There is a sound reason why OSHA’s Flammable Liquid Standard has required a deadman valve for over 40 years and it is the same reason why I have written about their use for 20 years… When things go bad and you need to get the heck out of dodge quickly, you can do so AND stop the flow of the flammable liquid.
1910.106(e)(2)(iv)(d) flammable liquids shall be drawn from or transferred into vessels, containers, or portable tanks within a building only through a closed piping system, from safety cans, by means of a device drawing through the top, or from a container or portable tanks BY GRAVITY THROUGH AN APPROVED SELF-CLOSING VALVE. Transferring by means of air pressure on the container or portable tanks shall be prohibited.
These videos, different angles of the same accident, show what happens when flammable liquids are transferred using gravity WITHOUT the aid of a “deadman valve”. Basically, without an emergency means to stop the flow, the flammable liquid will continue to flow with no means to STOP the flow once you have exited stage left!
PLEASE NOTE that when you see the feeble attempt to use a fire extinguisher, the fire is WELL BEYOND the incipient stage and should NEVER have been attempted.