SONDEX® Semi-welded plate heat exchangers

  • Overview
  • Related products
  • FAQ

SONDEX® semi-welded plate heat exchangers are designed for your peace of mind. With our solutions, you can safely operate with potentially hazardous media, high pressure levels, or extreme temperatures that are unsuitable for fully gasketed heat exchangers.

What does that mean for you?

For increased safety, the semi-welded product range uses cassette technology instead of regular plates. Each cassette features a gasketed side for the regular media, and a welded side for the aggressive media.

The welded side holds a custom, damage-resistant ring gasket. With a considerable reduction of the exposed gasket area, our semi-welded plate heat exchangers have a long product lifetime and provide safe operation with less risk of leakage.

Sustainable efficiency

No more off-the-shelf heat transfer solutions! With a SONDEX® heat exchanger, you can rest assured that your thermal performance is top tier, as you receive a customized solution that is tailored to your individual application, easy to install, and service-friendly.

Our extensive experience and deep process knowledge allow us to avoid the common pitfalls of complicated applications and deliver reliable and safe, high-performance heat exchangers.


  • HVAC industry
  • Marine/offshore industry
  • Dairy/food/beverage industry
  • Sugar industry
  • Refrigeration industry
    - e.g. duties that use ammonia as refrigerant
  • Pulp and paper industry
  • Heavy industry
  • Mining industry
  • Petrochemical industry
  • Chemical industry
    - e.g. chemical processing, such as rich/lean amine treatment
  • Evaporation and condensing duties
  • High pressure liquid/liquid applications

Technical specifications

  • Connections from DN65 to DN500
  • (Frames designed according to FEA and PED 2014/68/EU (EN13445) and ASME sec VIII, Div. 1 construction standards)
  • Plate materials: AISI 304/316, titanium, SMO, Hastelloy. Other materials available upon request
  • Gasket materials: EPDM-HT, NBR-HT, Viton. Other materials available upon request
  • Ring gasket materials: EPDM-HT, NBR-HT, Viton, Chloroprene, PTFE. Other materials available upon request
  • Plate heights up to 3 m (9.8 ft)
  • Flow rates up to 5,000 m3/h (22,014 gpm)
  • Working pressure up to 25 bar (363 psi)
  • Working temperature -25 °C to 200 °C (-13 °F to 392 °F)

Features and benefits

High efficiency means that fewer plates are needed for high performance, cuts the cost of each heat exchanger, and consequently lowers the hold-up volume.

Engineered to use smaller amounts of potentially hazardous media, the SONDEX® semi-welded range is a safe and responsible choice for demanding duties.

Unique gasket system intended for high working pressures and vacuum applications. A closed gasket groove keeps the gasket firmly in place and prevents misalignment of the plate pack during assembly and operation.

Fishbone plate technology

Engineered to maximize turbulence, even at low flow rates, this pattern achieves unparalleled heat transfer. The pattern has proved its effectiveness through rigorous testing and is the default choice for plate heat exchangers.

Related products

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    SONDEX® Fishbone plates

    SONDEX® Fishbone plate pattern technology is used for the vast majority of our plate heat exchangers. The pattern is designed for high thermal performance while using the allowed pressure drop in the most efficient manner. Available with different pressing depths, pattern pitch and angles – each plate has a pattern that is optimized for a certain duty.

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    SONDEX® Traditional plate heat exchangers are the ideal choice for a wide range of applications across numerous market segments. We have the largest plate portfolio in the world, and customize each heat exchanger to meet your exact requirements. Innovative technologies and smart design make our traditional plate heat exchangers a stellar investment.

  • if (isSmallPicture) { SONDEX® Evaporators- Danfoss; } else if (isBigColumns) { SONDEX® Evaporators- Danfoss } else { SONDEX® Evaporators- Danfoss }
    SONDEX® Evaporators

    SONDEX® evaporators are designed to handle advanced evaporation duties. Using semi-welded plate cassettes, the media are guaranteed to never mix. The plate cassettes are designed to ensure the optimal level of turbulence on both sides, while providing an even distribution of the media for superior performance and product quality.

  • if (isSmallPicture) { SONDEX® Condensers- Danfoss; } else if (isBigColumns) { SONDEX® Condensers- Danfoss } else { SONDEX® Condensers- Danfoss }
    SONDEX® Condensers

    Our SONDEX® condensers are the perfect choice for special applications that regular plate heat exchangers cannot handle. Designed to accommodate high-volume vapor flows, this product features a large inlet for the vapor stream. Combined with a short residence time, the optimal condensation conditions are created – even for low-pressure vapor duties.


The choice of heat exchanger depends on many factors. Our skilled sales engineers design the heat exchanger with the appropriate dimensions and correct specifications based on your input and requirements, to ensure that you receive a quality solution that performs optimally.

Our heat exchangers are approved and certified according to industry standards and requirements. For specific details, please reach out to your local SONDEX® brand sales representative.

Please contact your local SONDEX® brand sales responsible.

Please contact your local SONDEX® brand sales office. For the most accurate quotation, please prepare the following data:

  • Duty,
  • Type of media,
  • Pressure drop,
  • Flow rate,
  • Working pressure,
  • Thermodynamic properties, Temperature,
  • Working temperature.