A field stone and concrete settling tank at the Knouse Foods applesauce factory in Orrtanna, Pa., was severely deteriorated and cracked. Groundwater infiltrated and some commercial wastewater – an acidic slurry of diced apples, seeds, cores and water – exfiltrated.
The corroding tank was an ongoing problem, and maintenance supervisor Pat Balog didn’t know what to do. Replacement wasn’t an option, as the cost was prohibitive and the plant couldn’t afford to lose two or more weeks of production.
At a trade show, Balog’s plant engineer met Gary Mock of Advanced Rehabilitation Technology (ART) of Bryan, Ohio, who evaluated the tank and found it a candidate for relining with SpectraShield. The multi-component stress skin panel liner system from CCI Spectrum in Jacksonville, Fla., stops infiltration and prevents exfiltration. Its installation saved Knouse Foods some $67,000 and kept the factory’s applesauce production on schedule.
Preparation
Built in the 1930s, the 21- by 30- by 7-foot-deep outdoor settling tank is connected to the 5- by 8- by 7.5-foot-deep interior tank by a 24-inch-square opening. A smaller enclosure inside the outdoor tank filters wastewater before it flows into the larger settling tank. All tanks are uncovered.
The plant treats its own wastewater, and 25 percent of the volume was groundwater infiltration. Treated water is used for irrigation.
“The 12-inch-thick walls in the outdoor tank were eroded 4 to 5 inches, and the 6-inch-thick walls of the smaller enclosure were eroded 2 to 3 inches,” says Mock. “I was amazed at the corrosiveness of apple juice.”
Mock, Matias Garcia Jr., and Josh Kimple arrived on a Wednesday morning to prep the tanks. Balog used the opportunity to shut down two production lines for maintenance, and workers replumbed the wastewater from a third line to a backup tank. They also drained the settling tanks, then the ART crew loosened the solids on the bottom using the plant’s fire hose.
CV Wenger Co., Chambers-burg, Pa., service provider to Knouse Foods, was unable to pump out the slurry because of a water main break at another Knouse plant. Mock’s crew couldn’t start hydroblasting until the vacuum truck arrived the following morning. ART uses the trailer-mounted Model 40201D high-pressure Ultra-Clean water blasting system from NLB Corp. in Wixom, Mich.
Cleaning the tank using 6 gpm at 40,000 psi was a slow, laborious process. The men rotated shifts, as pulling the trigger on the hand-held lance asserted 80 pounds of pressure against their bodies. After two hours of fighting the tool, they were exhausted.
One corner of the interior tank was badly broken out and full of whole apples. The vacuum truck couldn’t dislodge them until ART jetted the tank. By Thursday night, the men had removed all traces of applesauce.
28-hour day
Four inches of rain fell Thursday night, activating numerous leaks around the big field stones in the tank. “The surface of the walls must be dry before we can apply the primer,” says Mock. “Most leaks were minor, but they were all over. We saw about two dozen.”
Mock set up three heavy-duty high-performance livestock fans inside the tank to facilitate drying. To stop severe leaks, Garcia and Kimple bored into the walls and injected fast-acting SpectraGrout, but the drill bit kept encountering field stones. A direct hit stopped them cold. “Moving a few inches up or down sometimes got us around the rock,” says Mock. “Other times, we probably were on the edge of one and forced our way through it.”
Minor leaks were stopped with quick-setting hydraulic cement. The men applied the powder with their gloved hands, and could feel the heat from the chemical reaction. Plugging one leak often forced the water down the crack and out another opening.
The 6-inch-wide by 5-foot-tall missing corner section in the interior tank was rebuilt using cement bricks for backing. “We used a lot of grout to plug severe leaks and the hydraulic cement to repair missing areas,” says Mock. The repair took two hours, and stopping infiltration in all the tanks took seven hours.
Drying the walls of the interior tank was more difficult, too. As evening worn on, cool air formed condensate on them. The ART crew fought back with propane torches.
“The tank had to be online when employees returned from their three-day weekend,” says Mock. “To meet that deadline, we worked from 8 a.m. Friday until the lining process was completed at noon on Saturday.”
The first layer of the Spectra-Shield system is a proprietary primer designed for saturated concrete. The thin film provides adhesion to the substrate. As Kimple sprayed it on, leaks returned through different outlets.
“That was our next big challenge,” says Mock. “Work stopped while Junior or I plugged the leaks, then we’d look for new ones as Josh began spraying again. We’d know right away if something was wrong. The primer becomes runnier or has a milky appearance if water mixes with it or the surface is too wet.”
The men and hoses went back and forth between the outside and inside tanks by ducking through that 2-foot-square hole. They fought excessive heat in the tank and fatigue, but took breaks to cool off, rehydrate and catch catnaps when possible.
Home stretch
After the primer dried the required four hours, Kimple sprayed on a 50-mil layer of silicone-modified polyurea followed by a 1/2-inch thick layer of tight closed-cell polyurethane foam to fill voids and restore placement. “Building back the eroded thickness wasn’t necessary,” says Mock. “We wanted a fair surface that looks good and cleans easily.”
The foam dried tack-free in 8 to 12 seconds. Kimple then applied a second thin film of silicone-modified polyurea, which provided the final corrosion barrier and dried just as quickly. The tank was ready to go online. Balog gave the ART team free bottles of apple juice and asked Mock to evaluate another corroded concrete tank requiring cleaning and resurfacing.
