Tempco Process Heaters for Tenter Frame Line Oven System

Rolls of Plastic Film

Tempco was approached by one of the world's leading mechanical and plant engineering firms. They were seeking an oven system to aid in the research and development of biaxially oriented films on a tenter frame line. Tempco designed a series of duct heaters for the production of plastic films by the tentering process.

The tentering process is used to stretch the width and length of materials under tension with a tenter frame. During the process, a thick extruded sheet is heated and mechanically stretched in both longitudinal and transverse directions. The most common plastic films produced with this method are biaxially oriented polypropylene (BOPP) and polyester (BOPET) which are often used in the packaging industry. The machine is designed to produce products for several other industries as well such as automotive, medical, graphics, etc.

The process heater system consists of eight units with three different duct heater designs and a maximum air temperature of 500°F. Tempco designed the duct heaters with tubular heating elements so that the units could hang vertically. Because of the high operating temperature, each heater also has a 6-inch insulating panel. The panels help to keep heat inside the oven and also protect the terminal housings from heat damage.

Each duct heater produces about 100 to 200 KW of heat while maintaining low watt densities, about 20 W/in.2 per element. The oven system produces a total of 1350 kW split into three heat zones:

Preheat Zone - 380 kW
- heats the raw material from extruder to prepare it for stretching
Stretch Zone - 280 kW
- stretches the material using rolls with progressively increasing speeds to lengthen the film and using chains and clips moving apart in the transverse directions to widen the film
Heat Set Zone - 690 kW
- high temperature zone permanently sets the material to the stretched size

Duct Heater for Tenter Frame Line Oven System

Continuous communication and feedback from the customer were important to this project. Tempco designed and manufactured the finished products in less than 8 weeks. These heaters can easily heat a large volume of air and maintain the system at high temperatures.