Heater Catalog - Watlow

Cartridge/Insertion HeatersHeatersMetric FIREROD Cartridge HeatersMaximum Allowable Watt DensityThe following four graphs detail maximum allowable wattdensities for applications involving metal heating or steam,air and gas heating. Please review these respectivegraphs and applicable data to determine the correct wattdensity for the application.Heating MetalsThe Maximum Watt Density—Heating Metals graph willshow either the maximum hole fit or recommended wattdensity of the heater. Enter the chart with either knownvariable, part fit in hole dimension or watt density. Then,find the application temperature by reading up or over onthe chart.If the fit of the heater in the hole dimension is not known,it is easily determined. Subtract the minimum diameter ofthe metric FIREROD (nominal diameter minus tolerance)from the maximum hole diameter. For example, take ahole diameter of 16.1 mm minus a heater diameter of16 mm - 0.08 mm. The hole fit would be 0.18 mm.For metric FIREROD heaters in square holes or grooves,contact your Watlow representative for fit in holedimension.Correction Factors:Also note, the Maximum Watt Density—Heating Metalsgraph depicts metric FIRERODs used in steel parts.Therefore, for either stainless steel, aluminum or brass,refer to applicable correction factors a and 2 .2.52.0Maximum Watt Density—Heating Metals1.00.5Fit in Hole (mm)0.250.10800°C700°C600°C500°C400°C300°C200°C100°C0.050a For SS, enter the graph with afit 0.04 mm (0.0015 in.) larger thanactual.2 For aluminum and brass, enterthe graph with a temperature 55°C(100°F) above actual temperature.0.0101 2 3 4 5 6 7 8 9 10 20 30 40 50 607080 100Watt Density—W/cm 250 WATLOW ®