Barrel Heaters - Hasmak.com.tr

<strong>Heaters</strong>MI BandApplications andTechnical DataCalculating 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:1.Locate the no-heat factor fromthe chart below that correspondsTypeFactor(in.)1 pc. lead unit Type B, C,H, E or 90°B (1.37)1 pc. post terminal (1.60)2 pc. expandable post term (3.18)2 pc. expandable lead unit (3.00)to the type of heater beingconsidered.2.To use the formula below, insertthe no heat factors, diameter andwidth (in inches).Heated Area =(3.14 x Diameter - No-HeatFactor) x WidthMaximum Allowable Watt DensityThe following derating factors applyto the Maximum Allowable WattDensity chart, which are shownin both metric and inch base forconvenience. Please review thesefactors and the chart to determinethe correct watt density curve foryour application.Derating Factors:• For units over 51 mm (2 in.) inwidth, multiply wattdensity by 0.8.• In applications where unusualoperating conditions are present,such as irregular mountingsurfaces, contact the Watlowfactory in St. Louis, Missouri,for watt density limitations.• For two-piece units used invertical applications, refer toClamping Matrix ApplicationGuide, page 21.• For applications where insulatingblankets are used, multiply W/cm 2(W/in 2 ) by 0.75.Maximum Allowable Watt DensityWatt Density–W/cm 25 10 15 20 25 30 35Part Temperature–°F1300120011001000900800700600500355.6 mm I.D. & 2 Piece (14 in.)152.4 mm I.D. (6 in.)254 mm I.D. (10 in.)76.2 mm I.D. (3 in.)Allowable watt density for 38.1 mm (1.5 in.) wideMI Band heaters:• Moderate cycling• <strong>Heaters</strong> properly clamped• <strong>Heaters</strong> mounted on a smooth cylinder38.1 mm I.D. (1.5 in.)700600500400300Part Temperature–°C304.8 m mm I.D.400300200(12 in.)20010010 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230366Watt Density–W/in 2