By Joyce Jin    Photo：CANVA

Flat Rack containers (FRs), as a specialized type of ocean freight container, play an irreplaceable role in the transport of out-of-gauge and heavy-lift cargo due to their open structure without side walls or a roof. However, this "open-top" design also leaves cargo without the passive protection of standard containers, exposing it to significantly higher damage risks. Statistics show that lashing failures and improper stowage account for 31% of global flat rack cargo damage incidents. Adopting scientifically designed, efficient securing solutions has therefore become a core priority for freight forwarders and foreign trade enterprises seeking to eliminate transit damage.

1. Understanding the Risks: Where Does Flat Rack Damage Originate?

Damage to flat rack cargo is rarely accidental—it results from the accumulation of multiple factors. During ocean voyages, ships experience continuous rolling, pitching, and yawing, subjecting flat racks to dynamic loads including sea-induced sway, crane vibrations, and terminal handling impacts. Designing securing plans based solely on "static" conditions grossly underestimates the actual risks of the marine environment.

Common damage types for flat rack cargo include:

• Transverse sliding displacement: Insufficient lashing tension allows cargo to slide laterally across the flat rack floor. The resulting friction and rigid impacts can deform equipment frames and cause fracture or failure of internal precision components.
• Fatigue damage from resonance: Loose lashing systems cannot dampen hull vibrations. Precision parts may resonate with the ship's vibration frequency, leading to progressive microscopic cracking. Most lashing-related defects do not cause immediate visible damage; instead, they manifest as micro-cracks and component shifts that only become apparent upon arrival at port.
• Overturning risk from center-of-gravity (COG) offset: This is the most critical hazard in flat rack transport. In one notable case, a cargo unit with a severely eccentric COG overturned instantly when the flat rack was hoisted onto a truck chassis. The root cause was a significant weight bias combined with an incorrectly marked COG on the outer packaging—opposite to the actual center of gravity.
• Stress concentration from uneven force distribution: Asymmetric lashing arrangements lead to unbalanced loading on the cargo, causing localized pressure spikes that can crack brittle materials and disrupt the overall structural balance of the equipment.

2. Overview of Efficient Securing Solutions

Solution 1: Material Selection – Choosing the Right "Weapons" Is Half the Battle

The choice of securing materials directly determines the effectiveness of the entire system. Currently, mainstream materials include:

• Steel wire ropes: Suitable for heavy cargo, capable of withstanding high tensile forces. Used in conjunction with turnbuckles (screw-type tensioners) for precise tension control.
• High-tenacity polyester lashing straps (tie-downs): Quick and convenient, with a single strap typically rated for less than 5 tons of load. For cargo with wooden packaging, flexible straps are safer than steel wire ropes.
• Hot-dip galvanized steel strapping: Highly corrosion-resistant, ideal for long-term marine exposure.
• Timber and wooden wedges: Used to prevent horizontal displacement and collisions between cargo units. Must be made of heat-treated (ISPM-15 compliant) or clearly marked fumigated wood.
• Anti-slip and cushioning accessories: Including flexible rubber buffers, anti-skid mats, etc., to reduce friction and impact damage.
• Edge protectors / padding: Where steel wire ropes or straps contact the cargo, protective padding (e.g., plastic hoses, rubber sheets) must be placed to prevent abrasion and surface damage.

Key principle: Always use high-strength, corrosion-resistant, non-brittle specialized materials. Avoid low-tension webbing, rusted steel bands, or substandard pads.

Solution 2: Lashing Arrangement – Symmetrical, Crossed, and Multi-Point Load Distribution

Lashing layout is the core technical element of flat rack securing. Recommended industry practices include:

• Symmetric lashing: Adopt a symmetrical multi-point arrangement to avoid unilateral loading. Each securing point on both sides of the flat rack is typically rated for 5 tons; avoid concentrating lashing forces on a single point.
• Cross lashing: Use diagonal, cross-symmetric patterns (e.g., a "figure-eight" or "grid" configuration) to ensure even tension distribution. Arrange 2–4 lashing points on each side (attached to the corner posts) and 1–2 at the front and rear ends (fixed to the end beams), with spacing between points not exceeding 3 meters.
• Multi-point fixation: All securing points must be attached to the flat rack’s original factory-fitted lashing rings and corner castings. Never lash to the floor, non-structural cross-members, or auxiliary parts.
• Tension control: Use turnbuckles or tensioners to tighten wire ropes, adjusting tightness to avoid over-tightening (which may damage cargo) or under-tightening (which allows movement in transit).

Solution 3: Support Structures – Let Lashing Not Work Alone

In practice, many shipments rely solely on wires or straps without adequate support. This is a common misconception—lashing restricts movement, while supports distribute weight and forces.

An effective support structure should include:

• Bottom dunnage: Place sleepers or wooden blocks between the cargo and the flat rack floor to spread pressure and increase friction. Timbers should cross multiple floor cross-members to avoid point loading.
• End supports: Fill the gap between cargo and the container's end bulkheads with support frames to prevent longitudinal shifting. Maintain at least 30–35 cm clearance between the cargo and the end walls to allow for handling.
• Anti-slip treatment: Apply anti-slip mats at the contact surface between cargo and the flat rack base. The larger the contact area, the higher the friction, reducing the risk of horizontal displacement.
• Anti-roll supports for curved cargo: For cargo with a curved contact surface (e.g., cylindrical or spherical items), use wooden wedges at no fewer than six points along both sides of the curve, and secure the wedges with nails.

Solution 4: Center of Gravity Management – The Invisible "Stabilizer"

COG management is the most easily overlooked yet critical element of flat rack securing. The cargo’s center of gravity should lie on the flat rack’s longitudinal centerline. For tall or top-heavy pieces, lower the overall COG by adding supports or ballast to prevent overturning.

A common mistake is focusing only on total weight within the container’s capacity, while ignoring load distribution and COG offset. Even if total weight is within limits, eccentric COG or localized overloading can still cause serious risks. The scientific approach is to calculate the COG before loading, then tailor the securing plan based on the shipping line's requirements for load-bearing points.

Solution 5: Critical Details – Success Often Hinges on the Small Things

Several details, if overlooked, can undo all prior efforts:

• Corner casting (lifting point) protection: Never block the four corner castings. These are essential for quayside crane handling during loading and discharge. If blocked, the container cannot be loaded and must be pulled out for re-securing, incurring significant costs.
• Clearance reservation: Maintain at least 35 cm clearance between the cargo and the outer edge of the flat rack end frames; otherwise, the container cannot be stowed below deck.
• Prohibited fixing methods: Do not use nails to secure sleepers or wedges into the wooden floor of the flat rack. Ensure lashing buckle hooks face inward, not outward, to avoid exceeding dimensional limits.
• Plan upfront: Flat rack securing is not something to figure out after loading. The plan must be defined before booking. Different shipping lines and routes have varying emphasis on securing specifics—early communication is key to reducing rework.

3. Conclusion

The value of a flat rack container lies not in "how much it can hold," but in "how securely it holds." In the complex environment of international shipping, the rigor of every securing plan directly determines the stability of final delivery. From material selection to lashing layout, from support structures to COG management, every step demands professional judgment and meticulous execution.

There is no shortcut to eliminating transit damage. Only by confirming the securing plan in advance, ensuring load-bearing structures are clearly justifiable, coordinating loading with terminal operations, and double-checking critical points before vessel departure can we achieve safe delivery via flat racks. After all, packing is the sole link in the entire transport chain that is entirely controllable by human effort—and that control is the decisive factor in whether cargo reaches its destination intact.

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