Lashing

Lashing is securing cargo by tying it down: web straps, chains, wire rope, steel band or fibre rope, tensioned between the cargo and fixed securing points on a container, flat rack or road vehicle. Lashings transfer tensile forces, where blocking and bracing with dunnage work in compression. The CTU Code, the IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units (2014), says that whenever cargo cannot be secured by blocking, it must be lashed: the weight of the cargo alone, even on a high-friction floor, does not stop it moving under vibration.

Lashing points and their ratings

• General-purpose containers: most have a limited number of lashing rings or bars. Where fitted, the floor-level anchor points have a maximum securing load (MSL) of at least 10 kN in any direction, many recently built boxes 20 kN, and the lashing points on the top side rails at least 5 kN (CTU Code 6.2.5, citing ISO 1496-1 Annex C). 10 kN is roughly one tonne of force, so a single ring holds far less than a heavy crate weighs
• Flat racks and platforms: lashing brackets welded to the bottom girders are rated at least 30 kN under the standard and often 50 kN, and end walls may carry points of at least 10 kN (6.2.11)
• Open tops: built like a closed container apart from the roof, and used for cargo that is over-height but not over-width (6.2.8 and 7.2.6)
• Reefers: thermal containers are generally not fitted with anchor and lashing points, so cargo that must be lashed needs fittings added to the floor gratings (6.2.12)

Lashing materials and strength

A lashing's strength is given as its breaking load; its maximum securing load is the share of that which should not be exceeded in service. The CTU Code (annex 7, 2.4.2) puts the MSL at 75% of breaking strength for single-use web lashings and 50% for reusable ones, 80% for single-use wire rope and 30% for reusable, 50% for chains and mild-steel shackles and turnbuckles, and 33% for fibre rope. Those figures assume smooth edges; sharp corners cut them substantially, so edge protectors should be used. Lashings should be pre-tensioned, fastened with hooks or shackles rather than knots, and never tightened so hard that they damage the cargo or overstress the container.

Cargo lashing vs container lashing on the ship

• Inside or on the unit: securing the cargo is part of packing. The CTU Code places responsibility for poor packing and securing with the shipper, who in turn may hold the packer or consignor responsible (4.1.2)
• On the vessel: the carrier secures the containers themselves to the ship and to each other with its own locking and lashing gear. That secures the box, not what is inside it

Heavy and out-of-gauge cargo

The CTU Code notes that granite and marble blocks in a closed container need bracing and blocking against the frame and/or lashing to the securing points, and that because the points in a general-purpose container have limited capacity, a platform or flat rack may suit large, heavy items better (7.2.5). Stone is regular cargo on the India to USA lane. Cargo too wide or tall for an enclosed box goes on a flat rack or platform, or in an open top if it is only over-height.

Common mistakes

• Counting on a container's floor rings to hold a heavy item they are not rated for
• Lashing over sharp edges without protectors, or knotting web straps
• Nailing to the floor of a closed container, which the code says is generally unsuitable for nailing
• Releasing lashings at destination without checking whether the cargo will shift or topple, which the code warns about for low-friction items such as stacked steel plate

See FCL ocean freight for heavy, flat rack and open top bookings.