Building a stainless reputation
Seeing is believing when it comes to appreciating the benefits of thin-wall stainless-steel for building-services applications — as Dugald Craig of DH Stainless explains.
A year ago in Modern Building Services I discussed value engineering through stainless-steel pipework — explaining the benefits and cost savings of using thin-wall stainless-steel pipe as a replacement for standard-wall carbon-steel pipe and fittings for services pipework. The ensuing time has been interesting, with the acceptance of stainless-steel pipe growing rapidly.
Five major benefits were identified in the original article: lowest product price; significantly quicker to fabricate; less support structure required, quicker to commission; corrosion and maintenance free.
This product had been well established over many years in other industries but was in its infancy as a piping product in the building-services sector. Over the course of the last year, stainless-steel thin-wall pipe has become the fastest growing system for building-services pipework.
We have conducted many piping seminars and CPD presentations for main contractors and consultants. It was always the case that everyone is interested in using stainless steel because it requires no coating and is a corrosion-free and generally maintenance-free product.
However, stainless steel has always been considered a premium metal with a premium price. As this product has a lightweight nature, more suited to the pressures in these systems than traditional thick-walled pipeline products, we can actually show material-cost savings —much to the surprise of most clients. There are also cost savings in welding when compared to thicker-walled carbon steel, the support structure and lifting equipment through the lighter weights and, finally, installation and commissioning savings (it is generally three times quicker to install). Once commissioning is completed on a large project, total savings can be over 25%.
As we have had more success with the product, other benefits to clients have come as more of a surprise.
Contractors are in an extremely competitive environment and always looking, or being forced, to offer more value to the end user. We have been involved in contracts where maintenance agreements are being offered for the pipework, some for 15 to 20 years, so apart from cost savings in general the longevity and low maintenance requirements of stainless steel have made it the natural choice.
We have also had to respond to unexpected concerns.
It is clear that the market is used to the thicker wall of the carbon-steel product.
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Although stainless steel is more expensive than carbon steel kilo for kilo, the lighter weight of an equivalent pipe makes stainless steel pipes competitive with those of carbon steel. Lower installation costs for stainless steel result in installed-cost savings of 15 to 27%.
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As our product has a lighter wall, many clients have had concerns about its robustness. Indeed we have been in meetings where clients have almost expected to have to wrap stainless-steel tube in cotton wool. Of course we always have samples which instantly prove the strength of the product and dispel such issues. In fact, once clients have handled the product all conversations tend to be turn to how light it is whilst giving the strength required.
The technical reason for the inherent strength is because the stress/strain behaviour of stainless steel differs from that of carbon steels. In layman’s terms, that means stainless steel can absorb considerable impact without fracturing due to its excellent ductility and actually work hardens when dented so the dented area becomes stronger rather than weaker.
Also thinner-walled carbon steel pipes would be more subject to brittle fracture, but this is not the case with stainless steel due to its superior toughness.
Thin-wall stainless-steel tube is now physically being used as a replacement for carbon steel on a daily basis at all levels from small jobs upwards.
Most encouraging are five large projects (worth over £500 000 each in materials alone) which have obviously gone through an extremely rigorous process to ensure the product is fit for purpose. All these projects were originally specified in carbon steel but were then value engineered to stainless steel due to material and cost benefits.
Feedback from main contractors on the cost benefit of stainless steel thin-wall pipework includes an installed cost saving of 15 to 27% compared to the equivalent carbon-steel pipework installation. The savings depend on the size and complexity of the pipeline. Stainless steel thin wall is at its most competitive in sizes 100 mm and above and gets particularly competitive on sizes 250 mm and above — when the cost savings can be even higher.
Thin-wall stainless also has strong benefits in aerobic digestion and bio-energy applications
Another major benefit of stainless-steel thin-wall piping is that these modern manufactured and tested piping products have a weld factor of Z=1.0. In design codes terms this ranks these pipes and fittings as an equivalent to seamless, but at a significant cost saving. Having a weld factor of Z=1.0 has the large advantage in aerobic digestion plants of being perfectly suited for critical pipework applications such as inflammable gases; also the resistance to impact-damage rupture is another major benefit.
It is important that stainless-steel pipes and fittings are purchased to the relevant and correct specification in these applications to ensure you receive and install the correctly tested and pressurised products.
One of the largest main contractors has carried out an extensive survey on the costs and benefits of the stainless-steel piping system and stated, ‘It is difficult to find a fault with this system, and the fact it is stainless steel just caps it off as the material capabilities are so well understood and it is easy for the customer to accept.’
It should also be remembered that this piping product has an impressive track record for applications such as food, drink, chemical, pharmaceutical, paper and water treatment in over 30 years of rigorous process-pipework applications where stainless steel would be the natural choice of material.
Dugald Craig is managing director of DH Stainless.
