Atmosphere control in a 5 million cubic foot warehouse is a challenge.

IF NATURAL AGING IS TO OCCUR PROPERLY, THE CHEDDARS from Tillamook County Creamery in Tillamook, OR, require consistent temperatures slightly higher than a refrigerator for up to 18 months. The dairy cooperative built an AS/RS facility that doubles as an aging room and a finished-goods warehouse in early 2000. Two of the six zones are for aging, preferably at 42°F. They are separated by a 70-ft. door from the finished goods zones, where temperatures are held at 38°F. By 2001, it was apparent that intermittent shifts in aging-room temperature were posing a problem.

"It's not easy to make natural cheese, but the finished product is worth the effort," observes Jim Heffernan, Tillamook maintenance technician. "Part of the care and effort that goes into the process is making sure that storage-temperature conditions remain at a consistent 42°F. If it's a little too warm, the aging happens too fast. If it's too cold, the aging doesn't happen at all."

Retrofitting the storage area with hard-wired temperature sensors would have been difficult and expensive. As an alternative, Heffernan deployed about 30 data loggers to capture temperature and humidity data at strategic points. He selected HOBO H8 devices from Onset Computer Corp. Watch batteries that can last well over a year power the data loggers, depending on the frequency of data collection and variables such as atmospheric temperature.

Using a shuttle device equipped with a cable that plugs into the data loggers, Tillamook maintenance technicians downloaded temperature and humidity information and fed it into a Windows-based graphing and analysis program called BoxCar Pro to determine where and when aging temperatures were out of spec. Based on the analysis, airflows were modified with two 20-inch, high-capacity fans. An air curtain was created, and refrigeration equipment was altered to create greater temperature stability.

Heffernan's rule of thumb is that the devices can store data measurements taken every six minutes for 33 days. If data collection is a low priority, a wraparound function can be selected, overwriting data that is more than 33 days old.

Besides temperature and humidity tracking, the units can perform event tracking and monitor DC voltage and AC current. The data loggers have helped monitor current in the refrigeration compressors to optimize efficiency. They also were deployed to monitor the temperature of wastewater being discharged from the production area. Temperature spikes were uncovered, raising concerns of possible leaks. Ultimately, the problem was traced to a malfunction in the effluent cooling tower.

"We could still be looking for a leak without the data logger," Heffernan says. "It's like a pathologist: you learn about a problem when it's too late to prevent it, but at least it tells you how well your defrost is doing, how well you're controlling temperature, how consistently you're keeping doors closed."

For more information:
Scott Ellis, Onset Computer Corp., 508-759-9500, ext. 153