Introduction
Diaphragm
Seals Protect Pressure Instruments. We will explore the
construction, principle of operation and the significant advantages
that diaphragm seals provide.
Diaphragm Seals
can go by different names depending on their application. For
example, when a diaphragm seal is used to isolate a pressure
instrument from corrosive media, it is often called a Chemical
Seal. When it’s used to protect against pressure pulsations
and shocks it is often referred to as a Snubber.
Construction of Diaphragm Seals
Diaphragm seals consist of two key elements: A Flexible Diaphragm and a Pressure Transfer Fluid. The flexible diaphragm, often crafted from durable materials like stainless steel, an exotic alloy, PTFE, or elastomer, acts as a barrier between the process medium and the pressure-measuring instrument. Commonly, there is an Upper Housing where the pressure instrument is connected, and the Diaphragm & Lower Housing which are exposed to the process media. A Fill Fluid fills the void between the diaphragm and the pressure instrument.
The pressure instrument is either directly connected to the diaphragm seal, or a pipe fitting, or a long capillary is used. Capillaries are used for remote mounting of the pressure instrument and also for temperature reduction.
PDF comparing high-temperature assemblies.
Rather than a pipe fitting, a pressure snubber can be used to connect the instrument to the diaphragm seal, providing pressure pulsation dampening. The snubber's correct amount of restriction, or porosity, must be chosen for the application.
Principle of Operation
The principle behind diaphragm seals is based on hydrostatic pressure transmission. When the process medium exerts pressure on the diaphragm, it flexes or deforms accordingly. This deformation is then transmitted through a filling fluid, allowing accurate pressure measurement by the connected instrument. There must be no air or gas mixed with the fill fluid. Special vacuum pumps and heating systems are used to pretreat the fill fluid and evacuate the void between the diaphragm seal and the pressure instrument. Any presence of gas in the fill fluid is compressible so pressure will not be accurately transmitted. This procedure is usually done by a supplier with the needed lab equipment.
Benefits of Diaphragm Seals in Industrial Applications
1. Protection: Diaphragm seals provide a protective barrier, shielding the pressure-measuring instrument from corrosive, abrasive, or viscous process media. This safeguarding enhances the longevity of the instrument and reduces maintenance requirements.
2. Temperature Resistance: Diaphragm seals enable pressure measurement in high-temperature environments. Their flexible nature acts as a thermal barrier, ensuring accurate readings even in extreme temperature conditions encountered in applications such as steam systems or chemical processes.
3. Handling Challenging Conditions: Diaphragm seals excel at pressure measurement in applications involving solid particles or viscous substances. The seal's design prevents particles from entering the pressure instrument, enabling accurate measurements in demanding process conditions.
4. Multiple Instruments: Multiple instruments can be connected to one diaphragm seal, utilizing the same pressure connection.
Choosing the Right Diaphragm Seal
Selecting the appropriate diaphragm seal is crucial for optimal performance and longevity. Consider factors such as compatibility with the process medium, pressure range, accuracy requirements, and specific process conditions. Lower pressure applications or when instruments with higher volumetric displacements are used, are times when larger diaphragm diameters are needed. Defining the application and consulting with experts can provide invaluable guidance throughout the selection process.
Conclusion
Diaphragm seals
play a crucial role in industrial applications. By effectively isolating
the pressure instrument from the process medium, these seals provide
reliable and precise readings while offering protection against
corrosive substances and for other difficult applications.
Understanding the construction, principle of operation, and benefits of diaphragm seals allows for informed decision-making when selecting the appropriate seal for a specific application. With the use of diaphragm seals, industries can enhance the performance, efficiency, and safety of their processes by obtaining accurate and reliable pressure measurements.
Store link to Pressure Gauge and Diaphragm Seal Assemblies.
Do you have a question about using a diaphragm seal or how it operates? Would you like assistance with your application? We can help.
