Section 8.3: Grains (Pest Control, Fumigation, Ventilation, Shifting)

Grains – encompassing a wide variety of cereals like wheat, corn (maize), barley, oats, rye, sorghum, as well as oilseeds like soybeans and pulses – constitute one of the largest agricultural commodity groups transported by sea in bulk. The safe carriage of grain presents unique challenges primarily related to its propensity to shift (which can severely impact vessel stability), the need for effective pest control (often involving fumigation), and careful ventilation to prevent moisture damage and spoilage. The carriage of grain in bulk is governed by the International Code for the Safe Carriage of Grain in Bulk (International Grain Code or IGC), which is mandatory under SOLAS Chapter VI.

1. Definition and Characteristics of Grain:

Definition (as per International Grain Code): “Grain includes wheat, maize (corn), oats, rye, barley, rice, pulses, seeds and processed forms thereof, whose behaviour is similar to that of grain in its natural state.”

Key Characteristics Relevant to Carriage:

Free-Flowing Nature: Most grains are free-flowing and have a relatively low angle of repose (typically 20° to 30°, though it varies). This makes them highly prone to shifting if not properly stowed and secured.

Hygroscopic: Grains can absorb moisture from or release moisture to the surrounding atmosphere, depending on their own moisture content and the ambient relative humidity and temperature. This makes them susceptible to moisture damage, caking, and mold growth.

Respiration: Being organic material, grain respires, consuming oxygen and producing carbon dioxide, water vapor, and heat. The rate of respiration increases with temperature and moisture content.

Susceptibility to Pest Infestation: Grains are attractive to various insects, rodents, and birds.

Dust Generation: Handling grain can generate significant amounts of fine, organic dust, which can be a health hazard (respiratory issues, “grain fever”) and, under certain conditions (a confined space with a specific dust concentration in air and an ignition source), an explosion hazard.

Stowage Factor: Varies widely depending on the type of grain (e.g., barley is lighter than wheat). Typically ranges from about 1.20 to 1.80 m³/tonne. Vessels carrying light grains are often “cubic limited.”

2. International Grain Code (IGC) – The Primary Regulatory Framework:

The IGC provides detailed requirements for vessels intending to carry grain in bulk, focusing on ensuring adequate stability to counteract the effects of a potential cargo shift.

Applicability: The Code applies to all ships carrying grain in bulk, regardless of size, including general cargo ships and bulk carriers.

Document of Authorization (Grain Loading Stability Booklet):

Vessels intending to carry grain must have a Document of Authorization issued by their Flag State Administration (or a Recognized Organization on its behalf).

This document certifies that the vessel is capable of complying with the stability requirements of the IGC.

It is accompanied by a Grain Loading Stability Booklet (or Grain Stability Manual), approved by the Administration, which provides the Master with:

Ship-specific stability data and grain heeling moments (volumetric heeling moments due to a presumed cargo shift).

Permissible grain heeling moments for various conditions of loading.

Instructions on how to calculate stability for grain voyages, including worst-case scenarios for cargo shift.

Details of any specific grain loading procedures or fittings approved for the vessel (e.g., if using specially suitable compartments, saucers, bundling of bagged grain, etc., as shifting counter-measures).

Stability Requirements (Key Principles): The IGC mandates specific intact stability criteria that must be met for any grain loading condition, assuming a transverse shift of the grain surface. These criteria are more stringent than the standard IMO intact stability criteria and typically require:

The angle of heel due to the assumed grain shift shall not be greater than 12 degrees (or the angle at which the deck edge is immersed, if less).

The residual area between the righting lever curve (GZ curve) and the grain heeling arm curve shall not be less than 0.075 metre-radians.

The initial metacentric height (GM), after correction for free surface effect of liquids in tanks, shall not be less than 0.30 metres.

Trimming Requirements:

To reduce the risk of shifting, the IGC requires that all free grain surfaces in ‘filled compartments, trimmed’ shall be trimmed so as to fill all the spaces under the decks and hatch covers to the maximum extent possible.

In ‘filled compartments, untrimmed’, the grain shall be trimmed within the hatch coamings but may be left at its natural angle of repose outside the periphery of the hatchway. Specific calculations for volumetric heeling moments apply to this condition.

In ‘partly filled compartments’, the grain surface must be secured against shifting, for example by overstowing with bagged grain or other suitable cargo, or by strapping/lashing, unless the stability calculations show the vessel can withstand the assumed shift of the unsecured surface.

3. Key Hazards and Precautions Associated with Grain Carriage:

A. Cargo Shifting and Loss of Stability:

This is the most significant hazard associated with grain carriage.

Mechanism: Due to the ship’s motion at sea, the free-flowing grain can settle and compact, creating void spaces, particularly in the wings of the hold if not properly trimmed. A subsequent roll can cause the grain surface to shift, filling these voids on one side and creating a void on the other. This results in a transverse shift of the cargo’s center of gravity, causing the vessel to list.

Volumetric Heeling Moments (VHM): The IGC provides methods for calculating the VHM produced by an assumed shift of grain. The ship’s stability characteristics (righting moments) must be sufficient to counteract these heeling moments and meet the IGC stability criteria.

Master’s Responsibility:

Strict Adherence to Grain Loading Stability Booklet: All stability calculations for grain voyages must be performed in accordance with the procedures and data in the approved Grain Loading Stability Booklet.

Verification of Stability Criteria: The Master must ensure that for the proposed stowage, and for all stages of the voyage, the IGC stability criteria are met.

Proper Trimming: Ensure grain is trimmed in accordance with IGC requirements for the type of stow (filled trimmed, filled untrimmed, partly filled).

Securing Partly Filled Compartments: If holds are partly filled, the grain surface must be secured to prevent shifting, unless calculations prove the vessel can withstand the heeling moment from an unsecured surface. Common methods include overstowing with bagged grain (forming a “saucer”), or using timber shoring and strapping (less common now).

B. Pest Infestation and Control (Fumigation):

Risk: Grains are highly susceptible to infestation by insects (weevils, beetles, moths), mites, and rodents, which can lead to significant cargo loss, quality degradation, and rejection by importing countries.

Prevention:

Hold Cleanliness: Holds must be scrupulously “grain clean” – free of all previous cargo residues, insects (live or dead), and odors. This is a primary defense.

Inspection of Cargo at Loading: While difficult to inspect the entire bulk, the officer on watch should look for any obvious signs of infestation in the grain coming aboard.

Fumigation:

Common Practice: Many grain cargoes are fumigated, either in the silo before loading, during loading, or “in-transit” (during the voyage).

Purpose: To kill any insect pests present in the grain.

Common Fumigants: Phosphine (PH₃) gas, generated from solid formulations of aluminium phosphide or magnesium phosphide (tablets, pellets, sachets), is widely used. Methyl bromide was previously common but is now largely phased out due to its ozone-depleting properties.

Safety Precautions for Fumigation (Critical):

IMO Recommendations on the Safe Use of Pesticides in Ships (MSC.1/Circ.1358 and subsequent amendments): This is the key guidance document and must be strictly followed.

Performed by Professionals: Fumigation should only be carried out by qualified, certified pest control operators/fumigators. Ship’s crew should not normally apply solid phosphide fumigants themselves unless specifically trained, authorized, and equipped, which is rare.

Notification: The Master must be notified in advance if in-transit fumigation is to be performed.

Sealing of Holds: Holds to be fumigated must be made as gas-tight as practicable to retain the fumigant. Ventilators are sealed, and sometimes hatch cover joints are further sealed with tape.

Dosage and Application: As per fumigator’s instructions and label requirements.

Warning Placards: Clearly worded warning signs must be posted at all entrances to fumigated spaces, indicating the fumigant used, date of fumigation, and safety precautions.

Gas Detection Equipment: The ship must be provided with appropriate gas detection equipment for the specific fumigant used (e.g., phosphine detector tubes or electronic meters) to check for leaks into accommodation or working spaces, and to verify safe gas levels before ventilation and entry.

Aeration (Ventilation) After Fumigation: Before personnel entry into fumigated holds or discharge of cargo, the holds must be thoroughly ventilated to reduce fumigant gas concentrations to below the safe Threshold Limit Value (TLV) or Occupational Exposure Limit (OEL). This aeration period can be lengthy. The space must be certified “gas-free” by a competent person before entry without respiratory protection.

Disposal of Fumigant Residues: Spent fumigant material (e.g., dust/powder from phosphide formulations) is toxic waste and must be disposed of safely according to fumigator’s instructions and MARPOL regulations (often collected by fumigators at the discharge port or disposed of ashore). It should never be swept into the sea or mixed with cargo.

First Aid / Medical Advice: Information on symptoms of exposure and first aid for the specific fumigant must be available.

Master’s Responsibilities for Fumigation:

Ensure all safety precautions as per IMO guidelines are followed.

Ensure crew are aware of the hazards and procedures.

Supervise the sealing of holds and posting of warning signs.

Ensure regular checks for gas leakage into accommodation/working spaces during transit.

Manage the ventilation/aeration process at the discharge port according to instructions and safety requirements.

Ensure safe disposal of residues.

C. Ventilation and Moisture Control:

Purpose: To prevent moisture damage (mold, caking, spoilage) from ship’s sweat or cargo sweat, and to remove heat and CO₂ generated by grain respiration.

Dew Point Rule: As discussed in Chapter 2, Section 4, the decision to ventilate is often based on comparing the dew point of the hold air with the dew point of the ambient air.

Ventilate if: Ambient air dew point is lower than hold air dew point (i.e., outside air is drier).

Do NOT Ventilate if: Ambient air dew point is higher than hold air dew point (i.e., outside air is more moist).

Hygroscopic Nature of Grain: Grain will try to reach moisture equilibrium with the surrounding air. Excessive ventilation with very dry air can dry out the grain (leading to weight loss claims), while ventilation with moist air can add moisture.

Surface Ventilation vs. Through Ventilation:

Surface Ventilation: Generally preferred for most grain cargoes to remove moist air from the ullage space above the cargo, preventing condensation on the underside of hatch covers and deck beams (ship’s sweat).

Through Ventilation (forcing air through the grain mass): Generally not recommended unless the grain is loaded at a very high moisture content and temperature, and there is a risk of significant self-heating or spoilage within the stow. Requires careful control and understanding of the grain’s condition. Can sometimes do more harm than good if not managed correctly.

Monitoring: Regular checks of hold air temperature and relative humidity (or dew point) and ambient air conditions are necessary to make informed ventilation decisions.

Sealed Holds: If fumigated in transit, holds will be sealed, and no ventilation is possible until after the required exposure period and subsequent aeration.

D. Dust Explosions:

Risk: While relatively rare on ships compared to grain elevators, a suspension of fine grain dust in air within a confined space can explode if the concentration is within the explosive limits (typically 40-50 g/m³ or higher) and there is a source of ignition (e.g., static electricity, sparks from prohibited smoking or hot work, faulty electrical equipment).

Prevention:

Good Housekeeping: Minimize dust accumulation on deck and in accessible areas of holds. Clean up spills promptly.

No Smoking / Naked Lights: Strictly enforce prohibitions in and around cargo areas.

Proper Electrical Equipment: Ensure all electrical equipment in or near cargo spaces is intrinsically safe or suitably protected for dusty environments.

Avoid Creating Dust Clouds: During loading/discharge, minimize the free fall of grain.

Ventilation (for dust removal): Can help to reduce airborne dust concentrations, but ensure flame screens are in place if there’s any associated flammable gas risk (less common with pure grain, more if other commodities are involved).

E. Oxygen Depletion / CO₂ Enrichment:

Risk: Grain respiration consumes oxygen and produces carbon dioxide. In a sealed or poorly ventilated hold, the atmosphere can become oxygen-deficient and/or have elevated CO₂ levels, posing an asphyxiation hazard.

Precautions: Always follow strict enclosed space entry procedures before entering any grain hold, including thorough ventilation and atmosphere testing for O₂, CO₂, and any fumigant gases.

4. Pre-Loading Preparations:

Hold Cleanliness: “GRAIN CLEAN” is mandatory. This means meticulously clean, dry, free of all previous cargo residues, loose rust/paint, insects (live or dead, including eggs/larvae), and odors. Surveyors (e.g., USDA, NCB, AQIS, Canadian Grain) are extremely strict.

Bilge Wells: Clean, dry, strum boxes in place and clear, suctions tested. Protect from grain ingress (e.g., with burlap covers over strum boxes, ensuring they don’t impede drainage).

Grain Loading Stability Booklet and Document of Authorization: Must be onboard and readily available. The Master and Chief Officer must be thoroughly familiar with its contents and how to perform the required stability calculations.

Ventilation Systems: Ensure ventilators are clean, operational, and that closures are working.

Fumigation Arrangements (if applicable): Liaise with shippers/charterers regarding any planned fumigation. Ensure all necessary safety equipment (gas detectors, SCBAs, medical first aid for fumigants) is onboard and crew are aware of procedures.

5. Loading Operations:

Stability Calculations: Calculate stability for the proposed stowage and ensure compliance with IGC criteria before loading starts.

Trimming: Ensure grain is trimmed according to IGC requirements for the stowage type (filled trimmed, filled untrimmed, partly filled). Supervise stevedores closely.

Dust Control: Take precautions to minimize dust.

Monitoring Cargo Quality: Visually inspect grain for obvious signs of infestation, foreign matter, or excessive moisture/damage as it is being loaded.

No Smoking/Naked Lights: Strict enforcement.

Secure Partly Filled Compartments: If any holds are only partly filled, ensure the grain surface is secured against shifting as per IGC requirements (e.g., saucering with bagged grain, strapping) unless stability calculations prove it unnecessary (which is rare for an unsecured surface).

6. Precautions During Voyage:

Stability: Be aware that grain can settle during the voyage, potentially creating voids. The initial stability calculations must account for the assumed grain shift. Avoid excessive rolling.

Ventilation: Ventilate (or not) based on dew point comparisons and cargo condition. Keep detailed ventilation logs.

Fumigation Safety (if fumigated in-transit):

Regularly check spaces adjacent to fumigated holds for any gas leakage.

Ensure all personnel are aware of which holds are under fumigation and that entry is prohibited.

Follow all instructions from the fumigator-in-charge.

Monitoring: If there are concerns about cargo condition (e.g., high moisture at loading), consider periodic temperature checks if safe access to sounding pipes is possible, but avoid unnecessary entry into holds.

7. Discharge Operations:

Aeration (if fumigated): Thoroughly ventilate holds to safe gas levels before discharge personnel enter or cargo discharge begins. This must be certified by a competent person.

Dust Control: A major concern during discharge.

Safety of Personnel: Ensure stevedores and crew are aware of any remaining fumigant hazards or dust risks.

Complete Discharge: Ensure holds are discharged as completely as possible.

8. Master’s Key Responsibilities Specific to Grain:

Absolute Compliance with IGC Stability Criteria: This is paramount. The Grain Loading Stability Booklet is the Master’s guide.

Ensuring “Grain Clean” Holds: Failure to meet this standard will lead to rejection and severe delays.

Managing Fumigation Safely: If in-transit fumigation is performed, the Master has ultimate responsibility for the safety of the crew during and after the process, including proper aeration.

Correct Ventilation Practices: To prevent moisture damage.

Vigilance on Pest Control: Both in terms of hold preparation and monitoring during the voyage.

Carrying grain in bulk demands a high level of diligence from the Master and crew, particularly concerning stability, hold preparation, and the safe management of fumigation. Adherence to the International Grain Code and associated best practices is essential for protecting the vessel, the crew, and the valuable cargo onboard.