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Water based fog machines are the most commonly available types
for both consumer use and commercial applications, and while there
are many manufacturers of fog machines, and while there can be great
differences in the design and quality of the components used by
fog machine manufacturers, there operation is quite simple and almost
always the same.
The fog fluid in the fluid tank is forced through a heat exchanger
by a high pressure pump. The heat exchanger maintains a high temperature
at which the fluid vaporizes in a process commonly known as "flashing".
As the fluid is "flashed" it rapidly expands, and that
expansion forces the vapor through the nozzle of the machine. When
the vapor mixes with cooler air outside the fog machine, it instantly
forms an opaque aerosol we see as fog. That's basically how most
fog machines work. Below are more specific details of how the main
components of a fog machine work.
The Pump: In a fog machine, the pump plays the critical
role of delivering fog fluid from the fluid tank to the heat exchanger.
The most commonly used pump is a piston pump, and is carefully matched
to the design of the heat exchanger. If a pump delivers fluid too
quickly, the heater will turn off relatively quickly since too much
fluid is moving through the metal block. This results in the machine
shutting down to re-heat in a shorter time. The piston pump is the
source for most of the noise generated by a fog machine.
The Heat Exchanger: Heat exchangers vary widely in design,
materials, wattage and quality. A well engineered fog machine have
take into account all these factors for optimum fog output and safety.
Essentially, the heat exchanger is a block of metal, usually aluminum,
with a heating element built into it to heat the metal block. The
temperature of the block is regulated by a thermostat. A channel
inside the metal block allows the fluid to travel through it to
the nozzle. The wattage used to heat the exchanger is the specification
most manufacturers use to describe how powerful their fog machines
are.
The Nozzle: As the fog fluid is pumped through the heat
exchanger, it is super-heated and then immediately forced through
the exit nozzle at the front of the fog machine. These nozzles are
usually made from solid brass and have an extremely small nozzle
hole where the vaporized fog fluid is expelled under high pressure.
The nozzle and it's protective shroud will become very hot during
operation of the fog machine. Do not touch it or place it near anything
that could catch on fire.
Remote Controls: Most fog machines come with a basic on/off
switch remote control. Operation is very basic, you hold down the
button for fog, you release the button to stop the fog. The problem
with this type of controller is that it shackles you to the remote
control. The best option is a Timer Remote Control designed to give
"hands free" operation of the fog machine. This remotes
allows you to control both the interval at which the fog machine
comes on, and the amount of time it stays on during the interval
eliminating the need for you to spend precious Halloween time manually
operating a remote. For more information on Timer Remote Controls
see our Fog Machine Faq section.
Fog Machine Fluid: Water based fog fluids are typically
made from glycol and water. It is important to understand that fog
machines and there fluids are designed as systems. Specific fluid
formulas require a specific temperature range for optimum aerosolization
during the "flashing" process. Fog machine manufacturers
design their machines to be compatible with their fluids. If a machine
is calibrated at too low a temperature for a given fluid, the result
can be "wet" fog that can leave a residue. If the temperature
is too high, the fluid can "burn" or decompose the fluid,
thus changing its chemical composition. This "burning"
can create harmful byproducts. Well designed fog machines have removable
fluid tanks for the convenience of the user.
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