Home Podcasts THMG031 – DOT 412 Tankers

THMG031 – DOT 412 Tankers


In this episode, Mike and Bob review DOT 412 tankers, which are some of the most prevalent over-the-road containers out there.

Complete Show Notes

5:00 DOT 412 Tankers Overview

  • They exclusively carry corrosives, which are substances with pH (can be acids or bases)
  • This presents a new set of problems and identification rules that we have to know in order to mitigate potential problems
  • Construction
    • Typically made from stainless steel, but there are some variations out there
    • Ribs (stiffeners) – necessary because of the weight of the corrosives they’re carrying
    • Ribs provide increased stiffness over the length of the barrel to prevent the barrel from flexing under the load and splitting (either catastrophically or a small crack)
    • Ribs can be visible or invisible (they’ll be invisible if they’re covered with insulation)
    • Unlike DOT 406 and DOT 407 tankers, you won’t find any bottom valving or ports – all of the loading and offloading will be done from the top via a tube and pressures

10:10 Identifying Characteristics of DOT 412 Tankers

  • You can identify the tank based upon the diameter of the barrel
  • If you’re viewing the rear of the tanker looking forward, typically the diameter of the barrel will be within the inside of the inner tires (even with insulation on the barrel)
  • DOT 412 tankers can have up to 4 compartments, but typically only have 1
  • Due to the amount of product they carry and the movement of the product inside the barrel, they’ll probably have some kind of baffle installed
  • DOT 412 tankers are smaller in diameter than DOT 407 tanks
  • This is because the specific gravity (and weight) of corrosives are substantially higher than other products (like petrochemicals and other types of “regular” chemicals)
  • Over-the-road regulations are based on weight transported, rather than by the amount carried
  • Since corrosives are much heavier and need more substantial tanks to be transported, DOT 412 tankers can carry less product (and therefore have a smaller barrel cross-section)

11:10 Hazmat Drill Nugget from HazSim

  • Dexterity drill – learning to work and operate in PPE
  • Do everyday tasks in your gloves to get used to operating with layers on

15:35 Loading and Offloading DOT 412 Tankers

  • DOT 412 tankers are usually offloaded through a tube that extends from the top to the bottom and rests inside a sump
  • Sumps are large bowls that are welded to the bottom of the tank to create a depression – the liquid pools there, making removal more efficient
  • DOT 412s use the same method to offload, but in reverse

16:55 Lining and Chemical Protection

  • The bands that go around the tank offer chemical protection – this is the same protection that may be on the inside of the tank
  • Lining is sprayed inside the tank to increase its contact protection – some of these corrosives are incredibly damaging
  • Tankers have a metal structure that lessens the impact to valving and parts of the tank that would leak in case of an accident – found at the back or middle of the tank and sometimes coated with liner material
  • DOT 412s don’t need to be lined if the tank material is immune to attack by the transported materials
  • Has to be able to resist attack for 10 years of normal service without any point of the shell being reduced to a thickness of less than what the regulations require

20:55 Loose Ends on DOT 412 Tankers

  • The tank itself must be able to withstand any pressures it might encounter – this may be from the weight of the product itself or from any external forces
  • Tanks that exceed 15 psi must be ASME (American Society of Mechanical Engineers) certified
  • Pressure (not exceeding ASME limits) can be used to pressurize the tank and move the product
  • If the tanker has a bottom valve, there must be some means to remotely activate that valve
  • Also needs a sealing cap or blind flange at the end of the outlet
  • A blind flange is a flaring at the end of the pipe with holes for bolts to connect to – designed to completely make sure that liquids won’t escape and also prevents any venting or safety from operating through that port
  • If there’s a safety appliance installed, it has to open with 150% of the MAWP (maximum allowable working pressure) – has to be at 130% when using pressure or promoting offloading

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