Used as protective devices designed to isolate pressure gauges, pressure transmitters, and pressure switches from potentially damaging process media, diaphragm seals provide effective solutions to protecting pressure instruments when and if applied. They are typically used in refining, petrochemical, and chemical plants, dramatically extending the lifetime of various instruments by preventing contact between dangerous hot or corrosive media and the gauge itself.
Seals were especially designed to meet the safety demand requirements of the process industry to offer the utmost of protection against harsh temperatures, variable pressure ranges, pulsation, vibration, aggressive chemicals, and steam. The AWS design is strong enough to endure high vibration and thermal cycling applications, making it suitable for pump discharge applications.
Understanding How the Seal Actually Works
A diaphragm seal is usually connected to the measuring instrument using a direct connection or capillary. It is an elastomer or flexible metal diaphragm that keeps the process media from coming into contact with the workings of the gauge. The chamber between the diaphragm and the instrument contains system fill fluid, which transfers the pressure of the process media. When fluctuations in pressure of the process media occur, the change is transmitted across the flexible diaphragm through the system fill fluid, which is hydraulically transmitted to the measuring instrument.
Diaphragm seals are easily mounted onto gauges using threaded, flanged, in line, sanitary, or other types of connections, and in most cases, are made out of stainless steel. Others materials such as carbon steel and Hastelloy® C-276 can also be used for specific applications. There are also times that they are installed on pressure transmitters and switches that can be exposed to extreme conditions.
When to Use a Diaphragm Seal
Simply put, a diaphragm seal should be used whenever there is highly toxic or dangerous media present that could potentially harm an instrument. Most of the time, an all-welded process gauge and diaphragm seal system can provide protection to minimize the chance of any toxic media escaping. The usage of a diaphragm seal should also be considered under other conditions including:
• High-temperature media – Contains a cooling element that can protect the instrument, such as a diaphragm seal with an 8″ cooling tower that can tolerate temperatures of up to 750°F.
• Viscous or crystallizing media – Reduces the number of connections in a process by minimizing internal cavities where clogs usually form.
• Media with suspended solids – Minimizes clogging in process applications that include pharmaceutical, pulp and paper, food and beverage, chemical, and waste water.
• When overpressure protection is required – There are seals available with continuous-duty contoured diaphragm beds for robust overpressure protection.
• Corrosive media – Seals can be made using a variety of custom alloys, including PTFE, gold and silver, or carbon steel.
Recommended Remote Seals
These are the recommended remote seals for the refining, petrochemical, and chemical industries:
• Standard Flush Diaphragm Seal, Flanged
• Pancake Type Water Seal with Flush Diaphragm, Flanged
• Rotatable Flush Diaphragm Seal, Flanged
• Standard Version, Welded Diaphragm Seal, Threaded
• All Welded System (AWS), Threaded
Let Us Help
For more information on top quality diaphragm seals specifically designed to fit your wants and needs, contact REAL SEAL. Sometimes, a small investment in the right seals can definitely pay off over the long run by not only lengthening the lifetime of your pressure measurement instrumentation, but also leading to significant cost savings.
