If not designed and installed properly, wiring inside cable trays may pose hazards such as fire, electric shock, and arc-flash blast events. 305(a)(3), or comparable standards promulgated by States operating OSHA-approved State plans. In addition, this document contains several references to provisions of the National Electric Code. Working with cable trays is not just a routine installation job. Most of engineers take it as a mechanical formation to be taken care of it. The process described here takes a systematic approach to ensuring that cable tray installations meet safety, reliability, and project-specific needs while following to. - Obtain PTW before the start of the activity. Overloading cable trays can lead to a.