Electrical trace heating refers to the process of maintaining or raising the temperature of pipes and vessels through specially engineered cables. During the winter season, temperatures are extremely cold and can fall below freezing levels.
When this occurs, businesses can turn to trace heating as a solution to protect their important pipes and vessels from freezing at sub-zero temperatures. When temperatures drop to freezing levels, pipes can get frozen which may cause them to burst as a result of ice expansion. Thus, trace heating helps to prevent frost from building up in water pipes and vessels by maintaining temperatures at a designated level.
Heat tracing can also be implemented in processes that require temperature maintenance such as the insulation for steam pipes. Another example would be when certain liquids require being kept at a specific temperature in order for them to be transported safely. For these processes, heat tracing can still be applicable even in the absence of freezing temperatures.
Trace heating is achieved by connecting specially engineered cables made of a resistance element to the pipe or vessel. The electric cables are then used to maintain temperatures by replacing heat loss with their power output. According to Ohm’s law, connecting a voltage through a wire or cable will result in a supply of power, which is subsequently converted to heat energy by the heat tracing system.
Trace heating cables contain two copper conductor wires that are parallel in length which creates a heating zone with a resistance filament in place. With a fixed voltage supplied, a constant wattage is produced which then heats up the zone. Trace heating cables are monitored by a thermostat to ensure that the right amount of thermal energy is produced so that the cable does not overheat or underheat.
Different Types of Trace Heating
Series Resistance Trace Heating
A series resistance heating cable comprises of a high-resistance wire that is typically insulated and encased in a protective cover. When powered at a certain voltage, thermal energy is produced from the resistance of the wire. The advantage of a series resistance heating cable is that it generally cost lower and is able to maintain very high temperatures for longer lines. As a result, series resistance trace heating cables are usually fixed in length and cannot be shortened in the field as a break or failure anywhere along the line would cause the entire cable to fail. Therefore, series resistance trace heating cables are typically used for longer pipe line heating processes.
However, there is still a need to monitor and control the circuit as the resistance material might melt due to overheating. Series resistance trace heating is usually applied when there is a need for long pipe line process heating, such as the quay side of load pipes on oil refineries and along oil pipe lines.
Constant Wattage Trace Heating
A constant wattage trace heating cable design consists of a heating element wrapped around two parallel wires that are insulated. There are multiple zones throughout the trace heating cable that experiences constant wattage. A notch is created in the insulation on the opposing sides of the conductors. A small heating circuit is then produced by fusing the heating element to the exposed conductor wire and this is repeated throughout the entire cable. The parallel wires are then separated from the grounding braid by an inner jacket.
One advantage that constant wattage trace heating provides over series resistance trace heating is that the former is able to function even during the event of a fault somewhere along the cable. Also, the length of a constant wattage trace heating cable can be adjusted on the field itself, thanks to its parallel functionality. Therefore, many businesses and industries prefer installing constant wattage trace heating systems due to the flexibility that comes with it.
A constant wattage trace heating cable is always accompanied with a thermostat during installation to monitor and regulate the power output of the cable. This is done to prevent it from overheating and burning out, in the event that the cable comes into contact with itself.
Self-regulating trace heating cables have resistances that vary with the temperature. Fundamentally, when temperatures fall below the specified limit, the resistance of the cable will drop as well. Conversely, the resistance of the cable will increase when the temperature exceeds the designated level. Self-regulating trace heating cables are made from two parallel wires that are enclosed in a polymer that is semi-conductive. The polymer is usually made with carbon which prevents current from overflowing at higher temperatures. The carbon in the polymer can be expanded or contracted to produce different levels of resistance and heat energy output.
Self-regulating trace heating cables are able to adjust their length in the field. The self-limiting ability of the cable allows it to be more energy efficient as it is able to reduce its output at higher temperatures. Due to its ability to conserve energy when the temperature increases, self-regulating heat cables can help businesses to save costs thanks to this power saving feature.
Furthermore, self-regulating trace heating cables have improved safety levels which is highly desirable characteristic in hazardous locations. This is because power output of the cables will not exceed a certain level as output drops when temperature of the cable increases. Therefore, it is not possible for self-regulating trace heating cables to overheat, which might pose a threat especially in an area with flammable gases and vapours.
Applications of Trace Heating
Trace heating can be used to protect pipes and vessels from freezing by maintaining the temperature at a certain level above freezing point. This is done by supplying heat energy to balance the amount of heat lost through conduction. Bear in mind that thermal insulation is only able to slow down the process of heat loss but cannot prevent it from occurring entirely. Therefore, trace heating is a solution to heat loss and offers frost prevention for your business.
Gutter and roof de-icing
Trace heating cables can be installed on the roofs and in gutters of your business to prevent ice or snow from accumulating. The cables also act as a draining path for water from the melted ice to flow so as to prevent overflowing in gutters and rooftops. Overflowing can be detrimental to the structural integrity of buildings as it can result in water seeping through cracks or joints. Also, the extra weight from the overaccumulation of snow or melted ice can result in indentations and depressions on the rooftops and gutters. Therefore, trace heating is essential in preventing any unwanted water build-ups for your business.
Trace heating helps to decrease the likelihood of cavitation in pipes as heating a liquid reduces its thickness and viscosity. Cavitation refers to the formation of vapour bubbles in a liquid that is caused by rapid pressure differences. Shockwaves are produced when these vapour bubbles or cavities in the liquid implode or collapse, which can damage the inside of the pipe over time. Cavitation can also disrupt the flow of liquid inside the pipes. Therefore, installing heat tracing cables will reduce the chances of cavitation as it helps to lower the pressure difference in the liquid.