Electric Resistance welded (ERW) carbon steel tubes have been successfully used in building and industrial pipework installations for many years.

However, we are now seeing the increasing use of imported, commodity welded tubes that may prove to be less suitable for typical piping applications.

Such imports are invariably produced by a cold-formed process. This means that the tubes are simply cold formed to shape from strip and welded without any further processing to the tube or the weld region.

Therefore, cold-formed tubes contain a Heat Affected Zone (HAZ), an area of micro-structural distortion around the weld region; this can be undesirable as it results in internal stresses and inconsistent mechanical properties that can lead to fabrication, installation, service-life and performance issues.

Inconsistent weld properties can also be a particularly issue for tubes being used in applications under the European Pressure Equipment Directive (PED), where it is inferred that the properties of the weld must be equal to that of the tube itself.

Pipework, such as that manufactured by Tata Steel use a High Frequency Welding (HFW) process, which is superior to the other forms of ERW tube making.

In addition, Tata Steel’s HFW building and industrial services tubes are hot-finished, a process sometimes also referred to as Normalising or Weld Line Annealing (WLA).

During this hot process, tubes are taken to temperatures of 850 to 1000 degrees C and cooled down in a controlled manner to deliver improved characteristics.  During this process the Heat Affected Zone (HAZ) and any internal stresses or mechanical inconsistencies are removed.

Therefore, hot-finished tubes are superior to cold-formed ones, as they offer uniform and stress free performance, consistent and reliable mechanical properties and improved service life.

The enhanced ductility of hot-finished tubes also means that they can be shaped or readily manipulated, without the risk of cracking, thereby providing fabrication and installation advantages.

Hot-finished tubes are also typically able to operate at high temperature and pressures than cold-formed tubes, making hot products more suitable and safer for a wider range of applications.

Hot-finished tubes also provide a viable and cost effective alternative to other hot-finished products such as seamless tubes.

Furthermore, being produced from strip, HFW tubes have more consistent roundness and thickness than seamless enabling better end matching for pipe joining. In addition, HFW tubes are supplied as standard in fixed lengths, unlike seamless tubes where random lengths may vary considerably causing logistic, storage and installation challenges.

Not all tubes are the same.  Therefore, it is vital that tubes are correctly specified to ensure the right product is supplied.

Tata Steels hot-finished tubes have been specifically developed to satisfy a wider range of applications.  Hot-finished and multi-certified tubes provide both fabrication, installation, service-life and application advantages, and can provide specifiers and end-users with a degree of confidence that cold-formed alternatives simply cannot offer.

For more information regards the differences between pipework properties as a result of the manufacturing process, please contact BISPA, or for specific information regards Tata Steel’s building and industrial services tubes, please refer to www.tatasteelconstruction.com/hotvscold.