Pressure Measurement: Types and Applications

Pressure measurement is an essential activity in instrumentation and control engineering, ensuring the safe and efficient operation of industrial systems. From monitoring critical processes to optimizing equipment, pressure instruments enable monitoring and controlling gases, liquids, and steam with precision and reliability. Each technology used to measure pressure has its own unique operating principle, advantages, limitations, and specific applications.

In this note, we will explore in detail the types of pressure instrumentation, their characteristics, applications and the factors that determine their selection, offering a complete guide for industry professionals.

1. Types of Measured Pressure

Before describing the instruments, it is important to understand the types of pressure that can be measured:

Absolute Pressure: Measured with respect to absolute vacuum (absolute zero pressure).
Gauge Pressure: Measured relative to atmospheric pressure.
Differential Pressure: Represents the difference between two pressure points in a system.
Barometric Pressure: Corresponds to atmospheric pressure.

2. Mechanical Pressure Instrumentation

a. Bourdon pressure gauges

Measuring Principle: They use a curved tube that deforms under pressure; this deformation translates into a scale reading.
Advantages:
- Simple and economical design.
- No power supply required.
Disadvantages:
- Limited to applications where accuracy is not critical.
- Sensitive to vibrations.
Uses:
- Pressure measurement in water systems.
- Pressure monitoring on compressors and pumps.

b. U-tube manometers

Measuring Principle: They use a liquid as a medium to balance the pressure; the difference in level indicates the pressure.
Advantages:
- High precision for low pressures.
- No moving parts, low maintenance.
Disadvantages:
- Difficult to read in dynamic applications.
- Limited to clean environments.
Uses:
- Laboratories and calibration processes.
- Differential pressure applications.

3. Electronic Pressure Instrumentation

a. Pressure Transducers

Measurement Principle: They convert pressure into a proportional electrical signal using piezoresistive or capacitive elements.
Advantages:
- High precision and stability.
- Ability to integrate with automated control systems.
Disadvantages:
- Sensitive to extreme conditions such as high temperatures.
- Higher cost compared to mechanical instruments.
Uses:
- Control systems in chemical plants.
- Pressure measurement in mobile applications such as heavy machinery.

b. Pressure Transmitters

Measurement Principle: Similar to transducers, but capable of transmitting standard signals (such as 4-20 mA or HART) over long distances.
Advantages:
- Compatible with SCADA and PLC systems.
- Robustness for harsh industrial environments.
Disadvantages:
- They require a stable power supply.
- Sensitive to electromagnetic interference.
Uses:
- Pressure control in oil and gas pipelines.
- Remote monitoring systems.

4. Differential Pressure Instrumentation

a. Differential Pressure Gauges

Measurement Principle: Compare the pressure between two points in a system using diaphragms or U-tubes.
Advantages:
- Ideal for flow and level measurement.
- Compatible with liquids, gases and steam.
Disadvantages:
- Higher installation cost.
- They require periodic maintenance in corrosive environments.
Uses:
- Filtration systems.
- Monitoring flow rates in pipelines.

b. Differential Pressure Transmitters

Measurement Principle: They use electronic sensors to measure the pressure difference and transmit data.
Advantages:
- High precision and reliability.
- Ideal for integration into advanced control systems.
Disadvantages:
- Expensive for simple applications.
- They require regular calibration.
Uses:
- Petrochemical plants and refineries.
- Power generation.

5. Specialized Pressure Instrumentation

a. Piezoelectric Sensors

Measuring Principle: They generate an electrical charge in response to applied pressure.
Advantages:
- High response speed.
- Ideal for dynamic measurements.
Disadvantages:
- Limited in static pressure applications.
- Greater sensitivity to interference.
Uses:
- Internal combustion engines.
- Shock and vibration tests.

b. Optical Pressure Sensors

Measurement Principle: They detect changes in pressure through variations in the light transmitted through optical fibers.
Advantages:
- Resistance to extreme environments (high temperatures, radiation).
- They do not generate electromagnetic interference.
Disadvantages:
- High initial cost.
- Greater installation complexity.
Uses:
- Aerospace and nuclear applications.
- Critical chemical plants.

6. Fluid Based Pressure Instrumentation

a. Barometers

Measurement Principle: They measure atmospheric pressure using mercury columns or electronic sensors.
Advantages:
- High precision in absolute pressure measurement.
- Durable in static applications.
Disadvantages:
- Limited to atmospheric pressure.
- Strict regulations for mercury.
Uses:
- Environmental monitoring.
- Weather applications.

Criteria for the Selection of Pressure Instruments

When selecting a pressure instrument, it is essential to consider the following factors:

Pressure Range: The ability of the instrument to operate within the expected pressure conditions.
Fluid Type: Liquid, gas or vapor, and its properties such as corrosiveness and viscosity.
Required Accuracy: Within tolerable limits of the process.
Environmental Conditions: Temperature, humidity and vibrations.
Compatibility: Instrument materials versus fluid.

Conclusion

Pressure instrumentation is essential for the control and safety of industrial processes. From simple pressure gauges to advanced piezoelectric sensors, each type of instrument offers specific solutions for diverse applications. Understanding the measurement principles, advantages and limitations of each technology is key to selecting the right instrument.

At Acciomate Engineering & Projects , we offer customized solutions for the implementation of pressure measurement systems, optimizing your processes and guaranteeing their efficiency.