Safety

SOLAS Chapter VI — Carriage of Cargoes & Oil Fuels

Statutory cargo declarations, IMSBC Code groups, liquefaction soil mechanics, Grain Code stability criteria, and Cargo Securing Manual architecture.

15 min read

Intermediate

Safety

Key Principles at a Glance 6 points

SOLAS Chapter VI governs all non-bulk-liquid and non-gas cargoes, establishing legal liability on the shipper to provide verified gross mass and physical/chemical cargo declarations prior to loading.
IMSBC Code classifies solid bulk cargoes into Group A (may liquefy if moisture > TML), Group B (chemical hazards such as self-heating, toxic emission, or oxygen depletion), and Group C (neither Group A nor B).
Liquefaction occurs when cyclic ship rolling increases pore water pressure until effective granular stress drops to zero; cargoes can only be loaded if actual moisture content is strictly below the Transportable Moisture Limit (TML = 90% of FMP).
The International Grain Code mandates three statutory intact stability criteria under an assumed grain shift: angle of heel <= 12 deg, residual dynamic stability area >= 0.075 m-rad, and initial GM >= 0.30 m.
Cargo units, containers, and heavy breakbulk must be stowed and restrained strictly in accordance with an Administration-approved Cargo Securing Manual (CSM) based on calculated transverse, longitudinal, and vertical accelerations.
Enclosed cargo holds carrying oxygen-depleting or toxic gas-emitting cargoes require dedicated portable multi-gas detectors and atmospheric clearance (< 0.3 ppm PH3 for phosphine fumigants; 20.9% O2) before entry.

1. Statutory Scope, Cargo Information & Hull Stress Control

REG 2 Shipper Declaration Mandate

VGM Verified Gross Mass (Containers)

t / m² Tank Top Permissible Load Limit

100% Max Allowable SF & BM at Sea

Legislative Scope & Legal Framework

SOLAS Chapter VI applies to the carriage of all cargoes—except bulk liquids and gases covered under Chapters VII, IBC, and IGC Codes—across all cargo ships down to under 500 GT. The chapter bridges commercial cargo operations with naval architectural survivability, holding both the shipper and the Master strictly accountable for vessel structural integrity.

Under Regulation 2, the shipper is statutorily obligated to provide the Master or his representative with comprehensive cargo information confirmed in writing well in advance of loading. Without this certified declaration, the Master possesses the statutory right and duty to refuse loading.

Figure 1: Bulk Carrier Longitudinal Profile & Hull Girder Stress Envelope. Alternate hold loading (Holds 1, 3, 5 loaded with heavy ore; Holds 2, 4 empty) generates massive sheer force steps at transverse bulkheads and high sagging bending moments midships that must remain within statutory IACS and loading manual envelopes.

Mandatory Cargo Declaration Elements (Reg 2)

Cargo Physical State

Precise commercial and chemical designation, bulk stowage factor ($m^3/t$), stowage category, and angle of repose for granular dry goods.

Verified Gross Mass (VGM)

SOLAS VI/2 requires container shippers to verify gross mass via calibrated weighbridge (Method 1) or cumulative weight calculation (Method 2) prior to vessel arrival.

Chemical & Toxicity Profiles

Group classification under IMSBC, self-heating liabilities, flammability limits, dust explosion indices, and gas evolution rates ($H_2, CH_4, CO, PH_3$).

Moisture & TML Certificates

For Group A cargoes, certified actual moisture content (tested within 7 days of loading) and certified Transportable Moisture Limit (tested within 6 months).

Master's Loading & Stress Verification Procedure

Examine Shipper Cargo Declaration & Laboratory Test Certificates

Verify that moisture sampling was conducted within 7 days of loading date and that the testing laboratory is accredited under ISO 17025 or recognised by Administration.

Run Hull Stress Calculations on Class-Approved Loading Computer

Model all intermediate deballasting and loading sequences. Confirm that Shear Forces (SF) and Bending Moments (BM) never exceed 100% of sea/harbour allowable limits.

Verify Tank Top Local Load Limits ($t/m^2$)

Ensure that high-density cargo cones do not concentrate weight exceeding the double bottom structural plating modulus defined in the ship's stability booklet.

Synchronize Ship-Shore Loading Plan (BLU Code)

Agree with terminal representative on pour rates, conveyor stops, deballasting pump head capacity, and trimming protocols to avoid asymmetric hull twisting.

2. IMSBC Code Groups & Geotechnical Liquefaction Mechanics

GROUP A Liquefaction Liability

GROUP B Chemical Reactivity Hazard

TML 90% of Flow Moisture Point

≤ 35° Trimming Angle of Repose

Soil Mechanics & Physics of Dynamic Liquefaction

Cargo liquefaction is a geotechnical failure occurring in unsaturated, fine-grained particulate materials containing moisture. Under calm conditions, inter-granular friction maintains internal shear strength ($ au = c + sigma' anphi$, where $sigma' = sigma - u$).

During ocean transit, cyclic wave-induced rolling and vibration compact the cargo particles, diminishing void volume. Because the trapped interstitial pore water cannot drain instantly through low-permeability ores, pore water pressure ($u$) surges until it equals the overburden confining stress ($sigma$). Effective stress drops to zero ($sigma' o 0$), inter-particle friction collapses, and the solid bed transforms instantaneously into a viscous, thixotropic slurry.

Figure 2: IMSBC Geotechnical Liquefaction Dynamics & Hold Slurry Collapse. Cyclic vessel roll builds pore water pressure ($u$) until effective stress ($sigma'$) drops to zero. The cargo liquefies and flows to the low side, permanently shifting the vessel center of gravity ($G o G_1$) and collapsing the residual stability envelope.

IMSBC Code Tri-Partite Cargo Classification

Category	Physical / Chemical Nature	Typical Representative Cargoes	Key Statutory Carriage Safeguards
Group A Liquefaction Hazard	Fine particulate materials (>10% particles <1 mm) with high natural moisture content. Susceptible to liquefaction under cyclic motion.	Iron ore fines, nickel ore concentrates, copper concentrates, bauxite, lead sinter, fluorspar.	Shipper must certify actual moisture content < TML. Moisture test valid for 7 days; TML valid for 6 months. Can-testing mandatory during loading.
Group B Chemical Hazards	Possess dangerous chemical properties under the IMSBC Code: self-heating, toxic gas emission, hydrogen evolution, or extreme oxygen depletion.	Direct Reduced Iron (DRI A, B, C), Coal, Charcoal, Seed cake, Metal turnings, Ammonium nitrate fertilisers.	Inert gas blankets ($N_2$ purging to <5% $O_2$), continuous monitoring of $CH_4, CO, H_2$, explosive dust suppression, and hold boundary temperature logs.
Group C Non-Hazardous Bulk	Cargoes that are neither susceptible to dynamic liquefaction nor exhibit hazardous chemical or toxic reactivity.	Coarse iron ore, cement clinker, quartz, granite, pig iron, scrap metal, dry sand, salt, grain (covered separately under Grain Code).	Trimming per IMSBC general schedule to level surfaces, compliance with tank top load ratings ($t/m^2$), and continuous hold bilges dewatering.

The Can Test Field Protocol (IMSBC Section 4.6.4)

The shipboard Can Test is an auxiliary physical check, not a substitute for certified laboratory test results. An engineer fills an open-top metal cylindrical can (1 litre capacity) halfway with representative cargo, vigorously drops it flat onto a solid steel deck from a height of 0.2 metres 25 times at 1-second intervals. If free moisture, liquid meniscus, or surface fluid slurry appears on top, the cargo is dangerously wet (moisture above FMP) and must be rejected immediately.

3. International Grain Code & Grain Stability Criteria

≤ 12° Max Allowable Grain Heel Angle

≥ 0.075 Min Residual Dynamic Area (m·rad)

≥ 0.30 m Statutory Initial GM After Shift

DOA Document of Authorization

The Physics of Grain Shifting & Statutory Criteria

Bulk grain (wheat, maize, barley, oats, rye, soybeans, and rice) is a free-flowing granular commodity with an inherent angle of internal friction. During ocean transit, continuous wave rolling causes the settled grain surface beneath upper deck stiffeners and hatch coamings to cascade across the hold, resulting in an uncorrectable transverse list.

Under the International Code for the Safe Carriage of Grain in Bulk (International Grain Code), every vessel loading bulk grain must demonstrate compliance through volumetric heeling calculations and hold an Administration-issued Document of Authorization (DOA).

Figure 3: International Grain Code Stability Criteria & Void Shift Geometry. Filled compartments assume a 15° surface shift under the deck coaming. The resulting grain heeling arm curve ($lambda$) intersects the vessel $GZ$ curve at equilibrium heel $ heta_h le 12^circ$, leaving a residual dynamic area $ge 0.075 ext{ m}cdot ext{rad}$ and initial $GM ge 0.30 ext{ m}$.

Grain Hold Securing & Void Reduction Methods

Trimming to Boundaries

Mechanical trimming using bulldozers or throwing machines to pack grain tightly into upper hopper corners and reduce under-deck void depths.

Saucers & Bundling

Constructing a dished saucer in the hatch coaming lined with tarpaulins or filter cloth and filled with bagged grain to mechanically wedge surface voids.

Overstowing Heavy Cargo

Covering the leveled grain bed with separation cloth, wood boards, and high-density bagged cargo or general breakbulk to physically pin the grain surface.

Longitudinal Shifting Boards

Installing grain-tight centerline bulkheads or portable steel shifting boards spanning from deck to one-third hold depth to cut transverse volumetric moment in half.

4. Cargo Securing Manual (CSM), Gas Safety & Bunker Management

MSL Maximum Securing Load Rating

< 0.3 ppm Safe Phosphine Re-Entry Limit

20.9% Hold Normal O₂ Clearance

≥ 60°C Minimum Fuel Flashpoint

Cargo Securing Manual (CSM) Engineering Principles

Under SOLAS Chapter VI Regulation 5.6 and VII Regulation 5, all cargo-carrying vessels other than bulk liquid tankers must carry an Administration-approved Cargo Securing Manual (CSM). The manual translates ship accelerations (transverse roll, longitudinal pitch, and vertical heave) into dynamic load vectors.

Every lash, twistlock, stacking cone, and chain must comply with certified Maximum Securing Load (MSL) limits—typically 50% of the Minimum Breaking Load (MBL) for wire ropes and chains, and 70% for steel rods and twistlocks.

Figure 4: Cargo Securing Manual Container Lashing Mechanics & Hold Multi-Gas Monitoring. Left: Diagonal cross-lashing rods and turnbuckles prevent container stack racking under cyclic wave acceleration. Right: Aspirated multi-gas detection circuit continuously samples cargo atmospheres for oxygen depletion, combustible gases, and toxic fumigant residues.

Securing Gear Rating & Maximum Securing Load (MSL)

Lashing Gear Type	Statutory MSL Formula (CSS Code Annex 13)	Standard Marine Working Value	Primary Failure Mode / Inspection Requirement
Lashing Rods (Rigid Steel)	70% of Minimum Breaking Load (MBL)	175 kN (on 250 kN MBL rod)	Thread galling at turnbuckle, deformation from over-tightening, corner casting elongation.
Wire Ropes & Bulldog Grips	30% to 50% of Minimum Breaking Load (MBL)	~50–80 kN depending on lay	Strand fatigue, flattening over coaming edges, improper saddle orientation on dead-end rope.
High-Tensile Steel Chains	50% of Minimum Breaking Load (MBL)	100 kN (on 200 kN grade-80 chain)	Link stretch, gouging under timber chocks, hook disengagement under heavy dynamic rolling.
Semi-Automatic Twistlocks	Upper cone: 250 kN tension / 420 kN shear	Standard ISO container ratings	Internal spring fracture, dirt jamming lock mechanism, failure to engage corner casting bottom.

Bunkering & Low-Flashpoint Fuel Safety (Reg 7 & SOLAS II-2)

SOLAS Chapter VI Regulation 7 tightly regulates oil fuels carried for shipboard propulsion and auxiliary generators. All marine residual fuels (VLSFO, HSFO) and distillates (MGO, MDO) delivered to conventional cargo ships must have a certified closed-cup flashpoint not less than 60°C (verified via the Bunker Delivery Note, BDN, under MARPOL Annex VI).

For ships operating on alternative low-flashpoint fuels—such as Liquefied Natural Gas (LNG), methanol, or ammonia—compliance shifts to the statutory provisions of the IGF Code (International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels) under SOLAS Chapter II-1.

Surveyor Oral & Written Examination Bank

What is the distinction between Transportable Moisture Limit (TML) and Flow Moisture Point (FMP)?

The Flow Moisture Point (FMP) is the exact percentage moisture content at which a granular bulk sample loses internal friction and begins to flow under standardized laboratory vibration testing. The Transportable Moisture Limit (TML) is the maximum legally allowable moisture content for ocean carriage, statutorily defined by the IMSBC Code as 90% of the FMP (TML = 0.90 × FMP). The 10% margin is the safety buffer against dynamic wave compaction.

State the three intact stability criteria mandated by the International Grain Code under assumed grain shift.

1. The angle of heel due to grain shift ($ heta_h$) must not exceed 12° (or the angle of deck edge immersion, whichever is less). 2. In the statical stability ($GZ$) diagram, the residual dynamic stability area between the heeling arm curve and righting lever curve up to 40° (or flooding angle $ heta_f$) must not be less than 0.075 m·rad. 3. The initial metacentric height ($GM_0$) after taking grain shift into account must be at least 0.30 metres throughout the entire voyage.

How is a shipboard Can Test conducted, and what is its statutory significance?

A cylindrical 1-litre metal can is filled halfway with cargo and dropped vertically from 0.2 m onto a rigid steel deck 25 times at 1-second intervals. If liquid slurry or free water rises to the surface, the cargo is unsafe and exceeds FMP. It is an auxiliary red-flag test for the Master to refuse loading; it cannot be used to certify cargo safety or override a laboratory moisture test.

What constitutes the statutory contents of an approved Cargo Securing Manual (CSM)?

An approved CSM contains: 1. Specifications and Maximum Securing Loads (MSL) for all fixed and portable securing devices. 2. Transverse, longitudinal, and vertical acceleration profiles for the specific hull. 3. Calculated lashing arrangements for standard cargo units (containers, roll-on/roll-off vehicles, timber deck cargo). 4. Procedures for heavy lift securing. 5. Inspection, maintenance, and discard criteria for worn securing gear.

What are the atmospheric entry requirements for a cargo hold following in-transit phosphine (PH₃) fumigation?

Continuous mechanical ventilation must be carried out until atmospheric testing by a qualified gas chemist or trained ship officer confirms that the phosphine concentration is strictly below 0.3 ppm (OSHA/IMO Threshold Limit Value), oxygen is exactly 20.9% by volume, and toxic decomposition residues have been cleared. An enclosed space entry permit is required prior to unsealing hatch accesses.

Explain ship sweat vs cargo sweat, the dew-point rule, and ventilation for hygroscopic vs non-hygroscopic cargoes.

Ship sweat is condensation on the ship's steel when warm moist hold air from the cargo meets cold steel on a hot-to-cold run — overhead drips and bottom water that damage cargo. Cargo sweat is condensation on the cargo surface itself. Ventilate by the dew-point rule: compare hold dew point against outside air and ventilate to hold the favourable temperature band. Hygroscopic cargoes (plant products with natural water content) absorb, retain and release water — heating, caking and spoiling without ventilation. Non-hygroscopic cargoes carry no water but spoil in a moist atmosphere. Hold ventilation also supplies fresh air, clears poisonous gases and previous-cargo smells, and removes cargo heat and moisture.