Bourdon Tube, Diaphragm, and Bellows Gauges
Accurate pressure measurement is vital in industrial, commercial, and laboratory applications. From steam boilers and hydraulic presses to HVAC systems and pneumatic tools, pressure monitoring ensures safe and efficient operation. Among the various instruments used, Bourdon tubes, diaphragms, and bellows gauges are widely trusted for their reliability and precision.
1. Bourdon Tube Pressure Gauges
Working Principle
The Bourdon tube is one of the oldest and most commonly used mechanical pressure sensors. It consists of a curved, hollow metal tube sealed at one end. When pressure is applied inside the tube, it tends to straighten due to the force exerted by the pressurized fluid. This movement is mechanically linked to a pointer that moves over a calibrated dial.
Applications
Steam boilers
Hydraulic systems
Compressors
Process industries
Advantages
Cost-effective
Simple and robust
Suitable for a wide range of pressures (vacuum to very high pressures)
No external power needed
2. Diaphragm Pressure Gauges
Working Principle
A diaphragm gauge uses a flexible membrane (usually metal or elastomer) that deflects when pressure is applied on one side. The deflection is proportional to the pressure and is transmitted to a mechanical or electronic indicator. These gauges are especially useful for low-pressure measurement.
Applications
Gas pressure measurement
Chemical and pharmaceutical industries
Water treatment plants
Food and beverage production
Advantages
Accurate for low pressures
Can be designed with corrosion-resistant materials
Can handle contaminated or viscous fluids with less clogging
3. Bellows Pressure Gauges
Working Principle
Bellows-type pressure gauges operate using a set of collapsible, accordion-like components that expand or contract when pressure is applied. These bellows can be metallic or synthetic and are extremely sensitive to pressure changes. Their movement is transmitted via linkages to a pointer or sensor.
Applications
HVAC and refrigeration
Medical instruments (like anesthesia machines)
Differential pressure measurement
Environmental monitoring
Advantages
High sensitivity and accuracy
Good for low differential pressure readings
Can measure both positive and negative pressures
Suitable for compact instruments
Comparative Summary
| Feature | Bourdon Tube | Diaphragm | Bellows |
|---|---|---|---|
| Pressure Range | Wide (Low to Very High) | Low to Medium | Very Low to Medium |
| Sensitivity | Moderate | High (at low pressures) | Very High |
| Suitability | General Industrial Use | Clean Gases, Corrosive Media | Delicate, Precision Applications |
| Cost | Low | Medium | Medium to High |
| Size | Compact to Medium | Compact | Compact |
Understanding the right pressure gauge to use depends on your application's range, sensitivity, and environmental conditions. Bourdon tubes are great for rugged, high-pressure environments. Diaphragm gauges excel in low-pressure, sensitive media. Bellows offer unmatched accuracy where minimal pressure changes need to be detected.
Choosing the correct pressure measurement instrument ensures safe operation, system integrity, and optimized performance.