Hazardous Materials and Tank Vehicle Loading/Unloading
Hazardous Materials and Tank Vehicle Loading/Unloading
This domain covers the paperwork, the physical hookup, and the discipline of staying with the vehicle while product moves. Test items ask about placards, shipping papers, grounding and bonding, outage, and the attendance rule.
Before product moves
- Shipping papers: proper shipping name, hazard class, UN/NA number, total quantity, and an emergency response phone number, within reach while driving.
- Placards: required on both sides and both ends of a cargo tank and matching the product. Table 1 materials (for example Division 2.3, 4.3, and Division 6.1 Packing Group I) need placards for any quantity; Table 2 materials at 1,001 pounds or more.
- Tank and product match: check the specification plate before the hose goes on.
- Attendance: a placarded tank being loaded or unloaded may not be left unattended; you must be present and able to shut it down. Engine off unless it powers the pump, parking brake set, wheels chocked.
Grounding, bonding, and static
Bond the tank to the source or receiving container with a clean metal-to-metal connection before you open any hatch or valve, and leave the bond connected until everything is closed again. Where a ground is available, connect it too. Splash loading generates static; loading through the bottom or a downpipe limits it. No smoking, open flame, or lighted matches within 25 feet of a tank containing a flammable liquid or of a loading or fueling operation.
Outage and filling limits
Never fill a tank to the brim. Leave expansion space (outage), commonly about 1 percent of tank volume, so product can expand with temperature rise without being forced out the vent or hatch.
Unloading
Open valves slowly, watch pressure and the hose, stay at the controls, use the emergency shutoff if anything goes wrong, drain and confirm empty before disconnecting, then cap every outlet.
Worked example
You load a 9,000-gallon DOT 406 trailer with gasoline on a 95-degree day; the shipping papers show UN1203. Reasoning: gasoline is a flammable liquid and the 406 tank is the correct specification, and 95 degrees means the product will expand after you leave. You stop loading at about 8,900 gallons, leaving roughly 1 percent outage, confirm the bond is still connected, close the hatch and check the gasket, verify all four placards read FLAMMABLE, and only then disconnect the bond.
Traps
- Bonding after the hatch is open.
- Loading until product shows in the hatch.
- Leaving a placarded tank to sign paperwork in the office.