Home Podcasts THMG012 – DOT406 Tank Leaks

THMG012 – DOT406 Tank Leaks


In this episode, Mike and Bob discuss over-the-road fuel tank trucks and the problems associated with them. They also talk a little bit about the nuts and bolts of the liquids they carry, some plumbing tips, and tactical considerations.

Complete Show Notes

7:00 Tankers

  • Most common tankers are DOT 406 – very little difference between 306 and 406 tankers, but it’s crucial to know the difference between the two
  • Oval is the most common tank shape – fat bottom tanks that stick out over the wheel wells
  • Most tanks are made from aluminum

8:30 Tech Specs on Tankers

  • Can have one big tank or multiple compartments (trucks carrying gasoline often have multiple compartments)
  • 406 tankers have manways on top with ladders so people can walk on them
  • Don’t assume that weep holes in the bulkhead are dry on the top and bottom – unsavory truckers may modify them so they can carry more
  • Dome covers can be used to fill and visually inspect the tank – accompanied by covers (several different types available
  • Tankers have gas fill sensors that use optical sensors
  • When tankers roll over, the dome covers usually aren’t able to hold back the pressure of the fuel pushing down on them

14:05 Assessing Tankers at the Scene

  • Several ways to determine where the tank separations are
    • Gallon labels at the top
    • Dome covers
    • Piping from each tank
    • Weld marks for bulkheads (different than baffle heads)

15:55 Tanker Piping and Valving

  • Two main systems
    • Vapor recovery system – used to recover vapors when trucks are doing things like offloading fuel; usually on the back of the truck; connected to each tank
    • Piping – allows trucker to offload and onload the fuel; clustered underneath the truck; valve terminals are capped, locked, and have a breaker bar in front of them

17:20 Emergency Shut-Offs

  • All of the shut-offs are pneumatically driven – lots of redundancies built into the system
  • Air brakes engage in both the tractor and the trailer
  • Breaker bar is designed to release the internals, which is a secondary valve located on the inside of the belly
  • If the breaker bar isn’t locked, the driver won’t be able to drive the truck
  • Emergency slap switches inside the cab engage internals and shut down transmission
  • If air lines are cut, all of the valves open up and the emergency shut-offs are disengaged
  • Most tankers have above-ground head pressure pumps – generally in the front behind the cab and can potentially be used to offload the tank

22:55 Saddle Tanks

  • This is where the truck holds the fuel it needs to drive – particularly important if you’re carrying diesel, but the truck runs on gasoline
  • These come in all different sizes and configurations – can be connected through the engine or pipes
  • Saddle tanks are the most common thing hazmat techs deal with when responding to leaks

24:25 Overview of Hazards

  • Unstable vehicle – the tractor and the trailer are two separate entities and should be treated accordingly; always chock the wheels (even if it’s rolled over), especially on grades
  • Contents – 406s are typically transporting some type of flammable hydrocarbon or diesel (occasionally milk)
  • Flammability is generally the biggest hazard, so you should always wear PPE, fire gear (including fire gloves), and SCBA
  • Use dome cover clamps on every dome to anticipate and control leaking

27:25 Places Where Tankers Can Leak

  • Body – this can be difficult to stop depending on how the truck is situated
  • Tank deterioration – corrosion around the weld points (welds are the strongest points, but the area around welds is weak)
  • Internals (located between the bulkheads)
  • Between tanks – leaking can tear weld points
  • Tank to trailer
  • Pipes connected to the tanks
  • Gouges, scrapes, abrasions, etc. – there are lots of patches out there to handle these
  • No matter the damage, you can always slow down the leak to reduce the hazard (there’s no way of stopping leaks)

31:50 Damage to Tankers

  • Tanker can be upright (still on its wheels) – damaged due to punctures, tears, gouges, severe dents, etc.
  • Tanker can be on the ground (off its wheels) – damage can be obscured by the ground, which can be dangerous
  • Internal baffles and bulkheads can be damaged – don’t open holes that could be holding back thousands of gallons of fuel

34:25 Roles When Responding to Leaking Tankers

  • Operations level – damming and diking to get fluid onto pavement; prepare to deal with the entire contents of the tanker; create pools to collect contents
  • Technician level – mitigation; might drill into the tank or do some welding
  • Can try plugs, inflatable air bags, goop, water replacement, gas replacement, pipe patch kits
  • If you can’t handle all of the contents, you can give free tanks of gas to passing cars, recirculate the fuel, etc.
  • Never upright a 406 with anything in it – these tanks aren’t designed to take any kind of impact (especially on the side)

Have a question? Send an email to feedback@thehazmatguys.com or leave a message on our Haz Mat Guys comment hotline: 843-628-1484

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