Understanding Lockout and Tagout in Electric Power Facilities

Lockout refers to the procedure of disconnecting the source of power and installing a lock to prevent the power from being turned on. In order to maintain the safety of personnel working with equipment, all electrical, pneumatic, and hydraulic power need to be disconnected, and the equipment must be locked out and tagged out. Tagout is the procedure of applying a danger tag to a power source, indicating that the equipment may not be used until the danger tag is removed. OSHA standards require equipment to be locked out and tagged out prior to any installation or preventive maintenance (see Figure 1).

 

Figure 1. Per OSHA standards, equipment must be locked out and tagged out before any installation or preventive maintenance is performed.

 

A danger tag serves the same purpose as a lock, and it's only used when a lock doesn't fit the disconnect device. The danger tag must be attached to the disconnect device using a tag tie or equivalent and must include the technician's name and other details required by the company. A danger tag must be able to tolerate the elements and the extreme atmosphere that exposure is expected (see Figure 2).

 

Figure 2. A danger tag serves the same purpose as a lock, and it's only used when a lock doesn't fit the disconnect device.

 

Lockout/Tagout Use Cases

Lockout/Tagout is used in the following situations:

• Power is not required to be on to a piece of equipment to perform a task

• There is the possibility of being injured or caught in moving machinery

• In the case of bypassing or removing machine guards or other safety devices

• When jammed equipment is being cleared

• There is a risk of injury if equipment power is turned on

 

Lockout/Tagout Procedure

Lockout and tagouts do not by themselves remove power from a machine or its circuitry. The OSHA provides a standard procedure for lockout/tagout of equipment. Lockout is performed, and tags are attached only after the equipment is turned OFF and tested. Typical company lockout/tagout procedures are as follows:

1. Notify all affected persons that a lockout/ tagout is required. Notification must include the reason for the lockout/tagout and the expected duration.

2. When the equipment is operating, shut it down using normal procedures.

3. Operate the energy‐isolating device(s) so that the equipment is isolated from all energy sources. Stored energy in springs, elevated machine members, and capacitors must be dissipated or restrained by blocking, discharging, or other appropriate methods.

4. Lockout/tagout the energy‐isolating devices with assigned locks and danger tags. See Figure 3.

5. After ensuring that no personnel are exposed, operate the normal operating controls, verifying that the equipment is inoperable and that all energy sources have been isolated.

6. Inspect and test the equipment with appropriate test instruments to verify that all energy sources are disconnected. Multiphase electrical power requires that each phase be tested. The equipment is now locked out and tagged out.

 

Figure 3. Lockout devices are resistant to chemicals, abrasion, and temperature fluctuations and are available in colors that match ANSI pipe colors. These devices are designed to fit standard industry control device sizes.

 

A lockout/tagout must not be removed by anyone other than the person who installed it, except in an emergency. In an emergency, only supervisory personnel may remove a lockout/tagout and only upon notification of the lockout/tagout person. A list of company rules and procedures is given to authorized personnel and any person who may be affected by a lockout/tagout.

When more than one electrician is required to perform a task on a piece of equipment, each electrician must place a lockout /tagout on the energy‐isolating device(s). A multiple lockout/ tagout device (hasp) must be used because energy‐isolating devices typically cannot accept more than one lockout/tagout at one time. A hasp is a multiple lockout/tagout device.

 

Lockout/Tagout OSHA Requirements

Lockout/tagout procedures must conform to OSHA 29 CFR 1910.147 – The Control of Hazardous Energy (Lockout/Tagout) and company rules and procedures. A lockout/tagout must not be removed by anyone other than the person who installed it, except in an emergency. In an emergency, only authorized personnel (persons who have been trained in proper lockout/ tagout procedures) may remove the lockout/tagout. Tagouts must be attached by hand, easy to read, self-locking, and resistant to accidental removal. Lockouts and tagouts must be tough and must resist damage from environmental and working conditions. Written procedures must be established for each piece of equipment in the facility.