Section 12.4 Ballasting/De-ballasting Operations: Planning and Execution

Ballasting and de-ballasting are fundamental and frequently performed operations on bulk carriers, essential for managing the vessel’s stability, trim, drafts, and longitudinal stresses, particularly during the dynamic phases of loading and discharging cargo, and for achieving suitable sea-going conditions for ballast voyages. These operations involve moving very large weights of water into or out of the ship’s dedicated ballast tanks. If not meticulously planned and executed, improper ballast operations can rapidly lead to dangerous stability conditions, overstressing of the hull structure, or delays to cargo work. The Master, with the Chief Officer taking the operational lead, must ensure that all ballasting and de-ballasting is conducted safely, efficiently, and in full compliance with the vessel’s approved procedures and limitations, as well as environmental regulations (e.g., Ballast Water Management Convention).

1. Purpose and Importance of Ballast Operations:

Ballast water is used to:

Control Stability:

During Cargo Operations: As cargo is loaded, ballast is typically discharged to make space for cargo weight and to prevent excessive drafts or stability. As cargo is discharged, ballast is taken on to maintain adequate stability (positive GM), prevent excessive listing or lolling, and ensure sufficient draft.

On Ballast Voyages: Sufficient ballast is carried to ensure adequate propeller immersion, maneuverability, seakeeping, and to avoid excessive slamming or structural stresses.

Manage Trim and Drafts:

To achieve desired arrival or departure drafts and trims.

To maintain an even keel or slight working trim during cargo operations to facilitate efficient loading/discharging.

To ensure propeller and rudder immersion.

To meet air draft restrictions or under-keel clearance requirements.

Control Hull Stresses (Shear Forces and Bending Moments):

Strategically distributing ballast can help counteract stresses induced by uneven cargo distribution, especially during loading/discharging or in specific ballast voyage conditions (e.g., heavy weather ballast condition).

Improper ballast distribution can, conversely, induce or exacerbate stresses.

Improve Seakeeping on Ballast Voyages: Adequate ballast provides the necessary displacement and draft for better vessel behavior in waves, reducing excessive motions and slamming.

Facilitate Hold Cleaning/Inspection: Sometimes specific tanks are ballasted/de-ballasted to provide a list or trim to aid in washing or draining holds.

2. Planning Ballast Operations:

Thorough planning is essential before commencing any significant ballast operation. This is typically done by the Chief Officer using the loading instrument and in accordance with the ship’s approved Ballast Water Management Plan (BWMP) and Loading Manual.

A. Integration with Cargo Operations Plan:

Concurrent Operations: Ballasting/de-ballasting is almost always carried out concurrently with cargo loading/discharging to save time. The ballast plan must be synchronized with the cargo operations sequence.

Rate Matching: The rate of ballasting/de-ballasting should ideally match the rate of cargo loading/discharging to maintain desired drafts, trim, stability, and stress levels. The ship’s ballast pumping capacity is often a limiting factor for the overall speed of cargo transfer, especially during high-rate discharge operations.

B. Stability and Strength Calculations (Using Loading Instrument):

Sequence Simulation: Before starting, the entire planned sequence of ballast tank operations (which tanks, how much, in what order, at what rate) alongside the cargo sequence must be simulated on the loading instrument.

Intermediate Stage Checks: It is critical to check that stability (GM, GZ curve against IMO criteria) and longitudinal strength (SF and BM against permissible still water limits) remain acceptable at all intermediate stages of the combined cargo and ballast operation.

Free Surface Effect: The creation of large slack ballast tanks during filling or emptying significantly reduces GM. The plan must manage the number and size of slack tanks at any one time, especially if initial stability is low. Filling tanks sequentially rather than all simultaneously can help mitigate this.

Tank Pressurization: Avoid over-pressurizing or under-pressurizing ballast tanks during pumping, which can damage tank structures. Ensure air pipes are clear.

C. Ballast Water Management (BWM) Considerations (Covered in detail in Chapter 13):

Compliance with BWMC: All ballast operations must comply with the International Ballast Water Management Convention and the ship’s approved BWMP.

Ballast Water Exchange (BWE) or Treatment (BWMS):

If BWE is to be performed, the sequence and safety aspects (stability, stress, weather, crew safety) must be carefully planned.

If using a BWMS, ensure it is operational, and that ballasting/de-ballasting rates are compatible with the system’s treatment rated capacity (TRC). Plan for any system-specific requirements (e.g., holding times, neutralization).

Record Keeping: All ballast operations must be recorded in the Ballast Water Record Book.

D. Tank Selection and Sequencing:

Prioritize Tanks: Consider which tanks will have the most impact on trim, list, stability, or stress for the desired outcome.

Symmetry: Fill or empty wing tanks (topside or hopper) symmetrically (port and starboard simultaneously or in close succession) to avoid inducing a list, unless a list is intentionally required for a specific purpose (e.g., drainage) and stability allows.

Order of Filling/Emptying:

For stability, it’s often better to fill double bottom tanks first (lowers G) and empty topside tanks last when taking on ballast. The reverse applies when de-ballasting.

For stress, the sequence depends on the cargo distribution.

Avoid Slack Tanks: Press tanks full or strip them empty as quickly as operationally feasible to minimize free surface effects.

E. Communication and Coordination:

Bridge-Engine Room Coordination: Essential for starting/stopping pumps, monitoring tank levels (if engine room has some controls/indicators), and managing power requirements.

Coordination with Deck Watch: The officer on deck supervises tank levels and valve operations.

Coordination with Terminal (if rates are critical): Inform the terminal if the ship’s ballasting capacity will limit the cargo handling rate.

3. Execution of Ballast Operations:

Diligent execution and monitoring are key to ensuring the planned ballast operations are carried out safely and effectively.

A. Pre-Operation Checks:

Valve Line-up: Ensure all valves in the ballast system (tank suction/filling valves, sea chest valves, pump suction/discharge valves, cross-over valves) are correctly set for the intended operation. A valve checklist or mimic diagram is essential. Incorrect valve settings can lead to accidental transfer between tanks, overfilling, or pumping overboard unintentionally.

Pump Readiness: Confirm ballast pumps are primed (if necessary) and ready to start. Power available.

Tank Vents (Air Pipes): Verify that air pipe heads for the tanks being worked are open and clear to allow air to escape (when filling) or enter (when emptying). Blocked vents can lead to tank damage due to over/under pressure.

Sounding/Gauging System: Ensure remote tank level gauging systems are operational. Have manual sounding tapes ready for verification.

Communication: Establish clear communication between the control station (e.g., Cargo Control Room or bridge if remote operated) and personnel on deck or in the pump room (if locally operated).

B. Starting and Monitoring Pumping:

Start pumps and gradually open relevant valves.

Monitor pump pressures and motor amperage (if electric) for normal operation.

Continuously Monitor Tank Levels: This is the most critical monitoring task.

Use remote gauging systems, but verify their accuracy with manual soundings periodically, especially when starting, approaching full/empty, or if readings seem suspect.

Do not rely solely on one system.

Monitor Drafts, Trim, and List: Observe the vessel’s response to ballasting/de-ballasting. Compare with predictions from the loading instrument.

Check for Leaks: Visually inspect overboard discharges (if de-ballasting to sea) for any signs of oil or pollution. Inspect pump room and valve areas for leaks.

Update Loading Instrument: Regularly input actual tank levels into the loading instrument to verify stability and stress conditions are progressing as per plan.

C. Controlling Flow and Preventing Overflows/Emptying Pumps:

As tanks approach full, gradually throttle down the filling valves to avoid over-pressurization and overflow through vents.

When stripping tanks, listen for changes in pump sound (cavitation) indicating the tank is nearly empty, and stop the pump or switch suction promptly to avoid running the pump dry.

D. Securing from Operations:

Once tanks are at the desired level (full or empty), close all relevant valves securely.

Stop pumps.

Secure any remote operating systems.

Take final soundings and record them.

4. Safety Precautions During Ballast Operations:

Enclosed Space Entry: Ballast tanks are enclosed spaces. Never enter a ballast tank without following full enclosed space entry procedures (ventilation, atmosphere testing, permit to work, standby person, rescue equipment), even if it is “empty” of water (it may be oxygen deficient or contain other hazardous gases).

Valve Operation: Be aware of the direction of handwheel operation for manual valves. Use steady pressure; avoid excessive force if a valve is stiff (investigate cause). For remote valves, ensure indicators accurately reflect valve position.

Pressure Surges: Rapidly closing valves against a high flow rate can cause pressure surges (water hammer) in the pipelines, potentially damaging pipes, valves, or joints. Operate valves smoothly.

Working on Deck: Be aware of open manholes, valve spindles, or other tripping hazards when managing ballast operations from deck.

Communication: Ensure clear and unambiguous communication, especially if multiple persons are involved in different locations (e.g., CCR, deck, pump room).

BWMS Operation: If a Ballast Water Management System is being used, follow all manufacturer’s safety precautions related to its operation (e.g., chemical handling, UV exposure, electrical safety).

5. Master’s and Chief Officer’s Responsibilities:

Master:

Overall responsibility for safe ballast operations.

Reviews and approves all ballast plans, especially those integrated with cargo operations or BWE.

Ensures the Chief Officer and other responsible personnel are competent in planning, executing, and monitoring ballast operations, including the use of the loading instrument and BWMS.

Ensures compliance with the BWMP and all MARPOL regulations.

Chief Officer:

Develops detailed ballast operation plans.

Supervises the execution of ballasting/de-ballasting.

Ensures accurate monitoring of tank levels, stability, and stress.

Manages the Ballast Water Record Book.

Coordinates with the Chief Engineer regarding pump operation and maintenance.

Safe and efficient ballasting and de-ballasting operations are fundamental to the overall safety and structural integrity of a bulk carrier. They require meticulous planning based on accurate calculations, diligent execution with continuous monitoring, and a thorough understanding of the vessel’s systems and limitations. The Master and Chief Officer’s expertise in this area is critical for every voyage.