Application of Amendments to Gas Carrier Codes Concerning Type C Tank Loading Limits

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Published Date

January 2012

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Application of Amendments to Gas Carrier Codes Concerning Type C Tank Loading Limits

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This booklet is designed to serve as a reminder to ship owners and terminal operators of the improvements in safety codes for cargo tank loading limits provided by the 1998 amendments.


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Changes to the IGC Code have made compliance less precise than conforming to the original code because the criteria for determining the lowest cargo density anticipated becomes the highest operational cargo temperature encountered. Predicting this temperature requires judgement on the part of the shipowner and the ability to convince Administrations that the selection is reasonable.


At its 14th session in December 1984, the IMO Bulk Chemicals Sub-Committee expressed its willingness to consider amending the codes governing cargo tank loading limits.


SIGTTO and IACS believed that for Type C tanks the codes reduced protective measures available under fire conditions or increased the risk of unwanted venting of cargo. By updating the codes, protection could be improved.


The IMO’s Marine Safety Committee, at its 61st session (MSC61), agreed to change the IGC Code and made that protection available.


These new amendments mean that Type C tanks, under fire conditions, can become filled with liquid. In this situation, the Code requires that the tank’s internal pressure does not exceed 20% above the Maximum Allowable Relief Valve Setting (MARVS). IACS/SIGTTO were able to demonstrate that Pressure Relief Valves (PRVs) could prevent the tank pressure exceeding 1.2 x MARVS.


To be certain that PRVs will perform as designed, inlet pressure losses and built-up back pressures must be within the PRV manufacturer’s limits.


IMO delegated the production of these guidelines to IACS/ SIGTTO who submitted the document to the 65th session of the Marine Safety Committee (MSC65). MSC65 recommended that the guidelines should be accepted, and they came into force on 1st July 1998.


The object of this booklet is to remind shipowners and terminal operators of the improvements in safety that these amendments provide.

1 Introduction
2 Changes to the Codes - What they are and what they Mean
2.1 Loading Limits - Unamended Procedures
2.2 Code Changes to Increase Protection
2.3 The New Amendments
2.4 The Effects of the New Amendments
3 Advantages Realised - A Guide to Administration Recognition
4 Recommendations
5 Summary
Appendix 1 Confirmation of Vent System Adequacy
Appendix 2 Highest Temperatures
Appendix 3 Loading Limit Assessment Method

The purpose of SIGTTO is to promote shipping and terminal operations for liquefied gases which are safe, environmentally responsible and reliable. To fulfil this mission it will:

  • Proactively develop best operating practices and guideline

  • Sustain a learning environment by sharing lessons learned

  • Promote training and development of all within the industry

  • Foster mutually beneficial relationships with regulatory authorities and other stakeholders

  • Conduct its business with professionalism and integrity

Title: Application of Amendments to Gas Carrier Codes Concerning Type C Tank Loading Limits
Number of Pages: 52
Product Code: WS1363K
ISBN: ISBN 13: 978-1-85609-125-1 (9781856091251), ISBN 10: 1-85609-125-2 (1856091252)
Published Date: January 2012
Binding Format: Paperback
Book Height: 180 mm
Book Width: 120 mm
Book Spine: 5 mm
Weight: 0.10 kg
Author: SIGTTO

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