By Mike Pehanich, Plant Operations Editor | 06/14/2007
A Top 10 U.S. food company has applied the Process Safety Management (PSM) template for ammonia refrigeration safety to renovation and construction scenarios in operating food plants.“Plant personnel must go through a checklist dealing with key elements to separate activities,” says Chris Harmon of Hixson Architects & Engineers, Cincinnati. “That list includes how to maintain refrigeration temperatures and traffic control of personnel and materials — how to get old materials out and new materials in — without affecting production flow or exposing product to contaminants.”Harmon stresses that the key to maintaining product safety and integrity during renovation activities is to “make it a team effort,” involving all parties involved with the renovation and plant production.Quality assurance should also do increased sampling around construction areas to make certain that product passes the test. |
Comeau sees many more plants looking to – or returning to – ammonia-based refrigeration systems. One reason is the inherent advantage in using a natural refrigerant. “They are very efficient, and they won’t be regulated away like R-502 (CFC), R-22 (HCFC) or R-12 (CFC),” he says. (Production of R-22 will slow in 2008 and will be eliminated by 2020.) There’s a cost factor, too. “When they were phasing out R-12, it went from a dollar a pound to $20 per pound. That was dramatic.”
He recommends that plants with refrigeration systems operating on R-22 develop contingency plans to use alternate refrigerants.
“If you don’t want ammonia, try R-507,” Comeau adds. “It’s a new refrigerant, and the price is getting competitive.” So far, plants that have installed systems that use R-507 are working well, he reports.
Replacing refrigeration systems requires very rapid turnaround since product safety and quality are often at risk during this period. Sometimes the new system has to be built side-by-side with the old system to facilitate a quick switch. Multiple systems may be replaced in sequence.
When Recco converted an ammonia refrigeration system to all glycol, Comeau was uncomfortable with the ammonia piping. His solution was to put in a parallel piping system that tied into the central system. “We had glycol available on five floors,” he recalls with pride.
Piping is always an issue when renovating older facilities. “The pipes of 30 years ago were not made to today’s standards,” says Comeau. Addressing the deterioration of steel piping or hot gas defrost lines can be an important aspect of a plant renovation. Non-destructive testing methods will help determine if pipe walls have thinned.
“Typically, the pipes are insulated with urethane,” says Comeau. “The vapor barrier breaks down and the vapor passes through the insulation and hits the piping. Mix the condensation, the water and steel with the temperature cycles, and you have a corrosion situation.”
Gel-coated piping can be a very effective defense against corrosion, he notes. Some paints and primers work, as well.
Motorized valves offer greater efficiency and reliability. They can quiet banging and shaking pipes and enhance the effective life of the valve as well. “They will also smooth out your plant operation, stabilizing compressor usage,” says Comeau. “Your compressor stays in one position throughout the daily cycle of the plant. You get no surges with motorized valves. It makes a dramatic difference.”
That’s what can happen when your plant has a plan.
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