Equipment used for electrical safety-related isolation on industrial machines

On an industrial machine there is often more than one entry point that might be used during the operation and maintenance functions. Typically the lockout tag-out procedures prior to entering the machine has been done using series connected conventional load break disconnect switches. Unfortunately the required verification is problematic for applications requiring only one disconnect switch and almost impossible when more than one disconnect switch is applied. This paper reviews some of the problems and proposed solutions. The context of this paper is energy from electrical sources and does not address other energy sources that may be present on a particular machine.