Lockout/Tagout Basics

As stated by the Occupational Health and Safety Administration OSHA, Lockout Tagout or LOTO are a set of specific practices and procedures to safeguard employees from the unexpected energization or the release of hazardous energy during service or maintenance activities.

The purpose of Lock out tagout is to protect the worker from any physical injury while performing maintaining a machine. In case of an equipment malfunction, it is imperative for the authorized employee to isolate the machine from its power source.

Participate Now!


It is the process of applying a lockout device on an energy isolation device to prevent the accidental activation. For example, a disconnect switch, circuit breaker or control valve may be kept locked while performing any associated work. This ensures that the equipment cannot be activated until and unless the lock is removed.

The energy isolation device should have a hasp or dedicated part for the placement of lockout device. Lockout devices should be robust enough to prevent accidental breakage or inadvertent activation of the energy isolating device.


Tagout means placing a prominent warning sign on the energy isolating device. The tagout device should warn about the hazards in case the machine is activated. It should display clear instructions of not operating or energizing the machine until the maintenance work is completed.

Additionally, the lockout tagout devices should also be labelled to identify the authorized employee for their access.

A tag out device should be securely attached as well as clearly visible and understandable. There are various factors for the durability of tagout devices which should be kept in mind as well.

Why Lockout/Tagout is crucial?

Compliance with the lockout/tagout standard prevents an estimated 120 fatalities and 50,000 injuries each year and an average of 24 workdays for recuperation.

The unexpected startup of a machine, or a sudden release of any type of stored energy during maintenance work can result in catastrophic results for a worker.

Thus, lockout tagout is necessary to ensure the safety of employees by preventing such incidents from occurring.

What is Hazardous Energy?

In industries, we refer to energy as anything which powers a machine, process or a system.

Hazardous energy, however, can be defined as:any electrical, mechanical, hydraulic, pneumatic, chemical, nuclear, thermal, gravitational, or other energy that can harm personnel

There are a few key examples of hazardous energies which can potentially prove to be lethal.

Lockout/Tagout Standards

There are three main Lockout/Tagout Standards employed globally by organizations such as OSHA and CSA. However, these standards differ from each other in terms of their application and target audience.

Lockout/Tagout Procedures

OSHA has listed some pre-defined steps to perform the lockout procedure which are as follows:

  1. Notification: All the employees working nearby should be informed that maintenance work is scheduled and the equipment needs to be powered off and locked out.
  2. Identification: An authorized person may identify the type and magnitude of the energy which powers the machine.
  3. Shutting down: The equipment or machine will be shut down using its standard operating procedures such as switching off, pressing a button or closing a valve.
  4. De-activation: Energy isolating devices are de-activated to completely isolate the machine from its energy source.
  5. Locking out: The energy isolating devices are locked with their respective locking devices.
  6. Dissipation of Residual energy: Equipment such as capacitors, springs, elevated machine members, rotating flywheels, hydraulic systems contain stored or residual energy in them.
  7. Verification: The isolation of equipment is verified by trying to operate it using its normal operating procedure such as ON button.
  8. The machine or equipment has now been properly locked in compliance with OSHA standards.
Lockout / tagout procedure”, by NAVFAC , is licensed under CC BY 2.0

LOTO Training

An employer must ensure that their employees are aware of the purpose and functions of Lockout/tagout. They should have the knowledge and skills to safely apply lockout/tagout procedures.

OSHA has three levels of trainings for different employees which are comprehensively described.

Sudden Energization of industrial equipment can give rise to high magnitude voltage transients. However, the probability of their occurrences can be effectively removed through a well-structured Short-Circuit Study which can be done by hiring a professional Power Systems Engineer.

This will result in an overall better equipment protection in the event of a massive power surge, induced by the sudden energization of machinery.

Let us know if you have any queries regarding this topic and do provide us with your feedback in the comments.

About The Author

Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.

Abdur Rehman is the CEO and co-founder of allumiax.com and creator of GeneralPAC by AllumiaX. He has been actively involved in various roles in the IEEE Seattle Section, IEEE PES Seattle, IEEE Region 6, and IEEE MGA.

Leaders in Industrial & Commercial Power Systems Engineering