### Tubes with internal ribs

Application examples:

• in heating and cooling systems (ribbing increases the internal surface of the pipe, which in turn increases the efficiency of heat or fluid flow);
• in ventilation and air-conditioning systems, steel pipes with internal fins ensure better heat exchange between the air and the pipe;
• in the chemical and petrochemical industries, they can be used to transport chemicals that require controlled temperature or need to be cooled;
• in the case of waterworks, steel pipes with internal ribs can be used to transport water that needs frost protection or needs to be heated.

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### Properties of tubes with internal ribs

Seamless tubes with internal ribs (internal riffling) are made by cold drawing. They are used as boiler tubes or heat exchangers tubes.

Steel grades according to EN 10216: P235GH, 16Mo3

Compared with tubes that have a smooth internal surface, tubes with ribs offer the customer many advantages:

• improved level of heat transfer even with a higher share of steam;
• very good level of heat transfer, retained also at lower medium flow;
• lower temperature of tube walls = lower risk of tube’s distortion;
• internal riffling prevents from sedimentation of solid particles present in the medium = lower risk of corrosion process = increased lifetime of a tube;
• improved heat transfer by a suitable optimization of the riffle geometry.
 Parameter Range [mm] Range [inch] Outside diameter D 18-72 .750-3.000 Tube wall thickness T 1-6,5 .047-.250 Number of ribs 6-8 Rib height h 0,3-1,0 .016-.047 Rib width at the top f 3-8 .125-.313 Rib side angle ß 30° Rib radius r 0,1-0,15 .004-.006 Rib pitch angle a 25°-35° Rib pitch length (360°) depending on outside diameter Distance of rib centers in the longitudinal direction upon agreement Rib width at the top upon agreement Width of the distance between ribs at the top upon agreement Inside tube circumference upon agreement Transversal tube diameter upon agreement Tube length upon agreement