Bulk Carriers: Guidance and Information on Dry Cargo Loading and Discharging to Reduce the Likelihood of Over-stressing the Hull Structure

Published Date

August 2020

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Bulk Carriers: Guidance and Information on Dry Cargo Loading and Discharging to Reduce the Likelihood of Over-stressing the Hull Structure

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This publication is intended to provide the shipping community with guidance and information on the loading and discharging of bulk carriers to remain within the limitations as specified by the Classification Society to reduce the likelihood of over-stressing the ship's structure.

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IACS Member Societies and other parties involved in bulk cargo shipping are concerned with the possible damage and loss of bulk carriers carrying heavy cargoes. Of particular concern are the potential problems which may result during operations such as the introduction of very high capacity loading systems, lack of communication between ship and terminal and inadequate planning of cargo operations. It is also of concern to IACS Members that some seafarers, and ship and cargo operators do not have a clear understanding of the limitations imposed by the ship's classification society regarding the strength capability of the hull structure.


IACS considers that a positive step must now be taken to provide adequate guidance and information to all parties involved in the loading and unloading of dry bulk carriers so that there is an awareness and better understanding of the possible problems that may be encountered. To serve this purpose, it is the intention of IACS to make this publication available to all shipowners, ship masters, ship and cargo terminal operators and other interested parties worldwide.



The loads that affect the ship's structure are generally discussed with special reference to the structural strength limitations imposed by the ship's Classification Society.


The process of planning and controlling cargo operations is addressed with special reference to the derivation of the loading and unloading plans and the requirements for ship/shore communication.


A review of the potential problems that could be encountered during cargo operations is presented. Guidance is given on the measures that should be taken to monitor and control cargo and ballasting operations in order to reduce the possibility of over-stressing the ship's structure.



1 Introduction

1.1 Factors Contributing to Hull Structural Failure

1.2 Actions Taken by IACS

1.3 Aims of This Publication

2 Loads and Hull Structure

2.1 Typical Bulk Carrier Structural Configuration

2.2 Design Limitations

2.2.1 General

2.2.2 Hull Girder Shear Forces and Bending Moments

2.2.3 Local Strength of Transverse Bulkhead, Double Bottom and Cross Deck Structure

2.3 Cargo Distributions Along Ship’s Length

2.3.1 General

2.3.2 Homogeneous Hold Loading Conditions (Fully loaded)

2.3.3 Alternate Hold Loading Conditions (Fully loaded)

2.3.4 Block Hold Loading and Part Loaded Conditions

2.3.5 The change of weight distribution arising from fuel and ballast water


3 Onboard Loading Guidance Information

3.1 Loading Manual

3.2 Loading Instrument


4 Planning and Control of Cargo Loading and Unloading Operations

4.1 Preparation for Cargo operations

4.1.1 Cargo and Port Information

4.1.2 Devising a Cargo Stowage Plan and Loading/Unloading Plan

4.1.3 Ship/Shore Communication Prior to the Commencement of Cargo Operations

4.1.4 Before Commencing Cargo Operations

4.2 Monitoring and Controlling Cargo Operations

4.2.1 Monitoring of Stevedoring Operation

4.2.2 Monitoring the Ship’s Loaded Condition

4.2.3 Hull Damage Caused by Cargo Operations

5 Potential Problems

5.1 Deviation from the Limitations Given in the Approved Loading Manual

5.2 Loading Cargo in a Shallow Draught Condition

5.3 High Loading Rates

5.4 Asymmetric Cargo and Ballast Distribution

5.5 Lack of Effective Ship/Shore Communication

5.6 Exceeding the Assigned Load Line Marks

5.7 Partially Filled Ballast Holds or Tanks

5.8 Inadequate Cargo Weight Measurement During Loading

5.9 Structural Damage During Loading/Unloading


6 Ballast Exchange at Sea

1.1 Factors Contributing to Hull Structural Failure

Concern regarding the high casualty rate of single side skin dry bulk carriers and the associated loss of life and cargo in the early 90s, where structural failure may have been a contributory factor, led the International Association of Classification Societies (IACS) to carry out comprehensive investigations to identify the likely causes of these ship casualties and to introduce measures to minimise their recurrence. The evidence available indicates that most of the ships lost were over 15 years old and were predominantly carrying high density cargo, such as iron ore, at the time of loss. The investigations identified that the principal factors contributing to the loss of these ships were corrosion and cracking of the structure within the cargo spaces. Other factors that could have contributed to the hull structural failure were over-stressing of the hull structure due to incorrect loading of the cargo holds and physical damage to the side structure during cargo discharging operations.

Dedicated to safe ships and clean seas, IACS makes a unique contribution to maritime safety and regulation through technical support, compliance verification and research and development. More than 90% of the world's cargo carrying tonnage is covered by the classification design, construction and through-life compliance rules and standards set by the twelve Member Societies of IACS.

IACS is a not for profit membership organisation of classification societies that establish minimum technical standards and requirements that address maritime safety and environmental protection and ensures their consistent application.  It carries out this responsibility through its panels, expert groups and project teams and provides a Quality System Certification Scheme (QSCS) that its Members comply with, as an assurance of professional integrity and maintenance of high professional standards.  IACS is recognized as the principal technical advisor of IMO.

Title: Bulk Carriers: Guidance and Information on Dry Cargo Loading and Discharging to Reduce the Likelihood of Over-stressing the Hull Structure
Series Details: IACS Rec No. 46
Edition: Rev. 2
Number of Pages: 62
Product Code: WS1745K
ISBN: ISBN 13: 978-1-85609-930-1
Published Date: August 2020
Binding Format: Paperback
Book Height: 230 mm
Book Width: 160 mm
Weight: 0.40 kg
Author: IACS

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