Electrofilm will design, develop and manufacture a heater to meet your specific requirements.

Electrofilm heating elements offer:

• UL COMPONENT RECOGNITION
• TEMPERATURES TO 500ºF
• HIGH RELIABILITY
• ECONOMICAL
• EFFICIENT HEATING
• PRECISE RESISTANCE VALUES
• LIGHTWEIGHT/FLEXIBLE
• LOW OUTGASSING PROPERTIES
• HIGH CHEMICAL RESISTANCE

Electrofilm heating elements generate heat over the entire heater surface resulting in even temperature distribution. This enhances heat transfer throughout the system by eliminating localized high temperature and providing an even surface temperature for conduction and/or convection and radiation. These heat transfer advantages permit efficient fast temperature rises.

Due to the extreme thinness of the insulation between the heated part and the source, little resistance to heat flow exists. The result is an extremely small temperature difference between the heating element and the part to be heated which yields little or no thermal inertia.

All Electrofilm heaters are durable with leads anchored to internal tabs so that the elements are protected from external strain. Joints are welded or soldered and are protected by extra insulation.

Lead wires ranging from #8 to #30 stranded or solid, with Teflon®, Neoprene or Silicone insulation are available. All colors and lengths are available to meet UL, CSA, ISO, and MIL specifications.

When additional circuits are required for rapid warm-up or varied watt densities, multiple circuits can be laminated in one layer. Voltage designs up to 480 volts, three-phase are available.

Electrofilm heating elements have been designed to solve the heating problems of any part of any shape, size, or material.

Electrofilm heating elements have been designed, and are operating under the following conditions:

• Fast temperature rise
• Supplying heat input in an amount equal to heat loss
• Maintain constant temperature independent of ambient conditions.
• Operating under extreme thermal shock

The following graph shows two thermal functions that might be considered in the design of a heating element.

• The temperature rise time (A): Where a rapid rise in temperature is required, high watt densities are necessary. The slope of the temp. vs. time curve is a function of watt density and heat dissipation.
• Maintaining temperate (B): When the desired operating temperature is reached, the thermostat takes over, cycling the element and maintaining a constant temperature within prescribed limits.

Controls

In many cases Electrofilm heating elements are furnished with temperature control thermostats, set at a temperature specified by the customer. Normally the thermostats are miniature size, and in all cases meet the environmental requirements of the heater.

The thermostats furnished are procured from approved, major thermostat suppliers, and if desired, can be procured by the customer directly from the manufacturer. Thermostats are off-on type of temperature controls.

For finer differential temperature control and faster response, Thermistor mag-type or thermocouple bridge sensor types may be more desirable. Electrofilm will also supply all commercially available controls of this nature, when specified.

Typical Insulation Properties

1. Determined on heaters which had 1 ply of insulation on each side of the conductor.
2. Determined on samples similar to those in note 1. Heaters were weighed, placed in boiling water for ONE hour. Surface was wiped dry, and sample weighed
3. Solvents: (1) Tap Water (2) Saline Solution (3) Silicone Fluid DC200 (4) Hydrocarbon Test Fluid MIL-H-3136 (5) Skydrol 500 (6) Oil MIL-O-5606 (7) Oil MIL-O-7870 (8) Monsanto OS45

Element Configurations and Electrical Characteristics

Different Element configurations are available:

• Single Circuit laid down on a desired resistive path
• Printed Circuits to increase reliability when required
• Spiral wiring which permits maximum unit resistance. This is accomplished by wrapping the wire around an insulated core
• In addition, bifilar winding is available to eliminate electromagnetic field generation.

Thermal Characteristics

Thermal efficiency is the ratio of useful energy to the energy being expended. The energy being expended is a result of the power dissipation of the heater blanket. The useful energy is that energy that is actually transferred into the part you are heating.

The ratio, or efficiency, is affected by the wasted energy convected and radiated from the surface of the heater into the air. This situation may be improved by adding thermal insulation. However, the conductor area coverage is very significant and the etched foil conductors afford the optimum results.

The spacing between conductors is held to a minimum. Because close tolerances can be met when etching or chem-milling a circuit pattern, the resultant conductor pattern will cover nearly 100% of the surface to be heated. This results in even heat distribution over the surface and significantly lowers element operating temperatures. It allows the use of increased watt densities yielding faster warm up times.

The purpose of a surface type heating element is to distribute the necessary power as evenly as possible over all the area that is available for the heater.