Come on friends, today we are going to tell you about Diaphragm Seal. A diaphragm seal is a flexible membrane that seals and isolates an enclosure. The flexible nature of this seal allows pressure effects to pass through the barrier but not contain the material. The common use for diaphragm seals is to protect the pressure sensor from the fluid whose pressure is being measured.
Material
Because diaphragm seals need to be highly flexible, elastomers are commonly used, and include a wide variety of both general purpose and specialty rubber. Elastomers are limited to low pressure applications and those that are chemically compatible with the use of various plastics and rubbers.
Metal diaphragms of stainless steel (many grades), Carpenter 20, Hastelloy, Monel, Inconel, tantalum, titanium and many other metals are in common use where high pressure ratings and specific chemical compatibility are required. Flanged assembly or flush welded versions are available. Depending on the PSI levels of the ceiling application, the diaphragm may require fabric reinforcement. Typically, a PSI of less than 5 does not require fabric reinforcement. A PSI between 5 and 10 is dependent on the application. Anything above 10 will almost always require fabric reinforcement.
Application
Diaphragm seals (also known as chemical seals or gauge guards) are also used to protect the process fluid from the pressure sensor. Examples of this usage are:
- Sanitary procedures (food, pharmaceuticals, etc.) where allowing process fluid to accumulate in the pressure port of the sensor would compromise the purity of the fluid (such as milk entering the pressure port of the pressure gauge and spoiling)
- Very pure process fluids, where the metal surface of the pressure sensor may contaminate the fluid (such as copper ions in ultra pure water from brass leaching.)
- Pneumatic systems where small changes in pressure must be eliminated, such as those that control air bearings .
Seal failure
Diaphragm seals are susceptible to failure through several mechanisms, including cracking . Ozone cracking can occur in many elastomers for example those used in pneumatic systems. If gas contaminates the air supply, many rubber diaphragms are at risk from the problem.
