Bourdon tube pressure gauge: Definition, Diagram, Working, Principle, Construction, Application, Advantages and disadvantages [with Pdf]

what is Bourdon tube pressure gauge ?

A Bourdon tube pressure gauge is a mechanical device used to measure the pressure of gases or liquids in various industrial applications. It is named after its inventor, Eugène Bourdon, a French engineer who developed the design in the mid-19th century.

The gauge consists of a curved, hollow metal tube, typically made of brass or stainless steel, which is closed at one end and connected to the pressure source at the other end. When pressure is applied, the tube tends to straighten due to the internal pressure, which causes the free end of the tube to move. This movement is then converted into a rotational motion through a series of linkages and levers, and it is displayed on a dial as the pressure reading.

It is also known for their reliability, accuracy, and durability. They can measure a wide range of pressures, from a few inches of water column to several thousand pounds per square inch (psi). These gauges are commonly used in industries such as oil and gas, chemical processing, power generation, HVAC systems, and automotive applications.

They are available in various configurations, including different pressure ranges, connection types (such as bottom or back entry), and dial sizes. Some gauges also incorporate additional features like dampening mechanisms to mitigate pointer oscillation caused by pulsating pressures.

Regular calibration and maintenance are essential to ensure accurate readings over time. Bourdon tube pressure gauges are often calibrated against known pressure standards to maintain their reliability and accuracy.

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history

The Bourdon tube pressure gauge was invented by Eugène Bourdon, a French engineer, in the mid-19th century. Bourdon developed the design in 1849 while working at the Conservatoire National des Arts et Métiers in Paris.

The inspiration for the Bourdon tube came from observing the behavior of flexible metal tubes under pressure. Bourdon noticed that when pressure was applied to a curved tube, it tended to straighten out. This observation led him to create a closed-end, curved tube that could be used to measure pressure.

In 1851, Bourdon patented his invention, which was initially used in steam engines and locomotives to monitor and control pressure. The Bourdon tube pressure gauge quickly gained popularity due to its reliability and accuracy compared to existing pressure measurement devices of the time.

Over the years, advancements were made to enhance the performance and versatility of Bourdon tube pressure gauges. Different materials were used to improve durability and resistance to corrosion, with brass and stainless steel being common choices.

Bourdon tube pressure gauge working principle

The Bourdon tube pressure gauge operates based on the elastic properties of the Bourdon tube. When a pressure is applied, the oval or elliptical-shaped tube tends to regain its circular shape due to hoop stresses acting on the tube wall. This causes the C-shaped tube to straighten.

To amplify this movement, a gear sector and pinion arrangement is employed. The rotational motion of the Bourdon tube is transferred to a gear sector, which in turn engages with a pinion. This mechanism converts the linear movement of the Bourdon tube into rotational motion.

The rotational motion is then transmitted to a pointer or needle, which moves along a calibrated dial. The dial is marked with pressure values, allowing the user to read the pressure directly.

In summary, the elastic nature of the Bourdon tube enables it to deform and straighten under pressure, while the gear sector and pinion arrangement amplify this movement for accurate pressure measurement.

Bourdon tube pressure gauge working Step by step

The working principle of a Bourdon tube pressure gauge involves the following steps:

Bourdon Tube Structure: The Bourdon tube is a curved, hollow metal tube usually made of brass or stainless steel. It has a fixed end and an open end, and its cross-section is typically elliptical or oval-shaped.
Pressure Application: The open end of the Bourdon tube is connected to the pressure source through an inlet. The pressure being measured enters the tube.
Elastic Deformation: As the pressure enters the Bourdon tube, it exerts a force on the tube’s walls. Due to the tube’s elastic properties, it tends to regain its circular shape, resulting in the straightening of the curved tube. This deformation occurs primarily due to the hoop stresses acting on the tube wall.
Tube Movement: The straightening of the Bourdon tube causes the free end (opposite the fixed end) to move. This movement can be in the form of an arc or rotation.
Linkage Mechanism: The movement of the free end of the Bourdon tube is transmitted to a linkage mechanism. The linkage consists of gears, levers, and pinions that convert the linear motion of the Bourdon tube into rotational motion.
Pointer and Dial: The rotational motion is then transferred to a pointer or needle, which is mounted on a central axis. The pointer moves along a calibrated dial that is marked with pressure values.
Pressure Reading: The position of the pointer on the dial indicates the pressure being measured. The user can read the pressure value directly from the dial, typically in units such as pounds per square inch (psi), bar, or kilopascal (kPa).

It’s important to note that the calibration of the Bourdon tube pressure gauge is essential to ensure accurate readings. The gauge may need periodic calibration against known pressure standards to maintain its accuracy over time.

Overall, the working principle of a Bourdon tube pressure gauge is based on the elastic deformation of the curved tube under pressure, which is converted into rotational motion and displayed as a pressure reading on a dial. This mechanical design has made Bourdon tube pressure gauges widely used and reliable instruments for pressure measurement in various industrial applications.

Bourdon tube pressure gauge construction

The construction of a Bourdon tube pressure gauge involves several key components:

Bourdon Tube: The primary component is the Bourdon tube, which is a curved, hollow metal tube. It is typically made of materials like brass or stainless steel. The tube is C-shaped or helically coiled and has a fixed end and an open end.
Pressure Inlet: The open end of the Bourdon tube is connected to a pressure inlet. The inlet allows the pressure being measured to enter the tube.
Linkage Mechanism: The movement of the Bourdon tube is transmitted to a linkage mechanism. This mechanism typically consists of gears, levers, and pinions that convert the linear motion of the Bourdon tube into rotational motion.
Pointer and Dial: The rotational motion is transferred to a pointer or needle, which is mounted on a central axis. The pointer moves along a calibrated dial that is marked with pressure values. The dial may also include other markings or indicators.
Case: The components of the Bourdon tube pressure gauge are housed within a case. The case provides protection and support for the internal components, ensuring their proper functioning.
Window: The case often features a transparent window made of glass or plastic. The window allows for easy viewing of the dial and pointer, protecting them from external elements.
Connection Fittings: The Bourdon tube pressure gauge may include connection fittings at the pressure inlet. These fittings can vary depending on the specific application and requirements. Common types include bottom entry and back entry connections.
Mounting: The pressure gauge is designed for mounting on a panel, instrument cluster, or other suitable surfaces. It may feature mounting holes or brackets to facilitate installation.

The construction of a Bourdon tube pressure gauge may vary slightly depending on the manufacturer and specific model. However, the key components mentioned above form the basic construction of these pressure measurement instruments.

How Bourdon Pressure Gauges Work

The Bourdon tube is indeed the central component of the Bourdon gauge. It is typically manufactured in a semi-circular C-shape or a coiled shape. The tube has one end open to the atmosphere and the other end sealed closed.

When the system pressure increases, it applies pressure to the inside of the tube, causing it to expand and straighten. Although the change in shape is relatively small, it is magnified due to the inherent design of the tube. This straightening or expansion of the tube is directly proportional to the applied pressure.

The movement of the Bourdon tube is then transferred to the indicator needle through a mechanical linkage. As the tube expands or straightens, the needle moves accordingly, allowing personnel to visually observe the pressure within the system. The dial of the gauge is calibrated with pressure values, enabling direct readings of the system pressure.

The Bourdon tube’s design and elasticity make it a reliable and accurate mechanism for pressure measurement in various applications. Its small but significant changes in shape provide a proportional indication of the pressure being measured, allowing for effective monitoring and control.

types of bourdon tube pressure gauge

There are several types of Bourdon tube pressure gauges, each designed to suit specific applications and requirements. Here are some common types:

C-Type Bourdon Tube: This is the most basic and widely used type of Bourdon tube pressure gauge. It has a C-shaped curved tube, and the movement of the free end is directly translated into pointer rotation.
Spiral or Helical Bourdon Tube: In this type, the Bourdon tube is coiled into a spiral or helical shape. The spiral design allows for greater movement and sensitivity, making it suitable for measuring low pressures or differential pressures.
Spiral Wound Bourdon Tube: This type consists of multiple layers of thin, corrugated Bourdon tubes wound together. It provides higher sensitivity and is often used for precise pressure measurements in laboratory or research applications.
Diaphragm Bourdon Tube: In diaphragm Bourdon tube gauges, a flexible diaphragm is attached to the end of the Bourdon tube. The diaphragm amplifies the displacement, resulting in increased sensitivity and accuracy. These gauges are commonly used for low-pressure applications.
Compound Bourdon Tube: A compound Bourdon tube gauge combines two C-shaped tubes with different curvatures, forming an S-shaped tube. This design enables the measurement of both positive and negative pressures, making it suitable for applications that require pressure differentiation.
Differential Pressure Bourdon Tube: These gauges are specifically designed to measure pressure differences between two separate sources. They have two or more Bourdon tubes connected to different pressure inlets, allowing for the measurement of differential pressures.
Capsule Bourdon Tube: In capsule Bourdon tube gauges, two curved metal diaphragms are sealed together to form a capsule. The pressure difference between the inside and outside of the capsule causes deflection, enabling the measurement of very low pressures.

These are some common types of Bourdon tube pressure gauges. The selection of the appropriate type depends on factors such as the pressure range, sensitivity requirements, and the nature of the application.

calibration of bourdon tube pressure gauge

Calibration of a Bourdon tube pressure gauge can be carried out using a deadweight tester. A deadweight tester is a device that applies known and traceable pressures to calibrate pressure gauges accurately. Here’s how the calibration process is performed using a deadweight tester:

Setup: Prepare the deadweight tester and ensure it is properly calibrated and traceable to national or international standards. Set up the equipment according to the manufacturer’s instructions.
Reference Pressure: Set the deadweight tester to the desired reference pressure. This is typically done by adjusting the weights on the piston assembly of the deadweight tester.
Pressure Application: Connect the Bourdon tube pressure gauge being calibrated to the deadweight tester. Ensure a proper seal is formed to prevent pressure leakage. The deadweight tester applies the reference pressure to the gauge.
Comparison: Compare the reading on the Bourdon tube pressure gauge with the known reference pressure applied by the deadweight tester. Take note of any deviations or differences between the gauge’s reading and the reference pressure.
Adjustment: If there are significant deviations, adjust the gauge to align its readings with the known reference pressure. This may involve mechanical adjustments, such as modifying the pointer position or adjusting the tension within the Bourdon tube.
Verification: Repeat the process by applying different reference pressures across the gauge’s range. Verify the gauge’s readings against the corresponding known reference pressures. Make any necessary adjustments to improve accuracy if deviations are found.
Calibration Certificate: Document the calibration process by generating a calibration certificate. The certificate should include details such as the date of calibration, reference standards used, adjustments made, and the gauge’s calibration results. This certificate serves as a record of the gauge’s accuracy and compliance with calibration standards.

Using a deadweight tester provides a reliable and accurate method for calibrating Bourdon tube pressure gauges. However, it’s important to follow proper procedures and use calibrated and traceable deadweight testers for accurate calibration results.

application of bourdon tube pressure gauge

Bourdon tube pressure gauges have a wide range of applications across various industries. Some common applications include:

Industrial Processes: Bourdon tube pressure gauges are extensively used in industrial processes to monitor and control pressure. They are employed in chemical processing plants, oil refineries, power generation facilities, and manufacturing industries. These gauges provide crucial pressure measurements for maintaining operational efficiency and safety.
Oil and Gas Industry: In the oil and gas industry, Bourdon tube pressure gauges are utilized in upstream exploration and production operations, as well as downstream refining and distribution processes. They are employed to measure pressures in pipelines, storage tanks, wellheads, and offshore platforms.
HVAC Systems: Heating, ventilation, and air conditioning (HVAC) systems rely on Bourdon tube pressure gauges to monitor pressure in various components. They help ensure efficient functioning of boilers, chillers, pumps, and other HVAC equipment.
Automotive Industry: Bourdon tube pressure gauges are used in automotive applications to measure pressures in engines, fuel systems, and hydraulic systems. They provide vital information for engine performance and safety monitoring.
Process Control: Bourdon tube pressure gauges are employed in process control systems to maintain desired pressures in various stages of industrial processes. They help regulate pressure in systems such as water treatment, pneumatic systems, and hydraulic systems.
HVAC and Refrigeration: Bourdon tube pressure gauges find applications in HVAC and refrigeration systems. They are used to measure refrigerant pressures, helping ensure proper functioning and efficiency of cooling systems.
Aerospace and Aviation: Bourdon tube pressure gauges are utilized in the aerospace and aviation industries to measure pressures in aircraft hydraulic systems, pneumatic systems, and aircraft engines. They play a critical role in maintaining safe operation and performance of aircraft.
Research and Testing: Bourdon tube pressure gauges are employed in research laboratories and testing facilities for various scientific and engineering applications. They assist in conducting experiments, monitoring pressure changes, and ensuring accurate data acquisition.

These are just a few examples of the wide-ranging applications of Bourdon tube pressure gauges. Their robustness, reliability, and accuracy make them suitable for numerous industries where pressure measurement is crucial for operational efficiency, safety, and process control.

Advantages of bourdon tube pressure gauge

Bourdon tube pressure gauges offer several advantages, which contribute to their widespread use in various industries. Here are some key advantages:

Reliability: Bourdon tube pressure gauges are known for their reliability and long service life. They are robustly constructed and can withstand harsh operating conditions, including high pressures and temperature ranges.
Accuracy: These gauges provide accurate pressure measurements within their specified range. The Bourdon tube’s elastic deformation ensures precise readings, making them suitable for applications that require precise pressure monitoring.
Wide Pressure Range: Bourdon tube pressure gauges are available in a wide range of pressure ratings, allowing them to measure pressures from very low (e.g., inches of water column) to very high (e.g., thousands of psi) ranges. This versatility makes them suitable for diverse applications.
Simple and Cost-Effective: Bourdon tube pressure gauges have a simple mechanical design, making them cost-effective compared to other pressure measurement technologies. They do not require external power sources or complex electronics, which reduces maintenance and operational costs.
Ease of Installation: These gauges are relatively easy to install and use. They are typically mounted directly on the process line or panel, making them readily accessible for pressure monitoring.
Compatibility: Bourdon tube pressure gauges are compatible with a wide range of fluids and gases, making them versatile in different applications. They can handle various media such as water, oil, air, steam, and corrosive substances, depending on the gauge’s material and design.
Visual Readability: The dial display of Bourdon tube pressure gauges offers clear and easy-to-read pressure values. The pointer or needle movement provides instant visual feedback, enabling quick and accurate pressure readings.
Mechanical Fail-Safe: In the event of power or electronic failures, Bourdon tube pressure gauges continue to function independently, ensuring continuous pressure measurement. This mechanical fail-safe feature enhances their reliability in critical applications.

Overall, Bourdon tube pressure gauges combine reliability, accuracy, versatility, and cost-effectiveness, making them a preferred choice for pressure measurement in numerous industrial and commercial applications.

disadvantages of bourdon tube pressure gauge

While Bourdon tube pressure gauges offer many advantages, there are also some limitations or disadvantages associated with their use. Here are a few:

Sensitivity to Vibrations and Pulsations: Bourdon tube pressure gauges can be sensitive to vibrations and pulsations in the system being measured. These external factors can cause the pointer to vibrate or fluctuate, leading to potential inaccuracies in the pressure reading. Dampening mechanisms or additional accessories may be required to mitigate this issue.
Limited Resistance to Overpressure: Bourdon tube pressure gauges have a defined maximum pressure limit that they can withstand without causing permanent damage. If the pressure exceeds this limit, it can cause the Bourdon tube to permanently deform or even rupture, rendering the gauge inoperable. It is crucial to select gauges with appropriate pressure ratings for the specific application.
Temperature Effects: Extreme temperature variations can affect the accuracy of Bourdon tube pressure gauges. High temperatures can lead to expansion or contraction of the metal tube, impacting the calibration and readings. Some Bourdon tube gauges are specifically designed for high-temperature applications to mitigate this issue.
Limited Ability for Remote Monitoring: Bourdon tube pressure gauges provide local visual readings on the dial. They do not have built-in electronic sensors for remote monitoring or data logging. If remote pressure monitoring or integration with control systems is required, additional devices or transmitters may be needed.
Gradual Wear and Aging: Over time, Bourdon tube pressure gauges may experience wear and aging due to mechanical movement and exposure to harsh operating conditions. This can lead to a gradual decrease in accuracy and reliability. Regular calibration and maintenance are necessary to ensure accurate readings and extend the gauge’s lifespan.
Size and Weight: Compared to some other pressure measurement technologies, Bourdon tube pressure gauges can be relatively larger and heavier. This factor may limit their application in certain space-constrained or weight-sensitive environments.

It’s important to note that while these disadvantages exist, Bourdon tube pressure gauges remain widely used and trusted for pressure measurement in numerous industries due to their overall reliability, accuracy, and cost-effectiveness. However, it’s essential to consider the specific requirements and potential limitations when selecting a pressure gauge for a particular application.

Reference : https://www.wika.com/en-in/lp_bourdon_tube_pressure_gauge.WIKA