The present booklet was prepared by the specialists of the Liquid Natural Gas Ship Fuel Safety Advisory Group and then published by SIGTTO together with SGMF on behalf of the Group. The twenty-two members of the Group possess huge professional experience in the LNG industry and include shipbuilders, marine class societies, vessel and terminal operators, makers, regulators and other parties.
The primary objectives of the above stated Group is the promotion of the use of LNG as a safe marine fuel friendly to the environment, retaining meanwhile a level of safety that would be considered equivalent to the safety level of the large scale liquid natural gas transport industry as well as the identification of the key issues and providing necessary technical guidance and valuable relevant information basing on the professional experience of the members.
They also try to provide required assistance to SIGTTO in developing of practical policies concerning the implementation of the natural gas as a fuel. This booklet does not have the standards themselves; it has been rather developed to provide the users with the list of the industry guides and recognized standards to be references so it will still be useful to the people in the shipping industry.
A ship in distress is usually in a condition where outside assistance is required to supplement the resources available on board to deal with the abnormal situation. A distress situation may have many facets ranging from disablement of power and/or steering to more fundamental damage to the hull or cargo system brought about by stress of weather, fire or other abnormal condition.
Thus, the safest place for a ship in distress is in sheltered waters where the necessary external assistance can be brought to bear to bring the situation under control. Once under control, plans can then be made for the long term rectification of the situation, damage or other factors causing the distress situation. In many cases, the ability to move the vessel to a safe, sheltered location is the most important single contribution that a port or coastal authority can make but this should be done in the full understanding of the risks that attach to the damaged condition of the ship. Liquefied gas tankers have unique construction features and their cargoes have unique properties that set them apart from other classes of ship and other categories of hazardous cargo.
This document describes the most important features of gas tankers and gas cargoes for those who may possibly become involved in seeking or granting a temporary refuge for such a ship, or be responsible for the contingency planning for such an event. This edition also includes details of actual incidents involving gas tankers.
This is the Discussion Paper dedicated to the Types of LNG (Liquefied Natural Gas) Carriers, prepared by the Shipping International Ltd. It was abbreviated from the Tanker Safety Training (LNG) publication. All gas cargoes can be transported only in a form of a liquid (i.e. neither gas nor even vapor) and, taking into account their physical/chemical properties, they have to be either at pressure greater than atmospheric pressure, or at temperatures below ambient temperature; the third option is in fact a combination of first two.
That is why all gas carriers are usually divided in three groups - fully-pressurized, semi-pressurized and refrigerated, and fully refrigerated. However, it shall be noted that the grouping names stated above are mostly used when discussing the types and classes of LPG rather than carriers of natural gas.
Take your time and just go through this short but very informative booklet and you will get a good knowledge of the nomenclature of the gas carriers and will be much more familiar with their types, general technical characteristics, descriptions of the construction and equipment, main advantages and disadvantages of the particular type etc. - excellent for training purposes.
The first three decades of the LNG industry, i.e. until the end of the 1990s, were dominated by base load projects with long-term sale and purchase and associated shipping contracts, typically of 20 years duration. With such arrangements the project partners had an equity share or knowledge in all facets of the project, from gas gathering to gas distribution, including shipping.
Furthermore, their technical staff had a detailed knowledge and familiarity with all the individual sections of the contractual chain. By the end of the 20th century, however, a short-term or "spot" market was starting to develop within the industry. In this market LNG vessels are hired on "spot" and "short-term" charters, with the charterer often having little or no knowledge of the history of such vessels. This has led to charterers and buyers and sellers of the cargoes drawing upon their oil industry experience and insisting on vetting these vessels prior to accepting them.
This has occasionally raised questions about aspects of the vessels' operation and maintenance that partners in the original long-term projects had previously understood and accepted. One area, unique to the LNG trade, in which this has occurred is the maximum, operationally acceptable, gas concentration to be found in the insulation spaces of the cargo containment system of the membrane-type liquefied natural gas carriers, particularly those of older design.
This guidance was produced by SIGTTO to members' concerns about the some of the interpretations of the functional requirements for emergency shutdown systems; in particular, differences between the needs of the liquid natural gases industry and those of liquid petroleum gases industry. It was also aimed to encourage and promote the use of linked emergency shutdown systems at both LPG and LNG terminals, especially where cargo transfer rates are quite high or where they handle one of the cargoes stated in IGC Code 1993/Chapter 17.
However, this SIGTTO publication is not intended to contradict any international or national requirements or standards for operational practices at the liquefied gas ship-shore interface. One of the primary objectives of this guidance was to advise the operators/owners of gas carriers about the rollover-related issues. The rollover itself mainly refers to the quick release if the LNG vapor occurring when the layers of different densities of LNG are spontaneously mixed in a cargo or storage tank. While for the conventional onshore terminals all such issues are known and understood, for LNG vessels the associated circumstances are a bit unusual and have to be paid serious additional attention...
These guidelines were developed in 1998/99 for Exxon Chemical Europe Inc., Basic Chemicals Europe by Captain C. Allport of Standard Marine Services Limited and replace earlier guidance. They are based upon the report and advice from an LPG Measurement Survey conducted by Srini Sivaraman of ER&E in May/June 1997 and incorporate the earlier guidelines for Liquefied Gas Cargo Measurement and Calculation, produced in 1987 for Exxon Chemicals International by the Centre for Advanced Maritime Studies, Edinburgh.
The earlier guidelines were adopted by Exxon Chemical International Inc. and approved by Regional Audit in 1988. The key to accurate cargo measurement based upon ship's figures depends on the precision of the tank calibration and calibration of associated level, temperature and pressure measuring devices in addition to the use of consistent methodology. Conformance to the recommendations made in these guidelines will result in transfer custody quality that is within the expectation of Exxon Corporation controls. The practices and procedures described in this document provide guidance for improving or maintaining liquefied gas measurement level of uncertainty within the accuracy requirements of Exxon's Hydrocarbon Measurement Practices (HMP) .
Contrary to the general recommendations contained in the HMP, these practices and procedures will demonstrate that quantity determination can be based upon ship or barge measurement. Custody transfer integrity is comparable to and in some cases can be better than shore systems and match HMP requirements.
This training course has been intended to help people get better understanding on liquefied gases handling. It is actually the continuation of the training commencing with the Gas Tankers - Familiarization Course. It consists of fourteen chapters - Introduction; Actual Gas Cargoes; Compartment Systems; Freighting; Chemistry and Physics; Cargo Handling Equipment; Monitoring and Control; Safety and Environment; Gas Measurement; Cargo Pumps; Cargo Handling Routines; Cargo Calculation; Cooling Processes and associated calculations; Insulation; Heat Transfer.
It is critically important training for everyone involved in any way in marine transportation of various liquefied gases, and also in operation/maintenance of related machinery, and calculations. During the period 1984-1992 some serious limitations to the STCW became apparent. People did feel that some of its requirements were vague and left to the sole discretion of the Parties, while others declared the problems with no any IMO oversight of compliance with the requirements, limited PSC, lack of clear competence standards, etc. It does make sense for personnel dealing with running the gas tankers to go through the materials of this course.
The present training course is aimed to help the key ratings and officers that have not previously served on board LG tankers. The book covers all mandatory minimum training requirements as prescribed by Regulation V/1, paragraph 1.2 of the STCW-95; it also includes basic pollution-prevention and safety precautions and applicable procedures, layouts of various types of liquefied gas tankers, types of transported cargo, their handling equipment and hazards plus the general sequence of operations and gas tanker terminology.
The whole training material has been arranged in two halves; the first part of the course providing some basic safety training for ship officers and ratings, while the second part provides the additional technical training for officers, masters as well as all others having immediate responsibilities for handling of cargo/equipment.
The main portion of the course starts with listing the most important stages in the LNG transportation by ships and some historical information on the development of liquefied gas handling, followed by the terminology used, properties of the liquefied gases and hazards associated with their transportation, types of gas carriers, cargo handling equipment and instrumentation etc...