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What is Electrical Heat Tracing (Raychem)?
Feb 08, 2017

Electrical Heat Tracing is an engineered system designed to maintain or protect process piping, equipment, vessels and instruments at defined temperatures and within specified design criteria.

Electric cables are used to trace heating and to maintain temperature of non-flowing fluids by replacing the heat lost through thermal insulation on pipes, vessels and associated equipment.

There are two principles of Heat Tracing, Electrical and Heat Transfer.

There are three modes of heat transfer or heat loss:

Conduction –     transfer when bodies are in contact i.e. standing barefoot on a cold floor.

Convection –     transfer by movement of gases or liquids or migration of molecules i.e. the “wind chill” factor.

Radiation -         transfer through electromagnetic waves i.e. feeling the heat of the sun on your face

If a Voltage is applied to a Resistance, Current would flow and Power would be dissipated.

E = I • R

P = I • E (Easy as a piece of pie)

where   I = Current

              R = Resistance

              E = Volts

              P = Power

Ohm’s Law is the basic operating principle of heating cables.

Power dissipated in the form of thermal energy = HEAT!

Everyday examples: Toasters, Iron, Light bulbs, Electric range, Heating cables.

To summarize, power output of the electrical cable replaces heat lost from conduction or convection.

Examples of Electrical Heat Tracing Application are tank heaters, pipe heat tracing (for freeze protection & temperature maintenance), roof and gutter de-icing on roofs, control and monitoring (power distribution panels), snow melting for ramps and driveways, and longline heaters.

EHT cable technologies include self-regulating, power limiting heating, mineral insulated and skin-effect heat tracing (STS).

As the leading provider for EHT, Supermec relies on Raychem for its self-regulating cables (SR)and power- limiting (VPL) cables.

Raychem is the inventor of SR cables which are cut to length capability. The cables have regulated power output, lowering in operating cost and uniform pipe temperature. Furthermore, the cables have unconditional T-rating, safe and easy system design. They are cross linking technology with increased product life and highly reliable. Lastly, no overheating at cross-over which makes installation faster and easier.

At low temperature with many conductive paths, the Raychem self-regulating cables will allow higher level of current to flow between the bus wires.

At high temperature when the polymer expands, the Raychem self-regulating cables reduce the number of paths thus, electrical resistance rises hence heater reduces power output.

BTV

QTVR

XTV

65°C Max Maintain Temperature

85°C Max Exposure Temperature

Power at 10°C: 3, 5, 8, 10 W/ft

110°C Max Maintain Temperature

110°C Max Exposure Temperature

Power at 10°C: 10, 15, 20 W/ft

121°C Max Maintain Temperature

215°C Max Exposure Temperature

Power at 10°C:  5, 10, 15, 20 W/ft

·       Freeze (frost) protection and process temperature maintenance

·       T6 temperature rating

·       Temperature sensitive applications

·       Used for:

-          safety showers

-          fire water lines

-          chocolate production

-          caustic lines

·       Freeze (frost) protection of large pipes and process temperature maintenance

·       Higher wattage than BTV

·       T4 temperature rating

·       Used for:

-          fuel oils

-          acids

-          fertilizers

 

·       Freeze (frost) protection and process temperature maintenance

·       Pipes which are steamed clean

·       T2 to T3 temperature rating

·       Used for:

-          oils

-          heavy fuels

 


Raychem power-limiting cables have coiled resistor alloy heating element wrapped around parallel bus wires. Resistance increases with temperature (PTC effect). PTC effect results in decrease in power output at elevated temperature. This allows the VPL to cross over itself without damage from overheating. It can also withstand temperature continuous to 260°C and can maintain up to 235°C.

Click here for Raychem heat trace cables.


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