Large Drying Oven Exceeds Expectations

October 25, 2019 - "Applications "

Recently, LEWCO, Inc. delivered a 500°F enhanced duty walk-in oven to a world-class manufacturer. The oven is used to dry various parts in one step of the manufacturing process.
The enhanced duty electric walk-in oven features a top-mounted heater-box with a 144kW heat capacity. The oven is equipped with a 26,000 CFM high-efficiency circulation fan delivering horizontal airflow and providing uniform heat throughout the workspace. A 500 CFM exhaust fan is included to aid in the drying of the parts, but it was also required per NFPA 86, Class A due to solvents being present in the workspace.
Special features include zero speed switches, a variable speed drive, and a moisture analyzer. Zero speed switches replace the standard differential pressure switches on the fans, which are required due to variable speeds. The variable speed drive will turn down the motor speed on the circulation fan as process time increases. This is to mitigate the parts from becoming airborne inside the oven. A moisture analyzer is used to measure the absolute humidity from 0 -100% with +/- 1% accuracy.
The customer required the oven to meet strict temperature uniformity requirements of +/- 10°F at an operating temperature of 500°F. A 9-pt. temperature uniformity survey wasconducted, with the results exceeding customer expectations by achieving better than +/-5°F at maximum temperature.
Oven controls include a Watlow F4T temperature controller and redundant high-limit controller. Control functions include the ability to create, edit, and save multiple recipes, control oven operations, check oven status, and also monitor, record, and retrieve process data. A humidity sensor is included to control the fan speed as the parts dry.
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