Key Takeaway
A Bourdon tube pressure gauge operates using a C-shaped, hollow metal tube that flexes when internal pressure increases. As fluid enters the tube, the pressure causes the tube to straighten slightly. This movement is transferred through a mechanical linkage to a pointer on the dial. The amount of movement is proportional to the pressure applied. Bourdon tubes are made from materials like brass, stainless steel, or phosphor bronze, depending on the application. They are widely used due to their robustness, wide pressure range (from vacuum to thousands of psi), and mechanical simplicity. They require no external power and are commonly used in hydraulic, pneumatic, steam, and gas systems for accurate and reliable pressure measurement.
C-Shaped Tube and Its Response to Pressure
The C-shaped Bourdon tube is the classic pressure sensing element. When pressure enters, the inner arc experiences more force than the outer, causing the tube to straighten slightly.
This movement may only be a few millimeters, but it’s enough to rotate a dial needle across a scale. C-tubes are cost-effective, durable, and widely used in steam, water, and air systems.
But overpressure, vibration, or thermal stress can permanently deform the tube. When this happens, zero error and non-linearity increase. Proper sizing and dampening prevent early failure.
Mechanical Linkages for Pointer Movement
Mechanical linkages bridge the gap between elastic deformation and visible pointer movement. The most common system includes:
Link arm from the sensing element
Pivot shaft that rotates with movement
Sector and pinion gears that amplify small motions
The gear ratio determines how much pointer deflection corresponds to pressure change. This design is simple and rugged — ideal for harsh environments. But it’s also prone to wear, backlash, and vibration.
That’s why precision applications often use electronic sensors or digital displays instead of mechanical linkages. Still, for many applications, this tried-and-true method works flawlessly when maintained.
Material Selection for Tube Durability
The sensing tube (Bourdon, diaphragm, or bellows) must withstand:
Internal pressure
Media chemical attack
Environmental factors (temperature, humidity)
Common Materials:
Brass: General purpose; low cost
316 SS: Resistant to moisture, mild chemicals
Monel: For seawater or sulfuric acid
Hastelloy: Handles aggressive acids, chlorides
PTFE-lined: Non-stick and chemical-resistant for corrosive gases/liquids
Tube failure = total gauge failure. Always select based on max pressure, media type, and exposure risks.
Common Applications and Limitations
Common applications of pressure instruments:
Pneumatics and hydraulics
Boiler systems
Water treatment
Filter monitoring
Cleanrooms and HVAC
Oil & gas pipelines
Limitations:
Mechanical wear over time
Inaccuracy under vibration or extreme temperatures
No data transmission (for analog gauges)
Limited readability in poor lighting or dirty conditions
Overcoming limitations:
Use digital or smart gauges for remote data
Use snubbers, seals, or filled cases in harsh environments
Calibrate regularly to reduce drift and error
Proper selection and care reduce the impact of these limitations.
Why Bourdon Gauges Dominate Industrial Use
Bourdon tube pressure gauges are the most widely used mechanical pressure instruments in industry. Their design, invented in the 1840s, remains the standard today.
Reasons for dominance:
Wide pressure range: 0–60000 psi
Simple and cost-effective
No external power needed
Durable and shock-resistant
Customizable dials and scales
They work by flexing a curved metal tube when pressure is applied. This motion is converted to dial movement. Available in many materials (brass, bronze, stainless steel), they serve industries from HVAC to oil & gas.
Their versatility, affordability, and simplicity make them the default choice wherever pressure needs to be displayed locally.
Conclusion
The Bourdon tube pressure gauge has stood the test of time for a reason—its simple mechanical principle offers durability, reliability, and accuracy across a wide range of applications. The design features a curved tube that straightens under pressure, converting force into pointer movement. It’s cost-effective, requires no power, and can operate in harsh environments. Bourdon gauges are widely used in industries like oil and gas, manufacturing, HVAC, and power generation. They perform best in medium to high-pressure systems and offer long service life with minimal maintenance. This classic design continues to deliver dependable performance where precision and ruggedness are required daily.