A diaphragm seal pressure gauge makes use of chemical seals that isolate the pressure gauge, switch and transmitter from clogging and/or corrosive media. A standard material that is often used on the diaphragm seals is stainless steel however; other materials like carbon steel can be used based on the specific demands of the industrial application. What makes the diaphragm seal pressure gauge different form all other gauges is its pressure application from 10” H2O to 15,000 psi and media temperature between -130oF and 752oF.

Typical applications of the diaphragm seal pressure gauge

  • Where the media is corrosive and bound to damage a sensitive element such as a pressure switch or transmitter diaphragm
  • When the temperature of the media may be quite high for a standard gauge, switch or transmitter to function properly
  •  When media is highly viscous with a tendency to crystallize or polymerize which can clog the pressure port of the gauge, switch or transmitter
  • In situations where remote reading is required. The diaphragm seal with the capillary line allows for the remote installation of the pressure instrument
  • When a high level of sanitary cleanliness is required
  • When the media is either toxic or hazardous to pollute the environment. The diaphragm seal will provide the necessary protection
  • When the industrial applications requires high pressure protection and mandatory exact pressure data. The diaphragm seal with a contoured diaphragm bed can be configured to provide the overpressure protection as well as protection for the instrument.

Details that must be considered in selecting a diaphragm seal pressure gauge

  • Process composition – it is critical to choose the materials of the diaphragm and lower housing of the diaphragm seal that will be compatible to the process medium. There are many reference guides and tables that will assist in the selection of materials.
  • Temperature – for accuracy of the final output, it is important that the temperature of the process and the environment must be specified when selecting the diaphragm seal. For temperatures above 330oF, a cooling element or capillary is suggested in order to protect the pressure instrument.
  • Pressure range –  Normally, the lower the pressure range, the larger the diaphragm is required to “drive” the system and conversely, the higher the pressure ranges, the smaller the diaphragm is necessary.
  • Pressure instrument – the general rule is the smaller sized gauges are better for low pressure applications since less displacement volume is required on the part of the diaphragm seal to drive the pressure instrument.
  • Process connection – most of the process connections are threaded, flanged or clamped.
  • System fill fluid – it is important to consider chemical compatibility of the system fill fluid and the process fluid in the event of a leak. Special system fill fluids like oxygen and chlorine are available for oxidizing media.
  • Mounting position – important for the diaphragm seal pressure gauges that include a capillary.  The level difference between the diaphragm seal and the pressure instrument can cause a hydrostatic pressure to act on the sensing element.