Pressure Gauge and its internal parts

In this post, we will discuss the Pressure gauge, Pressure unit conversion chart, outer and internal parts of a pressure gauge

Pressure Gauge
Pressure Gauge

The pressure gauge is used to indicate the pressure of any process line, body or tank.

Outer Parts of Pressure Gauge

  • Glass
  • Glass cover
  • Outer Body
  • Process Connection

Internal parts of Pressure Gauge

  • Scale
  • pointer
  • Bourdon Tube
  • Spring
  • Pinion
  • Sector
  • Pivot
  • Adjustable Link
  • Segment Lever
  • Tip
Pressure Gauge
Pressure Gauge

Pressure is defined as the amount of force applied over a unit area.
P= F/A
Where F is the force and A is per unit area.
  Unit of Pressure    
A kilogram-force per square centimeter (kgf/cm2), often just kilogram per square centimeter (kg/cm2), or kilopond per square centimeter is a unit of pressure. kilogram-force per square centimeter is also known as ksc instead of kg/cm2.
Pressure measurements can be made in a number of units.  we see PSI ( pounds per square inch), bar. Other units of measure are mmwc (millimeter of water column), inH2O, mmHg (millimeter of mercury), Pa(Pascal), MPa (Mega Pascal) and many others.

Now we will see the relation between the units of the pressure gauge

1 kg per square centimeter = 14.22 PSI ( pounds per square inch)

1 kg per square centimeter = 10000 mm wc( millimeter of water column)

1 kg per square centimeter = .9807 bar

1 kg per square centimeter = 735.56 mmHg (millimeter of mercury)

1 kg per square centimeter = .9807 MPa ( Mega Pascal)

To know the relation between the other units we can go through with the pressure unit conversion chart on any search engine like- google, bing, yahoo. we can find the pressure unit conversion chart easily.

Dial Size:- Dial size is the diameter of the dial of a pressure gauge. Pressure gauges are available in different dial sizes according to the application. Dial sizes are measured in inches.

Range:- Range of a pressure gauge is the range of pressure indicated by a pressure gauge. Pressure gauges are available in different ranges.

Bourdon tube Pressure Gauges

Bourdon tube pressure gauges are 3 types-


Helical Type

Spiral Type

The following are the commonly used Bourdon tubes used in industries:

Spiral –Low range 0-1 kg/cm2.

C type –Medium range  0 –  up to 50kg/cm2.

Helical – High range 0 –  up to 300kg/cm2 and above.

So we will use the Pressure gauge according to the process requirement.

When pressure is above than 50 kg/cm2 we don’t use a C- type bourdon tube because on high-pressure C- type bourdon tube may be bend.

Use of spring in Pressure Gauge

A spring is used for come back the pointer when pressure is released.

Purpose of hairspring is to push the pointer back to zero when there is no pressure in the tube and to reduce play between gears. It is also called as backlash spring.

Types of pressure gauges  According to Range

Pressure gauges are of three types according to the range.

1. Pressure Gauge.

2. Vaccum Gauge.

3. Compound Gauge.

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