Graphite Tube Heat Exchangers

Schmidt® SIGMA G-TUBE Graphite Tube Heat Exchangers

Our SIGMA G-TUBE graphite tube heat exchangers are ideal for use with corrosive materials. Made from graphite tubes that are cemented into graphite tubesheets, with the tube bundle inserted into a metal or polymer shell, the solutions from API Heat Transfer use the highest strength materials available on the market and offer nearly universal corrosion resistance.

We offer two types of graphite tube heat exchangers:

  • Our GT-TUBE-A has been optimized for high-fouling processes. Special surface properties reduce the fouling process, which results in a longer time between cleaning cycles. This reduces operating costs for many applications, such as the need to add phosphoric acid during fertilizer production.
  • Our GT-TUBE-B was developed for higher corrosion resistance and higher temperatures.

How it works.

  • Corrosive material flows through the tubes
  • Service medium passes through the shell
  • The complete unit is maintained under compression with a special STABLE LOAD® springs system


  • Agrochemicals and heavy chemicals
  • Electrolytic refining and mining; pickling of metals
  • Fine chemicals and pharmaceuticals
  • Food
  • Petrochemicals
  • Synthetic fibers
  • Photovoltaics

Graphite grades available.

Type of Graphite Standard Fine grain Standard or fine grain
Impregnant Phenolic Phenolic Carbon
Relative Mechanical Resistance 1 1.5–3 1.1–1.7
Corrosion Resistance Good Better Excellent
Thermal Shock Resistance Low Better Excellent
Recommended for: Mild operating conditions (pressure, temperature, corrosion) Higher pressure and temperature; frequent thermal cycles Highest corrosion and temperature (non-oxidative media)

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Performance Notes

  • Largest heat transfer area possible
  • High process/service section for large flow rates (15,000 m3/h)
  • Low pressure drop on shell side
  • Outstanding corrosion resistance (GT-KELITE)
  • STABLE LOAD® limits stress fatigue on the compression springs
  • Erosion resistance is available as an option
  • Tubes are available with carbon fiber reinforcement for applications with high vibrations and mechanical stress
  • Gasketed baffles on service side for cooler
  • Standard design pressures up to 85 psig (6 barg)
  • Standard design temperatures up to 356°F (180°C) (higher temperatures available on request)
  • Heat transfer surface from 45 ft2 to 9,000 ft2 (5 m2 to 1,000 m2)
  • Customized design for client-specific applications


  • Food and Beverage
  • Food ingredients
  • Process Industries
  • Chemical
  • Metal processing
  • Petrochemical
  • Pharmaceuticals, nutraceuticals, and cosmetics

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