Tubes: Check they comply before you buy
Here, Stewart Jones, Customer Technical Services Field Engineer at Tata Steel discusses the importance of traceability and compliance when using steel tubes.
Competition within the marketplace is best described as ‘healthy’ and often is the catalyst for innovation and improving best practice. However, a significant increase in availability and product choice can often lead to difficulties in differentiating between the options actually available.
This is certainly the case with steel tubes. The range of alternatives being offered can lead some companies to take shortcuts by moving away from trusted suppliers, either deliberately or unknowingly, and using cheaper, untraceable products.
Traceability is of paramount importance when specifying a product that incurs a significant investment, fulfils an essential role within a building and has an expected lifespan.
Traceability provides reassurance that, in the case of a product issue or failure, the full history of the product’s manufacture and legislative compliance are known. Without this one could be left facing significant issues when dealing with future warranty or insurance claims.
Steel tubes that are used within commercial environments for Heating, Ventilation, Air Conditioning (HVAC) and general building services conveyance applications, may suffer from such traceability issues. This is because carbon steel tubes can be made in the UK, elsewhere in the EU or come from outside the EU, and can be manufactured in one of two ways, by either cold forming or hot finishing.
Problems typically arise when a hot-finished tube is specified for a project but a cheaper, commodity cold-formed tube is utilized instead. Cold-formed tubes will perform differently during fabrication, installation and when in-service to hot-finished products. Hot-finished tubes are superior as they undergo an additional, essential, manufacturing step in that the tubes are subsequently heated to a sufficiently high temperature to refine the structure and relieve any internal stresses.
These stresses are introduced through the welding process, where the internal grain structure is altered, increasing the likelihood of cracking and failing during service. The hot-finishing operation eradicates this highly stressed region, known as the Heat Affected Zone (HAZ) and can offer many tangible benefits over cold-formed products, including:
• A more ordered and consistent microstructure
• No internal stress that can promote cracking
• More consistent and reliable mechanical properties
• Improved structural integrity and ductility
• Improved and more consistent toughness
• A higher pressure integrity
• A greater factor of safety
• No loss of strength due to additional welding or heating
• An improved performance against corrosion
• The ability to be threaded, grooved or bent to tight radii without splitting, creasing or collapsing
Typically, HVAC applications refer to tubes being manufactured to BS1387; however, this standard was withdrawn in 2004 and replaced by BS EN10255. Nevertheless, even specifying tube to BS EN10255 does not guarantee that a hot-finish product will be supplied. It is only by additionally requesting a BS EN10217 Part 2 compliant product, with its GH (Get Hot) grade, that a hot-finished tube will definitely be supplied.
Furthermore, for building services applications, it is best practice to ensure that the product is fully CE marked to the Construction Products Regulations, for both CAT3 (fuel and gas) and CAT4 (water). The tube manufacturer should be providing such compliance information to ensure that the product is fit for its intended purpose, as well as demonstrating 3rd party approval of their manufacturing and testing processes.
Using a reputable well known, market leading, brand not only improves traceability, but can also increase product reliability.
An example is Tata Steel’s Install® Plus 235 hot-finished, multi-certified carbon steel tube range. Specifically developed and manufactured within the UK, the range is aligned with both the Construction Products Regulations (CPR) and the Pressure Equipment Directive (PED) in accordance with BS EN10255 and BS EN10217 Part 2.
The superior durability and strength of the hot-finished tube range ensures that Tata Steel Install® Plus 235 products can withstand design temperatures between -20oC and 300 oC. More importantly, Tata Steel hot-finished tubes can be readily identified, ensuring that the correct product has been supplied.
Authenticity should always be confirmed by checking the product for the correct markings as well as verifying its origins through documentation, such as the product description, order acknowledgement, test report and declaration of conformity issued by the manufacturer. These are important documents that should be supplied with the product. If not, then ask why not.
These vital indicators provide reassurance for both the installer and building management team that, should an issue arise, the material used is correct and as specified and hence the installation is fully compliant and so will meet both warranty and insurance policy requirements.
As the market becomes more buoyant, new manufacturers and distributors will continue to enter the scene, however, it is vital that traceability and compliance are not compromised.
All tubes are not created equal; therefore specifiers and installers should ensure that the correct standards and products are specified and used, using key identifiers to confirm, check and ensure authenticity.