Per the OSHA requirement, training of employees needs to happen annually at the very minimum. Employees should also be retrained anytime there is a change in energy control procedures for equipment or if new equipment is installed. Often near-misses and accidents arise from an employee being unaware or lacking understanding of the change in hazardous energy to a piece of equipment.
For example, you add an additional water line to a chiller. Your maintenance employee has been servicing this same chiller for years knowing there is only one water input. Your employee does not realize that this second input has been added; therefore he does not lock it out during his service, which in turn could result in an accident, increased insurance costs, lost work time and high operating costs.