Among the various operations that the farmer needs
to manage in the field is spraying. To avoid financial losses, it is necessary
to pay proper attention to the equipment. Improper calibration, for example,
could be causing you to lose product. At this point, an essential device is the
pressure gauge. But do you know what the function of the
pressure gauge is?
This instrument is responsible for measuring the
pressure of gases and liquids inside containers, and for this reason it helps
the farmer to calibrate the pressure of the spraying system. Read on and learn
more!
What is the
function of the pressure gauge?
A pressure gauge is the tool used to measure
pressure within a spray system. It informs the actual working pressure at the
time of application. Through it, it is possible to identify the flow and the
diameter of the drop.
Using a pointer, it shows the exact pressure within
a closed system, whether fluid or compressed gas. It normally doesn't need any
electrical power.
This measurement is important for the spraying
operation, as the pressure determines the amount of product that is applied to
the crop. While the operator regulates the drop size class to apply a certain
application rate (l/ha) of the spray liquid, it is possible to monitor the
performance of the regulation by means of the pressure gauge.
If there are faults, the operator will be able to
see the pressure change right away. For example, if a clogging occurs, the
system pressure increases. If there are leaks, the pressure drops. That's why
it's so important to know how to read the information the gauge displays.
Often, however, we come across situations in which
we have doubts about how to best read the information contained in the
manometer. Below, we will detail how to proceed with this reading in a simple
way.
How to read?
Unit of
measurement
It is possible to find different units of measure.
However, pressure gauges typically have two measurements: bar and lbf/in² (pound
force per square inch) — 1 bar equals 14.5 lbf/in². There is also the kgf/cm²
(kilograms force per square centimeter).
Scale
The choice of the gauge unit of measurement — bar
or lbf/in² — must be made considering the pressure limits that each application
suggests. The sprayer bar typically use spray nozzles which require less
pressure (below 150 lbf / square inch) , and can use pressure gauges that
provide read up to 200 lbf / square inch.
On the other hand, sprayers for perennial crops,
such as citrus and coffee, have manometers with a greater reading scale due to
the tradition that in these crops the pressures used are higher (greater than
150 lbf/in²).
It is necessary to choose a manometer that allows
the working pressure to be between 30% and 70% of its scale, since in this
range the probability of reading errors is reduced.
What are the
types of pressure gauges?
There are different types of manometers, including
mercury ones and digital ones. Let's consider the main ones.
Standard
gauges
This is the most used and is mounted on hydraulic
or pneumatic pumps (fluid or gas). It is used for gauges undergoing
calibration. Therefore, they need to have high precision, as they serve as a
standard for calibrating industrial models.
Liquid
U-column type pressure gauges
Calibrate lower ressure gauges. The measurement
here assumes that the applied pressure supports a liquid column against the
pulling force of gravity. After all, higher pressure levels can withstand a
greater volume of liquid column.
The basis of measurement will be the length of the
liquid column of water or mercury. Mercury, especially, has a very high
density, generating smaller columns in the tube. The parameters adopted to ensure
greater measurement accuracy are:
·
expansion of the liquid within a graduated
scale;
·
precise value of local gravity acceleration;
·
no tube upright;
·
difficulty in reading the meniscus of the fluid
generated by capillary action;
·
Density of the liquid.
Dead weight
gauge
The mechanism used in the deadweight manometer is
the relationship between a known mass weight in a given area and the action of
pressure on it. Thus, the pressure is calculated based on the force it impinges
on the weight. This gauge is also known as a deadweight piston.
Bourdon Tube
Manometer
This is one of the most widely used types of
mechanical pressure gauge tools. A flexible tube curved in a C-shape is used,
having an oval cross-section that changes when there is pressure inside, moving
the indicator gears.
Bellows
pressure gauge
In this type, the device has wrinkles that expand
and contract depending on the level of pressure applied.
What are the types of pressure and how do they
affect the measurement?
Pressure refers to a force acting on a certain
area. There are, however, different types of pressure, depending on the
pressure reference. Check it out.
Absolute
pressure
The basic pressure reference is zero pressure, a
condition that is found in an airless space in the universe, that is, in a
vacuum. On Earth, everything is subject to a certain measure of force. If a
pressure is related to zero pressure, we call it absolute pressure, which uses
the acronym “abs” (from the Latin absolutus, which means separate, or independent).
Therefore, as the measurement base is zero, the
result will not be affected by environmental conditions such as weather or
altitude above sea level. Therefore, it opposes the manometric pressure, which
we will see later.
Atmospheric
pressure
This is the basic pressure of the environment
(pamb), as it considers the weight of the atmosphere around the Earth, which
has an approximate height of 500 km, where the pressure is equal to zero
(absolute pressure).
Thus, the higher the altitude, the lower the atmospheric
pressure. In addition to altitude, weather fluctuations also affect pressure.
At sea level, the pressure averages 1,013.25 millibars (mbar).
Differential
pressure
Differential pressure is the pressure difference
between two points in a system.
It is the most frequently used type in the
technology field. Unlike absolute pressure, which does not take into account
variations in the environment, gauge is the difference between an absolute
pressure (pabs) and atmospheric pressure, also known as overpressure, or
relative pressure.
What
precautions do you need to take with the manometer?
To increase the life of the gauge, the valve must
be closed and no pressure held during work. This action prevents the equipment
from absorbing sudden pressure variations that affect the internal devices that
read the pressure.
When mounting the pressure gauge on the control,
use a suitable wrench to ensure tightness of the part. Never tighten the
pressure gauge by hand as this can compromise the entire internal device
responsible for the reading, and the information shown on the display will
therefore not reflect the actual working pressure.
What are
application technologies and how can they help the farmer?
Application technologies, better known as agricultural
spraying, use a variety of tools and machines to optimize operations. Whether
through the methods adopted or through the defined strategies, the objective is
always to achieve maximum control and efficiency in spraying.
Thus, the idea is to make the product reach the
target with economy and safety. For this, application technologies make use of
different equipment, which are selected according to the needs, characteristics
and demand of the crop.
In this context, self-propelled machines , tractors
with coupled bars or of the trailer type , as well as simpler models, such as
back sprayers , enter the arsenal . With proper planning and choosing the right
instruments, it is possible to:
·
increase the efficiency of the work of the bars;
·
reduce or prevent gaps in application ranges;
·
achieve conscious water consumption;
·
reduce drift;
·
reduce overlap;
·
select the most suitable spray nozzles for each
type of application;
·
correctly dose the pesticide to avoid soil
contamination and high toxicity to the plants.
Together with the Pressure Gauge Syphon, application technologies help the farmer
to ensure spraying in the right place and at the most suitable dose. In other
words, they are tools that make field operations increasingly safe and
efficient.
Now that you've figured out what the gauge is for,
subscribe to our newsletter to receive more information directly in your inbox!
Read also: HOW
INDUSTRIAL PRESSURE GAUGES WORK
Read also: PRESSURE
GAUGES AND TRENDS FOR THE INDUSTRIAL NICHE
