At present, the volume of construction of buildings for various purposes is increasing every year in Russia. This growth is due to the introduction and further application in practice of new construction technologies. Most of the industrial facilities are built from pre-fabricated metal structures. And not a single building, no matter how complex configuration it is, can do without enclosing structures, which, in addition to their main functional purpose, give a particular building its aesthetic expressiveness.
In the last decade, in our country, three-layer panels with effective insulation, the so-called sandwich panels, have been used as enclosing structures. There are many different fastening systems for their installation, produced by various foreign and domestic manufacturers. From all this wide assortment of fasteners, the Swiss company “SFS intec” has established itself with the best side, the options of the offered products allow to solve any construction problems associated with fastening the enclosing structures.
SFS intec offers several systems for fastening construction sandwich panels to load-bearing structures. These systems allow high-quality installation of panels, without any additional construction measures, on any type of load-bearing structures, such as reinforced concrete and metal.
When installing panels on a metal frame, self-tapping screws are used, which at the end have a drill of various lengths as a cutting tool. The self-tapping screw is able to drill a metal structure without preliminary drilling with a thickness of 1.5 to 14 mm. The special design of the drill, manufactured using a special technology by cold forming, allows the screws to realize this ability. Self-tapping screws allow you to fix the panels without much effort, both on cold-formed thin-walled structural elements and on thicker hot-rolled profiles.
Another distinctive feature of the SFS intec self-tapping screws is the second thread rolled under the screw head. The diameter of the main thread is 5.5 mm, and under the head is 7.0 mm. Both threads have a metric knurl profile. There is a free zone of a certain size under the screw head, i.e. the second thread ends before reaching the inner surface of the head cap. This zone allows the face of the panel to be sealed. The outer metal cladding of the panel with its inner surface rests on the last thread under the screw head, and the outer surface of the cladding is pressed with a sealing washer.
Basically, the sealing washers are made of galvanized sheet. As practice shows, galvanized washers have a limited time to resist corrosion. Washers “SFS intec” are made of aluminum. Aluminum washers will last for the entire life of the building. This is confirmed by the salt spray tests carried out. SFS washers have an EPDM (synthetic rubber) layer as a sealing layer, the thickness of this layer is 3 mm and has a soft, elastic structure that is reliably vulcanized to the base. The inner diameter of the seal fits tightly to the self-tapping screw, which reliably seals the adhesion of the screw head to the washer. Such a washer will serve as a reliable protection against the penetration of atmospheric precipitation into the joint (as you know, it is the joint under the washer that is more exposed to moisture).
It’s not a secret for anyone that during the operation of the building, the fastening system of the enclosing structures remains the most loaded. And at the same time, self-tapping screws are most susceptible to the effects of environments of different aggressiveness, because they are located in the closed space of the panel insulation. Any metal object in such a situation will begin to corrode and, in the end, collapse, it’s a matter of time. Corrosion begins to develop intensively where the protective coating is broken. When using self-tapping screws with an ordinary zinc coating, contact with the metal parts of the panel and substructure occurs. In this case, damage to the anti-corrosion coating is inevitable, scratches, galls and zinc flaking appear. The exposed areas of the screw and the edges of the metal sheets will begin to corrode. How long this mount will last – it’s hard to say.
Self-tapping screws “SFS intec” are made of stainless or carbon steel and have a special patented anti-corrosion coating based on polymer material (Durocoat). When installing self-tapping screws with a duracoat coating, the following occurs. Scratches, inevitable in these cases, due to the elasticity of the polymer component, themselves tighten, restoring the integrity of the anti-corrosion coating. Moreover, in contact with the edges of the metal sheets, the coating from the screw is transferred to these edges, thereby preventing edge corrosion in the joint. Fasteners with such an anticorrosive coating will last long enough, which is confirmed by tests in various aggressive environments in the manufacturer’s laboratories. The durability of this coating is guaranteed for 50 years..
The above features make it possible to achieve undeniable quality indicators of fastening sandwich panels that arise during installation.
Technical information for the entire range of self-tapping screws is reflected in the SFS catalogs. Other companies that represent fasteners on the Russian market do not present this information, and since there is no information, it means that no tests were carried out and no one will give guarantees of the long-term service of self-tapping screws.
Chief Project Engineer