SJ Gauge diaphragm seals for pressure instruments

Diaphragm Seals

A diaphragm seal is a protective device installed between the process media and pressure instruments such as pressure gauges, pressure transmitters, or pressure switches. It is designed to isolate viscous, corrosive, high-temperature, or crystallizing media, preventing direct contact with the measuring element and improving operational stability and service life. Diaphragm seals are widely used in food processing, chemical, pharmaceutical, semiconductor, and petrochemical industries.

For more detailed information, please refer to this article:
In What Situation Should A Diaphragm Seal Be Integrated to Your Pressure Gauge?

Diaphragm Seals FAQ

Selection questions for diaphragm seals used with gauges, transmitters, switches, and difficult process media.

When should a diaphragm seal be used?
Use a diaphragm seal when media is corrosive, viscous, high-temperature, crystallizing, contaminated, toxic, sanitary, or likely to clog the pressure instrument. The seal isolates the instrument while transmitting pressure through fill fluid.
How do I choose between threaded, flanged, and sanitary diaphragm seals?
Threaded types are common for compact process connections, flanged types are used for tanks and pipelines, and sanitary clamp or DIN/IDF/SMS designs are selected for food, beverage, pharmaceutical, and clean-in-place systems.
Which diaphragm seal is suitable for corrosive chemicals or PCB processes?
For corrosive media, plastic or corrosion-resistant wetted materials such as PP, PTFE, or suitable coated diaphragms may be required. DIT-PP, DIT-P, DIF-P, and upper-metal/lower-plastic designs are examples used for acidic or alkaline media.
Can a diaphragm seal be combined with capillary tubing?
Yes. Capillary tubing is useful when the instrument must be installed away from high temperature, vibration, inaccessible areas, or process connection points. The capillary length and fill fluid should be selected based on temperature and response requirements.
  • SJ Gauge pressure gauge fitted with an upper metal diaphragm seal
    Model: DIF-USLP

    Flanged Connection, Upper Metal, Lower Plastic

    • A metal upper body that connects to the instrument is tight and durable
    • Plastic lower body can protect pressure instruments from corrosive, contaminated or viscous media
    • Suitable for paint, electroplating, sewage treatment and the paper industry
  • SJ Gauge pressure gauge with a metal dual-diaphragm assembly
    Model: DIF-S

    Flanged Connection with Dual Diaphragm

    • Lower pressure ranges can be measured to meet pipeline connection needs and accuracy
    • An alternative when flange diaphragm seal – “I” section type cannot be used due to lack of space
    • Applicable for strict working environments including biogas, oil, gas fracking and biodiesel, etc
  • SJ Gauge pressure gauge fitted with a flanged diaphragm seal
    Model: DIF-F

    Flanged Connection with Flush Diaphragm

    • One-piece seal design bolts directly to process flange
    • Flush-mounted diaphragm prevents clogging of process media
    • Used in applications with difficult media such as machine building and automation
  • SJ Gauge extended diaphragm seal with flanged process connection
    Model: DIF-E

    Flanged Connection with Extended Diaphragm

    • Upper body of the diaphragm seal, the extended diaphragm and the wetted parts can be made of identical or different materials
    • As an alternative, the diaphragm and the extended diaphragm can be coated
    • Used for contaminated, solidifying, hot or highly viscous media such as thick walled or isolated tanks and pipelines
  • SJ Gauge cell-type sandwich diaphragm seal
    Model: DIF-C

    Flanged Connection, Cell (Pancake) Diaphragm

    • Instruments are connected via a side capillary connection and it is an ideal seal for transmitters or DP transmitters
    • Be mounted between an open process flange and an optional cover flange
    • Used for contaminated, solidifying, hot, or highly viscous media
    • An alternative with high compatibility and corresponding specifications to the WIKA 990.28
  • SJ Gauge pressure gauge fitted with a diaphragm seal stub pipe
    Model: DIFF-S

    Flanged Connection with Stub Pipe, Screwed Diaphragm

    • By using diaphragm seals, the measuring instruments can be used at extreme temperatures up to +300 °C
    • The double flange diaphragm can increase the size of the upper body and diaphragm to match the piping connection, requirements, and improve accuracy
    • Applicable to special working environments and corrosive fluids, such as high pressure, high vibration, and concrete
  • SJ Gauge pressure gauge with welded diaphragm stub seal
    Model: DIFF-W

    Flanged Connection with Stub Pipe, Welded Diaphragm

    • Optimizable through the adjustment of the upper seat and diaphragm sizes for precision and to meet the criteria for pipeline connections
    • The short pipe length on the lower body can be manufactured to match the piping’s thermal-insulation requirements.
    • Durability for working environments using liquids that are high temperature, corrosive, sewage, or prone to crystallization
  • SJ Gauge plastic diaphragm seal with corrosion-resistant stub pipe
    Model: DIFF-P

    Flanged Connection with Stub Pipe, Corrosion-resistant Plastic

    • Upper seat and diaphragm can be enlarged to ensure precision and compliance with pipeline connection standards
    • Applicable for media that are corrosive, viscous, powdery, harmful or toxic to the environment
    • Ideal for industries such as petrochemical, chemical equipment construction, sewage treatment, paper, etc.
  • SJ Gauge pressure gauge with metal-plastic stub pipe diaphragm seal
    Model: DIFF-USLP

    Flanged Connection with Stub Pipe, Upper Metal, Lower Plastic

    • Enlarged upper seat and diaphragm to enhance accuracy and meet the requirements for pipeline connections
    • The material of diaphragm or dual diaphragm can be different from the main body
    • Ideal for industries such as electroplating, chemical and petrochemical processing, etc.
  • SJ Gauge diaphragm seal for pulp and paper process pressure measurement
    Model: DIPI

    Diaphragm Seal for Pulp and Paper Industry

    • External chemical seal with welded diaphragm, designed to suit connections in the pulp and paper industries
    • Suitable for attaching to pressure gauges, pressure switches, and pressure instruments
    • Designed to be used for highly viscous process media such as pulp and plastic, and chemicals
  • SJ Gauge diaphragm seal for homogenizer pressure measurement
    Model: DIHO

    Diaphragm Seal for Homogenizer Machine

    • Available with process connections in various designs, fitting with all common measuring points
    • Designed to prevent aggressive or contaminating medium from entering a conventional pressure gauge
    • Widely used on homogenizers such as those found in sanitary applications, production of cosmetics and creams, dairies, and the pharmaceutical industry
  • SJ Gauge diaphragm seal for high-temperature melt pressure measurement
    Model: DIHI

    Diaphragm Seal for Melting High Temperature

    • Used to measure molten state process media
    • A capillary can be selected, suitable for remote observation
    • Widely used in the synthetic chemical, synthetic fiber, and plastic industries
  • SJ Gauge tri-clamp diaphragm seal for small pipeline connections
    Model: DIT-CS

    Welding Tri-Clamp Diaphragm Seal for Small-size Pipeline Connections

    • Special design for small-size pipeline connections
    • Enlarging the upper seat and diaphragm can ensure precision and fit different pipeline connections
    • Ideal for industries such as petrochemical, chemical equipment construction, sewage treatment, paper, etc.