Duraband Standard Specifications and Tolerances
Max. Temperature: Standard Sheath: 900°F (482°C)
Nominal Watt Density: 20-45 W/in2 (3-7 W/cm2)
Max. Watt Density: Dependent on heater size & operating temperature.
Max. Voltage: 480 VAC
Max. Recommended Voltage w/Leads 240 VAC
Max. Amperage: Lead wire termination: 10 amp
Resistance Tolerance: +10%, -5%
Wattage Tolerance +5%, -10%
Physical Size Construction Limitations
Standard Gap: 3/8'' (9.5 mm)
Min. Inside Diameters: 3/4'' (19.1 mm)
Min. Widths: 5/8'' (15.9 mm)
Width Tolerance: ±1/16'' (1.59 mm)
Heater Width: Number of Brackets
1-1/2'' to 3-3/4'' (38-95 mm) 1
3-7/8'' to 5-1/4'' (98-133 mm) 2
5-1/2'' to 7'' (140-178 mm) 3
7-1/2'' to 12'' (190-305 mm) 4
Duraband Maximum Watt Densities
Maximum Allowable Watt Density
The chart displays the maximum Watt Density curves for various diameter heaters. Use this chart when determining the appropriate wattage value for your chosen heater. Be aware that certain factors will require you to derate the watt density (W/in2) of your heater selection.
Failure to adhere to the maximum allowable watt density per heater size will result in poor operating life.
Calculating Maximum Watt Density__________________________________________________________
Factors to be taken into consideration:
A. Type of controls
B. Voltage variations
C. Machine cycling rate
D. Type of resin being processed
E. Coefficient of thermal expansion and conductivity of the cylinder.
F. Designing a heater that closely matches the wattage requirement
will decrease the frequency of cycling and temperature
overshoot, thereby increasing the life of the heater.
Once these factors have been established, proceed with the following steps:
1. Determine the maximum operating temperature.
2. Calculate the total wattage required to obtain the maximum operating temperature.
3. Determine the quantity and size of the heater bands to be used. 1-1/2" through 3" wide band heaters have long proven to be the most efficient and reliable in most cylindrical heating applications.
4. Determine individual band heater wattage by dividing the total required wattage by the quantity of band heaters selected.
5. Determine the band heater watt density by subtracting unheated areas from the band heater diameter created by screw terminals, gaps, holes, and cutouts.6. Determine if the required watt density previously calculated exceeds the maximum recommended watt density. Note the maximum cylinder temperature required on the left-hand side of the graph, follow the horizontal line until it intersects with the line of the band heater being used, and read directly down to obtain the maximum recommended watt density. (Watts per square inch.) See below for additional correction factors.
7. If the calculated watt density is higher than the recommended value, it must be corrected or it will cause poor heater life. This can be accomplished by using more band heaters, lowering the heater wattage, or using a different construction type or a different type of band heater.
8. Should you have a problem in selecting the proper band heater or establishing watt density for your application, consult with one of the qualified engineers at Tempco.
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