficult to apply, which is why it is crucial to have certified inspectors on site. With material product changeout and routine maintenance every five years by performing inspections and minimal spot repairs, any coating failures were fixed before they could continue to grow.
The success of New Brighton’s GAC tanks can be attributed to four things: good specifications, proper application, excellent inspection, and routine maintenance. By keeping up with inspections and spot repairs, the coatings have lived far beyond their normal expected lifecycle.
If it’s time for your community’s GAC tanks to be inspected, give KLM Engineering a call at 651-773-5111 today, and our team of water tank specialists will help you get started.