First regular LNG traffic begins
Although, as we know, transport by sea of gaseous cargoes is far from new, it may seem surprising that commercial international shipping of LNG began exactly 50 years ago.
A pair of tankers had entered service carrying liquefied methane gas from North Africa to Canvey Island in the UK. One of the pair, Methane Princess, was described in detail in the December 1964 issue of The Motor Ship. Carrying large volumes of gas under high pressure and at very low temperature was very much uncharted territory, and ship designers had followed different approaches to solving the many unknown parts of the equation – a French LNG ship, the Jules Verne, was nearing completion and our predecessors were looking forward to an interesting comparison.
Methane Princess and sister vessel Methane Progress were built by Vickers Armstrong and followed tried and tested oil tanker practice, but the nature of the cargo led to some significant design differences. Because the specific gravity of LNG is about half that of oil, ballast arrangements had to be totally rethought, and the 12,200dwt LNG tankers ended up to be of similar dimensions to a 28,000dwt crude oil tanker, at 618ft (188m) length oa. The different characteristics of the cargo meant that the LNG tankers had a shallower draught and higher freeboard, while to minimise boil off losses – and help offset the higher capital cost - the service speed of the LNG tanker was significantly higher. Boil off rate was estimated at about 0.3%/day, which by burning under the main boiler allowed a saving of about 30% in bunker fuel. The nature of the cargo meant that double hull construction was employed over the full length of the cargo space – now normal practice of course for any tanker, but unusual 50 years ago.
The cargo spaces were divided into three insulated holds, each containing three rectangular-shaped tanks of welded aluminium construction. This differed from the French design, which uses similar tanks, but cylindrical in form. The other notable feature for the time was the amount of instrumentation and the level of automation – all felt to be necessary for operational and safety reasons, and which no doubt contributed to the £4.75million cost of each ship – very high by the standards of the day. However, as the two ships were expected to complete 60 round trips per year, delivering about 10% of Britain’s total gas requirement (equivalent to 1.3million tons of coal) the operators obviously considered this a sound investment.
A supplement to the main issue celebrated the Burmeister & Wain large-bore engine range. A table listed some 150 840mm-bore engines completed and on order, representing approaching 3million bhp, while B&W director Mr Knud Møller looked forward to the next generation of engines which would be designed for outputs of 27,600bhp – “and possibly above”. One of the prime considerations for these new, more powerful, units would be reliability. Mr Møller considered B&W had a head start in this respect, citing two tanker customers, one French and one Norwegian, whose ships had, on average, been available for 352 and 360 days per year respectively. Another important feature for ‘future engines’ was simplified control and manoeuvring, allowing for remote control and high levels of automation.
In fact the magic 27,600bhp figure had already been reached with the company’s 84VT2BF-180 engine, which was proving a popular choice for tankers of around 100,000dwt and above, several of which were being built in Japan. One of these, the Hitachi-built Yamamizu Maru, was Japan’s second largest ship, second only to a 131,000dwt steam tanker, and was the first to be completed with the largest, 12-cylinder, 84VT2BF.
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