At 06:10, with the tide slack and the anchorage still grey, the bunker tanker Selat Pioneer came alongside the bulk carrier Tern Horizon in an anchorage off the Riau Islands. Over the next six hours the two crews completed a ship-to-ship transfer of ammonia fuel, the first either of them had attempted. The video below follows the operation from the first heaving line to the final purge.
Before the first line
The Tern Horizon is an 82,000-tonne bulk carrier delivered this year to Meridian Bulk with an engine that can burn ammonia or fuel oil. Until this morning it had only burned the second. The Selat Pioneer, a 5,000 cubic metre gas tanker converted for bunkering, carries ammonia fully refrigerated at minus 33°C.
The operation waited nine days for its weather: wind under 15 knots, swell under a metre, and a forecast that held for twelve hours. "We could do this in worse," said Captain Rafael Sumarno, master of the Selat Pioneer. "We chose not to find out on the first one."
The exclusion zone
Ammonia is poisonous at concentrations that fuel oil never reaches, so the anchorage was rearranged around the transfer. A patrol boat held a 500-metre ring clear of traffic. Both ships ran water curtains along the manifold side, since ammonia vapour dissolves readily in water spray. The pair lay head to wind, with the accommodation blocks upwind of the connection.
Every person on either deck carried a personal gas detector set to alarm at 25 parts per million and an escape hood on the belt. Fixed sensors around the manifold reported to both bridges.
Six hours on one hose
The single 8-inch hose, 22 metres long and rated for minus 50°C, was lifted across by the tanker's crane at 06:45. The crews pressure-tested the connection with nitrogen, then sent a small flow of cold liquid through to chill the hose before the main transfer. Pumping started at 07:30 at 90 cubic metres an hour and was raised to 150 once the tank pressures settled.
By 12:05 the Tern Horizon had taken 410 tonnes, about 600 cubic metres. The hose was drained, purged with nitrogen until the analysers read zero, and disconnected at 12:40.
Nobody smelled a thing
Most people notice ammonia at about 5 parts per million. The highest reading of the day, 2 ppm, came from a sensor beside the manifold during the purge and lasted under a minute.
"I kept waiting for the smell," said Joy Macaraeg, bosun of the Tern Horizon, who stood the manifold watch for the whole transfer. "In training they make you smell a sample so you know it. I never smelled it once today."
A crew trained twice
Both crews spent five days ashore before the pilot: two days of theory, two of drills with a live ammonia rig and one of full-scale rehearsal with water in place of fuel. Each ship carried an extra engineer seconded from the engine maker for the first month of operation. Meridian Bulk said it would double the training for crews joining its next four ammonia-capable ships.
What it costs
Ammonia holds about 18.6 megajoules per kilogram, less than half the energy of very low sulphur fuel oil. The Tern Horizon needs roughly 2.2 tonnes of ammonia to do the work of one tonne of oil, and bigger tanks to hold it.
Neither company disclosed the price of the pilot cargo. Straits Energy Brokers, which tracks quotes for ammonia delivered to ships, puts it at between 2.5 and 3 times the cost of fuel oil for the same energy. "Nobody runs a ship on ammonia this year to save money," said Wei Lin Toh, the broker's head of alternative fuels. "They do it to learn how, before a customer asks them to." For the other cargo that burns itself on the way, see our report on LNG boil-off.
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