Electric heat tracing, heat tape or surface heating, is a system used to maintain or raise the temperature of pipes and vessels. Trace heating takes the form of an electrical heating element run in physical contact along the length of a pipe. The pipe must then be covered with thermal insulation to retain heat losses from the pipe. Heat generated by the element then maintains the temperature of the pipe. Trace heating may be used to protect pipes from freezing, to maintain a constant flow temperature in hot water systems, or to maintain process temperatures for piping that must transport substances that solidify at ambient temperatures. Electric trace heating cables are an alternative to steam trace heating where steam is not available or unwanted
The most common pipe trace heating applications include:
· Freeze protection
· Temperature maintenance
Other uses of trace heating cables include
· Ramp and stair snow / ice protection
· Gulley and roof snow / ice protection
· Under floor heating
· Door / frame interface ice protection
· Window de-misting
· Pond freeze protection
· Soil warming
· Anti- cavitations purpose
Every pipe or vessel is subject to heat loss when its temperature is greater than ambient temperature. Thermal insulation reduces the rate of heat loss but does not eliminate it. Trace heating maintains the temperature above freezing by balancing heat lost with heat supplied. Normally, a thermostat is used to energize when it measures temperature falling below a set temperature value - usually between 3°C and 5°C and often referred to as the 'set point'. The thermostat will de-energize the trace heating when it measures temperature rising past another set temperature value - usually 2°C higher than the set point value.
Placement of heat traces cable on roofs or in gutters to melt ice during winter months. When used in gutters the cable is not meant to keep the gutters free of ice or snow, but only to provide a free path for the melted water to get off the roof and down the downspout or drain piping.
Hot water service piping can also be traced, so that a circulating system is not needed to provide hot water at outlets. The combination of trace heating and the correct thermal insulation for the operating ambient temperature maintains a thermal balance where the heat output from the trace heating matches the heat loss from the pipe. Self-limiting or regulating heating tapes have been developed and are very successful in this application.
A similar principle can be applied to process piping carrying fluids which may congeal at low temperatures, for example, tars or molten sulfur. Hit-temperature trace heating elements can prevent blockage of pipes.
Industrial applications for trace heating range from chemical industry, oil refineries, nuclear power plants, food factories. For example, wax is a material which starts to solidify below 70 °C which is usually far above the temperature of the surrounding air. Therefore the pipeline must be provided with an external source of heat to prevent the pipe and the material inside it from cooling down. Trace heating can also be done with steam, but this requires a source of steam and may be inconvenient to install and operate.
In laboratories, researchers working in the field of materials science use trace heating to heat a sample isotropic ally. They may use trace heating in conjunction with , so as to control the heat energy delivered. This is an effective means of slowly heating an object to measure thermodynamic properties such as thermal expansion.