Materials
All materials shall comply with the material requisition, and shall have a report according to EN 10204 – type 3.1.
A visual and dimensional inspection of both tubes and fin coils shall be performed at the material acceptance.
The finned tube must be reasonably straight and free of defects.
Only one fin junction is allowed on tubes up to 6 m in length; two fin junctions are allowed for tubes over 6 m in length,
provided that the junctions are not closer than 3 m.
The internal surface of the tube shall not show helical marks; a slight tracing under the finned length is allowed, provided
it’s not higher than 0.2 mm.
A fin pull test shall be performed on the sample tube.
The procedure shall include the following points:
‐ a fin must be isolated by bending the closer fins, having care not to detach them from the tube;
‐ a 90° sector must be cut as shown in figure 1; the fin shall be cut all way through the height;
‐ a clamp shall be tightened to the lower part of the fin section;
‐ the test force shall be applied either through a dynamometer with a suitable full‐scale value, or through the
gradual application of calibrated weights.
For carbon steel tubes, the force to be applied is F [N] = 2.16 ∙ OD [mm], with OD = outside diameter of the tube2
.
For stainless steel tubes, the force value (or the mass, as needed) must be reduced by a factor of 1/3.
