IMO and SOLAS Cargo Securing Standards for Shipping

International Maritime Cargo Securing Framework

Maritime cargo securing is governed by a hierarchy of international regulations designed to prevent cargo shift at sea — a leading cause of vessel capsizing, structural damage, and loss of life. The primary standards are established by the International Maritime Organization (IMO) and implemented through the Safety of Life at Sea (SOLAS) Convention.

Key Regulatory Documents

SOLAS Chapter VI — Carriage of Cargoes

SOLAS Chapter VI sets the legal framework for cargo operations on all merchant vessels of contracting states. Key requirements:

• Regulation 5: Cargo must be loaded, stowed, and secured to prevent damage to the ship or danger to persons on board throughout the voyage
• Regulation 5.6: Cargo units and transport units shall be loaded, stowed, and secured in accordance with the Cargo Securing Manual (CSM) approved by the Administration

CSS Code — Code of Safe Practice for Cargo Stowage and Securing

The CSS Code is the detailed implementation guide for SOLAS Chapter VI. It provides specific methods for calculating lashing forces, securing arrangements, and cargo stowage. The CSS Code includes:

• Annex 13: Methods to assess the efficiency of securing arrangements for non-standardized cargo
• Annex 14: Guidance on providing safe working conditions for securing operations
• Specific guidance for timber deck cargo, grain, containers, heavy lifts, and vehicles

CTU Code — Code of Practice for Packing of Cargo Transport Units

The CTU Code (2014) addresses how cargo is packed INSIDE containers and other transport units. It’s jointly published by IMO, ILO, and UNECE. While not mandatory, it’s referenced by most port state control authorities.

Cargo Securing Manual (CSM)

Every cargo vessel must carry an approved Cargo Securing Manual specific to that ship. The CSM must include:

• Specifications of all cargo securing equipment on board (lashings, turnbuckles, twist locks, etc.)
• Correct application methods for each type of securing equipment
• Stowage and securing arrangements for different cargo types
• Calculated lashing forces based on ship’s stability characteristics
• Inspection and maintenance procedures for securing equipment

Forces Acting on Cargo at Sea

Cargo at sea experiences forces from six degrees of ship motion:

Motion	Direction	Typical Acceleration (Design Value)
Rolling	Transverse (side to side)	Up to 0.6-0.8g at deck level
Pitching	Longitudinal (bow to stern)	Up to 0.3-0.5g
Heaving	Vertical (up and down)	Up to 0.5-1.0g combined with gravity
Surging	Longitudinal translation	Included in pitching calculation
Swaying	Transverse translation	Included in rolling calculation
Yawing	Rotational (horizontal plane)	Usually negligible for cargo securing

Critical insight: The transverse (rolling) force is typically the highest and most dangerous. A cargo unit on deck can experience lateral forces equivalent to 60-80% of its weight during heavy rolling — far exceeding what land transport generates.

Container Securing

Below Deck

Containers stowed below deck are restrained by cell guides — vertical steel structures that hold containers in fixed positions. Twist locks connect containers vertically. Cell guide systems require no additional lashing.

On Deck

Deck-stowed containers require extensive securing:

• Twist locks: Manual or semi-automatic devices that lock into container corner castings, connecting containers to each other and to the deck fittings
• Lashing rods: Steel rods with turnbuckles connecting container corner castings to deck lashing points. Typically applied to the lowest 2-4 tiers
• Stacking cones: Centering devices between container tiers
• Bridge fittings: Connect containers of different lengths in the same stack

Lashing Rules of Thumb

• Bottom tier always lashed (highest forces due to lever arm from ship’s roll center)
• Each lashing rod handles approximately 150-250 kN (33,700-56,200 lbs) depending on type
• Outboard stacks require more lashing than inboard stacks (greater roll acceleration)
• Forward stacks require more lashing than midship (pitching acceleration)

Break-Bulk and Project Cargo Securing

Non-containerized cargo (steel coils, machinery, vehicles, timber) requires custom securing arrangements calculated per CSS Code Annex 13:

Calculation Method

The CSS Code Annex 13 advanced method considers:

1. Cargo weight and dimensions
2. Stowage position on the ship (affects acceleration values)
3. Ship’s characteristics (GM, length, breadth)
4. Friction coefficient between cargo and deck/dunnage
5. Lashing arrangement (number, angle, type, MSL)

Common Securing Materials

Material	Maximum Securing Load (MSL)	Typical Application
Wire rope clip assembly	80% of MBS	Heavy cargo, project cargo
Chain (Grade 80)	50% of MBS	Steel coils, heavy machinery
Webbing lashing	50% of MBS	Vehicles, lighter break-bulk
Steel strapping	70% of MBS	Timber, bundled cargo
Turnbuckle	Per manufacturer rating	Wire lashing tensioning

Port State Control Inspections

Port state control officers can inspect cargo securing arrangements and detain vessels with deficiencies. Common findings include:

• Missing or outdated Cargo Securing Manual
• Insufficient lashing for the cargo type and voyage
• Damaged or missing securing equipment (rust, broken turnbuckles, missing twist locks)
• Cargo securing equipment not maintained per CSM requirements
• Crew unfamiliar with securing procedures in the CSM

Vehicle Carrier Securing

Ro-Ro (roll-on/roll-off) vessels carrying vehicles use:

• Wheel chocks: Block all four wheels to prevent rolling
• Lashing straps: Polyester webbing with ratchet tensioners, attached to vehicle recovery points and deck lashing rings
• Minimum 4 lashings per vehicle — one at each corner, pulling outward at 30-60° from horizontal
• Parking brake engaged, lowest gear selected, steering wheel secured

Common Mistakes to Avoid

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

• Using the Wrong Anchor Type: A Danforth/fluke anchor excels in sand and mud but fails on rock or coral. A Bruce/claw anchor handles mixed bottoms better. Wrong anchor type for your seabed can result in dragging in changing weather.
• Insufficient Scope Ratio: Scope is the ratio of anchor rode length to water depth. A minimum of 5:1 is needed for moderate conditions, 7:1 or more for storms. Many boaters anchor with 3:1 scope, providing inadequate holding power.
• Not Inspecting Mooring Lines: UV degradation, chafe, and internal fiber damage can reduce a mooring line’s strength by 50% or more before visible damage appears. OCIMF recommends retirement when a line shows 10% diameter reduction or visible core damage.
• Ignoring Chafe Protection: Mooring lines wear rapidly at chocks, fairleads, and contact points. Unprotected chafe points can cut through a line in hours during storm conditions. Use chafe guards at all contact points.
• Oversizing the Anchor Chain: While heavier chain provides better catenary, excessively heavy chain overloads the windlass and adds unnecessary bow weight. Match chain size to anchor manufacturer recommendations, typically 5/16 inch for boats under 35 feet.