The right heat tracing method for a viscous product line depends first on its job: holding hot product at a pumpable temperature, bringing a cold line back up to temperature, or making sure the product never solidifies. Combine that with the required maintain temperature, the highest temperature the line will ever see, the utilities available on site (power, steam or thermal oil) and the hazardous area classification, and the choice between electric cable, steam tracers and jacketed pipe usually becomes clear.
Heavier residual fuel oil grades typically need preheating for handling and for proper atomization at the burner. Heat tracing replaces the heat that escapes through the insulation so the product stays inside that temperature window from the tank to the point of use.
Define the duty: temperature maintenance or heat-up?
Most tracing systems are designed for temperature maintenance: the product enters the line hot and the tracing only offsets losses. Raising a cold line to temperature within a set time needs far more power and is a separate design decision. Steam tracing practice distinguishes several duties:
· Non-critical tracing: Keeps viscosity at a good pumping level. A short temperature dip will not ruin the product, but it will load the pump.
· Critical tracing: Holds temperature continuously for products that would solidify or degrade below a set point.
· Jacketed lines: The most demanding service, where the product must stay hot at all times and the line must pre-heat quickly.
· Instrument tracing: Protects small but exposed points such as flow meters, control valves, sample points and impulse lines.
Pour point is an index of the lowest usable temperature, not a design temperature. The temperatures needed for pumping, metering and atomization can differ, and each should be derived from the product's viscosity–temperature data.
Electric heat tracing options
Three cable families dominate electric tracing; the choice depends on maintain and exposure temperatures, circuit length and control philosophy.
Cable type | How it works | What to watch in selection |
Self-regulating heating cable | A carbon-loaded polymer between the bus wires passes less current as it warms, so output drops on its own | Its self-limiting behavior allows a temperature class rating in hazardous areas, but it does not hold a set point by itself, so a controller may still be needed |
Constant wattage cable (parallel or series) | Fixed-resistance heating zones deliver the same output regardless of ambient temperature | Suits higher exposure temperatures; because it does not self-limit, temperature control and overtemperature protection are part of the design |
Mineral insulated (MI) cable | Conductors in magnesium oxide insulation inside a seamless metal sheath, usually supplied as factory-terminated units | Used where high power density, high temperature or corrosion resistance is required; line lengths and connection points must be fixed early |
Steam and fluid tracing
Refineries, power plants and terminals that already run steam or thermal oil often trace with a heating fluid. Small-bore steam tracers attached to the product line replace the heat lost through the insulation, and steam releases that heat at a constant temperature set by its pressure. Heat transfer cement between tracer and pipe significantly improves heat transfer and helps avoid local hot spots.
Fluid tracing succeeds or fails on its distribution and return side. Steam supply manifolds, a steam trap at the end of each tracer circuit, condensate collection manifolds and temperature control devices have to be designed together. Jacketed pipe is a class of its own for lines that must hold product at the highest temperatures; jacketed piping and loading arms for bitumen are covered on a dedicated page.
Where cold spots form on heavy oil lines
Problems start wherever thermal mass and surface area increase: valve bodies, strainer baskets, pump casings, meter bodies, flange pairs, pipe supports and dead legs with no flow all need extra heat and careful insulation. If the line is steamed out or flushed with hot product, the highest temperature the cable sees can be far above normal operating temperature, and cable selection has to follow that figure. For the heating arrangement on a skid carrying meters and valves, see our page on heated metering skids.
Design inputs
Parameter | Why it matters in design | Effect on selection |
Maintain temperature and tolerance | Defines the band in which the product stays pumpable and meterable | Sets cable type, output and control accuracy |
Maximum exposure temperature | Steam-out or hot flushing can push the cable well above operating temperature | Decides between polymer self-regulating, constant wattage and MI cable |
Product upper temperature limit | For some products, overheating increases emissions or degrades the product | Drives the control method and the need for overtemperature protection |
Minimum ambient temperature and wind | Heat loss grows with temperature difference, insulation and wind | Number of tracers, cable output and insulation thickness |
Insulation type and thickness | Tracing cannot keep up with losses on an uninsulated line | Cable output and steam consumption depend directly on insulation |
Hazardous area classification | Heater surface temperature can become an ignition source | Affects cable temperature class, terminations and controller selection |
Available utilities | Fluid tracing needs extra infrastructure if there is no steam or thermal oil | Decides between electric and fluid tracing |
Control, monitoring and hazardous areas
Simple freeze protection may only need ambient-sensing control. For heavy oil, where viscosity reacts sharply to temperature, circuit-level control based on pipe-surface sensing, with low and high temperature alarms and fault reporting, gives safer operation. Sending these alarms to the plant PLC or SCADA system reveals a cooling line before a pump starts against it. Steam systems use self-acting temperature control valves and trap monitoring for the same purpose.
Where explosive atmospheres can occur, electrical resistance trace heating is selected with the general and testing requirements of the IEC/IEEE 60079-30 series in mind, while IEC/IEEE 62395-1 addresses the same topic for non-hazardous industrial areas. These documents shape how maximum sheath temperature, termination components and control methods are evaluated. Which requirements apply is set by the project specification and the site's hazardous area classification.
How TLY Enerji can support you
TLY Enerji treats heat tracing as part of the metering and transfer system. Depending on the project, our scope can cover setting target temperatures from the product's viscosity data, defining the heating needs at meters, valves and pumps, integrating temperature and alarm signals into the PLC or SCADA system, and site installation, testing and commissioning. The supply boundary for tracing equipment and responsibility for heat loss calculations are agreed for each project against the technical specification.
Data to prepare for an evaluation
· Line list or isometrics with diameters, lengths and the location of valves, strainers, pumps and meters
· Product grade and viscosity at two or more temperatures
· Required maintain temperature and the highest temperature the line will see, including steam-out
· Minimum design ambient temperature and wind exposure
· Existing or planned insulation type and thickness
· Hazardous area classification
· Available utilities: supply voltage, steam pressure or thermal oil circuit
· Control and monitoring expectations: local control, central panel or data link to the control system
Related pages
· Heated metering skids for heavy oil and fuel oil: How cold spots at meters, strainers and valves are prevented on the skid.
· Viscous product transfer systems: How pumps and line sizes are chosen for heated lines.
· Jacketed piping and loading arms for bitumen: Jacketed solutions for high-temperature lines where tracing is not enough.
· Heated transfer systems for pyrolysis oil: A viscous product where heating is capped by an upper temperature limit.
· Heavy oil and fuel oil facilities: Overview of temperature management and equipment selection in this sector.
Frequently asked questions
Do I still need a thermostat with self-regulating cable?
In most viscous product applications, yes. Self-regulating cable reduces its output as it warms, but it does not hold the product at a defined set point. For heavy oil, whose viscosity is highly temperature sensitive, a control circuit with a pipe-surface sensor is recommended to keep the target band, limit energy use and raise a low temperature alarm.
Should we choose steam tracing or electric tracing?
Where a site has a reliable steam or thermal oil supply, fluid tracing can be economical and robust, although condensate handling and steam trap maintenance add operating effort. On remote, scattered lines or sites without steam, electric tracing is easier to install and can be monitored circuit by circuit.
Can heat tracing bring a cold line back up to temperature?
Partly, if it is designed for that, but standard designs aim at temperature maintenance. Heating solidified or very cold heavy oil within a reasonable time takes far more power than holding it. If reheating is an operating scenario, state it at the outset so that jacketed pipe or a dedicated heat-up circuit can be considered.
What is the most critical point for tracing in hazardous areas?
Making sure the highest surface temperature the heater can reach under worst-case conditions stays within the temperature class permitted for the area. With self-regulating cable this limit comes from the cable's construction; with constant wattage and MI cable it is achieved by design calculation and limiting controls. Junction boxes, fittings and controllers must also suit the area classification.
How much does insulation quality affect tracing performance?
A great deal. Tracing is sized only to make up the heat lost through the insulation, so wet, crushed or missing insulation pushes losses far beyond the calculated value. Removable insulation jackets at valves and flanges preserve both maintenance access and thermal continuity.