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Mini Hermet Pressure Switches

Mini-Hermet pressure switches are robust field-mounted instruments. The pressure sensing assembly is similar to a conventional SOR type. The main difference is that the switching element assembly is hermetically sealed in an explosion proof steel capsule.

The pressure sensing element of the SOR Pressure Switch is a force-balance, piston-actuated assembly. The sensing element is sealed by a flexible diaphragm and a static o-ring. There are only three wetted parts in this arrangement: a pressure port, a diaphragm and an o-ring. A wide selection of wetted parts materials for media compatibility and containment are available. A metal diaphragm may be welded to the pressure port for certain applications, thereby eliminating the o-ring (Designators U8 and U9). Media pressure on the piston counteracts the force of the range spring (adjustable by the adjusting screw) which moves the piston shaft only a few thousandths of an inch to directly actuate the electrical snap-action switching element that is enclosed in the hermetically sealed steel capsule. This design results in low friction and virtually no wear. The electrical switching element is isolated from corrosive atmospheres.

Basic Mini-Hermet pressure switches in AG or AH housings with standard wetted parts are normally suitable for air, oil, water and non-corrosive process applications in hazardous locations and hostile environments where space is limited.

Mini-Hermet pressure switches in the AG and AH housings are normally suitable for a variety of process applications in hazardous locations and hostile environments because the electrical switching elements are hermetically sealed in a stainless steel capsule that is UL Listed, CSA Certified, ATEX and SAA Approved as an explosion-proof snap switch. Specific customer or code requirements for the complete pressure switch to be UL Listed, CSA Certified or ATEX/IECEx Approved can normally be met by specifying an AP, AS, BG or BH and U8 diaphragm system.

These switches utilize a Piston-Spring combination to determine the adjustable ranges. 

Configuration choices are available for:

  1. Housing - To be used in different application conditions such as Explosion Proof or Weathertight
  2. Switching Element - for different AC/DC ratings and dead bands
  3. Diaphragm and O-Ring - for different process medium compatibilities
  4. Pressure port - for different process mediums and process connection sizes
  5. Accessories - For miscellaneous such as Certificates, Special Coatings, Additional Tests

Specific application requirements can normally be met by selecting optional components, such as switching elements, diaphragm systems and pressure ports.

Pressure range: from 30 in. Hg vac. to 4000 psi in varying ranges and different configurations
Housings available: General Purpose NEMA 1, Weatherproof NEMA 4, 4X, IP66, Hazardous Locations Ex-Proof housings
Available O-Ring Material: 

  • Viton
  • Viton GLT
  • Kalrez*
  • Aflas
  • Buna-N
  • Neoprene EPR

Also available in a Fire-Safe/Welded Diaphragm System and TCP Teflon-Coated Polyimide Diaphragm.

For more information on the details and options available, please download Mini-Hermet Pressure Switches (Form CAT456)