A better understanding of NFPA 70E: Risk Control - Substitution and Engineering Controls

Blog Post created by ccoache Employee on Aug 15, 2017

The hierarchy of risk controls is required to be implemented, in descending order, whenever it is necessary to protect an employee from the risk of injury associated with the use of electricity. Elimination, the most effective control, was discussed in the prior blog. The next control that must be implemented is substitution followed by engineering controls. These two controls are more effective than the remaining three since they are less affected by human interaction. The hierarchy of risk controls is:
(1) Elimination
(2) Substitution
(3) Engineering controls
(4) Awareness
(5) Administrative controls
(6) Personal protective equipment (PPE)
Substitution is often more applicable in the design stage. This does not mean that substitution cannot be employed at a later date. For example, installing a remote racking system is a substitution method that could be employed during equipment installation or may be installed subsequently. In this context, the remote racking system may lower the risk of injury to the employee rather than have an effect on the hazard that the employee will be subjected to. Substitution could also be utilizing a faster acting overcurrent device or opting for components that limit the available fault current. Arc-rated equipment could be employed to lower the risk of injury to an employee.
This control method could fail for the same reasons as those used for elimination. Equipment could be constructed incorrectly or the equipment procurement process could deviate from the specified equipment. Incorrect or insufficient maintenance could defeat this control method. Substandard or counterfeit equipment must be avoided. However, removing the reliance on the actions of an employee for the creation of a safe work environment increases the probability of success.
Engineering controls often take the form of guards and barriers to reduce the probability of an injury. Zone-selective interlocking or differential relaying can reduce the incident energy. These methods are also not infallible. Guards may be removed to make performance of tasks or equipment operation easier. Barriers may be moved to provide greater access. Defeating this control often takes conscious human effort. Still, preventing access to a potential hazard greatly decreases the likelihood that an injury will occur.
Next time: Awareness and administrative controls.