What kinds of finned tubes are used in air cooled heat exchanger?

The fin tubes can be of virtually any material available, such as carbon steel, stainless steel, Admiralty brass, or more exotic alloys.

The minimum preferred outside diameter is one inch. Some manufacturers sometimes use smaller tubes, but most of the process coolers have tubes which are 1.0", 1.25", or 1.5" OD. The minimum tube wall thicknesses vary with the material. In some cases the design pressure and design temperature of the ex-changer govern the minimum thickness.

The fins are almost always of aluminum material. The most common type of fin is the helically wrapped, L-footed type. These are used where the process temperatures are below about 350 deg. F. The API specification calls for cast zinc bands at the ends of the tubes to prevent the fins from unwrapping. Some of the better manufacturers also use cast zinc bands at the tube supports. For higher process temperatures, most customers prefer either embedded or extruded fins. The embedded fins have the highest temperature capabilities. They are made by a process which cuts a helical groove in the OD of the tube, wraps the fin into the groove, then rolls the upset metal from the tube back against the fin to lock it into place. The tube wall must be thicker with embedded fins because of the groove.

In some applications customers often prefer extruded fins. Extruded fins are made by putting an aluminum sleeve (sometimes called a muff) over the tube, then passing the tube through a machine which has rollers which squish the aluminum out to form fins. The process is similar to a thread-rolling machine. The end result is a fin which has extremely good contact with the tube, and no crevices to allow corrosion to start on the tube OD. Extruded fins are often used in coastal locations or on offshore platforms for this reason.

Inspections and Tests G-fin; L-fin; LL-fin; KL-fin; Extruded-fin Finned Tubes
Generally speaking, Tension wound finned tubes, embedded finned tubes and extruded finned tubes are main devices for air coolers and the common application fields are:

A. Heat exchangers for power plants (electric, nuclear, thermal and geothermal power plants)

B. Steam condensate systems

C. Chemical and petrochemical industry

D.Food processing plants and refrigeration technology

E. Industrial (steel mills, incinerators, gas compression facilities)

For the inspection and tests on G-fin, L-fin, LL-fin, KL-fin and extruded-fin finned tubes, we usually do the following tests:

  • Chemical composition
  • Mechanical properties
  • Hydrostatic test
  • Pneumatic test
  • Boroscopic inspection
  • Eddy current test

Tensile Test (only for extruded finned tube)

The material certificate including all the tests can be provided, and also with EN10204 3.1standard.

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