One manufacturer improved its process by purchasing a single oven suitable for both process heating and cooling.

Therm-O-Disc's oven included auxiliary equipment that transformed it into a liquid nitrogen chamber, allowing the temperature switch manufacturer to employ heating and cooling in a single piece of equipment.

Engineers at a Canadian temperature controller manufacturer were dissatisfied with the cooling phase employed during its temperature switch manufacturing operation. Lower temperatures and a more efficient way of cooling were essential for refining the process. Installation of a cryogenically cooled oven with accessories resulted in manufacturing improvements at Therm-O-Disc Canada Ltd., St. Thomas, ON.

Within the first day of installation in June 2000, Shaun Bullen, manufacturing engineer at Therm-O-Disc Canada, noticed immediate improvements in the heating/cooling segment of the temperature switch manufacturing process.

"Since the implementation of this piece of equipment, the production time required to complete that portion of the manufacturing process has been reduced from more than an hour to 10 minutes," Bullen explained.

Colder service temperatures are the key to this oven's effectiveness. Therm-O-Disc researched various ovens and decided that Series 3710 with cooling option and accessories from Applied Test Systems, Butler, PA, delivered the coldest temperatures. General oven construction included a stainless steel shell and internal liner as well as a circulating fan plenum system and elements. Four removable shelves were added as well as a rear protection cover for added safety.

In addition to good basic design, the oven included auxiliary equipment that transformed it into a liquid nitrogen chamber. Cryogenic cooling system add-ons included an injector nozzle and solenoid valve, temperature control system and a zero-crossover SCR.

If using nitrogen dioxide instead of liquid nitrogen with you oven cooling option, extra attachments such as the injector nozzle must be added, and production requires that a few extra steps be performed.

Cryogenic Cooling

Bullen believes that without the cooling option, the oven would not have assisted in this particular part of the manufacturing. In the past, employees arranged the switches on dry ice (LN2), then waited for the moment when the items would be ready for the next phase.

"Watching and waiting for something to happen took up most of the employees' time, and freezers didn't deliver the temperatures we were looking for," Bullen said.

With the cryogenically cooled oven, items are placed on evenly spaced shelves, controls are set, and the oven's liquid nitrogen cooling assembly and temperature system takes over. Because they do not have to watch the switches, operators have more time to complete other tasks.

Installing the entire cooling op-tion required only a few simple procedures. However, if a manufacturer preferred to use carbon dioxide (CO2) rather than liquid nitrogen, extra attachments such as an injector nozzle would be required, and a few extra steps would be performed.

The temperature control system with a zero-crossover SCR works as a controller package. The temperature control system regulates the power applied to the resistive heating elements to reach and maintain the desired temperature (setpoint) as measured by a control thermocouple. The control system regulates the heating and cooling cycles in the oven while the zero-crossover SCR is an intermediary device that controls the power or infinitely variable output. In addition, for Therm-O-Disc's application, Ap-plied Test Sys-tems added to the cooling power of the liquid nitrogen injector assembly/solenoid valves. The temperature control system and shelf design created more even cooling for the temperature switches.

Although cooling was the primary concern when Therm-O-Disc purchased the oven, Bullen noted, "The Series 3710 also has heating capabilities that are currently being explored and possibly utilized in other manufacturing processes within Therm-0-Disc."

Implementing an oven with a cooling option and other accessories may be more efficient than using freezers and dry ice in manufacturing processes. Employee time is utilized more efficiently and evenly spaced shelving creates more efficient heating/cooling for samples.

For more information about Applied Test Systems' cryogenically cooled ovens, call (724) 283-1212 or visit