ALLOWABLE MAXIMUM WATT DENSITY

 

How to Order: 1. When ordering Cartridge Heaters specify: a. Overall Length b. Heated Length c. Nominal Diameter d. Lead Length e. Voltage and Wattage Diameter and length are determined by the space available and the requirements for even heat distribution. The standard leads consists of staggered 1" and 112" nickel pins.   3. Determine: Fit = maximum inside diameter of hole minus minimum O.D. of sheath Example: a 3/8" Cartridge Heater in a .375 ± .001 reamed hole would have a .007 fit .376 - .369 = .007 Check the required temperature against the watt density and fit indicated on the graph above. 2.   Example: a 3/8" diameter Mighty Watt, 3" long overall (with standard 3/8" cold end), rated at 300 watts .371 x 3.14 x 2-1/4" = 2.63 sq. in. heated area.   4. To extend heater life: A. Decrease the watt density by: 1. increasing the diameter 2. increasing the heated length 3. increasing the number of units used 4. reducing the wattage, allowing for longer heat-up time. B. Use a tighter fit. C. Consult Ogden for alternative design recommendations.   SELECTION OF OGDEN CARTRIDGE HEATERS   See separate listing for Stock Cartridge Heaters. Heater life is a function of several variables: operating temperature, heater fit, control, heat absorptivity characteristics of material being processed, watt density, contamination, etc. Immersion Heaters Immersion Heaters are intended to be used in liquids at all times. The heated portion must always be immersed. Sheath must be free of grease or foreign material for adequate thermal conductivity. Protect terminals from contaminants. Fit Tolerances The hole into which a cartridge heater is inserted, should be reamed to the nominal diameter of the heater. Might Watt and Bullet Heaters are .002" - .006" undersized. If close hole tolerances are not maintained, operating life of the heater will be reduced. The heated area of the cartridge should not extend beyond the hole. See watt density graphs. Spacing As a general rule, it is not recommended to space heaters in a die or platen any closer to each other than the diameter of the heater. Contamination Contamination consists of any foreign matter such as plastic, oil, grease, dirt or water entering through the terminal end. Proper Care and Maintenance 1. Heaters should be stored in a dry area, especially during periods of high humidity. 2. Protect leads from abuse and abrasion. 3. Maintain temperature control and accessories in good working condition to avoid over temperature operating conditions. 4. All cartridge heaters (especially of swaged design) have hygroscopic tendencies and can accumulate moisture in shipping and storage. Low heater insulation (less than 1 meg ohm) can be baked in an oven for several hours or started at low voltage to eliminate moisture. Removal Removal of heaters from one die to another is not recommended. Testing Information Quality control standards on Ogden Cartridge Heaters include the following inspection procedures; 1. Resistance test. 2. Voltage breakdown test (Hypot) 3. Inspection of physical size.