Failure analysis of an overhead traveling crane lifting system operating in a turbogenerator hall Eugeniusz Rusin ´ ski, Artur Iluk, Kazimierz Malcher, Damian Pietrusiak ⇑ Wroclaw University of Technology, Institute of Machine Design and Operation, Lukasiewicza 7/9, 50-371 Wroclaw, Poland article info Article history: Received 7 September 2012 Received in revised form 4 January 2013 Accepted 5 February 2013 Available online 17 February 2013 Keywords: Overhead traveling crane FEM Sling breakage abstract The paper presents investigation of the causes of the accident which took place in the tur- bogenerator hall. On the basis of the information given from the crane operator, witness and the Office of Technical Inspection report, the possible scenario of the event was recon- structed. The numerical simulation and studies of the supplied documentation allowed to say that the rotor drop was a consequence of a simultaneous occurrence of a series of unfa- vorable factors. The paper presents step by step the event course indicating all factors which validates assumed scenario of the accident. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction A rotor (approximate mass 45 t – marked in the article as G force) of a low pressure section of a steam turbine was being carried by a double-girder overhead traveling crane with load capacity of Q = 100 t, when the rotor was dropped from the height of approximately 14 m onto the ground level of the turbogenerator hall (Fig. 1) causing damage to itself and to the nearby equipment and the overhead traveling crane. The rotor was lifted using a special symmetrical lifting beam attached to a ramshorn hook on the crane (Figs. 2 and 3) and two pairs of special double lifting slings (four ropes per sling) designed for lifting such rotors. The slings were fastened to the lifting beam by means of clamps (Fig. 2 – one of the clamps on one end of the lifting beam) which are an integral part of the lifting beam and by sliding across it they enable the adjustment of the location of lifting slings. Fig. 2 shows the position of the lifting beam immediately after one of the clamps for lifting slings slid off the beam and the rotor dropped, whereas Fig. 3 shows the dismounted lifting beam, which is lifted by a ramshorn hook. The model representation in Fig. 4 depicts the positioning of individual elements of the load lifting system, i.e. the hook pulley block, lifting beam and the transported rotor, which corresponds to the uninterrupted steady lifting motion of the overhead traveling crane, i.e. the motion prior to the tilting of the lifting beam. Moving large loads at great heights in a workspace with many obstacles, such as machinery and equipment, is very com- plex, difficult and dangerous. It requires simultaneous observation of many potential collision points with the lifted load, which are distant from each other and which pose an immediate hazard to the life and health of staff and to the safety of the machines and equipment. The horizontal position of the load must be constantly controlled and changed to avoid any collision. If the load is lifted too high it usually contacts the elements of the overhead traveling crane superstructure, such as girders or the hoist trolley, which leads to an uncontrolled overload of the cable system for lifting loads. 1350-6307/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.engfailanal.2013.02.008 ⇑ Corresponding author. Tel.: +48 713204292; fax: +48 713203123. E-mail address: damian.pietrusiak@pwr.wroc.pl (D. Pietrusiak). Engineering Failure Analysis 31 (2013) 90–100 Contents lists available at SciVerse ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal