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LNG Shipping at 50||the safety regime

The feedback of surveyors has been an essential element in the development of class society rulebooks for gas carriers

The register of ABS-classed gas carriers encompasses all the LNG carrier containment systems in service today

A SIGTTO/GIIGNL commemorative issue LNG shipping at 50I 69I 69

rules were not applicable for ships intended to carry LNG. To ll the gap, ABS introduced a new Section 24 in the 1970 edition of its rules specically covering the construction and classication of steel vessels intended for the carriage of liqueed gases.

The French classication society Bureau Veritas (BV) has been closely associated with the development of gas carriers since the very beginning of this new technology. The society’s early involvement began in 1953 with the classication of various pressurised LPG carriers built in Europe, mainly under the French and Danish ags.

In 1958 BV became the rst class society to publish special recommendations for LPG carriers in its rules. These provisions were drawn up for vessels involved in the carriage of liqueed gases such as butane and propane at full pressure. BV followed this up with the publication of a guidance document entitledTechnical general conditions governing the sea transportation

of liqueed natural gasin 1962. To assist in the compilation of the guidance document, the Paris-based society had established, within its naval technical committee, a special commission made up of representatives from Gaz de France, shipowners, shipbuilders, steel manufacturers and other interested and duly qualied persons.

Det Norske Veritas (DNV, now DNV GL) has had gas carriers in its class since the late 1940s.Hydro andHerøya, a pair of 1,454m3 _{anhydrous ammonia carriers,}

were converted on behalf of Norsk Hydro in 1949 and 1950. The early DNV work on gas carriers was formalised in July 1960 when its research department published a document entitledPreliminary recommendations for the design and construction of ships for the transport of

liqueed gas.

DNV’s rst comprehensive rules for gas carriers were published in 1962 in its Rules for the construction and classication

of steel ships as ‘Chapter XIV – Recommendations for the design and construction of ships for the transport of liqueed gas’.

In the early 1960s DNV’s director of research Egil Abrahamsen was to the fore in presenting the extensive guidance on the classication of gas carriers compiled by his society. His paperSpecial Ships

for the Transport of Liqueed Gas, from

the Classication Viewpointwas heard in Oslo in 1960 whileGas Transport and

Ship Classicationwas presented to API in 1963. Another paper,The Carriage of

Special Liquid Cargoes, was delivered to an audience in Sandefjord, Norway in 1964.

Nippon Kaiji Kyokai (ClassNK) developed its rules for refrigerated and pressure-type gas carriers in 1959.

Goshu Maru, the rst ship classed with NK to carry LPG, was delivered by Mitsui Engineering and Shipbuilding in October 1961. This ship was a combined crude oil and LPG carrier with ve fully refrigerated prismatic LPG tanks providing a total capacity of 11,300m3_.

The ship design, in which 90 per cent of the available space for cargo was devoted to crude oil, was based on guidance plans from Esso and the ship was dual classed with ABS.

Registro Italiano Navale (RINA) published its rules for ships transporting liqueed gases in pressure vessels in 1966. The rules were based on the society’s experience during the building of six fully pressurised LPG carriers built in Italy since 1956. During the construction of these small gas carriers

RINA had generally relied on its rules for oil tankers. The new 1966 rules specically addressed gas carrier cargo tanks, piping and vent systems as well as other safety features.

Classication societies took on board the recommendations of the

IMCO Code for the Construction and

Equipment of Ships Carrying Liqueed

Gases in Bulk after it was published in 1976. Most class societies had taken an active part in developing the Code’s recommendations. By the time this set of provisions became the IMO’s

International Gas Carrier (IGC) Code, class societies had incorporated the essence of the Code’s recommendations into their rulebooks.

The success, progress and exemplary safety record of LNG carriers over the past 50 years owes much to class societies. The dedication, co-operation and foresight of their technicians, researchers and surveyors have been unparalleled.SH

Extensive research and testing programmes form a key part of class society involvement with LNG carriers

A SIGTTO/GIIGNL commemorative issue 70 I

70 ILNG shipping at 50

LNG Shipping at 50

LNG Shipping at 50||the safety regime

H

owever tentative it may have been in its earliest days, LNG transportation took hold quickly and went on to become a great success – both technically and commercially. LNG offered a clean and attractive alternative to gas derived from coal gasification or naphtha reforming and to other hydrocarbon fuels. The investment in liquefaction plant and shipping enabled companies to cash in on gas assets that were otherwise stranded or flared. This became increasingly important as environmental concerns developed and oil reserves became scarcer.

The pioneering exports from Algeria, Libya and Alaska were soon joined by those from Brunei, Abu

Dhabi and Indonesia and within the short span of 10 years the global LNG trades had developed into the pattern we recognise today.

The subsequent expansion of these trades was more evolution than revolution. The industry favoured established commercial practices, proven liquefaction plant technology and reliable ship designs. Ship size increased only marginally over the rst quarter of a century, in tandem with discreet rises in LNG production plant capacity. The conservative approach was understandable, as the industry gained familiarity with what is a challenging cargo and accommodated a relatively slow buildup in trade in the 1970s and 1980s.

LNG presents certain risks when carried as a cargo in signicant volumes. Its vapours are ammable and its cryogenic carriage temperature of –162˚C requires special precautions. The shipping industry realised early on that if LNG was to gain and maintain a place in the global energy mix, safety would have

to be given top priority. A measure of the success of the LNG shipping industry’s ongoing commitment to minimising risks is the exemplary safety record achieved over the past 50 years.

If asked what makes the LNG business unique and why a quality training regime is so important, there is no need to look beyond the ships themselves. From the birth of the industry LNG carriers have always been regarded as rather special. They are, in effect, a ‘oating pipeline’, linking gas exporters and importers where no pipeline alternative exists.

Also, given the very nature of the trade – which is closely linked to the fuel requirements of public utilities – the reliability of LNG deliveries has always been of paramount importance. The need to provide a continuous, seamless ow and to keep the supply chain functioning according to tight contractual terms is one of the key differences between LNG ships and most other liqueed gas carriers.

The highly engineered systems and equipment needed to contain and handle large volumes of valuable, cryogenic cargo make LNGCs expensive ships. In the early days it was possible to build seven (single-hull) very large crude carriers (VLCCs) for the price of a single LNGC. The high cost of entry ensures that the LNG domain is open only to the committed shipowner.

Early LNG carriers were steam turbine-driven vessels of relatively small size, in the 25,500–75,000m3

range. The relatively high cargo tank surface-to-volume ratio and the insulation technology at the time meant there was a comparatively high cargo boil-off gas rate to deal with. In order to avoid wasting this valuable product, it was used as propulsion system fuel in the ship’s boilers. Because ship service speeds were usually chosen to match fuel availability, this led to service speeds that were higher than the average for the time. Of course, most of the LNG carriers ordered today are dual-fuel motor ships and managing these propulsion systems requires a completely different set of engine room skills. At the same time, steam ships still account for the largest part of the eet, so the industry’s retention of a body of engine room staff familiar with the operation of steam turbines is essential.

Given the international nature of the shipping industry, it is perhaps surprising to note that IMO’s rst set of provisions aimed at standardising maritime training worldwide was not introduced until 1978. However, for gas carrier operators this Standards of Training, Certication and Watchkeeping (STCW) Convention proved to be an excellent example of joined-up thinking.

The ‘Lakey Group’ had just completed

Chris Clucas* shows how

In document COLEGIO DE CIENCIAS Y HUMANIDADES LICENCIATURA EN PROMOCIÓN DE LA SALUD (página 49-59)