HT-24

ELEC

TRIC

HEA

TERSOMEGALUX® HIGH/MEDIUM WATT

DENSITY CARTRIDGE HEATERSWith 300 Stainless Steel SheathingOMEGALUX Cartridge Heater Selection Guide

CSH SERIESSheath Material: Series 300 stainlesssteelMaximum Sheath Temperature:1250°F (676˚C)Leads: Fiberglass insulated, maximumtemperature 482°F (250˚C)Lead Length: 6"Diameters: 1⁄4" to 3⁄4"Lengths: 1" to 12"

CSS SERIESSheath Material: Series 300 stainlesssteelMaximum Sheath Temperature:1250°F (676˚C)Leads:

1⁄8" to 1⁄4" diameter: Teflon insulatedleads, maximum temperature 392°F (200˚C)3⁄8" to 3⁄4" diameter: Fiberglass leads,maximum temperature 482°F (250˚C)

Lead Length: 6"Diameters: 1⁄8" to 3⁄4"Lengths: 1" to 12"

SCB SERIESUsed as a space heater for closetsand control cabinetsMax. Work Temperature: 600°F (315°C)Wattage: 50-200 WattsLength: 43⁄4"DIameter: 13⁄8"Sheath Material: BrassMax. Sheath Temperature: 1000°F(538˚C)Type of Terminals: Edison screw base(light bulb socket)

SCB SERIES

3''

4 3/4''

1 3/8''

Cartridge heaters are mostfrequently used for heating metalparts by insertion into drilled holes.For easy installation, the heatersare made slightly undersize relativeto their nominal diameter.

The CIR high Watt density cartridgeheater is supplied with an Incoloysheath, type “F” long life strandedflexible leads and high watt densities.The Incoloy sheath allows operationat sheath temperatures to 1500°F.

The CIR series cartridge heatersfeature a high temperature Incoloysheath and swaged construction,which allows for higher Wattdensities and maximum life athigher operating temperatures. Themaximum sheath temperature forthe CIR series is 1500°F.

The CSH series cartridge heatersalso feature a swaged constructionfor higher Watt densities andefficient heat transfer from thenichrome resistance wire to thesurface of the heater. The maximumoperating temperature for the 300series stainless steel sheath is1250°F.

The CSS series cartridge heatersare constructed of coiled resistancewire which is wound throughceramic cores, and a 300 seriesstainless steel sheath. They areavailable in lower Watt densitiesand in diameters as small as 1⁄8".The maximum temperature for the 300 series stainless steel sheath is 1250°F.

All cartridge heaters are rated bywattage and Watt density (Watts persquare inch) for either 120 or 240Volt operation. In some applicationsit may be useful to derate thewattage by operating the cartridgeheater at a lower voltage. Whenoperating at lower voltages, thewattage is derated using thefollowing formula:

(Operating Voltage/Rated Voltage)2

x Wattage at Rated Voltage =Derated Wattage

Example: The CIR-1027/240cartridge heater is rated at 200Watts and 128 Watts per squareinch at 240 Volts. To determine thederated wattage when operating on120 Volts:

(120 Volts/ 240 Volts) 2 X 200 Watts= 50 Watts

When operating on 120 Volts, theWatt density of this heater wouldalso be reduced by a factor of 4from 128 Watts per square inch to32 Watts per square inch.

The tightly compacted refractoryinsulation provides excellent heattransfer to the heavy wall stainlesssteel sheath. This means theresistance wire runs at a lowertemperature than competitive unitswith loose-fill insulation. The resultis much longer life. This heavy-dutyconstruction also provides highdielectric strength as well as shockand vibration resistance required formany industrial applications.

HT-23

APPLICATION OF OMEGALUX®

CARTRIDGE HEATERS–CIR SERIES*OMEGALUX cartridge heaters aremost frequently used for heatingmetal parts by insertion into drilledholes. For easy installation, theheaters are made slightly undersizerelative to their nominal diameter.

Application at medium Wattdensities. Figure D-1 (page D-6)shows maximum allowable Wattdensity for various fits and operatingtemperatures . The vast majority ofapplications do not requiremaximum watt/in2, however. Use aWatt density only as high as youneed. Take advantage of the safetymargin provided by using ratingsless than the maximum allowed.Select space heaters for most evenheat pattern rather than for thehighest possible wattage per heater.

At medium Watt densities, generalpurpose drills are usually adequatefor drilling holes. Typically, theseresult in holes .003" to .008" overthe nominal size of the drill,resulting in fits of .010" .015". Ofcourse, the tightest fit is desirablefrom a heat transfer standpoint, butsomewhat looser fits aid in installingand removing cartridge heaters,especially long ones. Holes drilledcompletely through the part arerecommended to facilitate removalof the heater. After drilling, clean ordegrease the part to remove cuttinglubricants.

Application at high Watt density.OMEGALUX cartridge heaters aredesigned and manufactured toprovide Watt density capabilitiessecond to none. To obtain best lifeat the highest Watt densities closeattention to application details issuggested.

a. For closest fit and best heattransfer, holes should be drilled andreamed, rather than just drilled tofinal diameter with a generalpurpose drill.

Determining fit. At high wattdensities, a close fit is important.The fit is the difference between theminimum diameter of the heater andmaximum diameter of the hole. For

example, at 1⁄2" diameter anOMEGALUX cartridge heater isactually .498" plus 000" minus.005". If this heater is placed in ahole which has been drilled andreamed to a diameter of .503" -.493" = .010").

b. The sensor for the temperaturecontrol should be placed betweenthe working surface of the part andthe heaters. The temperature of thepart approximately 1⁄2" away from theheaters is used in selectingmaximum allowable Watt densityfrom the graph.

c. Control of power is an importantconsideration in high Watt densityapplications. On-off control isfrequently utilized, but it can causewide excursions in the temperatureof the heater and working parts.Thyristor power controls arevaluable in extending the life of highWatt density heaters, since theyeffectively eliminate on-off cycling.

Determining Watt density. Theterm "Watt density" refers to theheat flow rate of surface loading. Itis the number of Watts per squareinch of heated surface area. Forcalculation purposes, stockcartridge heaters have 1⁄4" unheatedlength at each end. Thus, for a 1⁄2" x12" heater rated 1000 Watts, theWatt density calculation would be asfollows:

Watt density = W

π n x D x HL

W = wattage = 1000WD = diameter = .5 in.HL= heater = 11.5 in.

Watt density = 1000

3.14 x 5 x 11.5

= 55 W/in.

Selecting sizes and ratings. Thecalculation of total heatrequirements for an application isoutlined in the technical section Z.

For assistance, contactOMEGALUX.

Once total heat requirements areestablished, the quantity, size andrating of cartridge heaters can bedecided. Plan for enough heaters topermit even temperatures throughthe part during heat-up andoperation. The sensor for thetemperature control should beplaced close to working surface foraccurate control.

After the wattage for each heaterhas been established, the Wattdensity and fit must be calculated.Then, use Fig. D-1 on page D-6 tobe sure that the Watt density iswithin allowable limits. For example,a 1⁄2" x 12" OMEGALUX CIR seriesrated 1000 Watts has a Watt densityof 55/in2. If it were used in a partwith an operating temperature of1000°F with a fit of 0.01", theallowable Watt density from thegraph would be 90W/in2, thus, theactual Watt density of 55w/in2 iswell below the maximum allowed. Asubstantial safety margin wouldexist and high reliability can beexpected.

If the heater selected had a Wattdensity higher than that allowableby graph, then those changes couldbe considered.

1. Using more heaters of lower wattdensity.

2. Using longer or larger diameterheaters.

3. Improving the fit.

4. Reducing heat requirements byreducing heat losses or byallowing for longer heat-up time.

*For information on the CIR Series, visit our website at omegacartridgeheater.info

D-5

HEATING PLATENS, DIES, MOLDS USINGCARTRIDGE HEATERS–CIR SERIES*

This heating application may usuallybe easily accomplished by usingcartridge heaters, although in someapplications strip or tubular heaterscan be inserted in grooved slots inthe metal. When cartridge heatersare used, it is essential that thefollowing factors are checked toinsure that the heater willexperience the longest possible lifeand provide sufficient heat for thejob:

1. Sheath watt density.

2. Proper fit of cartridge heater inmachined hole.

3. Provisions made to protect heaterfrom contamination from oil, oilvapors, etc.

4. Sufficient kW is installed toaccomplish work and make up forheat losses from the flat surface.

The maximum permissible sheathwatt densities for alloy sheathcartridge heaters at a given desiredtemperature on the metal are givenby Figure D-1. This curve gives wattdensities for various fits using CIRcartridge elements. Figure D-2 isuseful for using C series elements.

When cartridge heaters are installedin a drilled hole, the hole should bedrilled to the nominal diameter ofthe heater. Cartridge heaterdiameters are actually .003" to .005"smaller than the nominal diameter.This allows for easy installationwhen cold, but upon heating thecartridge heater expands for a snugfit and excellent heat transfer.

When cartridge heaters are used inplastic forming dies, extruders, etc.,care must be taken to protect the

heater from possible contaminationentering through the terminal end.Standard end opposite terminalconstruction for standard cartridgeheaters is a positive weld.

Special moisture and abrasiveresistant terminal construction isavailable and where moisture orcontamination problems are present,hermetic seals can be supplied (seepages D-15 and D-16).

CARTRIDGE HEATERSA plastic forming operation requires2 lb. of plastic to be processed perhour; the plastic has a specific heatof 0.45 BTU/lb/°F and reaches apliable state at 300°F. Two platens,each weighing 245 Ibs. andmeasuring 24 in. long x 12 in. widex 3 in. thick, must be preheated to300°F in 1⁄2 hour. The platens are notinsulated. The steel platens have aspecific heat of 0.12 BTU/lb°F.

Heat-up is accomplished with theplatens closed. In addition, lossesencountered during operation (fromopening and closing the platens) arenegligible. Room ambient is 70°F.The total exposed surface area isconsidered to be 7ft2.

kW = WT x Cp x ∆T

3412 x H

where

WT = weight of material to be heated

Cp = specific heat (BTU/Ib/°F)

∆T = temperature (°F)

H = heat-up time in hours

3412 is conversion factor of BTU tokWh

kW REQUIREMENTS FORINITIAL HEAT-UP

kW = 245 x 2x 0.12 x (300-70)

3412 x 1⁄2 (hr)

= 13524= 7.931706

Losses during heat-up are 150 w/ft2

at the operating temperature of 300°F.

kW = 7.0(ft2) x 150 (W/ft2)

1000(W/kW)

Average loss = 1.05= .53kW

(Note 1) 2

Total reqd. = 7.93 + .53 = 8.468.46 x 1.2(safety factor) = 10.15kW

OPERATINGREQUIREMENTS

kW = 2(lbs) x 0.45 x (300-70)°F

3412 x 1(hr)

= 207= 0.0613412

kW = 7.0(ft2) x 150 (W/ft2)

1000(W/kW)

= 1.05

Total reqd. = 0.061 + 1.05=1.111kW1.11 x 1.2 = 1.33 kW

NOTE 1:Average heat loss is the heat loss at the final operating temperature divided by an averagingfactor 2. The averaging factor is used since during initial heat-up, the platen is not at the finaloperating temperature all of the time.

*For information on the CIR Series, visit our website at www.omega.com

D-6

D

Since the heat-up requirement is greater than that foroperation, we should install 10 kW.

INSTALLATION AND SELECTION OFCARTRIDGE HEATERSHeater selection is often governed by available space.In this instance, however, space is not a problem sincewe can easily install 5 cartridge heaters CIR 3122 1⁄2 in.diameter x 12 in. sheath length in each platen. Eachunit can be rated 1000 Watts for a total installedcapacity of 10 kW. Holes for cartridge heaters shouldbe drilled and reamed to 0.500 in. max., since close fitsare important for best heat transfer. Holes in the platensshould be drilled completely through the 12" wide platento facilitate removal of heaters when necessary.

Using the maximum allowable Watt density graphs:FIGURE D-1This graph is useful for choosing OMEGALUX® Type CIRcartridge heaters. The curves should be considered asguides and not precise limits.

The graph is based on a 1600°F resistance wiretemperature inside the cartridge heater, when theheater is installed in an oxidized mild steel block. Wattdensity values from the graph should be lowered byabout 10% or more when block materials are usedwhich have a lower thermal conductivity or loweremissivity than oxidized mild steel.

200°F400°F600°F800°F

1400°F

1200°F

1000°F

Maximum Watt Density vs. Platen Temperature forVarious Fits Using Type CIR Cartridge Heaters

.001 .002 .003 .004 .005 .006 .008 .010 .020 .030 .040 .050.060 .080 .100

Fit in Hole (Maximum Hole I.D. Minus Minimum Heater O.D. in Inches)

Allo

wab

le W

att D

ensi

ty (W

/In)

15

20

30

40

50

607080

100

200

300

400

500

FIGURE D-1 Allowable Watt density vs platen temperature for various fits using OMEGALUX® Type CIR cartridge elements.

Graph Based on SteelPlaten Temperature

Measured 1⁄2" from Heater

D-7

HOW TO GET THE BEST PERFORMANCEFROM OMEGALUX CARTRIDGE HEATERS1. Installation recommendations.a. On moving machinery, anchor theleads securely. As little movementas possible should be allowed closeto where the leads emerge from theheater. A loop in the lead wire willfrequently extend lead life. Ifapplication conditions result incontinual lead flexing, terminate thecartridge heater leads at a terminalblock which moves from the heatedassembly. Flexing is transferred tothe extension leads which can beeconomically replaced.

b. For rapidly vibrating equipment,employ the terminal block describedabove. Keep leads from heater toblock short and well supported toprevent lead movement due tovibration.

c. Protect leads from spray, oil, andabrasive. Contaminating liquids andvapors can enter unsealed cartridgeheaters and cause insulationbreakdown.

d. Avoid tape on leads where theyemerge from the cartridge heater.The adhesive on some tapes canenter the heater and turn to carbonwhich is electrically conductive.Where glass tape cannot beavoided, a tape with a siliconebased adhesive is suggested.

e. Design the installation so that theleads are in an ambient temperaturewhich doesn’t exceed the rating onthe lead insulation (392°F forstandard leads).Wheretemperatures require it, use nickelor nickel plated copper wire withTeflon, silicone impregnatedfiberglass or rockbestos insulationto extend leaders. (See Section H.)

f. Graphite and other lubricants tohelp insert the cartridge heater intothe hole are generally notrecommended. These areelectrically conductive and can geton the lead end of the heater unlessextra care is taken.

g. As operating temperatures go up,thermal insulation on the heatedpart becomes more desirable toconserve heat. Thermal insulationresults in lower wattage

requirements and therefore lowerWatt density on the heaters. Otherbenefits are more even worktemperatures and greater operatorsafety and comfort.

h. Leads must not extend into thehole containing the cartridge heater.Generally, the lead end of theheater should be flush with surface.

2. Vacuum Operation. Whenheaters are operated in a blockwhich is in a vacuum, the inside ofthe holes should be preoxidized toimprove emissivity. Substantialreductions in maximum allowableWatt density are usually necessaryfor vacuum operation. Wherepossible, the installation should bedesigned so that the lead end of theheater is outside the vacuum. Whenthe lead end of the heater is insidethe vacuum, a voltage of 120 Voltsor less is recommended. On anunsealed heater, outgassing may beexpected.

3. Operation in square grooves.Round series CIR cartridge heatersmay be installed in square or V-shaped grooves if this provesconvenient. The inside of the grooveshould be treated to improve itsemissivity (by oxidizing oranodizing). Allowable W/in2 can beestimated by using the .050 fit linein Figure D-1 on page D-6,providing that the square isapproximately the same width asthe nominal diameter of the heater.

4. Operation on 480 Volts. (CIRSeries only) OMEGALUX CIRSeries cartridge heaters 5⁄8" diameterand larger can be operated on 480Volts. One approach is to take twostock 240-Volt heaters and connectthem in series on 480-Volts.Another is to order specially rated480-Volt cartridge heaters. ContactOMEGALUX.

Because of higher voltage stressesinside the heater, lower maximumWatt densities are allowable in 480-Volt applications, either with two240-Volt heaters in series or withspecially rated 480-Volt units. Todetermine maximum allowable Wattdensity at 480-Volts, enter the graphon page D-6 with an operatingtemperature value which is 200°Fhigher than the actual operatingtemperature. A maximum operatingtemperature of 1000°F issuggested.

An extra layer of high temperaturefiberglass sleeving is recommendedfor the leads to increase electricalinsulation.

5. Testing recommendations.Testing under simulated operatingconditions is suggested whenequipment manufacturers designnew products. Cartridge heaters ofthe appropriate physical size areoperated on a variable transformeruntil the heat output is at the properlevel. Then, voltage and currentmeasurements are taken andrequired wattage rating iscalculated. Heaters of the correctwattage rating are then ordered forproduct design.

D-8

D

U Type F Flexible LeadsU 1⁄4", 3⁄8"(1cm), 1⁄2", 5⁄8" & 3⁄4"

Inches in DiameterU 120 & 240 VU UL Component

Recognized & C.S.A.Certified

U Patented Design

FEATURESType F leads , standard on CIRseries, consist of standard, flexiblemanganese nickel wire insulatedwith impregnated fiberglass toapproximately 392°F. the leads canbe bent at a sharp angle where theyemerge through the flush terminalblock, without exposing bareconductors.

When leads longer than 10" (25 cm)are needed, additional lengths ofhigh-temperature wire can bespliced on stock heaters, either atthe factory or by the user. Speciallyfabricated CIR series heaters canbe supplied with unspliced leads upto 32" (81 cm) in length.

Sheath material. OMEGALUX® CIRseries cartridge heaters are madewith a high-temperature Incoloysheath material.

Higher temperatures, fasterproduction rates. The CIR seriespatented construction and high-Watt-density capability let you putmore heat in less space.

Welded end disc seals endopposite leads from contamination.

Black oxide sheath. Blacktransfers heat better than shinysurfaces. OMEGALUX heaters go towork immediately when energizedand operate at cooler sheathtemperatures. Shiny heaters beginoperating at higher temperatures,shortening life expectancy whilethey slowly oxidized and turn black.

Shock and vibration resistant.Tightly compacted refractoryinsulation for severe application.

Lead length. CIR series heatersare stocked with Type F leads 10"(24 cm) long, ±3⁄8"(1cm). Longer leadlengths can be readily spliced on.

Eliminating operational problems,the manganese nickel electricalleads are stranded, not solid. Theyremain continuously covered withfiberglass insulation even when bentsharply where they emerge from theheater. The construction is coveredby issued and pending patents.

Cartridge heater performancedepends upon adherence to basicheat transfer principles. In theresistance winding inside thecartridge, electrical energy isconverted to heat energy with100%efficiency. CIR units are designedand constructed to maximize heatenergy flow and thus keepresistance wire temperaturerelatively low.

Even temperature throughout theheater’s length is produced by theuniform winding of the wire on thesmooth supporting core. Close andeven spacing between wire andinside of sheath is maintained forgood heat transfer. Tight spacingbetween turns permits use oflargest gauge resistance wire.

CIR SERIES HIGH WATT DENSITYCARTRIDGE HEATERS - WITH INCOLOYSHEATHING

Excellent oxidation and corrosion resistance is provided by special OMEGALUX alloy sheath. Thermal expansion characteristics of sheath and refractory are closely matched.

Highest quality nickel-chromium resistance wire is used for the resistance winding. Long life and consistent performance from one unit to the next are assured.

Heavy-gauge end disc, securely welded, seals out contaminants. This rugged construction and oxidation resistance of sheath facilitate heater removal.

Terminal block is flush with end of sheath,adding strength and protection frombreakage..

Refractory Insulation between resistance wire and sheath is specially formulated and rigidly controlled to maintain high-temperature characteristics. Through special processes it is densely compacted to improve its thermal conductivity and dielectric strength.

Patented connector eliminates any chance of overheating where stranded lead is attached to resistance wire. Highly reliable, the connector eliminates life-shortening stress on the wire.

USAMADE IN

CAUTION AND WARNING!Fire and electrical shock may resultif products are used improperly orinstalled or used by non-qualifiedpersonnel. See inside back coverfor additional warnings.

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