High-strength lean duplex for tram shelters

While the project experienced delays due to the COVID-19 pandemic, it is now well underway. When completed, the new tram line will be approximately 5 km long and will connect to the pre-existing tram line network. The project is divided into two phases, with the first section of about two kilometres scheduled to be completed by next spring. There will be 22 tram shelters along the first route, which will largely be built from Finnish stainless steel.

Maintenance-free stainless

Stainless steel is a maintenance-free material that, after installation, does not require any maintenance, painting, or other chemical treatment to maintain its corrosion resistance. Moreover, stainless steel is a visually striking material. The design/engineering office chosen by the City of Barcelona aimed to find a material for the shelters that would not rust and would withstand the challenges posed by the maritime climate.

The designer’s initial idea was to use grade 316 austenitic stainless steel in the project. Khaoula Loukili, Sales Manager at Thyssenkrup Materials Ibérica, has years of experience working with stainless steel grades. When considering the best possible option for the project in question with her own customer, Khaoula, encouraged by Stalatube Oy’s Export Manager Heidi Simberg, ended up suggesting Stalatube’s high-strength LDX 1.4162 Lean Duplex instead of the 316 austenitic steel mentioned in the invitation for tenders.

Strong, corrosion-resistant, and environmentally friendly

Stalatube’s high-strength steel tubes guarantee that the rectangular hollow sections used in the shelters are, first and foremost, strong and corrosion-resistant. Being a seaside city, the air in Barcelona has a high salt content, which sets high requirements for the choice of steel grade. As stainless steel is 100% recyclable, it is also the most environmentally friendly option. Almost 80% of Stalatube’s raw materials already consist of recyclable materials. In addition, the thickness of the high-strength tubes could be reduced thanks to the strength of the material.

The size of the tubes could be shrunk from the original 160×80×6 mm to 150×100×5 mm, which also resulted in savings on raw material and transportation costs. Stalatube’s Account Manager, Heidi Simberg, is pleased with the seamless cooperation with the customer. “In every project, it’s important to understand not only the customer’s requirements but also what purpose Stalatube’s products will ultimately serve. The designer may not always be familiar with all the options available in stainless steel.”

Taking advantage of expertise

Using a shared tool proved worthwhile. The project’s design office provided the steel tube manufacturer with an Excel tool that was utilised to calculate the required tube measurements. The tool found an optimal outcome that best met the designer’s requirements.

Heidi Simberg: “We are the best experts of our own products, which is why we encourage customers not to hesitate to take advantage of our expertise and experience. We have a range of different options available, and we always want to offer the customer the most optimal alternative for their project. That’s why we’re happy to be involved in the design process from the outset.”

Documentation of the tubes is also an important part of the process. The tubes used for the tram shelters had to be CE marked. A material certificate was also delivered to ensure quality.

Savings with the cut-to-length service

The project required several different lengths of tube that differed from the standard length. The customer is very happy with Stalatube’s cut-to-length service. The tubes delivered to the customer were manufactured in the desired lengths at the Lahti plant, which spared the customer from having to cut the tubes on site. This also resulted in zero material loss in manufacturing. The surfaces of the tubes were polished to a satin finish by a Spanish subcontractor chosen by the customer. The round corners of the tubes were ground by hand.

Cheapest not always cost-effective

Since high-strength Lean Duplex as a raw material is generally more expensive than an austenitic material, did the project end up being more expensive than originally estimated? Khaoula Loukili: “In the end, the costs of the project are exactly the same because we achieved a more durable end result with a smaller amount of raw material and saved on transportation costs thanks to the reduced total weight of the tubes. In addition, the cut-to-length service saved the customer one entire work stage, which translates into a smaller amount of material needed and lower labour costs. On top of everything else, this solution is the most environmentally friendly one at all stages.”

The project is a demonstration of cooperation where all parties to the project – designer, wholesaler and tube manufacturer – work together to find the best possible solution for the end customer. All parties are satisfied with the result. And more shelters are in the pipeline, as construction of the second section of the tram line will begin as soon as the first section is completed.

A small part of steel tube expertise from Lahti is now a visible feature of the cityscape of Barcelona. The first tram shelter is already up on Gran Via. Next summer, the Lahti-based Stalatube’s steel tubes will be an eye-catching feature of the cityscape of Barcelona. Grade 316 flat bars welded together with Lean Duplex tubes were used as the roofing material.

About this Featured Story

This Featured Story appeared in Stainless Steel World June 2023 magazine. To read many more articles like these on an (almost) monthly basis, subscribe to our magazine (available in print and digital format – SUBSCRIPTIONS TO OUR DIGITAL VERSION ARE NOW FREE.

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