When piping is exposed to very low temperatures, there is a risk that the fluid inside will freeze, especially when movement is slow or intermittent. Note that freezing can occur naturally due to cold, or in applications where certain areas must be maintained at low temperatures with refrigeration. Freezing can be prevented with electrical thermal tracking which involves installing cables along the piping to provide resistance heating.
Heat tracing is not limited to freezing prevention. The concept can also be deployed in applications that require water or another fluid to be maintained above a specified temperature, even when there is no risk of freezing. Also note that some industrial piping systems transport fluids that freeze at room temperature, making heat tracing necessary.
Many types of heat trace cables are commercially available and are selected based on insulation material, voltage, and heat production per unit length. Typically, one foot of cable is installed for each foot of piping, but additional cable may be required to compensate for localized heat loss due to components such as valves and flanges.
Prevent freezing in your plumbing system with electrical thermal tracking.
Electrical heat tracing is also known as surface heating or heat tape. It is important to note that heat tracing is not limited to tubes, but also to vessels. Thermal tracking can also be implemented with Steam, although it is only viable when customers have access to Steam at a reasonable cost.
How an Electrical Thermal Tracking System Works
The output of a heating element based on electrical resistance can be described with a simple formula:
- Heat output (Watts) = I 2 R
For example, if we double the resistance while keeping the current constant, the heating increases by 2. On the other hand, if we double the current while keeping the same resistance, the conductor dissipates 4 times more heat.
Electrical heat tracing uses cables designed to deliver constant power per unit length to have uniform heating throughout the tubes. Insulation is applied on all sides except the direction of the tube to concentrate the heat output into the internal fluid. The following are some common applications of electrical heat tracing:
- Freeze Protection for Commercial or Industrial Piping Systems
- Temperature Maintenance for Domestic Piping Systems
- Snow Melting on Outdoor Sidewalks and Roads
Electrical heat tracing generally uses many cables around the pipe to provide heat flow from all directions. This configuration also increases reliability, as heating can continue even if one of the cables is damaged, providing time for maintenance personnel to carry out necessary repairs.
The modern electric heat trace cable has a self-regulating design, which adjusts heat production as needed. The conductive elements are embedded in a polymer that expands and contracts in response to temperature:
- When the temperature drops and the polymer contracts, more conductive paths are created and resistance decreases. The current through the heat tracing cable increases and as a result more heat is released.
- The opposite process occurs when the temperature increases: the polymer expands, the conductive elements separate and increase resistance, the current decreases and less heat is produced.
Electrical heat tracing can also be equipped with a control and monitoring system, allowing for programmed heating sequences, alarms and notifications.
Heat trace cable: classification and selection
Heat trace cable is selected based on required circuit length and operating temperature. The combination of these factors determines which type of cable is most suitable.
- Self-regulating polymer sheathed cables are typically used for temperatures up to 200°C and circuits up to 750 feet.
- Mineral insulated cables are suitable for up to 650°C and 3,300 feet.
- Skin effect heating systems are intended for applications with much longer heating circuits, reaching up to 82,000 feet (25 km). They are typically rated for up to 250°C.
Like many other building systems, electrical heat tracing is subject to standards from organizations such as CSA, FM, IEEE and NFPA (National Electrical Code). Although heat trace cable is typically applied to existing piping systems, there are also pre-assembled solutions that include the pipe, cable and insulation.
