Section 12.3 Practical Use of Loading Instruments/Software

Modern bulk carriers are mandatorily equipped with sophisticated electronic loading instruments (often referred to as loading computers or loadicators) that have revolutionized the way ship’s officers manage stability, trim, and longitudinal strength. These powerful software tools automate complex calculations, provide real-time feedback during cargo and ballast operations, and help ensure compliance with regulatory and safety limits. However, the effectiveness of a loading instrument is entirely dependent on the accuracy of the data input by the user and their correct interpretation of the output. For the Master and Chief Officer, proficiency in the practical use of this critical piece of equipment is not just a convenience but a fundamental requirement for safe ship operation. This section will focus on the practical application, best practices, common pitfalls, and verification procedures associated with shipboard loading instruments.

1. Purpose and Regulatory Requirement:

Primary Purpose: To enable ship’s officers to quickly and accurately calculate and assess the vessel’s stability (GM, GZ curve, compliance with IMO criteria), longitudinal strength (shear forces and bending moments at various stations), drafts, and trim for any given or proposed loading condition (including intermediate stages of cargo/ballast operations).

Regulatory Mandate:

SOLAS Chapter II-1, Regulation 22 (for bulk carriers constructed on or after 1 July 1998) and Regulation 23-2 (for existing bulk carriers): Requires bulk carriers of 150 metres in length and upwards to be fitted with a loading instrument capable of providing information on hull girder shear forces and bending moments. For newer vessels, this often extends to direct calculation of stability.

Classification Society Rules: Class societies have specific requirements for the type-approval, installation, and periodic testing of loading instruments. The instrument must be approved for the specific vessel it is installed on.

ISM Code: Effective use of the loading instrument is an integral part of the vessel’s Safety Management System (SMS) procedures for safe cargo operations and voyage planning.

2. Key Features and Functionality of Modern Loading Instruments:

Loading instrument software varies by manufacturer, but most approved systems offer a comprehensive suite of features:

A. Data Input:

Vessel Particulars Database: Stores the ship’s fixed data: hydrostatic tables, tank calibration tables (capacities, centers of gravity for all levels of filling), lightship weight and its centers (KG, LCG, TCG), permissible SF/BM envelopes, tank top strength limits, and specific loading conditions from the approved Loading Manual. This database is usually locked and can only be modified by authorized personnel or the manufacturer.

Variable Load Input: User interface for inputting:

Cargo: Weight/volume, stowage factor, VCG (if not automatically calculated based on trimmed level), and distribution per hold.

Ballast: Soundings/ullages or percentage full for each ballast tank. The software calculates weight and centers based on tank tables and liquid density.

Fuel Oil (HFO, MDO/MGO): Similar input for all fuel tanks.

Fresh Water (Potable, Boiler Feed): Similar input.

Other Liquids: Lube oil, sludge, bilge water, etc.

Deck Cargo (if applicable, though rare for bulkers).

Stores, Provisions, Crew: Often input as standard figures or can be adjusted.

Constant: An allowance for unaccounted weights.

B. Calculation Capabilities:

Hydrostatics: Displacement, drafts (FP, AP, MP, Mean), trim, list, TPC, MTC, LCF, LCB, KMT, KML.

Transverse Stability:

KG, GM (solid and fluid/corrected for FSE).

GZ curve generation (plotting GZ values against angles of heel).

Compliance check against all applicable IMO Intact Stability Code criteria (e.g., initial GM, areas under GZ curve, range of stability, GZmax).

Angle of loll calculation if GM is negative.

Longitudinal Strength:

Calculation of still water shear forces (SF) and bending moments (BM) at multiple pre-defined stations along the ship’s length.

Comparison of calculated SF and BM values against the ship’s permissible still water and sea-going limits (often displayed graphically as SF/BM curves against limit envelopes).

Calculation of percentage utilization of permissible limits.

Tank Capacities and Centers: Calculates weights and centers of gravity for all liquids in tanks based on input levels and calibration data, including free surface moments.

Tank Top Strength: For bulk cargoes, calculates the load intensity (tonnes/m²) on the tank top of each hold and compares it against permissible limits.

Draft Survey Calculations: Many loading instruments incorporate a draft survey module to calculate cargo loaded/discharged based on draft readings and deductibles.

Damage Stability (Optional/Advanced): Some advanced loading instruments include modules for performing damage stability calculations for specific damage scenarios, as required by SOLAS or Class for certain vessel types/ages. This is becoming more common.

Grounding Calculations (Specialized): Some may offer tools to assess stability and stress if the vessel grounds.

C. Output and Display:

Numerical Readouts: Clear display of all calculated parameters.

Graphical Displays:

GZ curve.

Shear Force and Bending Moment diagrams (actual vs. permissible).

Tank capacity gauges.

Vessel profile showing drafts and trim.

Alarms and Warnings: Audible and/or visual alarms if any calculated parameter exceeds pre-set warning levels (e.g., 95% of permissible stress) or actual permissible limits.

Printouts: Ability to print comprehensive reports of loading conditions, stability calculations, and stress diagrams for record-keeping and port authorities.

Saving/Loading Conditions: Ability to save and retrieve different loading conditions for planning, comparison, or record purposes.

D. Simulation Capabilities:

Loading/Discharging Sequence Planning: Allows users to simulate cargo and ballast operations step-by-step, checking stability and stress at each intermediate stage. This is vital for developing safe sequences.

“What-if” Scenarios: Test the impact of shifting cargo, consuming fuel, or encountering damage.

3. Best Practices for Practical Use:

Effective and safe use of the loading instrument requires diligence and adherence to best practices:

A. Accurate Data Input – The GIGO Principle (Garbage In, Garbage Out):

Meticulous Tank Soundings/Ullages: This is the most common source of error. Ensure tanks are sounded accurately using calibrated tapes, proper techniques, and that readings are correctly converted to weights/volumes using the software’s tank tables (which should account for trim and list).

Correct Cargo Data: Use the correct stowage factor for the cargo. Input the weight or volume of cargo per hold accurately. If estimating VCG of cargo, do so realistically.

Regular Update of Consumables: Fuel, water, and stores are consumed during voyages and port stays. These must be regularly updated in the loading condition to reflect the current status.

Verification of Constant: The ship’s “constant” (unaccounted for weights) should be monitored. If draft surveys consistently show a significant or fluctuating constant, it may indicate issues with lightship data or unaccounted weights onboard, which could affect the accuracy of the loading instrument.

B. Understanding the Software Interface and Functions:

Proper Training: All officers responsible for using the loading instrument (primarily Chief Officer, but also Master and other deck officers) must receive formal generic training and type-specific familiarization for the particular software installed onboard.

Know All Modules: Be familiar with all relevant modules (stability, strength, draft survey, sequence planning, etc.) and how to use them correctly.

Understand Alarms and Warnings: Know what different alarms mean and the appropriate action to take. Do not disable or ignore alarms without proper justification and understanding.

C. Regular Cross-Checks and Verification:

Sanity Checks: Always perform a “sanity check” on the output. Do the calculated drafts and trim look reasonable for the loaded condition? Does the GM “feel” right based on experience with the vessel?

Comparison with Manual Calculations (Periodically): While not expected for every condition, periodically (e.g., during training or if a result seems suspect) performing a simplified manual calculation for a key parameter (like GM or a basic stress check) can help verify understanding and instrument function.

Comparison with Approved Test Conditions: The loading instrument must be tested annually (or as per Class requirements) by inputting a standard test condition (provided by the manufacturer/Class) and comparing the software’s output with the approved results for that condition. Any significant discrepancies must be investigated and rectified. Records of these tests are mandatory.

Visual Inspection vs. Calculated List/Trim: Compare the calculated list and trim with visual observations of the vessel.

D. Use for Planning and Monitoring:

Pre-Stowage Planning: Use the instrument extensively to develop and refine stowage plans and loading/discharging sequences, ensuring all limits are met for final and intermediate conditions.

Real-Time Monitoring: During cargo and ballast operations, update the instrument frequently with actual loaded/discharged quantities and tank levels to monitor the evolving stability and stress situation in near real-time.

E. Printouts and Record Keeping:

For each departure and arrival condition, and often for critical intermediate stages or if requested by authorities, print out a comprehensive report from the loading instrument.

These printouts, signed by the Master and Chief Officer, form an important part of the voyage records and demonstrate due diligence.

File these reports systematically.

F. Software Updates and Maintenance:

Ensure the loading instrument software is kept updated as per manufacturer’s recommendations.

Report any software glitches or malfunctions to the company and manufacturer promptly.

Protect the computer hardware from harsh marine environments (vibration, humidity, temperature extremes).

4. Common Pitfalls and Errors in Using Loading Instruments:

Incorrect Tank Soundings/Ullages: Errors in reading, recording, or entering tank levels.

Wrong Density for Liquids: Using incorrect density for fuel, ballast (especially if in brackish water), or fresh water.

Incorrect Stowage Factor for Cargo: Using a generic SF when a specific one is available, or vice-versa.

Errors in Inputting Cargo Distribution: Assigning cargo to the wrong hold or inputting incorrect quantities.

Ignoring or Misinterpreting Free Surface Corrections: Though usually automatic, understanding their impact is vital.

Failure to Update Consumables: Using outdated fuel/water figures for current calculations.

Not Verifying the “Constant”: A significantly incorrect constant can skew all weight-based calculations.

Over-Reliance Without Understanding: Treating the loading instrument as a “black box” without understanding the underlying principles or critically evaluating the output.

Ignoring Alarms or Warnings: Assuming they are erroneous without proper investigation.

Using an Outdated or Unapproved Version of Software.

Failure to Perform Regular Test Condition Checks.

Data Entry Errors (Typos): Simple typing mistakes can have significant consequences. Double-check all inputs.

5. Master’s Oversight and Responsibility:

The Master has ultimate responsibility for the safe loading and stability of the vessel, and therefore for the correct use of the loading instrument.

Ensuring Competency: The Master must be satisfied that the Chief Officer and any other designated users are fully competent in operating the specific loading instrument onboard. This includes ensuring they have received appropriate training and familiarization.

Review and Approval of Calculations: The Master must personally review and approve all critical loading conditions (departure, arrival, any complex intermediate plans) calculated by the Chief Officer, paying attention to margins of safety for stability and stress.

Promoting Diligence: Foster a culture of meticulous data input and critical review of outputs.

Ensuring Instrument Integrity: Ensure that the loading instrument is Class-approved, that its software is current (as per company/manufacturer guidance), and that mandatory periodic test conditions are run and results verified and recorded.

Decision-Making Based on Output: Use the loading instrument’s output as a primary tool for making decisions regarding cargo stowage, sequencing, and ballast operations, but always tempered with sound seamanship and experience.

The loading instrument is a powerful and indispensable tool for the safe operation of bulk carriers. However, it is only a tool. Its effectiveness relies entirely on the knowledge, diligence, and critical judgment of the officers using it. A culture of meticulousness in its operation, from data input to result interpretation, is essential for leveraging its full potential in safeguarding the vessel against the perils of incorrect loading and instability.