Vilter VSM 71-701, Operation And Service Manual

Page: 185 / 244

21
FAST HEAT, INC.
CARTRIDGE
HEATERS
HI-TEMP OPEN AIR TEST
This test was conducted using a 5 /
8
” dia. x 6”
(15.8 mm x 152 mm) long, 750 watt 240 volt
Hi-Temp Cartridge heater. The test was con-
ducted in ambient air 70º F (21º C). A type ‘J’
thermocouple was attached to the heater at
the center of the sheath. The voltage was
varied through a variac to obtain proper
power input for corresponding watt density.
WATT DENSITY CALCULATIONS:
Watt density of a Hi-Temp Cartridge is
simply the total heater wattage divided by
the heated area of the cartridge in square
inches.
Heated Length = OAL – Unheated Sections
(OAL - Overall Length)
The subtraction of
3
/
4
” from the overall
length in the above equations is a general
allowance for the watt density calculations
on Standard Cartridge heaters only.
Hi-Temp Cartridge heaters, heated length
varies depending upon heater diameter
and length.
For specific unheated sections contact
Fast Heat.
Watt
Density
Total Heater Wattage
(Heated Length) x Cartridge Dia. x 3.14
=
1600º F (871º C)
1500º F (815º C)
1400º F (760º C)
1300º F (704º C)
1200º F (649º C)
1100º F (593º C)
1000º F (538º C)
900º F (482º C)
800º F (427º C)
10 w/in
2
(1.6 w/cm
2
)
20 w/in
2
(3.1 w/cm
2
)
30 w/in
2
(4.7 w/cm
2
)
45 w/in 2
(7 w/cm
2
)
40 w/in 2
(6.2 w/cm
2
)
WATTS PER SQUARE INCH / WATTS PER SQUARE CM SHEATH; HI-TEMP CARTRIDGE
HEATER (THIS GRAPH FOR REFERENCE ONLY)
APPROXIMATE TEMPERATURE IN DEGREES AT THE
CENTER OF THE HEATER