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 pressure 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:
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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:
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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.
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