Screw Plug - Immersion Heaters Datasheet

lHow is your resistancewire sized?lWhat grade ofmagnesium oxide isbeing used?lHow is your cold pinattached to yourresistance wire?lWhat is your standardelement diameter?lDo you passivatestainless steel heaters?lDo you repress U-bendswhen required?lDo you use terminalsealant as a standard?lHow are your elementsfixed to the screw plug?lAre screw plug hex andthreads to industrystandards?lDo you provide a standardthermowell?lIs the terminal housingrotatable?lDo you have a standardgrounding lug?lAre your heaters UL listedand CSA certified?lWhat quality assurancetesting is done on yourfinished products?lCan you ship out ofstock in 24 hours andprovide assembly stockproducts in 5 days?lCan you provide me experttechnical assistance whenneeded?PDS QUALITYwww.chromalox.com ©1998 Wiegand Industrial Division Emerson Electric Co. ®87654321 910111213141516On first impression, various manufacturers of screw plug immersionheaters appear to be all alike; but when you take a closer look at screw plugimmersion heaters, it becomes evident that considerable differences exist.The following information will help to explain the differences in constructionof Chromalox screw plug immersion heaters compared to other manufacturers.It will also describe Chromalox’s third party listing program, quality testing,and delivery capabilities.Before buying a screw plug heater, you should ask the manufacturerquestions to insure you are getting a quality heater that will last in yourapplication. Below, you will find a list of some of these important questions.PH: 412-967-3800 • FX: 412-967-5148Screw Plug Immersion Heatersinclude one, two or three hair-pin bent tubular element(s)joined to a threaded hex plug.Screwed into tank walls,this UL Listed / CSA Certifieddirect contact heat source heatsliquids, viscous fluids, forced airand gases with maximumenergy efficiency. In addition,elements can be bent into manyconfigurations to suit a varietyof applications. Most screw plugheaters come with a thermowell(for temperature control sensor)and a completely wired terminalenclosure for electrical connec-tion. Certain models availablewith a patented 360 ° rotatablescrew plug housing to facilitateeasy conduit connections. Selectfrom a variety of sheath materi-als, element lengths, plug sizesand ratings from 0.5 kW and up,for 120 to 600 volts.DifferencesAmongScrew PlugImmersionHeatershttp://www.chromalox.comBasic ConstructionElement DiameterStainless Steel HeatingElement Surface FinishChromalox® standard 0.475” Diameter10% more surface area than0.430” diameter typical of competitorsResults in longer life and loweroperating temperature0.475”Pickling & PassivationRemoves most carbon particles?????????ElementsThermowellRotatable TerminalHousingHex ThreadsResistance Wire-Computer Designed for correct gauge wireMetallicSheathCompactedMagnesium OxideInsulationSolid ColdPin JunctionHexElements InternalConstructionQuality - Differences Among Screw Plug Immersion HeatersChromalox connects the resistance wire to the cold pin with a weld. This provides asolid electrical connection that better withstands thermal cycling. Some manufac-turers press or braze the cold pin onto the resistance wire, making failure due tothermal cycling more common. Ask the heater manufacturer how they maketheir cold pin connections. Chromalox uses only high purity magnesium oxideinsulation to insure good dielectric resistance between the resistance wire and themetal sheath. In addition, Chromalox uses a rolling method to reduce the diameterand compact the MgO refractory. Other manufacturers often use lower grades ofMgO, and swage versus rolling down the element diameters, causing inferiordielectric properties which can lead to a less reliable heater. By utilizing highgrade materials and having controlled manufacturing processes, good thermalconductivity is achieved and a longer life heating element is produced. Ask theheater manufacturer how they compact element refractory.Chromalox® • 701 Alpha Drive • Pittsburgh, PA 15238 • PH: 412-967-3800 • FX: 412-967-5148 • www.chromalox.comCorrosion is often accelerated by a poor surface finish. Proper surface finish ofstainless steel heating elements is very important to prevent corrosion. Duringtypical heater manufacturing processes, steel dies and rollers come intocontact with the element sheath, and as a result, carbon steel particles areembedded into the surface of the element. If not removed, pitting and corro-sion will occur, eventually leading to premature heater failure. As standardpractice, Chromalox pickles and passivates stainless steel heaters by soakingthe elements in an acid bath. This process removes the carbon steel particlesfrom the surface of the heating element and prolongs heater life. Othermanufacturers will only passivate for an extra charge. Ask the heatermanufacturer if passivation is a standard practice.Although Chromalox makes elements that range from 0.315” to 0.475” indiameter, our standard 2” and 2-1/2” NPT screw plug immersion heaterelements are 0.475” in diameter. Other manufacturers have standardized on0.430” diameter elements to reduce costs. For an equivalent immersion length,the 0.475” diameter heating element provides 10% more surface area versus a0.430” diameter element. The greater the surface area, the lower the heaterwatt density and lower its operating temperature. Lower operating tempera-tures result in longer heater life. Ask the heater manufacturer whatdiameter elements they supply as standard.The basic construction of an immersion heater includes the terminal housing,standard NPT screw plug, thermowell and heating elements. If you take acloser look at the construction of a heating element, you will find the heart ofthe heater is the resistance wire. Chromalox’s resistance wire is computerdesigned in order to select the correct gauge wire for the required heatingelement wattage and voltage. Many manufacturers use limited sizes of wire,and may not choose the optimal wire for the application. Ask the heatermanufacturer how they determine resistance wire dimensions.http://www.chromalox.comWelded Stainless/Steel ElementsTerminal Seal TypesElements U-BendsAir gapsin MgoElectricalshortto sheathRecompactsMgoRemovesanyair gapsSilicone - Fluid, Resin, RTV200° F to 300° F continuous exposureModerate moisture barrierEpoxy200° F continuous exposureGood moisture barrierHermeticUp to1000 ° F sheath temperatureThe only true sealMinimizes corrosionat element attachmentSolder not a goodcorrosion resistant materialPrevents leakageinto terminal enclosureElements U-Bends -RepressedQuality - Differences Among Screw Plug Immersion HeatersMost screw plug immersion heater elements are bent in a U-bend configura-tion. When bending a heating element on a tight radius, air gaps can occur inthe magnesium oxide insulation within the element bend. Air gaps can permit adielectric (insulation) breakdown to occur, and cause an electrical short to themetal sheath of the heater.Chromalox represses U-bends to recompact the MgO and remove any air gaps,which ensures dielectric integrity. Many manufacturers do not repress bends tosave time and money. Ask the heater manufacturer if they repressU-bends when necessary.Heating element refractory can absorb moisture from the air, and if enoughmoisture is absorbed, high leakage current could occur during start-up.Chromalox screw plug immersion heaters contain heating element terminalsealant as a standard feature. A terminal sealant inhibits moisture from beingabsorbed by the heating element refractory.There are several optional types of terminal sealants to suit the particularapplication. Ask the heater manufacturer about terminal sealants beforemaking a purchase decision.Chromalox stainless steel, INCOLOY® and carbon steel elements are welded tostainless and carbon steel screw plugs. A welded element provides superiorcorrosion protection and element attachment. Some manufacturers brazeelements to the screw plug without concern for the heaters intended applica-tion. In heating a corrosive fluid, braze material is susceptible to being chemi-cally attacked by the fluid. A welded-in element prevents corrosive fluidleakage into the terminal housing which can lead to heater failure. Ask theheater manufacturer how they secure their elements to the screw plug.Chromalox® • 701 Alpha Drive • Pittsburgh, PA 15238 • PH: 412-967-3800 • FX: 412-967-5148 • www.chromalox.comhttp://www.chromalox.comThermowellsHex and ThreadsHex and Threads -Other Supplier AlternativesWide hex fitsstandard toolsLong threadsfortighter fitEasy to installStandard to acceptsensing bulbsIntegral and remotethermostat optionsIT DOESTHETWISTUnique with360 DegreeRotation FeatureRotatable TerminalHousingDifferences Among Screw Plug Immersion Heaters - QualityShort hex requiresspecial toolsShort threadssusceptible todamageShort threadscause loose fitinto tankDifficult to installChromalox® • 701 Alpha Drive • Pittsburgh, PA 15238 • PH: 412-967-3800 • FX: 412-967-5148 • www.chromalox.comChromalox heater design provides a screw plug hex and threads that are userfriendly. Wide hex and generous threaded lengths allow standard tools to beused and allows a secure fit.Other manufacturers often provide a narrow hex, making the hex difficult togrip, potentially damaging the screw plug threads, or short thread lengths thatmay not provide a tight seal. Chromalox screw plug immersion heaters are easyto install — no special tools are required. Ask the heater manufacturer iftheir Hex and Threads meet industry standards.Chromalox stainless steel and steel screw plugs come with a standard solid hexand threads. Others use stamped, cast or hollow plugs and threads that can failunder higher pressures.The NEMA 1 terminal enclosure of the Chromalox screw plug heater is fullyrotatable. This patented feature allows 360° rotation of the terminal enclosure(270 ° rotation for heaters with thermostat). Thus, you are able to rotate theenclosure (housing) to face the electrical conduit connection after the heaterhas been properly installed.During installation, it is preferred that the conduit for the wiring be in a downposition. This prevents any moisture that may accumulate on the conduit fromrunning down into the terminal enclosure of the heater and cause potentialheater failure. No other heater manufacturer offers this feature.Chromalox screw plug immersion heaters can be provided with or without anintegral thermostat. Regardless, a thermowell is standard on most heaters toaccept the sensing bulb of a thermostat. This allows an easy retrofit if later youlearn that a thermostat is necessary. Most manufacturers charge extra forthermowells. Ask the heater manufacturer if a thermowell is standard.http://www.chromalox.comDifferences Among Screw Plug Immersion Heaters - QualityElectrical GroundingThird Party ListingQuality TestingMost Extensivein the IndustryUnderwritersListing (UL)Canadian StandardsAssociation (CSA)NationalElectrical CodeRequirementChromaloxStandardGround lugsnot providedby all suppliers100% HydrostaticPressure Test forWeld Leaks100% Resistance Checkfor Element WattageInsulation ResistanceCheck for Moisture20 Megohms or greaterDielectric Hi-pot CheckUL®Chromalox’s stocking program is unequaled in the industry. Our distributionwarehouse can ship stock heaters within 24 hours of receipt of an order.Chromalox has over 1,000 different screw plug heaters in stock. In addition,most of our assembly stock products can ship within 5 days. And, we offer 10day shipment for many of our other thousands of pre-engineered designs. Wealso provide a toll free service number for replacement part orders and installa-tion assistance. 1-800-368-2493. Ask the heater manufacturer abouttheir delivery times and stock offering.Delivery and ServiceStock heaters shipped in 24 HoursOver 1000 Screw Plug heaters in stockToll free service number1-800-368-2493Chromalox® • 701 Alpha Drive • Pittsburgh, PA 15238 • PH: 412-967-3800 • FX: 412-967-5148 • www.chromalox.comProper electrical grounding is extremely important and is required by theNational Electrical Code. Some manufacturers do not provide a standardgrounding lug with their heaters. Grounding lugs are a standard feature withChromalox heaters. Ask the heater manufacturer if a grounding lug isstandard.Chromalox heaters undergo extensive quality inspection prior to shipment. Allscrew plug heaters are 100 percent hydrostatically pressure tested to insure atight leak-proof fit of the elements to the screw plug. We also perform a 100percent resistance check on all our heater elements to ensure proper heatingelement wattage. A two-step insulation resistance check is also performed.First, elements must have a test measurement of insulation resistance to insureminimal moisture content of the element refractory. Then, a dielectric highpotential check insures that no electrical short exists from the resistance wireto the metal sheath. Many manufacturers do not perform all of this qualityassurance testing. Ask the heater manufacturer about their testingprogram.Chromalox has the most extensive third party listing in the industry. We providemore heaters with Underwriters Laboratory listing and/or Canadian StandardsAssociation Certification than all other heater manufacturers combined.This assures the heater is built to stringent standards and allows you to receivequick electrical inspector approval. Ask the heater manufacturer about ULListing and CSA Certification.http://www.chromalox.comPD315-1PDS QUALITYOCT 9899-006In SummaryOver 80 years of experienceHighest quality heaterconstructionExtensive UL/CSAListings/CertificationsComprehensive testingprior to deliveryFast delivery andcustomer serviceChromalox has over 80 years of experience, the highest quality construction,extensive UL Listings and CSA Certifications, a comprehensive quality programand the largest stock and pre-engineered designs of any manufacturer.Chromalox also has the largest and most technically competent field salesforce in the industry. This means you get the best products and applicationsupport when you need itTo Chromalox, an educated customer is our best customer. We are proud tobuild the world’s highest quality and longest lasting screw plug heaters. Weask you to ask these questions to whomever you buy your screw plug heatersfrom. Remember, not all screw plug heaters are created equal.Benefit¤ Longer Lasting, More Reliable Heater¤ Higher Consistency and Quality¤ Longer Lasting Heaters¤ Higher Dielectric Integrity¤ Insulation Moisture Inhibitor¤ Resists Chemical Attack¤ Easier Installation, Better Fit¤ Insures NEC Compliance for Ground¤ Proper Enclosure Orientation Makes for Easy Installation¤ Insures Highest Quality and Strict ManufacturingProcedures¤ Greater Reliability¤ Large Stock & Assembly Stock Offering¤ Lower Lead Times for Assembly Stock and Special Order Products¤ Support and Assistance When You Need It MostFeature / Benefit AnalysisQuality - Differences Among Screw Plug Immersion HeatersChromalox® • 701 Alpha Drive • Pittsburgh, PA 15238 • PH: 412-967-3800 • FX: 412-967-5148 • www.chromalox.comFeature¤ High Quality Components¤ Strict Manufacturing Processes¤ Element Diameter as required¤ Repressed Bends where necessary¤ Standard Terminal Sealant¤ Welded Elements¤ Standard Hex Width and Thread Length¤ Standard Grounding Lug¤ Rotatable Enclosure¤ Third Party Listing (for a list, ask your Representativefor bulletin PD314)¤ Comprehensive Quality Assurance Testing¤ Product Availability¤ Responsive Production Facilitye¤ Highly Technical and Experienced Sales Forcehttp://www.chromalox.com