Tanks and vessels are oversize by diameter and often by length — so most are permitted loads. They ride cradled in saddles on a flatbed, step deck, or multi-axle trailer chosen by weight and height, secured against rolling, with permits and escorts in every state. Large-diameter vessels move as engineered superloads.
Storage tanks and pressure vessels are among the most common oversized loads on the road — and among the easiest to get wrong, because a round steel body doesn't sit still on a flat deck. Here's how tanks and vessels move.
Diameter makes it oversize
A tank's diameter drives both width and height on the trailer, and most process and storage vessels are wide enough that they're oversize the moment they're loaded. Length adds permit and overhang issues; weight decides the trailer and how many axles it needs. The legal envelope is 8'6" wide, 13'6"–14' tall (state-dependent), and 80,000 lbs gross — a mid-size vessel can bust all three. Tanks ship empty and purged; both the empty weight and the loaded height off the deck matter.
Trailer and cradle
Smaller tanks ride a flatbed or step deck; large or heavy vessels move on a lowboy or multi-axle trailer that keeps the diameter under the height limit and spreads the weight. The critical piece is the support: the tank sits in shaped saddles or cradles matched to its diameter, so the round body is held from rolling and the shell isn't taking load on a single point. Nozzles, manways, and fittings get protected or removed.
Securement: stop the roll
A cylinder wants to roll, so securement is built around that: chains or straps over the saddles and down to the frame, end blocking, and shell protection at every contact point. This is textbook blocking and bracing — the cradles and blocking do the work, the tie-downs hold it against them.
Permits, escorts, and superloads
Because diameter usually breaks the width and height limits, tank moves are permitted in every state, with pilot cars added by width and a height-pole car for tall loads. Large-diameter columns and vessels — refinery and process equipment — move as engineered superloads with route surveys and bridge review. It's core heavy haul work; see what counts as oversize for the thresholds.
Bottom line
- Diameter drives width and height — most tanks are oversize before they're loaded.
- Ship empty and purged; cradle the tank in saddles matched to its diameter.
- Secure against rolling — chains over the saddles, end blocking, shell protection.
- Permits and escorts in every state; large vessels route as superloads.
Moving a tank or vessel? Send the diameter, length, and weight and we'll spec the trailer, cradle, permits, and escorts — get a quote.