Consequently, only cables where mechanical protection is provided by a suitable sheath, for example, PVC sheathing, MICC, fire resistant cables to BS 7629-1 or steel wire armouring, can be used in conjunction with ladder and tray systems. Site. This publication is intended as a practical guide for the proper and safe* installation of cable ladder systems, cable tray systems, channel support systems and associated supports. Site modifications Many contractors will be familiar with. Whether you are designing and manufacturing a new cable or simply choosing an existing one for data, power, fiber optics, or industrial automation, the outer sheath (jacket) is much more than just a speaking cover to the eye; it is, in fact, an important job holder in mechanical protection. The cable sheath, a protective outer layer wrapped around the insulation and conductor, may seem like just a layer of “plastic skin,” but it is actually the cable's “first line of defense” against external damage. This misconception of “emphasizing the conductor and neglecting the sheath” often. maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. However, there are many different types of sheaths on the market such as PVC, XLPE, PE. So how to.