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Gas Technologies: Central Thermal Fluid Systems

Many different aspects of plastics manufacturing require process heat. Heating of molds / platens, rolls, and machine barrels are three leading examples. This heat requirement has frequently been met through the use of steam or circulating hot water. In most cases, circulating fluid systems have been modular units dedicated to a particular piece of production equipment. While generally acceptable, these systems do have some drawbacks. Temperature control may not be uniform from machine to machine due to differences in individual modules. On hot water systems, upper temperature capabilities are limited. In steam systems, which can obtain higher temperatures, higher pressure is required, which can result in system leakage.

The Central Thermal Fluid System, or CTFS, has solved many of these problems. It consists of a burner assembly that generates heat inside a combustion chamber. Thermal fluids - commonly oil based - are circulated around the combustion chamber, where they are heated by conduction and then piped out to the process equipment hooked to the system.

Both gas and electrically heated CTFS are now commercially available.

A gas CTFS offers the following advantages:

  • High Efficiency (60-90%)
  • Greater Temperature Flexibility (up to 650ºF)
  • Precise Temperature Control (+/- 2ºF)
  • Highly Uniform Heating
  • Lower Production Costs (due to less scrap)
  • Lower Maintenance Costs (virtually nothing needs to be maintained except flame rod)
  • Increased Productivity (due to operating temperatures)
  • Increased Floor Space Availability (no more modular units)

While CTFSs have enjoyed wide-spread acceptance in Europe, their market acceptance in the U.S. has been somewhat more limited. This is mainly due to the more modular nature of the U.S. production facility, which places a premium on being able to add or move equipment as required. Being tied to a central system can restrict this flexibility.

CTFS Heating Choices - At a Glance

How They Work
CTFS operation involves either a vertical or horizontal heating unit, equipped with a gas burner that provides heat through basic heat exchange to the thermal fluid as it circulates in a coil. Hot gases from the flame circulate between the coils and vessel walls, in a direction opposite that of the thermal fluid to achieve maximum efficiency. Once the thermal fluid has been heated, it is pumped by the main circulating pump through a central header and valve arrangement to deliver process heat at precise temperatures to the molds, platens, rolls and machine barrels of multiple machines that are processing thermoset materials.

To accomplish this the gas CTFS consists of the following major components:

  • Thermal Fluid Heater
  • Circulating Pump
  • Expansion Tank
  • Temperature Control Valve with Actuator
    - Electronic
    - Pneumatic
  • Microprocessor
    - CPU
    - Mini Processor
  • Distribution Loop

Common Processes:
Extrusion, Injection Molding, Compression Molding

CTFS - Conversion
Can an existing heating system be converted to a CTFS?
Definitely! Passages can be created to flow thermal fluids. The advantages of a CTFS clearly outweigh any conversion costs. The initial expenses may include a thermal fluid heater and ancillary equipment, platen replacement or conversion, retrofit of existing tool, central distribution system, temperature controllers (microprocessors), valves, and actuators. The conversion has a quick payback due to reduced energy and scrap material costs and increased productivity.