The baffled ISO tank uses 2 to 4 internal vertical perforated plates (each plate 30 to 50% open area) to divide the cylindrical interior into 3 to 5 compartments. The baffles dramatically reduce liquid surge during transit and discharge, and they lift the IMDG 4.2.1.9.1.1 surge floor that prohibits filling a tank greater than 7,500 L to between 20% and 80% of capacity. The build is required by ADR 6.8.2.1.22 and DOT 49 CFR 178.345-7 for hazardous partial fills outside the 20% to 80% range and is operationally helpful at any partial fill.
What baffled is built for
Cargoes where the operator needs to ship dense or partial-fill loads that would otherwise land in the surge-prohibited band. The canonical use case: 98% sulphuric acid (SG 1.84) where the weight cap in a 24,000 L T11 lands at 17,400 L = 72.5% fill, in the IMDG 20% to 80% surge band. A baffled T11 lifts this restriction, letting the cargo ship in the larger tank without escalating to a smaller-volume T14. For multi-drop routes (one tank delivering to multiple receivers en route) baffles let the operator partially discharge at each stop without surge issues during the next leg.
Construction and materials
316L stainless cylinder built to standard T11 spec, with 2 to 4 vertical perforated plates welded transversely inside the cylinder. Each baffle plate has 30 to 50% open area through evenly distributed perforations, allowing fluid flow during loading, mixing, and cleaning while restricting bulk surge motion. Baffle plates add 200 to 400 kg to tare. Capacity reduces slightly (to 23,500 L typical from 24,000 L) because the plates occupy internal volume.
The baffles complicate CIP cleaning: shadow zones behind each baffle require dedicated spray-ball coverage and longer cleaning cycles. Operators with deep baffled-fleet experience (Stolt, Hoyer, EXSIF, Bulkhaul) handle this routinely; a baffled tank in a fleet without baffled-tank cleaning expertise is a flag.
When baffled is the right choice
Baffled is the right tank for any DG cargo where the weight-limited fill ratio falls in the IMDG 20% to 80% surge band. Concentrated 98% sulphuric acid in T11 (the canonical case). Bromine in T20 (extreme density). Any partial-load shipment where the operator wants to use the larger-capacity tank for fleet-rotation reasons. The baffles are also operationally helpful at any partial fill (they reduce surge regardless of regulatory band), so some shippers prefer baffled tanks even when the IMDG rules don’t require them.
When baffled is the wrong choice
Baffled is the wrong tank for cargoes where the cleaning cycle’s shadow-zone challenge outweighs the surge-control benefit. Food-grade and pharma-grade cargoes typically prefer non-baffled tanks because the CIP cleaning is simpler and more reliable. Cargoes that ship at full fill (above 80% by volume) don’t need baffles for surge control, although operators with mixed fleet rotations may run baffled tanks even for these cargoes for fleet-flexibility reasons.
How a baffled booking is verified
Pre-loading inspection covers the standard plate stack plus the baffle-condition check (visual through the manlid for cracks, weld failures at baffle attachments, or mechanical damage). The CIP system test verifies spray-ball coverage of the shadow zones behind each baffle. EFTCO ECD documents the cleaning cycle used; cycle time on a baffled tank typically runs 30 to 50% longer than on a non-baffled equivalent.