A customer in the chemical industry recently purchased two LEWCO Walk-In Ovens to heat materials in 55-gallon drums. In this process the heat evaporates water inside the drums to recover the material's solid contents. This was a critical step in the customer's process. The ovens, model EWR06FD, are heated by direct-fired natural gas and have a maximum temperature of 650°F., with a guaranteed temperature uniformity of +/- 10°F.
The ovens are equipped with a Programmable Logic Controller (PLC) interfaced with a touchscreen Human Machine Interface (HMI). A Eurotherm 3216 temperature controller with a redundant high-limit controller provides precise temperature control and over-temperature protection. Included in the controls are analog outputs to communicate temperature data to the customer's central control room. Also, relay inputs were added to allow the ovens to be remotely shut down from the same room.
The ovens feature a rear mounted heater-box and employs (2) 22,000 CFM circulation fans and a 1,250 CFM exhaust fan which includes air proving circuits that are electrically interlocked with the burner. The high-efficiency circulation fan and integral plenums deliver uniform "dual" airflow throughout the workspace which will allow the drums to be evenly heated.
A door limit switch was included to prohibit the burner from lighting when the doors are open. Also, due to pallets being loaded via forklift, a pipe guard rail was added down both inside walls of the ovens, to help protect the plenums from pallet truck traffic. Safety lanyards were added to each door to hold them open during loading/ unloading. (16) Thermocouple jacks were also provided for monitoring the individual drum temperatures.