PTFE INSULATED RESISTANCE/HEATING WIRES & DEVICES

Poly
Tetra
Fluoro Ethylene (PTFE) is a plastic which is flexible up to -200°C and stable up to 260°C. These
features
have been utilised to develop safe, efficient and long-life PTFE
insulated
heaters. Such heaters find applications in
1.
Flexible
car seats, pads, carpet or blanket heating.
2. Floor heating
under
dry or moist conditions (heaters pre-cast and terminated during floor
installation);
such installation may be with or without parallel-laid/ spiral-wrapped
sensor
wire.
3. Temperature
control
for electronics display devices, obstruction/shadow-free, by using high
strength
fine conductor and thin wall insulation.
4. Immersion heating
insulated
coils for distillation with prescribed cold leads; Zone temperature
control
of distillation columns and heat tracer for pipes.
5. Anti-freeze roof
edge,
Window edge, Gasket heating. CONSTRUCTION Three main parts of heating
wires
and devices are
1.
Heating
resistance wire capable of long-life stability at the required
temperature.
These are single or multi-strand, or helically wound 1, 2, 3 strands
(on
glass-fibre cord) of plated/unplated Copper, Copper alloy, Stainless
Steel
or resistance alloy.
2. PTFE insulation
with
the desired Radial Thickness of Insulation (RTI), minimum 0.15 mm to
maximum
1.5 mm. This insulation is guaranteed concentric multi-layer
tape-wrapped
and heat-fused.
3. Temperature
Sensor;
protection system such as braid shields for ease of handling. PRECAUTIONS The maximum operating temperature of PTFE related
systems
are limited to 260°C (total maximum spot temperature, i.e.
temperature
rise plus ambient). Although PTFE is known to withstand 380°C
for
short durations (without mechanical stress), the transition temperature
is
only around 325°C. Therefore, suitable protection must be
provided
to prevent accidental increase beyond 260°C. This protection
is
very critical for liquid heating systems which generally operate at
high
heat fluex densities. Such systems must never be allowed to run
dry
(out of liquid). Any spot of the heating element, if exposed,
will
rise in temperature towards self-destruction, electrical hazard and
fire.
Explosion may follow. Alternate built-in protection is to provide
a
longer length element with low watts per linear metre so that the spot
temperature
even under dry condition does not rise beyond 260°C. The cost
will
be higher for such systems.
TYPICAL PRODUCT FORMS
a) Round, single and
multi-strand
with desired RTI of PTFE. These are simplest and most widely
used.
The slight oval, flat strip or twin parallel-laid constructions offer
better
heat transfer.
b) Multi-conductor bonded flat cables or
woven
flat cables for integrated surface heating.
c) 1, 2, 3 strands helically wrapped on
Glass
Fibre cord with PTFE insulation and Nickel Plated Copper/Stainless
Steel
braid shield for outdoor use.
d) Insulated heating wire with
parallel-laid
temperature sensor wire of pure Copper or Silver Plated Copper having
high
temperature coefficient of resistance, under a common PTFE jacket (with
zero
moisture absorption) for floor heating.
e) Fixed wattage and fixed length heating
elements
with integral heating leads under common PTFE cover with same or
different
colour to identify the heating zone, for heating of remote areas. TECHNICAL
CHARACTERISTICS
1. Ohmic value from 0.05
ohm/metre
to 500 ohms/metre.
2. Radial thickness of primary PTFE
insulation
(RTI) 0.15 mm to 1.5 mm.
3. The watts/sq cm or liner watts/metre can
be
designed to suit the application, subject to safe maximum spot
temperature
of 260°C.
4. These designs can
be
made to suit the prescribed working voltage from few volts to several
thousand
volts, subject to satisfactory protection system. SPECIAL
FEATURES
- Concentric PTFE primary insulation,
multi-wraps
and multi-pass tape-wrapped and sintered
- Integrated conductor facility
- R&D help towards optimisation with
more
than 30 years' experience
- Low set-up charges and short lead times
- Fine control on resistance, diameter,
weight
and end-piece break-down voltage
- 100% finished product testing with
actual
test certificate
- Flexible economic small volume
production
and prompt overseas door-delivery at low cost.
WIRES FOR
FLOOR
HEATING AND HEATING PADS/MATS
Following
is a list of standard Heating Elements for use at 230 V AC RMS.
The
typical product form consists of round Heating Wires with Stainless
Steel
Braid Shield and PTFE jacket with final OD 1.8 mm to 2.2 mm.
Conductor
used for heating element is multi-strand (dia 0.25 - 0.68 mm).
For Free Design Service, Contact:
mukul@druflon.com; druflon@gmail.com; nkrishna@druflon.com
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