NFPA 326-2020 Standard for the Safeguarding of Tanks and Containers for Entry, Cleaning, or Repair.
5.1 Lockout/Tagout. 5.1.1* All electrical circuits or other energy sources supplying power to pumps or other equipment connected to the tank or container that are a potential hazard to workers in the area of the tank or container shall be disconnected or disengaged and locked out or tagged out, or both, according to applicable regulations. 5.1.2 Where there is a need to test, position, or activate equip‐ ment by temporarily removing the lock or tag, or both, a proce‐ dure shall be developed and implemented to control potential hazards to the workers and shall be authorized by the qualifed person. 5.1.3* Any removal of locks, tags, or other protective measures shall be done in accordance with applicable regulations and the procedure set forth in 5.1.2. (See also A.5.1.1.) 5.1.4 Lockout or tagout, or both, of equipment, systems, and processes shall be confrmed by the qualifed person prior to performing work on the tank or container. 5.2 Removal of Flammable, Combustible, or Other Hazardous Substances, Liquids, or Gases.
5.3 Isolation. 5.3.1 Prior to opening, the tank or container shall be isolated from all supply and dispensing piping systems. If the tank or container on which work is to be performed is equipped with a manifold vent, vapor recovery system, fll line, siphon assembly, or other methods of connec‐ tion to other tanks or containers, the qualifed person shall determine the measures required to isolate that tank or container from all other tanks or containers. All piping connected to the tank that is capable of producing a hazard shall be isolated by being disconnected, plugged, double-blocked and bled, or blanked off. Pipe plugging shall be permitted only after an analysis is made by a qualifed person to ensure that the plug is suitable and capable of withstanding any potential pressure in the piping that might dislodge the plug. 5.3.2 The vents for the tank or container on which work is to be performed shall be isolated from the vents of other tanks or containers that might still be in service, and a separate, tempo‐ rary vent for the tank being entered shall be provided, if neces‐ sary. 5.3.3 Valves shall not be relied on to prevent the fow of mate‐ rial unless a locked and tagged double-block and bleed arrangement is provided.NFPA 326 pdf download.