• Threaded Design

  This design ensures a positive sealing surface. One benefit is that the diaphragm can be replaced if damaged.
• Welded or Bonded Design

  • Metallic Diaphragm: welded to top housing.
  • Elastomeric Diaphragm: bonded to top housing.

  Both of these configurations ensure maximum leak integrity.
• Clamped Design

  These are available with elastomeric diaphragms only. The diaphragm is clamped between top and bottom housing.

The maximum allowable working pressure is sometimes seen noted as MAWP. It can be the maximum psi on threaded and inline seals or the flange class on flanged seals.

Ensure the instrument full scale range does not exceed the rated pressure of the diaphragm seal. Flanged seal class ratings are in accordance with ASME B16.5.

If the diaphragm seal will be used with a differential pressure instrument, the instrument static pressure should not exceed the rated pressure of the diaphragm seal.

Some applications may require a flanged seal. These types of seals are often used when the media exhibits high temperature or the potential to clog an instrument connection.

Examples of flanges available raised face, flat face or ring joint flange.

When selecting the required system assembly fill fluid, lower housing and diaphragm material, ensure minimum and maximum temperature limits are compatible with the selected fill fluid, diaphragm and lower housing materials.

When the requirement is for a flanged seal, refer to ASME B16.5 for pressure and temperature limits.

• Flanged Type Seals

  Standard flange material is nickel plated carbon steel.
• Threaded Type Seals

  When a clamped ring is offered, standard material is black painted carbon steel.
• Clamping Bolts

  Standard bolt material is zinc plated carbon steel. In some instances this is not compatible with environmental conditions and a different bolt material will need to be selected.

Both the diaphragm and lower housing are 'wetted parts' and must be compatible with the process media. Be sure to confirm material compatibility.

Be sure to note that process temperature limits and concentration are a requirement when selecting lower housing and diaphragm material.

All diaphragm seals require a fill fluid as part of the final application assembly.

Process temperature and process media compatibility is important when selecting the correct system fill fluid.

A fill fluid other than glycerin is required for vacuum and compound gauge ranges. Glycerin fill is not available when capillary is required between the instrument and diaphragm seal.