How to make hot dip galvanized bolt sets even better

        Threaded fasteners are among the most important components of wind turbines, bridges and steel structures. In addition to various factors such as materials and tools, the coefficient of friction and overall thread retention are greatly influenced by various weather conditions.        A number of different threaded fasteners are currently in use: ISO bolt sets, friction grip bolt sets, and preload calibrated bolt sets, all consisting of a bolt, at least one washer and a nut. As a rule, they are made of high-strength materials.        The coefficient of friction is a key element of reliable screw fasteners. This value describes the ratio of preload to torque and is determined by two factors: thread friction and head friction. The load pressure acting on the surface is the preload, which is also responsible for the elongation of the bolt and the corresponding spring effect. Torque, on the other hand, affects the thread surface and contact area, and is divided into three parts of torque: thread torque, head friction, and the part that is directly converted into preload. Therefore, the final preload to achieve the specified torque depends on the coefficient of friction.        The friction coefficients µges and k are affected by many different factors such as material vapors, surfaces, lubrication or wear. However, ambient temperature, humidity and rain also have a significant effect on threaded connections. Here, not only elastic deformation occurs, which in the worst case can lead to shearing of the bolt or failure to achieve the required preload. This leads to a construction halt and significant costs and time delays for repairs or replacement of parts.        That is why DÖRKEN and Peiner Umformtechnik decided to develop a solution together. Peiner is a leading supplier of fasteners for wind turbines and steel structures, producing calibrated preload bolt sets as well as friction clamp bolt sets in sizes M12 to M36.        “The challenge for our collaborative project was to equip standard hot-dip galvanized bolts with extra-finished washers and nuts, which means that neither rain nor sun will affect the stability of the fastener,” says Christos, VP Sales, Industrial Coatings Tselebidis. explained. Delken. “To achieve this, we did a lot of experimentation and extensive testing of zinc flake topcoats for nearly six months before finding the topcoat solution.”       While hot dip galvanizing is a primer that protects threaded connections from corrosion, the specified coefficient of friction of the zinc flake top coat ensures that the nut is securely tightened without removing any of the hot dip galvanizing protection.        In addition to extremely rigorous laboratory testing, certain coating combinations have also proven their worth in various field trials. "The results are impressive - almost 3 million bolt sets have been delivered and installed without any failure," says Valery Shram, Head of Structural Engineering and Wind Energy at Peiner Umformtechnik. guarantees that never before seen levels of process reliability can be achieved on construction sites.”        Claire has worked in the fastener industry for ten years and has experienced every aspect from steel mills, fastener manufacturers, wholesalers, distributors, as well as machine builders and electroplating companies. Claire knows fasteners. Deep understanding of all aspects.       In addition to visiting numerous companies, trade shows and conferences around the world, Claire interviews prominent figures, focusing on key topics affecting the industry and keeping readers updated on the latest developments in the industry.