4.1 Container Recognition

4.1 Container Recognition

Quick Answer: Read the container before you commit people. Non-bulk under 49 CFR 171.8 means a liquid receptacle of 119 gallons (450 L) or less, a solid receptacle of 882 pounds (400 kg) or less and 119 gallons or less, or a gas receptacle with 1,000 pounds (454 kg) water capacity or less. Larger is bulk. Highway silhouettes: MC 306 / DOT 406 elliptical aluminum fuel tanks; MC 307 / DOT 407 circular chemical tanks; MC 312 / DOT 412 smaller diameter with external stiffener rings (corrosives); MC 331 rounded-head high-pressure liquefied gases; MC 338 vacuum-insulated cryogenic. Shape is a clue. The specification plate plus placards and papers are identification.

NFPA 470 technician job performance requirements in Chapter 11.2 assume you can tell a 55-gallon drum from a cargo tank and a pressure tank car from a general-service car before you predict behavior. OSHA 29 CFR 1910.120(q)(6)(iii)(B) still requires classification and identification; the container is often the first honest clue when the diamond is dirty, missing, or wrong. If you call every shiny highway tank a gasoline tanker, you will pick the wrong isolation, the wrong PPE, and the wrong kit.

Bulk versus non-bulk (DOT definitions, not slang)

Street language uses "bulk" to mean "a lot of product." PHMSA uses 49 CFR 171.8. Quote the thresholds; do not invent a gallon number of your own.

Non-bulk packaging means a packaging that has:

1. A maximum capacity of 450 L (119 gallons) or less as a receptacle for a liquid;
2. A maximum net mass of 400 kg (882 pounds) or less and a maximum capacity of 450 L (119 gallons) or less as a receptacle for a solid; or
3. A water capacity of 454 kg (1,000 pounds) or less as a receptacle for a gas as defined in 49 CFR 173.115.

Bulk packaging is a packaging, other than a vessel or a barge, including a transport vehicle or freight container, in which hazardous materials are loaded with no intermediate form of containment, and that exceeds those same three thresholds (greater than 119 gallons for a liquid; greater than 882 pounds and 119 gallons for a solid; greater than 1,000 pounds water capacity for a gas). A Large Packaging with inner packagings can still be bulk under the same definition.

Why the line matters: placarding, identification-number display, and many ERG "small package versus large package" instincts start here. A 275-gallon tote (IBC) of liquid is bulk. A 55-gallon drum is non-bulk. A chlorine ton container (about 2,000 lb of product, water capacity well above 1,000 lb) is bulk. A 150 lb chlorine cylinder is non-bulk as a gas receptacle. Do not call a tote a drum because both sit on a pallet.

Drums: steel, poly, fiber; open versus tight head

The workhorse non-bulk liquid/solid package is the 55-gallon (208 L) drum.

Tight-head (closed-head) drums have bungs in a non-removable top. They are the liquid package. Open-head drums have a removable cover held by a bolt ring or lever lock. They are the solids, sludges, and waste package. An open-head drum of liquid is a weaker liquid container than a tight-head drum of the same steel. Overpack and leak-control tactics later in this guide depend on that distinction.

A drum farm is not one product. Weathered labels, mixed colors, and missing bungs mean unknowns. Recognition of package type is not recognition of contents.

Cylinders and ton containers

DOT 3A / 3AA seamless steel cylinders are the common high-pressure compressed-gas package. In chlorine service the usual sizes technicians drill on are 100 lb and 150 lb (product weight, not the tare of the empty cylinder). The valve typically includes a fusible plug in the valve body. Chlorine Institute Kit A is built for those cylinders. Do not assume every 3A/3AA is chlorine — the same family carries many compressed gases. Read the stenciling, the collar, and the CGA valve connection.

A ton container in chlorine service is a horizontal welded tank built to DOT 106A500X, holding about 2,000 lb (907 kg) of chlorine (a short ton of product). Recognition points:

• About 30 inches in diameter and about 80–82 inches long.
• Two valves on one concave head, protected by a bonnet. With the valves aligned vertically, the upper valve draws gas and the lower valve draws liquid (eduction tubes reach the opposite sides of the shell).
• Six fusible plugs: three in each head, spaced about 120 degrees apart. The fusible metal is designed to melt at 158–165 °F (70–74 °C) per the 49 CFR 173.301(f) temperature window.
• Stamped data on the chime: specification, serial, tare, hydrostatic test date, water capacity.

Kit B is the Chlorine Institute kit for the 106A500X. The same DOT specification can carry other compressed gases; a "chlorine ton" silhouette is still not a laboratory identification.

Highway cargo tanks: silhouette first, plate second

MC specifications (MC 306, 307, 312, 331, 338) are the older cargo-tank specs. DOT 400-series specs (406, 407, 412) replaced 306/307/312 for new construction after the early 1990s. Both generations are still on the road. Teach them as pairs.

Exam trap: an oval aluminum tank with a red diamond is the gasoline picture — until you actually read 1203 or the papers. A circular tank with stiffener rings is the corrosive picture — Class 8, not "another fuel tanker." A rounded-head white tanker with a green or flammable-gas diamond is the pressure-gas picture, not a 406. MC 338 looks "fat" because of the vacuum jacket; it is not an MC 331.

Specification plates (name plates) are required on cargo tanks (49 CFR 178.345-14 for 406/407/412; 178.337-17 for MC 331). Typical data: specification number, original test date, MAWP, capacity, materials, serial, inspector. Find the plate (often on the left front / street side near the front of the tank) from a safe location. The plate tells you what the tank is built to, not what is in it today. A dedicated 331 in ammonia service that was last loaded with propane is a verification problem, not a silhouette problem.

Rail, intermodal, pipelines, and fixed facilities

Rail tank cars split visually into general-service / non-pressure cars and pressure cars.

• General-service (non-pressure) cars (legacy DOT-111, current flammable-liquid DOT-117 with thicker shell, jacket, thermal protection, and full-height head shields) carry many liquids at relatively low pressure: petroleum, alcohols, some corrosives and toxics. Fittings are less "armored" than on pressure cars.
• Pressure tank cars (DOT-105, 112, 114, 120 and related) are circular, heavily built, with a protective housing (dome) over valves on top. They carry liquefied gases — LPG, anhydrous ammonia, chlorine — and other high-vapor-pressure products. Treat a pressure car like a 331 on rails: the energy is in the lading, not just the wreckage.

Intermodal portable tanks (ISO tanks) sit in a frame that stacks on ships, rail, and chassis. Older plates still say IMO Type 1 / 2 / 5 / 7; newer UN portable tanks use T1–T22 (liquids), T50 (non-refrigerated liquefied gases), and T75 (refrigerated liquefied gases). IMO-1 / higher-pressure liquid tanks, IMO-2 lower-pressure liquids, IMO-5 gas tanks, and IMO-7 cryogenic tanks are the recognition set. Read the tank plate on the frame.

Pipelines do not present a cargo-tank silhouette. Markers (49 CFR 192.707 / 195.410) give operator name, product or "gas/petroleum," and a 24-hour number. Product is moving under pressure you cannot see. Isolation is a control-room and valve-station problem, not a drum-overpack problem.

Fixed facilities add ASME pressure vessels, process piping, atmospheric storage tanks, reactors, and totes / IBCs. Composite IBCs (plastic bottle in a cage, often 275 or 330 gallons) are bulk liquid packagings if they exceed 119 gallons. Process piping can contain the same product as the vessel at a different pressure and temperature. NFPA 704 diamonds on the building may not match every tote in the warehouse.

Exam scenario: five highway tanks, one mistake

You are staged uphill and upwind of a multi-vehicle pileup. Tank A is oval aluminum with manholes on top — 406 / gasoline picture. Tank B is circular stainless without ribs — 407 / chemical picture. Tank C is smaller diameter with external rings — 412 / corrosive picture. Tank D is circular with rounded heads and a rear valve cabinet — 331 / LPG or ammonia or chlorine. Tank E is a heavy vacuum-jacketed tank with a piping cabinet and a white vapor at the vents — 338 / cryogenic. Calling all five "tankers, foam the ditch" is how a technician takes a corrosive bath, a cryogenic freeze burn, or a pressure-gas BLEVE problem. Recognize the container, then verify identity with plate, placard, ID number, and papers — the same identify-then-verify duty as Chapter 3.