Diaphragm Seals

Brand: PIC Gauges

Your First Choice for Diaphragm Seals

Your pressure instruments are a major investment and you need to make sure they aren't damaged by process media.

The solution for this is the use of diaphragm seals, to protect your system from high temperatures and corrosive, toxic, and viscous process fluids, as well as fluids that solidify at low temperatures.

Diaphragm seals create a barrier between the process media and the pressure sensing element, without compromising the instrument's sensitivity or accuracy.

Made from a thin pressure-sensitive film comprised of either plastic or metal, diaphragm seals are typically threaded onto pressure gauges.

The air between the diaphragm seal and the pressure sensing element is then vacuumed out and replaced with a non-compressible fluid.

The process media presses on the seal, flexing it and pushing on the non-compressible fluid, in turn flexing the pressure sensing element.

Subsequently, the diameter of the diaphragm seal dictates the pressure at which the seal reads accurately.

Selecting a Diaphragm Seal

There are several factors to consider when choosing a diaphragm seals. Typical connection types to select from include threaded, flanged, welded, and sanitary options.

Sanitary connections are essential for industries such as food and beverage, where process media must not be contaminated.

The material used is usually selected to ensure that it does not react or corrode from contact with the process media.

With threaded diaphragm seals, the material that contacts the process media can be different than the non-contacting material, which could save money when an exotic metal is required.

Minimum and maximum system pressures must also be considered. Large seals measure lower pressures, while smaller seals measure higher pressures.

It's also important to consider the size of the diaphragm seal. Due to the limitations in the weight some threads and welds can hold, some seals will not work with disproportionately large pressure gauges.

Mini Seals

These miniature seals have a compact design to reduce the space they take up in your processes. The threaded connections are available with our without flush ports. These seals cover pressure ranges from 200 to 6,000 psi.

Flanged Seals

These seals match the ASME standards for flanged connections, with flange rates ranging from 150# to 1500#. Sizes range from 1.5" to 3." Seals include a through-hole flange design for easy installation.



Fill Fluid

  • Fillable = Glycerin, Low Temperature Glycerin, Silicone, Low Temperature Silicone, Fluorolube, Halocarbon Oil, Vaseline, Fluorocarbon, Slytherm, Paraffin Oil

Process Connection

  • Mini Diaphragm Seals: 1/4” FNPT, 1/2” FNPT, 3/4” FNPT, 1” FNPT
  • Sanitary Diaphragm Seals: 1/2” to 4” Tri-Clamp
  • Flanged Diaphragm Seals: 1/2” FNPT, 3/4” FNPT, 1” FNPT, 1-1/2” FNPT, 2” FNPT, 3” FNPT, Flange Class 150 #, 300 #, 600 #, 900 #, 1500 #

Connection Type

  • Mini Diaphragm Seals: Welded
  • Flanged Diaphragm Seals: RF Flanged

Available Options

  • Custom Upper Housing, Lower Housing, and Seal Materials
  • 1/4” Flushing Connection on Lower Housing
  • Special Connection Size
  • Male Threaded Process Connection
  • Oxygen Cleaned
  • Material Analysis Certificate
  • Without fill-port
  • 1/2” and 3/4” Tri-Clamp dimensions available upon request
  • RTJ or other facings available upon request
  • High temperature with Grafoil gasket

Upper Housing

  • Carbon Steel or Stainless Steel

Low Housing

  • Stainless Steel
  • Carbon Steel
  • Tantalum
  • Monel
  • PTFE
  • Carpenter 20
  • Hastelloy C-276


  • Carbon Steel
  • Stainless Steel
  • Tantalum
  • Monel
  • PTFE
  • Carpenter 20
  • Hastelloy C-276

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