STUDDED PIPES & HF WELDED FINNED

HAOHUA manufactures a wide range of extended surface tubes under the trade name BIRAGHI
Those extended surface tubes are adapted to all quality of gas: clean, dusty and corrosive gas.
Products include:
• High frequency welded finned tubes
• Studded tubes

Those surface tubes are approved by all the industry majors.

HIGH FREQUENCY WELDED FINNED TUBES

serrated plain
Major product
• In HAOHUA – heat recovery steam generator - within the combined cycle power plants as well as within the convection areas of fired heaters in the petrochemical industries.
• The fins are resistance welded to the base tubes using frequencies exceeding 400.000 Hertz. All tubes and fins material combination can be manufactured: Carbon, stainless, and alloy steels.

STUDDED TUBES

These tubes are specially used in petroleum applications.
The studs are arranged in staggered rows (rings).
All tubes and studs material combination can be manufactured: Carbon, stainless, and alloy steels.

Manufacturing Process
HAOHUA INDUSTRY supplies the highest quality welded finned tubes to any part of the world. The newly designed manufacturing facility, with our state-of-the-art high frequency resistance welding machines, enable us to perform large scale projects in reduced times.
The steel fin, that may be solid or serrated, is helically wound and continuously welded to the tube by high frequency electric resistance welding. This produces an homogeneous, clean and continuous fin-totube bond with no additional weld material, for a very efficient heat flow and resistance to corrosion.
There are some applications for which one or the other fin type is preferred. While in some cases fouling and cleaning considerations will favour solid fins, serrated fins are superior with respect to weight, compactness and price.
The use of high-frequency current results in very localised heating of the tube surface and the edge of the fin. This skin effect produces higher weld speeds, hence post-weld heat treatment is not considered necessary because of the superficial nature of the changes in the microstructure.
Tube bending:
Our finning machines are equipped with online single or duplex cold bending equipment that can manipulate both ends of tubes in a single operation, thus ensuring exact alignment of the ends. Our bending machines are capable of bending both bare or finned tubes with diameters from 31 mm to 76 mm.
Corrosion protection:
If required, the external surfaces of finned tubes can be treated with a protective coating. Our engineers are always ready to assist you with design considerations to meet your specific product needs.

Studded tubes
Forged Steel Studs are welded by a flashing resistance welding process onto the base tube.
The mainly applications for studded tubes is the process heat recovery of the petrochemical and chemical industry, in areas of convection furnaces.
Its high resistance to harsh environments, such as sections of Sulfuric Acid atmospheres, makes it very useful for the industries mentioned.
Focus
Base tube ranges from Ø 60.3 to 219 mm. 
Thickness is equal or higher than the stud radius
en lenght can go up to 13 mm as standard 
and 20 m on request.
Studs are arranged in staggered 
rows (rings) and their diameter 
ranges from 10 to 12.5 mm.
They can be made of Carbon steel, 
11% chromium (AISI 410) or 
Stainless steel (AISI 304).