EXAMINATION OF A FAILED 5TH WHEEL COUPLING

Examination of a fifth wheel coupling which had failed in service show ed that it had been modified and that the operating handle had been mo ved from its original design position. This modification completely el iminated the safety device designed to prevent inadvertent opening of the coupling locking mechanism. No alternative safety device was emplo yed to ensure the safety of the modified design. Furthermore, the rubb ing plate on the pup-trailer was significantly smaller than that on th e fifth wheel, with the result that the load transfer conditions were not optimal. This may have resulted in excessive damage to the wearing components such as the locking jaw, the locking bar and the king pin. (C) 1998 Elsevier Science Ltd. All rights reserved.