Disabled Tankers - Report of Studies on Ship Drift & Towage

Based on testing carried out by the British National Maritime Institute (NMI), and initiated by OCIMF members, the American Institute of Shipping (AIMS) and the International Salvage Union (ISU), this publication is a report on the most probably drift behaviour of disabled tankers. It is divided into three sections:

• Part 1 is an overview of model tests carried out by the NMI
• Part 2 is an exploration of full scale drift data taken from operational ships
• Part 3 describes tank test studies.

Tanker owners and operators have become increasingly concerned about the problems associated with the drifting and towing of disabled tankers.

A review of casualties involving freely drifting disabled tankers suggested that there is much to be learned about the behaviour of a disabled tanker under the influence of wind, waves and currents.

In order to provide Masters of disabled tankers with information about the most probable drift behaviour of their vessels, research was initiated by a group of companies, members of the Oil Companies International Marine Forum (OCIMF), together with the American Institute of Merchant Shipping (AIMS) and the International Salvage Union (ISU). The British National Maritime Institute (NMI) was commissioned to carry out intensive model testing with free floating and tethered models.

A steering group, known as the Disabled Ship Research Group (DSR), made up of marine representatives of the sponsoring oil companies and of the ISU was appointed to participate in the tests. Their involvement was an essential ingredient of the experiments.

To validate the results of the model tests, full-scale drift data were obtained from some vessels, predominantly VLCCs, with some smaller tankers.

This report presents the results compiled from the experiments and investigations.

The raw data on the experiments may be obtained from:

The National Maritime Institute,

Feltham, Middlesex, England.

Part 1

1. Introduction

2. Experiments with Free Models

3. Measurements of Drift Forces in Waves

4. Calculations of Wave Drift Forces

5. Conclusion

6. References

Part 2

1. Purpose
2. Data Gathering
3. Questionnaire Results
4. Summary of Results
5. Tables of Results
6. Questionnaire

Part 3

1. Introduction
2. Preliminary Results
3. Experimental Arrangements
4. Results Obtained
5. Discussion of Results
6. General Discussion
7. Conclusion
8. References
9. Nomenclature