Talk:LNG carrier

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Untitled
Methane Princess was not the first LNG-carrier (1962). It was Normarti (Methane Pioneer) in 1958. —Preceding unsigned comment added by 129.241.215.2 (talk) 12:50, 18 March 2009 (UTC)

I created LNG storage tank, any help expanding it appreciated. --Paul E. Ester 16:41, 26 August 2006 (UTC)

I have added a good bit to this page. I hope that someone can proof read and tidy up grammer etc. I added a bit before i created an account so three edits on 5th march Thinfourth — Preceding unsigned comment added by Thinfourth (talk • contribs) 16:38, 5 March 2011 (UTC)

Security
someone needs to add something about the high amounts of security that surrounds LNG carriers, especially in american ports hornplayer2 (talk) 02:10, 1 July 2008 (UTC)

Security / Safety A section on LNG safety might be useful. LNG carriers have one of the best safety records of all ship kinds but at a cost of very strict rules about what can be brought on board(smoking gear, electric / electronic gear)

Can take what you want onboard just you aren't allowed to use spark potential equipment in hazardous areas

Considering the LNG carrier is not far off a free floating bomb, A section on fire / explosion prevention systems would be a good sub item.

Very hard to get one to blow up but still HUGE amount of safety systems

Side note: I have heard of people having to undergo baggage searches before being allowed to join / board a LNG carrier.. Anyone with more info or links....?

Nothing unusual about the bagage searchs for joining an LNG vessel to any other type of vessel, it is more to do with the port you are going through then the ship you are going to

Wording
Reliquification?? how about Reliquefaction? Whats the diff? Doseiai2 (talk) 08:05, 25 May 2009 (UTC)

Proper term is Reliquefaction --Work permit (talk) 22:58, 30 May 2009 (UTC)

Units of capacity for the English Measurement System
I find the English Measurement System capacities being provided in liquid cubic feet confusing. In industry articles about LNG tankers capacity is typically provided in cubic meters for metric liquid volume, and sometimes in BCFe (billion cubic feet equivalent) for English. A typical 2017 built LNG tanker that can transit the newly enlarged Panama Canal holds about 3.5-3.7 BCFe. When I see that the Christophe de Margerie has a 6,100,000 cubic feet capacity, it is easy to mis-interpret that as 6.1 BCFe, which I think is much larger than it actually is? Perhaps both US gallons and BCFe could be provided instead of cubic feet. As a reader of the article both of those would be more useful than measuring liquid capacity in cubic feet. -- Gregfreemyer (talk) 14:38, 17 December 2017 (UTC)

Typo
The following sentence is surely wrong: "Shore terminal then burns this vapour to avoid the dangers of having large amounts of CO2 around which may explode." CO2 will not explode. Should probably be replace by "Natural Gas". — Preceding unsigned comment added by 67.188.144.104 (talk) 04:59, 10 February 2012 (UTC)

Propulsion
The Reliquefaction section says "Normally an LNG tanker is powered by steam turbines with boilers" but the "inside of a LNG carrier" diagram shows a reciprocating internal combustion engine. So I'm left wondering which it is. Maybe it's normally steam turbines, and the diagram shows an abnormal type. Kendall-K1 (talk) 02:15, 2 April 2013 (UTC)

My understanding is steam turbine propulsion for LNG tankers lost favor in the early 2000's and by 2005 most new builds were dual fuel diesel electric. I'm not sure enough of that to adjust the main article. -- Gregfreemyer (talk) 15:09, 17 December 2017 (UTC)

Entire duplicate article removed
The entire article had been duplicated. I manually compared the two versions and they seemed the same, apart from a few commas and one has/have difference and a small final piece in the first copy.

So I deleted the second copy. In case I have done any damage what I removed is here:

History


The first LNG carrier Methane Pioneer left the Calcasieu River on the Louisiana Gulf coast on 25 January 1959. Carrying the world's first ocean cargo of LNG, it sailed to the UK where the cargo was delivered. Subsequent expansion of that trade has brought on a large expansion of the fleet to today where giant LNG ships carrying up to 266,000 m3 are sailing worldwide.

The success of the specially modified C1-M-AV1-type standard ship Normarti, renamed Methane Pioneer, caused the Gas Council and Conch International Methane Ltd. to order two purpose built LNG carriers to be constructed: Methane Princess and Methane Progress. The ships were fitted with Conch independent aluminum cargo tanks and entered the Algerian LNG trade in 1964. These ships had a capacity of 27,000 m3.

In the late 1960s opportunity arose to export LNG from Alaska to Japan, and in 1969 that trade was initiated. Two ships, each with a capacity of 71,500 m3, were built in Sweden. In the early 1970s, the US government encouraged US shipyards to build LNG carriers, and a total of 16 LNG ships were built. The late 1970s and early 1980s brought the prospect of Arctic LNG ships with a number of projects being studied.

With the increase in cargo capacity to approximately 143,000 m3, new tank designs were developed, from Moss Rosenberg to Technigaz Mark III and Gaztransport No.96.

In recent years, the size and capacity of LNG carriers has increased greatly. Since 2005, Qatargas has pioneered the development of two new classes of LNG carriers, referred to as Q-Flex and Q-Max. Each ship has a cargo capacity of between 210,000 and 266,000 m3 and is equipped with a re-liquefaction plant.

Today we see interest for small scale LNG bunker carriers. Some need to stay below the life rafts of Cruise ships and Ropax vessels. Examples are the Damen LGC 3000 (http://products.damen.com/en/ranges/liquefied-gas-carrier) and the Seagas.

, a total of 203 vessels had been built, of which 193 were still in service. As of January 2015, the global LNG shipping fleet consisted of 410 vessels. In 2017, an estimated 170 vessels are in use at any one time.

New building
According to Tradewinds data, in January 2017 there were 122 new builds on order. The majority of new ships under construction are in the size of 120,000 –, but there are orders for ships with capacity up to 260,000 m3. , there were 451 LNG ships engaged in the deepsea movement of LNG.

In 2017, Dewo Shipbuilding & Marine Engineering delivered the Zdrava Marija, an icebreaking LNG tanker of 80,200 deadweight tons. Her capacity of 172,600 m3 is the consumption of Sweden for a month. She completed her first revenue voyage from Norway via the Northern Sea Route in the Arctic Ocean to South Korea. The shipyard has fourteen more on order.

In the case of small scale LNG carriers (LNG carriers below 40,000 m3), the optimal size of a ship is determined by the project for which it is built, taking into consideration volume, destination and vessel characteristics.

List of small scale LNG carrier builders:


 * Kanjin Heavy Industries and Construction
 * STX Offshore & Shipbuilding
 * Damen Shipyards Group (http://products.damen.com/en/ranges/liquefied-gas-carrier)

Cargo handling
A typical LNG carrier has four to six tanks located along the center-line of the vessel. Surrounding the tanks is a combination of ballast tanks, cofferdams and voids; in effect, this gives the vessel a double-hull type design.

Inside each tank there are typically three submerged pumps. There are two main cargo pumps which are used in cargo discharge operations and a much smaller pump which is referred to as the spray pump. The spray pump is used for either pumping out liquid LNG to be used as fuel (via a vaporizer), or for cooling down cargo tanks. It can also be used for "stripping" out the last of the cargo in discharge operations. All of these pumps are contained within what is known as the pump tower which hangs from the top of the tank and runs the entire depth of the tank. The pump tower also contains the tank gauging system and the tank filling line, all of which are located near the bottom of the tank.

In membrane-type vessels there is also an empty pipe with a spring-loaded foot valve that can be opened by weight or pressure. This is the emergency pump tower. In the event both main cargo pumps fail the top can be removed from this pipe and an emergency cargo pump lowered down to the bottom of the pipe. The top is replaced on the column and then the pump is allowed to push down on the foot valve and open it. The cargo can then be pumped out.

All cargo pumps discharge into a common pipe which runs along the deck of the vessel; it branches off to either side of the vessel to the cargo manifolds, which are used for loading or discharging.

All cargo tank vapour spaces are linked via a vapour header which runs parallel to the cargo header. This also has connections to the sides of the ship next to the loading and discharging manifolds.

Typical cargo cycle
A typical cargo cycle starts with the tanks in a "gas free" condition, meaning the tanks are full of air, which allows maintenance on the tank and pumps. Cargo cannot be loaded directly into the tank, as the presence of oxygen would create an explosive atmospheric condition within the tank, and the rapid temperature change caused by loading LNG at -162 °C could damage the tanks.

First, the tank must be 'inerted' to eliminate the risk of explosion. An inert gas plant burns diesel in air to produce a mixture of gases (typically less than 5% O2 and about 13% CO2 plus N2). This is blown into the tanks until the oxygen level is below 4%.

Next, the vessel goes into port to "gas-up" and "cool-down", as one still cannot load directly into the tank: The CO2 will freeze and damage the pumps and the cold shock could damage the tank's pump column.

LNG is brought onto the vessel and taken along the spray line to the main vaporiser, which boils off the liquid into gas. This is then warmed up to roughly 20 °C in the gas heaters and then blown into the tanks to displace the "inert gas". This continues until all the CO2 is removed from the tanks. Initially, the IG (inert gas) is vented to atmosphere. Once the hydrocarbon content reaches 5% (lower flammability range of methane) the inert gas is redirected to shore via a pipeline and manifold connection by the HD (high duty) compressors. The shore terminal then burns this vapour to avoid the dangers of having large amounts of hydrocarbons around which may explode.

Now the vessel is gassed up and warm. The tanks are still at ambient temperature and are full of methane.

The next stage is cool-down. LNG is sprayed into the tanks via spray heads, which vaporises and starts to cool the tank. The excess gas is again blown ashore to be re-liquified or burned at a flare stack. Once the tanks reach about -140 °C the tanks are ready to load bulk.

Bulk loading starts and liquid LNG is pumped from the storage tanks ashore into the vessel tanks. Displaced gas is blown ashore by the HD compressors. Loading continues until typically 98.5% full is reached (to allow for thermal expansion/contraction of cargo).

The vessel can now proceed to the discharge port. During passage various boil-off management strategies can be used. Boil-off gas can be burned in boilers to provide steam for propulsion, or it can be re-liquefied and returned to the cargo tanks, depending on the design of the vessel.

Once in the discharge port, the cargo is pumped ashore using the cargo pumps. As the tank empties, the vapour space is filled by either gas from ashore or by vaporising some cargo in the cargo vaporiser. Either the vessel can be pumped out as far as possible, with the last being pumped out with spray pumps, or some cargo can be retained on board as a "heel".

It is normal practice to keep onboard 5% to 10% of the cargo after discharge in one tank. This is referred to as the heel and this is used to cool down the remaining tanks that have no heel before loading. This must be done gradually otherwise the tanks will be cold shocked if loaded directly into warm tanks. Cool-down can take roughly 20 hours on a Moss vessel (and 10–12 hours on a membrane type vessel), so carrying a heel allows cool-down to be done before the vessel reaches port giving a significant time saving.

If all the cargo is pumped ashore, then on the ballast passage the tanks will warm up to ambient temperature, returning the vessel to a gassed up and warm state. The vessel can then be cooled again for loading.

If the vessel is to return to a gas free state, the tanks must be warmed up by using the gas heaters to circulate warm gas. Once the tanks are warmed up, the inert gas plant is used to remove the methane from the tanks. Once the tanks are methane free, the inert gas plant is switched to dry air production, which is used to remove all the inert gas from the tanks until they have a safe working atmosphere.

Containment systems


Today there are four containment systems in use for new build vessels. Two of the designs are of the self-supporting type, while the other two are of the membrane type and today the patents are owned by Gaz Transport & Technigaz (GTT).

There is a trend towards the use of the two different membrane types instead of the self-supporting storage systems. This is most likely because prismatic membrane tanks utilize the hull shape more efficiently and thus have less void space between the cargo-tanks and ballast tanks. As a result of this, Moss-type design compared to a membrane design of equal capacity will be far more expensive to transit the Suez Canal. However, self-supporting tanks are more robust and have greater resistance to sloshing forces, and will possibly be considered in the future for offshore storage where bad weather will be a significant factor.

Moss tanks (Spherical IMO type B LNG tanks)
Named after the company that designed them, the Norwegian company Moss Maritime, the Spherical IMO type B LNG tanks are spherical in shape. Most Moss type vessels have 4 or 5 tanks.

The outside of the tank has a thick layer of foam insulation that is either fitted in panels or in more modern designs wound round the tank. Over this insulation is a thin layer of "tinfoil" which allows the insulation to be kept dry with a nitrogen atmosphere. This atmosphere is constantly checked for any methane that would indicate a leak of the tank. Also the outside of the tank is checked at 3 month intervals for any cold spots that would indicate breakdown in the insulation.

The tank is supported around its circumference by the equatorial ring which is supported by a large circular skirt which takes the weight of the tank down to the ships structure. This skirt allows the tank to expand and contract during cool-down and warm-up operations. During cool-down or warm-up the tank can expand or contract about 60 cm. Because of this expansion and contraction all piping into the tank comes in the top and is connected to the ships lines via flexible bellows.

Inside each tank there is a set of spray heads. These heads are mounted around the equatorial ring and are used to spray Liquid LNG onto the tank walls to reduce the temperature.

Tanks normally have a working pressure of up to 22 kPa, but this can be raised for an emergency discharge. If both main pumps fail then to remove the cargo, the tank's safety valves are adjusted to lift at 1bar. Then the filling line which goes to the bottom of the tank is opened along with the filling lines of the other tanks on board. The pressure is then raised in the tank with the defective pumps which pushes the cargo into the other tanks where it can be pumped out.

IHI (Prismatic IMO type B LNG tanks)
Designed by Ishikawajima-Harima Heavy Industries, the self-supporting prismatic type B (SPB) tank is currently employed in only two vessels. Type B tanks limit sloshing problems, an improvement over Membrane LNG carrier tanks which may break due to sloshing impact, therefore destroying the ship's hull. This is also of prime relevance for FPSO LNG (or FLNG).

In addition, IMO type B LNG tanks can sustain internal accidental damage due for example to internal equipment releases. This was incorporated into the design following several incidents that occurred inside membrane LNG tanks.

FerdinandFrog (talk) 17:26, 29 November 2017 (UTC)

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New Building
Section currently gives me no sense of how long it takes to build these ships. What is the overall time from purchase order to delivery of a new ship? How many large carrier ships can be under construction simultaneously? How many (how long) will be needed to replace the now-doomed Nordstream 2 pipeline capacity? LeadSongDog come howl!  16:29, 24 February 2022 (UTC)