Image Credit: Thermon Manufacturing Co. | Tyco Thermal Controls
Trace line heaters are flexible, insulated cables that are heated with electricity or re-circulated fluids. They are used to prevent liquids in pipes from freezing, or to reduce heat loss in piping. Trace line heaters differ in terms of cable shape, cable size, and maximum temperature.
Trace Heating - The Basics
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When searching for trace line heaters, cable configuration, cable insulation and maximum temperature are the most important parameters to consider. Other considerations include fuels and/or energy sources, RoHS / WEE compliance, and various features.
Typically, the cross-sectional geometry of the straight (uncoiled) cable is round, square or rectangular. Coil width and uncoiled length are important dimensional specifications to consider.
Round cable - The cross-sectional geometry of the straight (uncoiled) heating cable is round.
Square or Rectangular cable - The cross-sectional geometry of the straight (uncoiled) heating cable is square or rectangular.
Coil Width - The coil width is the longest dimension measure across a cross section perpendicular to the length of the cable.
Uncoiled Length - Uncoiled length is the length of a straight cable.
Trace line heaters differ in terms of insulation options. Although heaters without insulation are available, these devices are not particularly energy-efficient. Typically, suppliers carry trace line heaters with ceramic, fiberglass, magnesium oxide, mica or mineral insulation, or a fluoropolymer. Each type of insulation offers different features. Some heaters may be available with multiple insulation options.
Trace line heaters with no insulation have a lower profile and are useful in areas where space is at a premium, but they are not energy efficient.
Ceramic insulation consists of nonmetallic minerals, such as clay, that are permanently hardened by high-temperature firing. Most ceramics resist heat and chemicals.
Magnesium oxide insulation has a high melting point (2800°C) and heat resistance (1700°C in the reducing and 2300 °C in oxidizing atmospheres.)
Mica insulation consists of colored or transparent mineral silicates that are crystallized in monoclinic forms and readily separated into very thin leaves. Mica is valued for its electrical insulating properties and resistance to heat and acids.
Fluoropolymer insulation is
Fiberglass insulation is strong, durable, and impervious to many caustics and extreme temperatures. Fiberglass fabrics are used widely in industry.
The maximum operating or sheath temperature for trace line heaters is the highest temperature that the device's protective cover may attain.
Note, however, that this is not the maximum temperature that a heated substance can reach.
Fuels and/or energy sources
Trace line heaters are primarily powered electricity or re-circulated fluids. Electrically powered trace line heaters are typically referenced as heat tracing cables. The most common thermal fluids used in other types of trace line heaters are steam and hot water.
Image Credit: Tyco Thermal Controls
Electrically powered trace line heaters may use either single-phase or three-phase power. Typically, these devices use alternating current (AC) instead of direct current (DC) and differ in terms of watt density. When listed as a range or maximum amount, watt density provides a good measure of how quickly the trace line heater can transfer heat to a heated surface.
To calculate watt density, suppliers divide the available wattage by the heated surface area.
Image Credit: Thermon Manufacturing Co.
Re-circulating fluids used in trace line heaters are typically steam or hot water. In some applications where steam or hot water supply is readily available, these types of trace line heaters are an environmentally friendly and cost effective method of heating a vessel, pipe or other surface.
RoHS / WEEE Compliance
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Restriction of Hazardous Substances (RoHS) is a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of the following hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether. RoHS became effective on July 1, 2006.
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Waste Electrical and Electronics Equipment (WEEE) is a European Union (EU) directive designed to encourage the reuse, recycling and recovery of electrical and electronic equipment. WEEE is also designed to improve the environmental impact and performance of this equipment. The WEEE directive establishes requirements and criteria for the collection, treatment, recycling and recovery of electrical and electronic equipment. It also makes producers responsible for financing these activities. Retailers and distributors must provide a way for consumers to return used or obsolete equipment without charge.
Self-regulating cables incorporate a temperature sensing device and are used to maintain temperature limits in order to prevent freezing or over heating of process fluids.
Corrosion resistant trace line heaters are made of corrosion-resistant materials and suitable for use in a corrosive or chemical environment.
Trace line heaters designed for hazardous location heaters are for use in places where there is a risk of fire or explosion. Underwriters Laboratories (UL) and other organizations rate these devices.
Some trace line heaters have an integrated, adjustable or preset thermostat. The thermostat regulates the temperature of the heated object.
UL approved trace line heaters are approved by Underwriters Laboratories (UL). Typically, documentation of UL certification is available from the manufacturer.