Pressure Gauges and Types of Pressure Gauges

This article’s topic is pressure gauges. We’ll cover the working principle of pressure gauges and the types of pressure gauges. We’ll examine the types of pressure gauges and their operating systems in detail.

Pressure Gauge

A pressure gauge is used to measure the pressure of the air used in pneumatic (air-pressure-operated) systems.

Working principle of the pressure gauge

A tube that can lengthen and shorten depending on the pressure of the air flowing inside it moves the needle through the linkage system it’s connected to. The tube flexes like a spring, and this helps it display different pressure values. The up-and-down movement resulting from the flexing of this tube-shaped spring is converted into rotational movement by a gear system, causing deflections in the needle. The pressure value is read as the value the needle points to on the scale.

Parts and operating system of the pressure gauge. (above)

By placing the pressure gauge at any desired point of the circuit, the pressure at that point is determined. The pressure shown by the pressure gauge is the effective (gauge) pressure.

With this device, the working pressure in the system is measured relative to atmospheric pressure. Measurements are made with a Bourdon tube or a diaphragm. When measuring pressure at test points under high dynamic load — with frequent and rapid load changes, pressure spikes, vibration, and shock — these devices are filled with a damping fluid (usually glycerin). If pressure gauges are to be used for controlling a hydraulic system, they can be connected with electrical contacts.

Types of Pressure Gauges

When examining the types of pressure gauges, we’ll define them according to their operating system and the type of area they’re used in. There are three types of pressure gauges by operating system: Bourdon tube pressure gauges, diaphragm pressure gauges, and differential pressure gauges.

Bourdon Tube Pressure Gauges

This type of gauge is used for measuring pressure in both liquid and gas fluid environments. However, they’re not used in environments with high viscosity, environments that crystallize, or fluid environments that react with copper alloys.

Allowed application range:

Upper limit for static load: 3/4 of full-scale value
Upper limit for fluctuating load: 2/3 of full-scale value
Can briefly reach the full-scale value.

Structure and Working Principle of the Bourdon-Type Pressure Gauge

The open end of the Bourdon tube takes a value based on the difference between the pressure in the tube of the spring measuring element (1) and atmospheric pressure. Linear measurement is pushed as motion through the connecting link (2) that touches it, and reflects the actual value on the display scale (4).

Diaphragm Pressure Gauges

Compared to Bourdon tube gauges, this type of gauge is more resistant to vibration. They’re also more suitable for gaseous, rusted, uncleaned, or highly viscous environments.

Where diaphragm pressure gauges are used:
Diaphragm pressure gauges are used in concrete and cement pumps, coking plants, sludge pumps, mine locomotives, and road construction machinery.

Structure and Working Principle of the Diaphragm Pressure Gauge

A concentric diaphragm (1), stretched between two flanges, divides the pressurized chamber into two separate sections. The pressure chamber (2) is connected to the outside and is pressurized with atmospheric pressure. Chamber (3), in the measuring position, is pressurized with the working pressure and forms the measuring section. The differential pressure between the pressure in chamber (2) and the pressure in the measuring chamber (3) causes deformation of the diaphragm in one direction. This deformation is transmitted through a push rod (5) to the display mechanism, and to a
needle that indicates the correct position on the scale. (4)

Differential Pressure Gauges

This device measures the pressure difference between two working pressures. This measurement is made with either a Bourdon tube gauge or a diaphragm gauge. When measuring pressure at test points under high dynamic load with shock and vibration, these devices are filled with a damping fluid (usually glycerin). Additionally, if these devices are used for controlling a hydraulic system, they can be connected with electrical or pneumatic switches.

Bourdon Tube Differential Pressure Gauges

These gauges are used for measuring pressure differences between fluids and gases that don’t have high viscosity and don’t crystallize.

This pressure measuring device has two independently operating Bourdon-tube measuring systems. The movements of the measuring element (arising from pressurization) are transmitted to the gauge in proportion to the measured pressure and shown on the scale.

Diaphragm Differential Pressure Gauge

These devices are suitable for differential pressure measurements of liquids and gases. They’re generally used to measure the pressure drop occurring between pipelines and a filter system.

Related Questions