Intermodal Container Lashing and Securing Best Practices

Container Securing Overview

Intermodal shipping containers (ISO containers) are the backbone of global trade, with over 800 million TEU (twenty-foot equivalent units) shipped annually. While containers are designed to stack and interlock, their securing on ships, chassis, railcars, and trailers requires specific hardware and procedures to prevent catastrophic loss during transport.

Container Securing on Ships

Below Deck (Cell Guide Systems)

Containers stowed below deck are held in position by cell guides — vertical steel rails that form a slot matching the container’s corner castings. Once lowered into the cell, the container is restrained in all horizontal directions by the guides. Twist locks connect containers vertically.

On Deck Securing Hardware

Hardware	Function	Capacity
Manual twist lock	Connects bottom container to deck fitting or container below	25-50 tonnes (shear/tension)
Semi-automatic twist lock	Same as manual but locks automatically when container is placed	25-50 tonnes
Stacking cone	Centers containers vertically, provides shear resistance	Varies by design
Lashing rod	Diagonal steel rod from container corner to deck lashing plate	150-250 kN per rod
Turnbuckle	Tensions lashing rods	Matches rod capacity
Lashing bridge	Elevated platform providing lashing points for upper tiers	Ship-specific

Lashing Pattern

Standard practice for on-deck container stacks:

• Tier 1 (deck level): Twist locks to deck fittings + lashing rods to the first tier corners
• Tier 2: Twist locks between tiers + lashing rods from tier 2 to deck or lashing bridge
• Tier 3+: Twist locks only (lashing rods typically only applied to bottom 2-3 tiers)
• Top tier: Twist locks + may require additional lashing in severe weather routes

Container Securing on Chassis/Trailers

Twist Lock Systems

Container chassis have four twist lock fittings that engage the container’s bottom corner castings. Proper engagement:

• All four twist locks must be engaged and locked before moving
• Verify visually — many twist locks have a colored indicator (green = locked, red = unlocked)
• Test by attempting to lift a corner — the container should not separate from the chassis

Pin Systems

Some chassis use pin-type locks instead of twist locks. The pin drops through a hole in the corner casting and is secured with a cotter pin or spring clip.

Cargo Inside Containers

The CTU Code (IMO/ILO/UNECE) governs how cargo is packed inside containers. Key requirements:

• Weight distribution: Center of gravity should be at or near the container’s longitudinal center. Off-center CG can cause chassis instability and crane handling problems.
• Blocking and bracing: Cargo must be blocked against all four walls or braced with dunnage to prevent shifting. Air bags (dunnage bags) are commonly used to fill voids.
• Weight limits: Maximum gross weight (container + cargo) is typically 30,480 kg for a 20′ container. Payload limits vary by container type and route restrictions.
• Floor loading: Container floors are rated for fork truck access (maximum point load specified per container). Don’t exceed the concentrated load rating.

Container Inspection Before Loading

Before packing, inspect the container for:

• Structural damage (dents, holes, bent corner castings)
• Door seal integrity (gaskets intact, doors close and latch properly)
• Floor condition (no holes, rot, or contamination)
• Cleanliness (no residue from previous cargo, especially chemicals)
• CSC plate present and current (Container Safety Convention plate shows approval date and next inspection date)
• Lashing rings/tie-down points functional inside the container

Common Container Securing Failures

1. Unlocked twist locks: Container separates from chassis during cornering or braking. Leading cause of container-related road accidents.
2. Overweight containers: Exceed chassis and road weight limits, causing tire blowouts and structural failures.
3. Improperly packed contents: Cargo shifts inside the container during transport, changing the CG and causing rollover.
4. Corroded lashing equipment: Lashing rods and turnbuckles on ships corrode in the marine environment. Corroded equipment fails at a fraction of rated capacity.

Common Mistakes to Avoid

Avoiding these common errors can prevent equipment failure, regulatory violations, and serious safety incidents in the field.

• Insufficient Aggregate WLL: FMCSA requires total WLL of all tie-downs to equal at least 50% of cargo weight. For a 40,000 lb load, you need at least 20,000 lbs of total tie-down WLL, which could be 10 ratchet straps rated at 2,000 lbs each.
• Relying Solely on Friction: While friction helps (rubber mats provide coefficient of 0.6-0.7), it cannot be the only securement. FMCSA requires positive securement devices in addition to friction to prevent cargo movement during emergency maneuvers.
• Not Securing Against All Directions: Cargo must be secured against forward, rearward, lateral, and vertical movement. Many drivers only secure against forward movement. Use a combination of direct tie-downs and blocking or bracing to prevent movement in all four directions.
• Wrong Securement for Cylindrical Loads: Coils, pipes, and drums require specialized methods per FMCSA 393.120. They cannot be secured like boxed cargo. Coils must use at minimum one tie-down per coil for eye-up positioning, or specific blocking arrangements for other positions.
• Failing to Re-Check Tie-Downs: FMCSA requires inspection within the first 50 miles and every 3 hours or 150 miles thereafter. Straps loosen due to load settling, vibration, and temperature changes. A tight strap at departure can be dangerously loose after 100 miles.