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Plastics catalog - Watlow - #29

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Text version of the page
O
A T
irrel Heate
Special Mica Band
No-Heat Area for Special Mica Band (Post Terminals)
Applications and Technical Data
Operating Factors
Use as a low watt density rating as the application permits. A close match of the heat supplied to the actual require­ments will reduce temperature over­shoot, reduce cycling and increase the life of any band heater used.
Calculate the safe maximum wattage
for the heater using:
Heated Area x Maximum Watt Density
Calculate the heated area of the band heater by subtracting the no-heat area from the total area in contact with the cylinder (3.14 x I.D. x width). Subtract the no-heat area at the terminals (from table) and any additional no-heat area caused by holes, slots or oversize gaps.
Determine the maximum watt density of the heater from the graph on this page. The curves are based on narrow heaters mounted on a smooth, steel cylinder. Apply the necessary correction factors:
• For heaters 57 mm (2.25 in.) to 127 mm (5 in.) wide, multiply watt density by 0.8.
• For high expansion cylinders (aluminum or brass), reduce the watt density by 0.46 W/cm2 (3 W/in2).
• For heaters 63.5 to 127 mm (2.25 in. to 5 in.) wide installed on a high expansion cylinder, reduce watt density by a total of 0.46 W/cm2
(3 W/in2) only.
• For regular cylinder surfaces other than smooth, machined finish, reduce watt density by 0.46 W/cm2 (3 W/in2).
• For heaters that will be insulated or enclosed, contact Watlow for specific watt densities.
Heater
Heater Size
No-Heat Area
Diameter
Width
at Terminals
Type
mm (in.)
mm (in.)
mm (in.)
One Piece
50.8 (Less than 2)
152.4 (Up to 6)
25.4 (1 x width)
50.8 (2 or more)
76.2 (Up to 3)
38.1 (1.5 x width)
76.2 (More than 3)
25.4 (1 x width)
Two Piece
76.2 (3 or more)
76.2 (Up to 3)
76.2 (3 x width)
76.2 (More than 3)
50.8 (2 x width)
j
00 O
IM
t
r O
Maximum Allowable Watt Density
Watt Density—W/cm2
24
8
1100 1000
900 800 700 600
500 400 300 200
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500
o O
Q.
(D
400
300
0)
>> O
200
100
10 20 30 40
Watt Density—W/in2
50
60
29
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pageCatalog pdf di En 2012-02-06-12