'Our part in every solution'

The Department of Public Works is working to replace and renovate its existing infrastructure in the coming years. "Many bridges, tunnels, locks and viaducts were built in the 1950s and 1960s and over the years have been intensively stressed by more and more and increasingly heavy traffic," says Pim van Leeuwen, commercial director of Stafa. "Because this increases the risk of malfunctions and breakdowns, the existing infrastructure is currently being replaced. Stafa is happy to contribute to this through high quality fasteners, at a competitive price."

Fasteners are everywhere and can be used in a variety of ways, says Van Leeuwen. "The importance of high quality fasteners is still sometimes underestimated. Especially in the case of crucial applications, as described above." In previous articles, Stafa has reported that it is responding to current events surrounding the loosening of bolted connections in structures, which at first glance are of a static nature. "However, under the influence of an opposing wind load, the bolt/nut combination can loosen. To eliminate this risk, the use of HV (Hochfest Vorgespannt) preload bolts can be chosen, in accordance with EN 14399." In the case of dynamic structures, as is the case with bridges, the use of prestressing bolts is the rule anyway, he says. "Many times these bolts have a hot-dip galvanized coating."

Hot-dip galvanized products have been one of Stafa's specialties for many years. "We supply an extensive package of high-quality hot-dipped galvanized pre-tensioned bolts," Van Leeuwen said. "Perhaps, at first glance, HV bolts look more expensive than non-prestressed fasteners, but because of their quality and resistance, they generally have a longer lifespan. They also require less maintenance, which reduces costs in the long run." Stafa is TÜV certified for both static (SB bolts according to EN 15048) and dynamic HV prestressing bolts (EN 14399). "We also have our own laboratory where we perform tensile tests, Charpy tests, hardness measurements and salt spray tests, among other things. Moreover, our Keyence optical measuring equipment allows us to zoom in on the dimensions of our incoming products down to the smallest detail."

To keep traceability transparent, Stafa's HV bolts and nuts feature an impression in which the strength class, manufacturer's marking, HV and lot number can be found. "Combined with the corresponding certificate, all the information required to trace the quality can be found."

Correctly specifying and installing HV bolts is essential for optimal performance and safety, Van Leeuwen emphasizes. "Engineers must consider factors such as loads, stresses, environmental conditions and installation procedures to ensure that HV bolts are used effectively. Depending on diameter and length, for example, a different tightening torque applies. Stafa offers a handy tool for this, which shows the correct torque based on the diameter, among other factors. In this way, an optimal connection is guaranteed."

Stafa is one of the largest distributors in the field of fasteners. From its extensive stock program, the family business from Maarheeze supplies, in addition to HV products, threaded rods, hook anchors, lock nuts, turnbuckles, washers, screws, hexagon nuts and inner and outer hexagon bolts in accordance with DIN or EN ISO throughout Europe, for example. "All our products are available in many sizes, in various surface treatments and directly from stock," said Van Leeuwen. "From standard fasteners to specially produced 'special parts': all options are possible!" In addition to an extensive range of products, Stafa's personal approach and wide range of services are also characteristic of the company. Coatings, private labels, assembly sets, Kanban and other services are now among the possibilities, relieving customers from A to Z. Sustainability is also an important pillar. Both the active preservation of our own premises and the relocation of business activities back to Europe (reshoring) make an important contribution to a sustainable society, in which quality and safety remain paramount at all times.