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Dalton
Split Sheath Cartridge Heaters |
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Watt-Flex®
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The
Revolutionary Split-Sheath Cartridge Heater
(Patented in the United States and Canada) |
| Maximized
Heat Transfer |
The
unique split-sheath design of the Watt-Flex® Cartridge Heater
allows the independent, bilateral expansion of each half of the heater
outward against the walls of the surrounding bore. Maximized metal-to-metal
contact results in greatly improved heat transfer under normal fit
conditions of .005" to .007". The thermal expansion of conventional
cartridge heaters limits heater contact to only one side of the bore
(Figure 1). The unique split-sheath expansion of Watt-Flex® heaters
assures superior heat transfer, more uniform process heat, greater
efficiency, and reduced consumption of electricity. |
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Figure
1: Watt-Flex Expansion Comparison |
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ENERGIZED
CONVENTIONAL CARTRIDGE HEATER
Conventional cartridge heaters limited to ordinary thermal expansion
cannot compensate for oversized bores.
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ENERGIZED
WATT-FLEX HEATER
The unique bilateral expansion of an energized Watt-Flex
heater produces superior metal-to-metal contact with the surrounding
bore, thereby maximizing heat transfer. |
DE-ENERGIZEDWATT-FLEX
HEATER
De-energized
Watt-Flex heater contracts for easy insertion and side-out removal
from bore. |
| Use
in Oversized Bores |
The
fit of a cartridge heater is measured as the difference between the
inside diameter (I.D.) of the bore and the outside diameter (O.D.)
of the heater. The suggested fit for a Watt-Flex Cartridge Heater
is .007" greater than the standard diameters shown in the Heaters
Accessories section of this page.
For example, the ideal bore diameter
for a 1/2" diameter Watt-Flex heater would be 0.502" to
0.505". At the maximum tolerance dimension of the heater and
the minimum bore diameter, the heater would have 0.005" fit,
allowing ease of insertion and removal. Generally, smaller diameter
heaters benefit from a bit tighter fit and fit can be slightly loosened
for larger diameters.
The unique expanding action of Watt-Flex
heaters eliminates the need for tight fits. This makes Watt-Flex heaters
ideal for use in oversized bores. Superior bilateral expansion permits
the use of Watt-Flex heaters in mores where conventional heaters could
no be used effectively. |
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Figure
2: Thermal Expansion Comparison |
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| Ease
of Removability |
Dalton
Electric will replace, free of charge, any Watt-Flex Cartridge Heater
that cannot be withdrawn from the bore.
Dalton Electric's standard product warranty
covers the removal of Watt-Flex heaters from bores, providing the
bore fit is a minimum of .005" and there is no bore contamination
to cause seizure. This warranty is possible because the split-sheath
design of Watt-Flex heaters eliminates warping, the primary cause
of bore seizure in heating applications.
As shown in Figure 2, temperature differentials
exist from one side of conventional cylindrically sheathed cartridge
heater to the other. These differentials occur because only one side
of the heater comes in contact with the bore. The resulting deflection
within a close-fitting bore often makes the heater blind during removal.
With the Watt-Flex heater's split-sheath design, each half of the
heater contracts independently when de-energized to provide ease of
removability. |
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| Higher
Watt Densities and Temperatures |
The
Watt-Flex Cartridge Heater is essentially a tubular heater bent back
on itself and swaged into a cylindrical format. Unlike conventional
heaters, Watt-Flex heaters have no ceramic core which can crack during
swaging, therefore, they can be compacted to a much greater density.
This process increases both heat transfer ability and insulative value
of the dielectric.
The greater insulation value accommodates
significantly higher watt-densities. In fact, Watt-Flex heaters produce
up to 50% higher warrantable watt-densities than conventional heaters
and can operate at much higher temperatures. |
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| Longer
Life |
The
life of a cartridge heater is directly related to its internal operating
temperature. Denser and more uniform compaction of the dielectric
provides greater heat transfer to the Watt-Flex sheath. This, combined
with more efficient heat transfer to the surrounding metal through
intimate contact with the wall of the bone, permits the Watt-Flex
resistance coil to run substantially cooler than conventional cartridge
heater coils. The result is up to five times longer life, decreased
downtime, and lower operating costs. |
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Figure
3: Watt-Flex® SPLIT-SHEATH CARTRIDGE HEATER |
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Split
Sheath (1)
- Expands when
energized to contact bone.
- Contracts
when de-energized for ease of removal.
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Continuous
coil (2)
- Produces
uniform temperature profile.
- Eliminates
the possibility of sections burning out.
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Tip
may be (3)
- Cool (as
shown)
- Fully heated
(by leaving coil unstretched)
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| CONVENTIONAL
CARTRIDGE HEATER |
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| (1)
Independent coil sections burn out leaving half the heater cold. |
(2)
Lack of coils at junctions produces cool spots. |
(3)
Design and construction prohibit heated tip. |
| Uniform
Temperature Profile |
Unlike
conventional cartridge heaters, Watt-Flex heaters have a continuous
heating coil for a more uniform temperature profile. Continuous coil
construction eliminates the cold spots which can occur at core junctions
in ceramic core heaters. (See Figure 3). With Watt-Flex heaters there
are no independent sections to burn out. Figure 4 shows the superior
temperature profile along the length of a torpedo probe heated by
a Watt-Flex heater. Uniform sheath temperature is vital when molding
heat-sensitive plastics where the temperature window between gate
freeze-off and material degradation is very narrow,
By varying the watt-density, the temperature
profile may be custom-matched to specific requirements. For example,
certain applications, such as those requiring temperatures higher
at the tip of a molding probe than along the sheath, can be accomplished
with Watt-Flex heaters but not with conventional cartridge heaters. |
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Figure
4: Superior Temperature Distribution Based on Actual In-Mold Tests |
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| Standard
Watt-Flex Heater Dimensions |
AVAILABLE
DIAMETERS |
NOMINAL
DIAMETERS1 |
STANDARD
COLD SECTION AT TERMINAL END |
MIINIMUM-MAXIMUM2
LENGTHS |
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1/4"
3/8"
1/2"
5/8"
11/16"
3/4"
1" |
0.245"
0.370"
0.495"
0.620"
0.683"
0.745"
0.9925" |
5/16"
3/8"
5/8"
5/8"
5/8"
5/8"
1" |
1
1/4" - 22
1 1/2" - 36"
2" - 50"
2 1/2" - 70"
3 1/2" - 64"
3 1/2" - 90"
10" - 60" |
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8.0
mm
10.0 mm
12.0 mm
12.5 mm
15.0 mm
16.0 mm
20.0 mm |
7.875
mm
9.875 mm
11.875 mm
12.375 mm
14.875 mm
15.875 mm
19.875 mm |
8.000
mm
9.500 mm
15.875 mm
15.875 mm
15.875 mm
15.875 mm
15.875 mm
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38
mm - 660 mm
38 mm - 915 mm
50 mm - 1140 mm
50 mm - 1140 mm
65 mm - 1250 mm
65 mm - 1775 mm
100 mm - 1525 mm |
| Hot
Tip Option |
Watt-
Flex heaters can be constructed to generate full heat at the tip (Figure
5). When selected for injection molding gate probes, the hot tip feature
minimizes undesirable gate freeze-off. |
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| Figure
5: Watt-Flex Hot Tip Heater vs. Conventional Heater |
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Conventional
cartridge heater construction prohibits a heated tip. |
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Only
Watt-Flex heaters are designed with a continuous coil which delivers
full heat to the tip. |
| Exclusive
External Thermocouple Option |
Watt-Flex
heaters can be manufactured with a groove along the exterior of the
cartridge to accommodate a needle-type thermocouple (Figure 6) for
more accurate temperature sensing and control. Unlike cartridge heaters
with internal thermocouples which measure the internal coil temperature,
Watt-Flex heaters measure the temperature at the point of heat transfer
from the heater to the host metal.
Another feature of this design is that
the temperature can be monitored at any point along the heater, unlike
internal thermocouples with fixed positions. And, the Watt-Flex design
allows for independent replacement of the heater or the thermocouple,
without having to discard an operational component as in conventional
designs.
The maximum lengths for grooved heaters
are 15" for 1/4" and 3/8" diameter heaters and 7"
for 1/2" diameters heaters. Longer heaters, 1/2" diameter
or larger, can be center grooved between the legs to a depth of 6".
Thermocouples are Type J with a lead length of 48". A 0.040"
needle diameter is used for 1/4" diameter heaters and all center
grooves. A 0.062" needle diameter is used for side grooved 3/8"
and 1/2" diameter heaters. |
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Figure
6: Watt-Flex Heater with Optional Thermocouple |
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| Heater
Accessories |
Watt-Flex
are available with a variety of options including abrasion resistance,
moisture resistance, mounting variations, high-temperature modifications,
and lead modifications. The illustrations below show a sampling of
the accessories available. |
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STRAIGHT
HEADER WITH STAINLESS
STEEL BRAID |
THREADED
POST TERMINALS |
HEADER
TYPE |
Watt-Flex
O.D. |
HEADER
O.D. |
HOSE
I.D. |
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Watt-Flex
O.D |
"A" |
"B"
Mounting |
| Straight
or Right Angle
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1/4" |
3/8" |
11/32" |
1/4" |
1" |
.080"
R on 1" BC |
3/8" |
1/2" |
11/32" |
3/8" |
1" |
.080"
R on 1" BC |
1/2" |
5/8" |
1/2" |
1/2" |
1" |
.080"
R on 1" BC |
5/8" |
3/4" |
1/2" |
5/8" |
1" |
.080"
R on 1" BC |
3/4" |
7/8" |
1/2" |
3/4" |
1
1/2" |
.080"
R on 1 1/4" BC |
1" |
1
1/8" |
5/8" |
1" |
2" |
.201"
D on 1 1/2" BC |
| The
following accessories are available on Watt-Flex heaters. Please consult
factory for special accessories or designs. |
| Abrasion
Protection
- Stainless
Steel Braid
- Stainless
Steel Flexible Hose
- Straight
or Right Angle Headers
Containment
Protection
- RTV Potting
- Ceramic Potting
Mounting
Variations
- Stainless
Steel Flange
- Puller End
Plug
- Mounting
Bracket
- NPT Fitting
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High-Temperature
Modifications
- High-Temperature
Leads
- Extra Cold
Section at Terminnal End
- Ceramic Beads
Lead
Modifications
- Extra Length
Leads
- Threaded
Post Terminals
- Fiberglass
or Silicon Rubber Sleeving
- Quick Disconnect
- Clip Support
- Integral
Ground Wire
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