These heaters are used to maintain or raise the temperature of pipes and vessels. Heater cables takes the form of electrical heating elements to run in physical contact along the length of a pipe. The pipe is usually covered with thermal insulation for retain heat losses from the pipe. The heat generated by the element then maintains the temperature or the pipe. Trace heating cable maybe used to protect pipes from freezing to maintain a constant flow of temperature in hot water systems or to maintain process temperatures for piping that must transport substances that solidify at ambient temperature.