A pressure gauge is a device that measures the amount of fluid in a container. Pressure gauges are necessary for setting up and regulating fluid power equipment, as well as troubleshooting them. Fluid power systems would be unpredictable and unreliable without pressure gauges. Gauges verify that there are no leaks or pressure variations that could damage the hydraulic system’s operation.
In this article, you’ll learn the definition, functions, types, diagram, working, advantages, and disadvantages of a pressure gauge.
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What is a pressure gauge?
A pressure gauge is an instrument for measuring the condition of a fluid (liquid or gas) that is specified by the force that the fluid would exert, when at rest, on a unit area, such as pounds per square inch or newtons per square centimeter.
A pressure gauge is a fluid intensity measurement device. Pressure gauges are required for the set-up and tuning of fluid power machines and are indispensable in troubleshooting them. Without pressure gauges, fluid power systems would be both unpredictable and unreliable. Gauges help to ensure there are no leaks or pressure changes that could affect the operating condition of the hydraulic system.
The major functions of pressure gauges are to measure pressure in a fluid system. Pressure gauges have been employed in fluid power systems for almost a century, therefore it’s not surprising that pressure gauge designs are still evolving. Pressure gauges for fluid power applications have evolved over time to include more application-specific characteristics. For example, to prevent system leaks, pressure gauges are increasingly being developed with hydraulic-friendly pressure connections (such as SAE/Metric straight threads). Digital pressure gauges with customizable software allow process measurement of pressure-based leaks or other parameters such as torque, load, force, and hardness. Analog gauges with custom scales are more prevalent.
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The followings are the applications of pressure gauges according to the types:
Differential pressure gauges are used to monitor filtration, liquid level, and liquid flow in a variety of industries. They’re important in refineries, petrochemical and chemical factories, power plants, and clean rooms, among other places.
Gauge pressure measuring devices are the most common pressure measuring equipment in the industrial world, especially in the power, refinery, chemical, petrochemical, pharmaceutical, food, refrigeration, air-conditioning, and sanitation industries.
Absolute pressure gauges are used to monitor adiabatic saturation pressure by meteorologists and to perform distillation operations in the oil refining industry. They can also be used to measure the vapor pressure of liquids, vacuum reactors, check leakage in tanks and circuits, and measure the fall in pressure of distillation vacuum columns. Vacuum pumps and the food packaging sector both employ absolute pressure gauges. Atmospheric pressure is measured via barometers.
Gauges verify that there are no leaks or pressure variations that could damage the hydraulic system’s operation.
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Diagram of a pressure gauge:
Types of Pressure Gauge
The various types of pressure gauges are classified according to the following:
- Absolute pressure gauge
- Gauge pressure measuring device
- Differential pressure gauge
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Absolute Pressure Gauge:
Absolute pressure is determined by comparing it to the pressure in a complete vacuum. In a complete vacuum, there is no pressure. As a result, it is referred to as ‘absolute’ pressure.
A measuring cell separated by a diaphragm makes up a conventional mechanical absolute pressure gauge. The reference chamber, which is a vacuum, is one part of the device. Absolute pressure can also be measured with a barometer, which is a hydrostatic gauge.
Gauge Pressure Measuring Device:
The gauge pressure is calculated using the standard atmospheric pressure at sea level as a reference (approximately 1013.25 mbar). When gauge pressure exceeds air pressure, it is positive; when it falls below atmospheric pressure, it is negative.
A Bourdon tube pressure gauge is the most popular device for measuring gauge pressure. It’s a mechanical device that’s made up of a C-shaped tube that’s sealed at one end. According to the applied pressure within the tube, which enters from the open end, the sealed end is free to move a pointer along a scale. Other mechanical devices that may measure gauge pressure include diaphragms and bellows. The u-tube manometer is effective among hydrostatic ones.
Differential Pressure Gauge:
The difference between two pressure readings is measured as differential pressure. It provides no information about the pressure levels at the two particular places it compares.
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Mechanical differential pressure gauges are the most common type. Piston-style, Diaphragm-style, and Bellows differential pressure gauges are the most common forms of differential pressure gauges. Each has a unique application in a variety of industrial operations.
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The working of pressure gauges can vary depending on the type. However, this article explains the common pressure gauge. Because the hydraulic system is designed to operate within a specific pressure range, the gauge must be rated for that range as well. Although maximum hydraulic pressure is normally in the 3,000 to 5,000 psi range, hydraulic pressure gauges may measure up to 10,000 psi. Hydraulic gauges are commonly installed at or near the pump’s pressure port for system pressure indication, but they can be installed anywhere on the machine where pressure needs to be monitored—especially if sub-circuits operate at a different pressure rate than the pump, such as after a reducing valve. Pressure-reducing valves frequently have a gauge port that can be tapped into to directly monitor the downstream pressure setting.
Depending on the type of gauge and the material it is composed of, the hydraulic gauge may sustain a wide range of pressures. As a result, two of the most essential selection factors for gauges are gauge style and material.
Gauges emerge in pneumatic and compressed air systems, as pressure is recorded at numerous points throughout the system. The receiver(s), as well as every FRL or stand-alone regulator in the system, are all monitored for pressure. Pressure is sometimes also measured at pneumatic actuators. Pneumatic pressure gauges are typically rated for no more than 300 psi, while most systems operate at around 100 psi.
There are three techniques to measure pressure: absolute, gauge, and vacuum. Absolute pressure is a measurement of actual pressure that includes ambient air and is zero-referenced with a perfect vacuum. At sea level, absolute pressure can reach 14.7 psi. In applications that deal with ambient air, such as the compression ratio calculation for flow (cfm) needs, absolute pressure values are taken into account. Gauge pressure is utilized in most applications that operate in, but not with, ambient air, such as fluid power systems, and is zero-referenced against ambient pressure. When the gauge pressure is disconnected from the device, it will indicate zero. Finally, vacuum “pressure” is expressed in Torr or in inches of mercury (in.-Hg) units, which measure pressure below ambient.
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Watch the video below to learn more about a pressure gauge:
Advantages and disadvantages of a pressure gauge
Below are the benefits of pressure gauges in their various applications:
- Pressure gauges are found useful in a wide range of applications and industries like mechanical engineering, pumps/compressors, hydraulics/pneumatics, and general service/test operations.
- Modern pressure gauges ensure gauge longevity and, as a result, reading accuracy.
- Digital pressure gauges are fast and precise.
- No operator interpretation required
- No parallax errors
- Back-lit capability
- Steady reading in high vibration
- Easy to re-range
- The Bourdon tube pressure gauges provide precise readings.
- The Bourdon tube is inexpensive.
- The construction of a Bourdon tube is straightforward.
- They can be made to provide electrical outputs by modifying them.
- Even for high-pressure measurements, they are safe.
- The accuracy is excellent, particularly at high pressures.
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Despite the advantages of a pressure gauge some limitations still occur. Below are the disadvantages of pressure gauges in their various applications.
- It’s difficult to observe the entire scale or trends.
- They are unable to read quantities that oscillate.
- They require a lot of energy except for the manual types.
- They react slowly to pressure changes.
- They are in a state of hysteria.
- They are susceptible to vibrations and shocks.
- Because the displacement of the free end of the bourdon tube is modest, amplification is required.
- The bourdon pressure gauge isn’t suitable for precise measurements.
A pressure gauge is a fluid intensity measurement device. Pressure gauges are required for the set-up and tuning of fluid power machines and are indispensable in troubleshooting them. Without pressure gauges, fluid power systems would be both unpredictable and unreliable. That is all for this article, where the definition, functions, types, diagram, working, advantages, and disadvantages of a pressure gauge are being discussed.
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