Better work environment with natural gas power

Det här innehållet kommer från vår tidigare hemsida och kan därför se annorlunda ut.

LNG (liquefied natural gas) is the new fuel for Destination Gotland’s new ferry, M/S Visborg, which improves several health and safety problems that used to be common in engine rooms. They are now brighter, quieter and have no diesel smells or messy oil. There is still a lot of work left with interior fittings and filling the stores in the newly delivered ship, however.
Four symbols are flashing to indicate gas mode on a screen in the control room, one for each main engine. Another display shows that the amount of diesel added to the fuel is decreasing, and is now down to less than 10%. The second ship’s engineer, Henrik Ottosson, is supervising the process.
“We always start up the engines on diesel – it’s not possible to do this on gas. But as soon as everything is running we switch over to LNG,” he says.
It is almost four o’clock in the afternoon and M/S Visborg is backing out of her berth in Visby for yet another crossing to Nynäshamn. The control room receives a call from the bridge to shut down one of the main engines – the ship can manage the crossing to the mainland on three engines. It is running on almost pure gas now, with only about 2% diesel required to ignite the gas.
Lower sulphur content
“It’s really just the starting process that is different with LNG, otherwise you don’t notice much difference here in the control room,” says Henrik Ottosson. “It is a completely new system to learn, though, and it takes a little time.”
LNG has become increasingly common as shipping fuel in recent years. Natural gas contains much less sulphur than traditional fuels and requires no purification equipment to comply with the emission rules for the Baltic Sea. As well as reduced emissions into air and water, LNG also ensures a much cleaner engine room compared with heavy fuel oil and diesel. There are no leaks from poor seals and no oil mist when pressure testing.
“The work environment is much better here than other engine rooms because we don’t need to heat any oil,” says Henrik
Ottosson, who has been employed by the shipping company since the beginning of the year.
“My last ship ran on heavy oil. The exhaust had to be cleaned using scrubbers, so we still had to deal with the sulphur. We don’t need to do any of that now.”
M/S Visborg’s chief engineer, Claes Ottosson, shows us around the engine department. The noise is a little less than usual in an engine room. It is clean around the four main engines and the room is bright and cool.
“It’s no longer a black hole you go into,” says Claes Ottosson. The biggest advantage of LNG is the improved work environment.”
It is not yet known how LNG will affect maintenance needs, but Claes Ottosson expects them to be less for parts directly linked to propulsion and intervals between overhauling the main engines and auxiliary generator set can be extended. On the other hand, LNG involves more peripheral equipment that will need service and maintenance, such as the heating system to convert LNG into a flammable gas and the gas valve units (GVUs) that control the supply of gas to the engines.
Night-time bunkering
“We will probably need to make a lot of checks on the equipment related to LNG power, and that will take extra time,” says Claes Ottosson. “Exactly how much more work is involved is an unknown factor – time will tell.”
The LNG is stored as a liquid in two tanks on each side of a ladder just fore of amidships. Each tank can hold up to 285 cubic metres of gas and they are rather like two giant thermos flasks with insulation. The LNG is kept at -145°C to prevent the pressure in the tanks from increasing too much.
“We don’t normally need to be here at all in our daily routines,” says Claes Ottosson as we walk down the well-insulated staircase to the tank area. “There is a certain amount of maintenance to be done on the control system down here in the TSCs (the spaces next to the tanks), but some of that work is done by Wärtsilä (the machine manufacturer, ed.) and some by the crew.”
“Using LNG has several advantages over traditional shipping fuel, but there are a few drawbacks, such as bunkering. This has to be done at night because that is the only time when the ship is remains still for long enough to complete the whole procedure, which includes pressure testing, bunkering and cleaning. It usually takes about two and a half hours from start to finish and last night we could not start until twenty past three. The chief engineer must always be present at the start of the bunkering process, together with another engineer officer and a motorman. The ship bunkers every other night in the high season, whereas it may be enough with a couple of times a week in the low season.” For Claes Ottoson and his relieving officer, this means less time for rest than in the past.
“It’s not ideal, at least not in the summer,” he says, “but we try to sleep when we can and I will go to bed for a while after the next departure from Nynäshamn.”
M/S Visborg has been in traffic on the Visby-Nynäshamn route since Easter. There is still a lot of work left before all the interior fittings are in place and the storerooms are filled. There are cartons and boxes along the bulkheads full of equipment and spare parts that have not yet been unpacked, and in the large storeroom by the workshops the packaging is being taken off new metal cabinets. When the company took delivery from the shipyard in China in November last year, there was not much else on board apart from instruction manuals and whatever was needed for the voyage to Europe.
Four hundred orders
“We were busy ordering parts and building up stocks and supplies during the whole of the voyage,” says the first ship’s engineer, Michael Jägervi, who was on board from China. “So far we’ve written 400 orders – and we’re not finished yet!”
M/S Visborg is the first LNG-powered ship purchased by Destination Gotland. They are now waiting for the delivery of her sister ship, M/S Tjelvar, which will also be powered by natural gas.
Linda Sundgren, text and photo

Share article: