What is a Pressure Gauge? Its Diagram and How it Works
A pressure gauge is a device that measures the amount of fluid in a container. It is necessary for setting up and regulating fluid power equipment and troubleshooting it.
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.
Well, in this reading, we’ll explore what a pressure gauge is, its applications, functions, diagrams, types, and how it works. We’ll also discuss its advantages and disadvantages.
What is a Pressure Gauge?
A pressure gauge measures the force a fluid (liquid or gas) would exert on a unit area, such as pounds per square inch or newtons per square centimeter, when at rest.
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. Fluid power systems have been using pressure gauges for almost a century, so it’s not surprising that pressure gauge designs are still changing.
Pressure gauges for fluid power applications have evolved over time to include more application-specific characteristics. For instance, companies are increasingly developing pressure gauges with hydraulic-friendly pressure connections (like SAE/Metric straight threads) to prevent system leaks.
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.
Applications
The types of pressure gauges can be used for the following applications:
Various industries use differential pressure gauges to monitor filtration, liquid level, and liquid flow. 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.
Meteorologists use absolute pressure gauges to monitor adiabatic saturation pressure 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. Barometers measure atmospheric pressure.
Gauges verify that there are no leaks or pressure variations that could damage the hydraulic system’s operation.
The following classifications apply to the various types of pressure gauges:
Absolute pressure gauge
Gauge pressure measuring device
Differential pressure gauge
Absolute Pressure Gauge
We determine absolute pressure by comparing it to the pressure in a complete vacuum. In a complete vacuum, there is no pressure. We refer to this 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. A barometer, a hydrostatic gauge, can also measure absolute pressure.
Gauge Pressure Measuring Device
We calculate the gauge pressure using the standard atmospheric pressure at sea level as a reference, which is 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. The mechanical device comprises a C-shaped tube, 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. Among hydrostatic devices, the u-tube manometer is effective.
Differential Pressure Gauge
Differential pressure is the measurement of the difference between two pressure readings. It provides no information about the pressure levels at the two particular places it compares.
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.
How Does a Pressure Gauge Work?
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.
Often, a gauge port on pressure-reducing valves allows for direct monitoring of the downstream pressure setting.
The hydraulic gauge can withstand a wide range of pressures, depending on its type and material composition. As a result, two of the most essential selection factors for gauges are gauge style and material.
Pneumatic and compressed air systems develop gauges as they record pressure at various points throughout the system. The system monitors the receiver(s) and every FRL or stand-alone regulator for pressure.
Pneumatic actuators occasionally measure pressure as well. Most systems operate at around 100 psi, and pneumatic pressure gauges typically have a rating of no more than 300 psi.
There are three techniques to measure pressure: absolute, gauge, and vacuum. Absolute pressure is a measurement that incorporates ambient air and establishes a zero-reference with a perfect vacuum.
At sea level, absolute pressure can reach 14.7 psi. Applications dealing with ambient air, like calculating the compression ratio for flow (cfm) needs, consider absolute pressure values.
Most applications, like fluid power systems, that operate in ambient air but not with it, use gauge pressure and zero-reference it against ambient pressure. The gauge pressure will indicate zero when disconnected from the device.
Finally, vacuum “pressure” is expressed in Torr or in inches of mercury (in.-Hg) units, which measure pressure below ambient.
Below are the benefits of pressure gauges in their various applications:
Many applications and industries, including mechanical engineering, pumps/compressors, hydraulics/pneumatics, and general service/test operations, find pressure gauges useful.
Modern pressure gauges ensure gauge longevity and, as a result, reading accuracy.
Digital pressure gauges are quick 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.
By modifying them, we can make them provide electrical outputs.
Even for high-pressure measurements, they are safe.
The accuracy is excellent, particularly at high pressures.
Disadvantages
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.
Conclusion
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. This article covers the definition, functions, types, diagram, operation, advantages, and disadvantages of a pressure gauge.
