World Grain - April 2007 - 59

GRAINOPERATIONS

though light-duty models are available
with electric drives. Your choice of
probe should focus largely on manufacturer preference and design quality, as
well as expected truck volume.
Installation of truck probes is usually
straightforward and involves following
the manufacturer's instructions. Care
must be taken to install the probe at the
proper height so it can reach over the
edge of the truck and still reach the bottom of the hopper.
Physical location of the probe is a basic
but critical item. It should be positioned
so that the truck doesn't have to stop on
an inclined ramp into the elevator. Also,
there must be enough space between the
probe and receiving pit to allow sampling
the rearmost hopper of the truck while
dumping the front hopper of the previous truck. As a guideline, the edge of the
dump hopper should be at least 175 feet
(53.3 meters) from the probe location.
SAMPLE LINES
The sample lines transferring the sample from the probe to the office can be
either above or below ground. If lines are
buried, flexible hose must be installed
in a larger sleeve so that they can be replaced when worn out or removed if they
become plugged. With buried lines, it is
important to make the sleeves watertight
where the sample lines exit from them.
Above-ground lines can be either
flexible or rigid steel, or aluminum tubing. Be careful to use the appropriate
inside diameter sample transport line
as recommended by the manufacturer,
since this must match the airflow capacity of the fans and blowers supplied. If
using flexible plastic tubing above or below ground, be sure to use tubing with a

smooth interior surface.
The other key installation concern is
to ensure the sample receiver is airtight
when not operating, particularly when
the outside temperatures are cold. If the
sample receiver is not airtight, warm, humid air from the grading room can enter
the sample lines, cool off and condense,
resulting in water in the sample.
It's also important to balance the air
flow to the probe. The air supplied to the

Care must be taken to install the probe at the proper
height so it can reach over
the edge of the truck and
still reach the bottom of the
hopper.

probe should just offset the air drawn out
of it. With the air balance set properly,
holding light chaff in your hand about
one-half inch from the probe tip should
result in the chaff neither blowing out of
your hand nor sucking into the probe.
One complaint that has been leveled
against truck probes is that they can damage the bottom of trucks, usually because
of either operator error or probe design
problems. Installing pressure relief systems in the downward pressure line to
the probe can reduce the likelihood of
significant truck damage by limiting the
downward force to that which is required
to push the probe through the grain. This
may require contacting a hydraulic expert
to oversee the installation. It is usually
not possible to achieve this by just reducing the main system pressure, as other
components typically require higher

pressures. In some cases, it may be possible to simply replace the cylinder with
a smaller diameter one or a larger rod to
reduce the force available.
VIDEO CAMERAS
Another important issue is how to see
where you are probing. The best way is
to install the probe next to an elevated
grading office where you can see the
probe and truck directly. However, in
many cases this is not possible and a
video camera system is necessary. Unfortunately, video cameras present only
a two-dimensional view, making it more
difficult to judge location and depth.
If a video camera is needed,
you should consider the following
recommendations:
* Use a high-quality color video security camera. Expensive features such as
remote zoom, pan and tilt aren't always
necessary. The most important thing is
to place the camera in the right location
and use good basic components.
* Install the power supply for the
camera in a weather-proof box adjacent
to the camera. The box is also handy to
make the signal connections in a protected area. Do not install the power
supply in the grading room, as it is difficult to avoid excessive voltage drop over
the distance to the camera.
* Using a regular color television
with a cheap coax to RCA video adapter
will save hundreds of dollars compared
to using a specialized video monitor.
* The camera should be positioned to
look at the truck from an angle to give
some perspective. Generally speaking,
the camera should be about 18 to 20 feet
high, parallel to the truck travel in line
with the probe on the outbound side of

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World Grain - April 2007

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