Trace heating

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.

Electric trace heating began in the 1930s but initially no dedicated equipment was available. Mineral insulated cables ran at high current densities to produce heat, and control equipment was adapted from other applications. Mineral-insulated resistance heating cable was introduced in the 1950s, and parallel-type heating cables that could be cut to length in the field became available. Self-limiting thermoplastic cables were marketed in 1971.

Control systems for trace heating systems developed from capillary filled-bulb thermostats and contactors in the 1970s to networked computerized controls in the 1990s, in large systems that require centralized control and monitoring.

One paper projected that between 2000 and 2010 trace heating would account for 100 megawatts of connected load, and that trace heating and insulation would account for up to $700 million CDN capital investment in the Alberta oil sands.

International standards applied in the design and installation of electric trace heating systems include IEEE standards 515 and 622, British standard BS 6351, and IEC standard 60208.

The most common pipe trace heating applications include:

Other uses of trace heating cables include

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 energise when it measures temperature falling below a set temperature value - usually between 3 °C and 5 °C and often referred to as the 'setpoint'. The thermostat will de-energise the trace heating when it measures temperature rising past another set temperature value - usually 2 °C higher than the setpoint value.

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Wikipedia