By Sandi Hague, HAGUEdirect LLC
About two years ago, a power plant in Georgia pulled covers to inspect eight of their A/C chillers and found that they showed substantial scale buildup on the inner surfaces of the tubes, the outer surfaces and the tube facings. The buildup resisted the facility’s standard mechanical cleaning procedures. The tubes’ inner diameters were narrowed to the point where adequately sized cleaning brushes could not be inserted into the tubes.
The power company asked Augusta Industrial Services, Inc., which services nuclear power plants throughout the southeastern United States, to help find a solution. Augusta Industrial Services, based in Augusta, Georgia, visited the plant to investigate the situation.
“The tube bundles were so bad – fouled with scale and grit – that you couldn’t put the correct brush in the chiller to clean it. Therefore the regular mechanical cleaning method was out of the question,” explains Augusta’s supervisor Shawn Conklin.
Often power plants will allow the chiller tubes to be cleaned by hydro blasting, but that method was not an option in this situation. “The number one concern is safety, and with the possibility of puncturing a tube by hydro blasting, the plant’s engineers would not allow us to use high pressure water on these chillers,” said Conklin.
The power company asked Augusta Industrial Services to find a chemical cleaning solution for clearing out the tubes. Two of Augusta’s on site supervisors (Shawn Conklin and Taylor Smoot) conducted its research. After considering the alternatives and discussing them with the plant’s engineers, they received approval to call Goodway Technologies Corp. to request a sample of the chemical ScaleBreak for testing. All involved parties liked that the independent studies showed that ScaleBreak dissolves calcium deposits, rust, lime and lithium carbonate on contact without damaging the equipment being serviced.
Augusta Industrial Services test-cleaning consisted of several chunks of the deposit, that was scrapped off of the tube face, being placed into a beaker and then adding a capful of the ScaleBreak at a time until the pieces started to.
As the test-cleaning satisfied the engineering staff, the Augusta supervisors were given the approval to proceed with an initial order of ScaleBreak and the cleaning of one unit.
“Actually, the first time we cleaned it we mixed it wrong – we were told the unit capacity was 400 gallons, but it was really 700 gallons, so our mixture was too weak. Even so, it was already starting to remove some scale,” said Conklin. “So we had more ScaleBreak shipped to us overnight. We got the calculations right, circulated it for four hours, drained it, rinsed it, and we just couldn’t believe how clean it was – we were really surprised.” Conklin’s crew ordered more ScaleBreak and took care of the other seven chillers without any difficulties.
Conklin explains how the process works. “We calculate the tube bundle’s volume – anywhere between 150 gallons to 1,000 gallons – then we calculate how much ScaleBreak versus water to use. Right now we like to use a 60-40 mixture – 60 percent ScaleBreak and 40 percent water. That works out really well for us.” Conklin continues.
Conklin said they circulate the solution with a machine which is similar to a swimming pool pump. After four hours of cleaning, his team checks the condition of the tubes. “If it needs more, then we’ll use a slightly stronger solution and circulate it for another two hours or so,” he said.
Conklin said the cleaning method is very safe.
“We keep the chemical solution in the tube bundle and circulate it from there to our cleaning equipment,” he said. “It’s cut off from all the other equipment, so there’s no contamination – no safety issue.”
The formula includes corrosion inhibitors and is approved for use on steel, iron, brass, copper, plastic and rubber. Specially formulated ScaleBreak-SS is safe for stainless steel.
Augusta Industrial Services reports that chemical cleaning is economical. Conklin said that’s because circulating the chemicals is a much faster method than standard manual cleaning.
After the first thorough cleaning, subsequent visits often take less time. “Next time we come out we might cut the time in half – it could take only two hours of descaling to clean everything,” he says.
ScaleBreak does not contain toxic cresols or other tar oils that need SARA Title III, Section 313 spill loss or disposal reporting. The waste product is mildly acidic and contains only nontoxic salts after being used to remove potable water scale. It rinses easily with water and requires no special equipment for handling.
Conklin also likes that chemical cleaning can take less of a toll on his crew. Mechanical cleaning and hydroblasting are physically taxing methods, and fatigue can contribute to accidents. ScaleBreak’s formulation makes it a safe choice for service personnel, since they don’t have to deal with caustic chemicals or noxious fumes.
Power Engineerng Issue Archives
View Power Generation Articles on PennEnergy.com