Society depends on engineers to design infrastructure, tools, and machines to operate in a safe and reliable manner, but at a cost which is economically feasible. To achieve this objective, the concept of Safety Factor, a.k.a. Margin of Safety has been applied which results in an over designed product which is then presented as being safe. More recently, the terms 'design factor', or 'reserve factor' have been used instead, but this has been mainly as a defense from potential legal issues that may arise from using the word safety and what it implies in this context. Building systems stronger than necessary is supposed to protect the user in cases of unexpected loads, misuse, and degradation and loss of properties over the design life. It should follow that the better the load, use, and degradation are understood, the lower the Design Factor can be. To be concise, we will use the following terms: Design Factor=Rope Strength / Working Load Margin to Failure(MBL)= Residual Strength -Working Load Margin to Failure(Life)=Residual Life-Expected Usage Design factors ranging from 2 to 15 are commonly applied to synthetic fiber rope, with a 5:1 safety factor being the most commonly selected value when little is known about the application. In principle, it is a function of the number of risks and consequences involved in its use. The more is knoss n about the performance of the rope, and the constraints on the conditions of its use, and if these are accounted for in the design process, the lower the design factor that is needed. Design factors based on lifetime rather than tensile strength should also be considered when evaluating innovative technologies. In the modern rope industry, ropes are increasingly being designed, tested, and validated for resistance against application specific lifetime failure modes. In cranes ropes, bending performance and tension fatigue (dynamic creep for HMPE) lifetime arc determining the operational usage of the rope. New modern rope designs last much longer than traditional rope designs. With modern designs, equal performance lower diameter ropes can be used that will benefit system designers. However, the breaking load of these ropes will be less, resulting in a reduced design factor. The latter is then traditionally associated with reduced performance. This despite evidence based in tests show equal performance. In aerospace engineering, design factors of 1.25 to 2.0 based on strength are regularly used. A plane designed with a 5:1 design factor would be too heavy to get off the ground. Yet our aviation industry is one of the most reliable of modern times. This is achieved through a very thorough understanding of the application, and the materials used in the construction of the aircraft. This paper will challenge the concept of Design Factor as it is applied in the field of ropes and cables. It will cover the topics of Rope Health Monitoring, Rope Health Management, and Inspection and retirement criteria, and the developments in understanding and predicting the failure mechanisms present in the application of Synthetic Fiber Rope.
