Home Hot Wash THMG184 – Leaking MC331 Scenario, Part II

THMG184 – Leaking MC331 Scenario, Part II


In this episode, Bob and Mike wrap up their review of an overturned MC 331 tanker scenario.

Thank to our sponsors, CavCom, Inc., First Line Technology, and All Safe Industries.

This was originally going to be a one episode hot wash, but it expanded – much like propane does! In this episode, Bob and Mike explore how propane works and get into the weeds on tanks and operations.

Complete Show Notes

2:35 Options if the Tanker Was Leaking (Continued)

  • The rig is on its side, so water injection wouldn’t help
  • Water injection works by overcoming the pressure in the container – water will fall to the bottom when it meets the liquid in the tank because it’s heavier
  • Goes from a straight-up propane leak to a water leak with a touch of propane
  • We could also burn the leak off with a flare
  • You can use vapor to burn off slowly or liquid to burn off 270 times faster
  • Transferring is also an option, but it has its own set of problems
  • Ask for a 331 rated for propane that’s empty – has to be the right kind of tank for transfer to work
  • We can pump it with a pneumatic double-diaphragm air pump (Mike’s choice) – some of them do up to 180 gallons per minute
  • An empty tank has the same head pressure as a full tank – this is why we can’t use pressure to determine how full your tank is
  • We can also use pressure differential (Mike’s last option) – difficult because you could release product into the atmosphere

15:15 Slowing Down the Leak

  • We can use a fiberglass wrap if you have one – this works well on vapor leaks, but not so much on liquid
  • Freeze on the wrap works well depending on the size of the liquid leak
  • If there’s too much liquid coming out (or if too much of the product has already auto-refrigerated), it won’t work as well
  • Keep in mind that the wrap is going to naturally weaken over time depending on your weather conditions
  • We can also use the emergency shut-off switch for everything but PRD

19:30 What Should Operations-Level Personnel Be Doing?

  • Set up 2-3 fog lines on the upwind side – helps with vapor dispersion
  • Secure the area
  • Determine possible evacuation routes if the tank is leaking – use ERG to determine isolation distance
  • Reduce ignition sources
  • Perform downrange monitoring

26:00 PPE Selection for Propane Situations

  • Bob and Mike agree that you’ve got to go with structural firefighting gear
  • None of the other levels make sense in this scenario, even with the “boom” aspect
  • We should definitely be wearing masks in this case just to be on the safe side

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