LIFTjournal 1/2020

Measurements of structure-borne noise emissions on the lift shaft wall according to DIN 8989 indicate that changes in the pretensioning force of screw connections have a direct influence on an increased noise level in rooms requiring protection. S tructure-borne noise or oscillation measurements on lifts or their compo- nents have revealed that the pretensio- ning force of screw connections is reduced over their service life if unsuitable screw locking devices are used. Screw connections subject to stress in lift construction and the attachment of lift com- ponents fail when they come loose on their own during operation. Independent loosening of screw connections is equivalent to comple- te or partial loss of pretensioning force. This loss greatly increases structure-borne sound emissions in the lift shaft wall and can result in permanent fracture of the screw. Particularly in the case of separation joints – for example, in the case of oscillation in- sulation, axial loads, eccentric operationally- stressed screw connections – insufficient pre- tensioning force can produce a system change in screws and stressed parts, which can in turn result in unexpected overloading of screw and nut. Experiments employing growing axial ten- sile loading have identified partial loosening of screw connections. Loosening of the screw connection is due to reduction in the friction grip as a result of radial sliding movements between the thread flanks (screw-nut). In 2003, a series of standards regarding locking ele- ments were withdrawn, which were assigned to the categories “mechanical locking devices” and “anti-settling locks” or were in practice incorrectly assigned to them (see box). According to DIN 820-1, standards must take the state of the art into account. This was no longer the case for the above-mentioned stan- dards, which made their withdrawal essential. ten versagen, liegt es daran, dass sie sich selbstständig während des Betriebes gelöst haben. Das selbstständige Lösen von Schrau- benverbindungen ist gleichbedeutend mit dem vollständigen oder teilweisen Verlust der Vorspannkraft. Dieser Verlust erhöht die Körperschallemissionen in die Aufzugschacht- wand deutlich und kann einen Dauerbruch der Schraube zur Folge haben. Besonders bei mehreren Trennfugen – et- wa bei Schwingungsisolierungen, Schubbelas- tungen, exzentrischen betriebsbeanspruch- ten Schraubenverbindungen – kann eine zu niedrige Vorspannkraft eine Systemverände- rung von Schrauben und verspannten Teilen hervorrufen, die zu einer unerwarteten Über- beanspruchung von Schraube und Mutter führen. Bei Versuchen wurde unter schwellender axialer Zugbelastung ein partielles Losdre- hen bei Schraubenverbindungen festge- stellt. Das Losdrehen der Schraubenverbin- dung wird begründet mit der Verminderung CEDES AG | Science Park | Kantonsstrasse 14 | CH – 7302 Landquart +41 81 307 23 23 | info@cedes.com | www.cedes.com Product safety Functional Safety Is your todays’ business limitation a lack of talents? The revolutionary, EN 81-20 compliant position supervisor unit iDiscovery is monitoring different position and different velocity of the elevator car as well as the status of the car doors and the hoistway doors. In combination with the safe (SIL 3) position and velocity information provided by the APS, iDiscovery takes over the safety relevant functions of an elevator. Guaranteeing a high safety-level does not necessarily mean that it must be complicated to deal with. On the contrary - CEDES engineers developed a practice-oriented, easy to handle system. iDiscovery significantly reduces the complexity and time of the installation and maintenance of the elevator for your service technicians at site. Do not be afraid of the latest safety-technology – it is simply simple! Scan me for more product information www.cedes.com 09 PERSPEKTIVEN  PERSPECTIVES