A hydraulic pressure gauge is a measuring instrument used to measure and display the pressure of the working fluid—most commonly hydraulic oil—in power hydraulic systems. It is a key component of these systems, enabling the monitoring of operating parameters, which translates into safety, efficiency, and the service life of the system’s components. Hydraulic pressure gauges are specially designed to operate under high-pressure conditions typical of such systems, reaching up to 700 bar.
Construction and operating principle
Key Components of a Hydraulic
Pressure Gauge A typical hydraulic pressure gauge consists of several basic components:
- Dial (gauge): The main component that measures fluid pressure and displays its value.
- Sensing element: This is most often a Bourdon tube, a diaphragm, or a bellows. When pressure is applied, this element deforms, and this deformation is transmitted to the pointer mechanism.
- Hand mechanism: Transfers the deformation of the measuring element into the movement of the hand across the dial.
- Reading scale: Calibrated in the appropriate units of pressure (e.g., bar, PSI), it allows for the reading of pressure values.
- Housing: Protects the internal mechanisms of the pressure gauge. It may be made of chrome-nickel steel.
- Connection: Allows the pressure gauge to be installed in a hydraulic system. There are bottom (radial) and rear (axial) connections.
- Filling fluid (in glycerin pressure gauges): Most commonly glycerin, which dampens needle vibrations, protects the measuring mechanism from damage, and lubricates moving parts.
Principle of
Operation Hydraulic pressure gauges operate on the principle of deformation of the measuring element under the influence of the working fluid's pressure. The deformation of this element is then mechanically converted into the movement of a pointer against a calibrated dial, indicating the current pressure value.
The most common operating principles for hydraulic pressure gauges are:
- Bourdon tube pressure gauges: These gauges use a curved, flexible tube with a flattened cross-section. One end of the tube is connected to the pressure inlet, while the other, sealed end is free and connected to the pointer mechanism. An increase in pressure causes the tube to straighten, which moves the pointer. This is a commonly used type in hydraulic systems.
- Bellow-type pressure gauges: These use a flexible bellow that expands or contracts depending on the pressure of the hydraulic fluid. The change in the bellow’s length causes the dial to rotate.
- Diaphragm pressure gauges: The measuring element here is a diaphragm (or set of diaphragms) mounted between flanges. The deflection of the diaphragm under pressure is transmitted to the pointer mechanism. They are used in applications involving high overloads, pressure surges, or pulsations, as well as for measuring low pressures in liquid media.
Pressure measurements on these pressure gauges are typically taken relative to ambient (atmospheric) pressure, which is referred to as relative pressure.
Types of hydraulic pressure gauges
Depending on their design and application, there are several types of hydraulic pressure gauges:
- Glycerin pressure gauges: These are pressure gauges with a case filled with glycerin. Glycerin dampens vibrations and shocks, protecting the measuring mechanism and stabilizing the pointer, which is particularly important in machines exposed to vibrations. They are suitable for measuring the pressure of gaseous media, oil, distilled water, and other liquids that are compatible with copper alloys.
- Digital hydraulic pressure gauges: State-of-the-art devices offering high accuracy and precision in measurement. They can be used in high-pressure applications (e.g., from over 6,050 PSI to approximately 4,300 PSI) and are compatible with most hydraulic fluids, including non-corrosive ones.
- Gauge pressure gauges: Used primarily to measure low pressures in dry gaseous media. The measuring element consists of a gauge made of two connected diaphragms. They are not suitable for wet or humid media.
Application
Hydraulic pressure gauges are essential in many industries and types of machinery where pressure monitoring is critical to proper and safe operation. Examples of applications include:
- Construction and agricultural machinery: excavators, bulldozers, cranes, and tractors, where hydraulic systems control many functions.
- Machinery industry: Hydraulic presses, actuators, machine tools.
- Hydraulic pumps: To monitor the pressure at the pump outlet, which allows for an assessment of its efficiency.
- Control systems: For recording the pressure in the actuator chambers during operation.
- Pressure testing: For the diagnosis and maintenance of hydraulic systems.
- The petrochemical industry (for digital pressure gauges).
- Electrical and automotive systems.
Pressure gauges help detect potential issues, such as pressure drops, leaks, or system overloads, enabling appropriate maintenance measures to be taken and preventing breakdowns.
