electrical heat tracking sc

8/2/2019 Electrical Heat Tracking Sc

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ELECTRICAL HEAT TRACING

by

T suneetha

(07511A0246)


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ABSTRACT

Electric trace heating, also known aselectric heat tracing or surface heating, is a systemused to maintain or raise the temperature of pipes andvessels. Trace heating takes the form of an electricalheating element run in physical contact along thelength of a pipe. The pipe must then be covered withthermal insulation to retain heat losses from the pipe.


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Uses

The most common trace heating applicationsinclude:

Freeze Protection Gutter and Roof De-icing

Temperature Maintenance


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Freeze protection

Every pipe or vessel is subject to heat loss when itstemperature is greater than ambient temperature.

Thermal insulation reduces the heat loss but does noteliminate it.

Typical residential applications for trace heating arethe protection of water pipes against freezing.


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Gutter and Roof De-icing

Placement of heat trace cable on roofs or in gutters tomelt ice during winter months.

When used in gutters the cable is NOT meant to keepthe gutters free of ice and/or snow.

The purpose is to keep a free path for the melted waterto get off the roof and down the downspout or drain

piping.


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Temperature maintenance

Hot water service piping can also be traced, so that acirculating system is not needed to provide hot waterat outlets.

The combination of trace heating and the correctthermal insulation for the operating ambienttemperature maintains a thermal balance where the

heat output from the trace heating matches the heatloss from the pipe. Self limiting or regulating heatingtapes have been developed and are very successful inthis application.


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Different Technologies

Constant Wattage "Series"

A series heating cable is made of a run of high-resistance wire, insulatedand often enclosed in a protective jacket

The downside of these types of heaters is that if they are crossed overthemselves they can overheat and burn out, they are provided in specific lengths andcannot be shortened in the field, also, a break anywhere along the line will result in afailure of the entire cable.
http://en.wikipedia.org/wiki/File:Pl_przewod_sta%C5%82ooporowy.JPG


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Constant Wattage "Zone" Typically series elements are used on long pipe line

process heating, for example long oil pipe lines andquay side of load pipes on oil refineries.

A constant wattage zone cable is made by wrapping a fine heating element around twoinsulated parallel bus wires, then on alternating sides of the conductors a notch is madein the insulation.
http://en.wikipedia.org/wiki/File:Zone-Heater.gif


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Self Regulating

Self-regulating cable uses two parallel bus wires whichcarry electricity but do not create heat.

They are encased in a semi-conductive polymer. Thispolymer is loaded with carbon; as the polymer elementheats, it allows less current to flow.
http://en.wikipedia.org/wiki/File:Pl_przewod_samoregulujacy.JPG


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Power supply and control

Trace heat cables may be connected to single-phase or(in groups) to three-phase power supplies.

Power is controlled either by a contactor or a solid-state controller. For self-regulating cable, the supply

must furnish a large warm-up current if the system isswitched on from a cold starting condition.

Electrical heat tracing systems may be required tohave Earth Leakage (Ground Fault or RCD) devices for

personnel and equipment protection.


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Control System

Industrial

: The three phase systems are fed viacontactors similar to a three phase motor 'direct online' starter which is controlled by a thermostatsomewhere in the line. This ensures that the

temperature is kept constant and the line does notoverheat or underheat.


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THERMOSTAT
http://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpg


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BOOST If a line becomes frozen because the heating was

switched off then this may take some time to thaw outusing trace heating.

. This thawing out is done on the three phase systemsby using an 'auto transformer' to give a few more volts,and so amps, and make the trace heating elements abit hotter
http://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpg


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References

Jane Mary. "Example of a frozen pipe protection kit"

http://mjaheattrace.co.uk/temp-controllers/frozen-

pipe-protection-kit/Retrieved 2010-11-19.
http://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpghttp://en.wikipedia.org/wiki/File:Pl_termostat_pogodowy.jpg


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electrical heat tracking sc

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