Barrel Heaters - Hasmak.com.tr

W A T L O WDie andFormer <strong>Heaters</strong>Mica StripApplications andTechnical DataContinuedCalculating Watt DensityWatt density is the amount ofwattage per square inch of heatedarea. To determine watt density,divide the total wattage by theheated area.Watt Density =Total WattsHeated AreaTo apply this equation we mustdefine the term “heated area.”Heated area is the total contactsurface of the heater less areas ofno heat that are found aroundterminals, mounting holes, etc.Heated Area =Total Contact Area - No-Heat AreaTo calculate the heated area:Heated Area =(Length - No-Heat) x WidthMaximum Allowable Watt DensityThe following derating factorsare applicable to the MaximumAllowable Watt Density graph.Please review these factors and thegraph to determine the maximumwatt density for the application.Derating Factors:• For heaters mounted less than25 mm (1 in.) apart on a metal part,derate by 5 percent.Application HintsTo maximize the performance of amica strip heater, ensure:• Small heaters with 32.3 cm 2 (5 in 2 )or less of heated area are120VÅ(ac). These heaters can bewired in series for a 240VÅ(ac)power supply.• The surface to be heated is cleanand smooth, so that heat is transferredefficiently. Even small airgaps can cause hot spotting.• Terminal post nuts are not overlytightened. Although the posts aresecurely riveted to the elements,excessive torque could break theconnection.Part Temperature—°F• For heaters mounted within76 mm (3 in.) of a reflectivesurface, derate by 10 percent.• For heaters mounted 51 to 150 mm(2 to 6 in.) apart and radiatingtoward each other, derate by10 percent.• For heaters mounted within25 mm (1 in.) of a reflectivesurface, derate by 20 percent.12001000800600400200Maximum Allowable Watt DensityWatt Density—W/cm 21 2 3 4 56 7 8Std.Std.5 10 15 20 25 30 35 40 45 50 55Watt Density—W/in 2• For heaters mounted less than51 mm (2 in.) apart andradiating toward each other,derate by 20 percent.• For termination Types 2 and 5,as well as lead Types C, E and H(see illustrations on pages 226and 228) that are less than51 mm (2 in.) wide, derate asfollows: zinc-coated units by10 percent and stainless steelunits by 20 percent.Suspended in airMounted to part using holesMounted to part using clampsStd.500400300200100Part Temperature—°CExtrusionDie and Former <strong>Heaters</strong>227