Crude, gas and containers
The lead article in The Motor Ship, October 1968, concerned using crude oil as a ship fuel. The motivation came from some tanker owners, operating in isolated locations without normal bunkering facilities.
Apparently some five years previously this journal had reported tests at the Sulzer works in Winterthur on a standard 6RD68 burning Libyan crude oil. There had been little interest at the time, but a number of requests had been received for reprints of the 1963 article. This culminated in US operator Conoco ordering two 115,000dwt tankers, each with a Sulzer engine adapted with “a newly patented crude oil burning process.”
As was remarked at the time, there would appear to be little economic justification for using crude, which was a more valuable product than residual HFO. But for Conoco, carrying crude from Libya to a new refinery on the English east coast, the ships could avoid diversions to bunkering ports. And with crude having a higher calorific value than residual, full load fuel consumption was improved, and exhaust temperatures were lower.
Interestingly in the light of current fuel discussions, Libyan crude was quoted at having a sulphur content of only 0.61% and is said to be a light oil, so a different pre-treatment would be needed. The main difficulty was the high paraffin content – 9.2% - which was thought to be potentially problematic due to separating and getting rid of wax.
The main ship report in October 1968 described Antilla Cape, said to be the largest European liquefied gas tanker yet delivered. Built in Bremen for Netherlands Antilles owners, she could carry 30,000m3 of butane, propane, propylene or anhydrous ammonia. This was one of the first ships to be built to transport LPG in refrigerated form, which allows much larger bulk shipments than the more common pressurised LPG cargo arrangements. Cooling and transporting gas to -40 degrees C presented quite a challenge to ship designers and builders of the day, and this ship employed four separate self-supporting tanks, fabricated from carbon steel to ensure ductility at low temperatures, and insulated by foam with a glass-reinforced epoxy sheathing. A similar high tensile carbon steel was used for construction of any parts of the hull likely to come into contact with escaping gas in case of leaks. This was in order to meet class requirements for secondary containment; using the same material for the hull as the tanks avoided the need for a separate containment system. As there was then no way of using boil off gas to fuel a diesel engine, the cargo handling equipment included extensive reliquefication plant, as well as inert gas generators for flooding the main LPG tanks and void spaces. Propulsion was by a Sulzer 8RD76 main engine, rated 13,200 bhp at 122 rev/min, controlled from the wheelhouse via a Sulzer-Westinghouse pneumatic system.
Another ship description focused on NYK Lines’ Hakone Maru, Japan’s first cellularised container ship, for operation on the Japan-USA routes. With containerisation becoming more common for US companies, and its growing popularity in Europe, it was surely time for Japan to enter the arena. This it had certainly done, with, at 16,300 dwt and 752 TEU capacity, the largest non-American container vessel. Operators were realising that speed was of the essence to gain full advantage of the container concept. So Hakone Maru had a hull developed from previous Mitsubishi-built fast cargo liners, and a Mitsubishi-MAN K10Z93 main engine rated 27,800 bhp at 115 rpm. With the machinery placed well aft, to maximise cargo space. This, along with the high installed power, meant that “special measures” had to be employed to minimise vibration.
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