[SCORPION]

Originally Posted by Ithaca

@Scorpion.
A few queries as you have commanded LNG Vessels and I haven't sailed on LNG.

At the onset, let me clarify that I have only sailed on LNG carriers with steam turbine engines. They do not have LNG liquefaction plants. There are LNG carriers that have reliquefacion plants and diesel electric engines. Steam turbine engines are still very popular and the Japanese ship yards like Kawasaki and Mitsubishi still swear by them. The Koreans are the pioneers in the Diesel/Electric propulsion system. Re-liquefaction of Methane is far more complicated than for Propane and Butane because the critical temperature of Methane is around -83 degC. The normal refrigeration cycle used to reliqefy propane and butane do not work in the case of methane and they require far more complicated equipment. Reliquefaction plants for methane on ships have not been a great success in my opinion, and there is lot of scope for improvement.

LNG is carried at around -160 degC in tanks that are, basically, heavily insulated flasks. It is a completely closed system and not a drop of liquid or gas ever escapes unless something goes wrong. However, some amount of heat exchange does take place and gas keeps evaporating from the liquid surface causing increase in the tank pressure. This evaporating gas is called boil off and if not removed from the tank, it can lead to disastrous consequences due to increase in tank pressure. That is why an LNG vessel is allowed to burn her cargo as fuel. On a steam turbine ship the boil off is burnt directly in the boilers. On a ship equipped with a reliquefaction plant, the gas is liquefied and returned to the tank. There is a provision to burn off the gas in a Gas Combustion Unit (GCU) at times when the reliquefaction plant is not working, or to burn excess gas. There are some newer types of LNG ships with IC engines, where the boil off gas is directly burnt in the cylinders. Again, maintaining tank pressure within a safe limit is the key and the most important task. It can neither be too high nor too low. For your information, the maximum tank pressure allowed is 25kPa (100 kPa is one Bar), above which safety valves lift and let the gas out into the atmosphere, and the minimum is 0 kPa. Of course, there are automatic safety systems built in which give adequate warnings and start shutting down equipment well before the pressure reaches these figures. The normal pressure within the tank is maintained between 5 to 18 kPa.

LNG ships are highly automated ships with a plethora of electronic systems monitoring and controlling the entire cargo and boiler management systems. They have the highest safety record in the shipping industry because of the amount of safety devices and the training that goes in before a person is allowed to take charge of the vessel, its cargo equipment or her engine and other machinery.

Now to answer your questions. Again, a reminder, I am talking about steam turbine engines, mostly:

1. The boilers are designed to burn either gas only, HFO (Heavy Fuel Oil) only , or both simultaneously. The superheated steam is then used to drive turbines. Boiler burning modes are called Gas only or dual burning modes where both gas and HFO are used. HFO alone is only burnt at rare times during a break down of the gas compressor or system or if the ship is completely gas free, like for instance, before going in for a dry dock. A trivia, newer designs from Mitsubishi, with something called reheat burners, have taken the boiler operating pressures to 100 bars from the normal 60 bars. My last 3 years of sailing were spent on such a ship, right from her delivery. During manoeuvering, an LNG vessel has to be on dual mode to allow for sudden changes in fuel requirement.

2. LNG vessels have this written into the charter party. Older LNG ships had a guaranteed boil off rate (from the maker) of not more than 0.15%/day of the total cargo capacity of the vessel. This means that the maker guarantees that the insulation system is so good that not more than 0.15% of the total cargo capacity will evaporate per day. The owners may reduce this rate further as a means to get a better charter rate. The latest LNG ships (with the 100 bar boilers) have a guaranteed boil off rate of not more than 0.08%. The 100 bar boilers also reduce consumption. So you are allowed to burn this amount (maximum) every day, as fuel, and it is normally mentioned in the charter party. Normal maximum consumption of gas in the 100 bar boiler ships is about 6.5 tons/hour at full sea speed of about 18~20 knots.

There are 2 types of voyages for an LNG vessel, dual voyage or gas only. Dual voyages are voyages where both HFO and only the natural boil off (within the guaranteed rate) are burnt in the boiler as fuel. A gas only voyage is where only gas is burnt in the boiler except during manoeuvering. In this case, the natural boil off is supplemented by gassifying LNG in heat exchangers (called vaporizers) to meet the boiler demand. The decision to burn gas only or HFO is normally taken by the charterer depending on the prevailing rates for LNG and HFO. There cannot be a HFO only voyage for obvious reasons.

3. There is only one grade of LNG. A certain amount of the LNG cargo is normally retained in one tank (called heel) to keep the tanks cool and to act as fuel depending on the type of ballast voyage. The tanks, pipelines and related equipment, have to be at a certain minimum temperature, depending on the type of tank, before you can start loading LNG in order to avoid thermal shocks. This again is part of the charter party and the ballast voyage may be dual or gas only. In some cases, the entire cargo may be discharged and the tanks warm up during the ballast voyage. A tank cool down operation will require to be carried out at the load port before commencing loading operations.

[Sutripta]

^^^
Are the LNG tanks initially filled with an inert gas like nitrogen or combusted gas?

Regards
Sutripta

[SCORPION]

Originally Posted by Sutripta

^^^
Are the LNG tanks initially filled with an inert gas like nitrogen or combusted gas?

Yes Sir, you are right. The tanks are kept as dry as possible always to avoid moisture in the tanks. Initially, the air is replaced with super dry air. Dew point less than -45 degC. The dry air is then replaced by super dry inert gas. Oxygen content is usually less than 1% in a good inert gas generator on an LNG ship. Once the ship is in a loading port, the inert gas is replaced by methane gas. This is done so that at no time does the atmosphere inside the tank pass through the flammable range of methane. Once it is completely gassed up, tank cool down starts. Once the tank structure and the vapour temperature are cold enough, loading of LNG commences.

We have nitrogen generators as well, but they are used for smaller areas like pipelines and seal gas of compressors.

[Sutripta]

^^^
If methane is vented into the atmosphere for whatever reason, do you have to file an environmental report?

Regards
Sutripta

[shashanka]

Originally Posted by Jeroen

That was quite the ordeal you and your crew mates went through. Fortunately, I never experienced anything like that during my merchant navy years.
Jumping into the lift raft is sort of natural thing for people to do. However, as your mates experienced, there is high risk of damaging the raft. Also, you might hurt yourself as there tends to be various metal objects (e.g. gas cylinder, box with supplies) stored in it as well. It looks inviting, sort of a springy cushion.
The only way to ensure people do not do is to ensure they get regular training in the use of rafts. Not just a bit of theory. But actually in a training facility where you can inflate the raft, though it in a pool and jump in. We did some training in a wave pool and it is not easy to climb in the raft in big waves. Can not image how it would be under real circumstances. You guys were sort of lucky with the weather and the sea temperature I guess.
Nice to see and hear the stories and the photographs, thanks for sharing.
Jeroen

Thanks Jeroen and you are right of course - safety & survival training has assumed huge importance in the past couple of decades. I too went through the training a few years back while serving on off-shore vessels. This included something called HUET ("helicopter underwater escape training"), an experience in itself! And as you said yourself, climbing on to the raft when you are treading water is no cakewalk!

[SCORPION]

Originally Posted by Sutripta

^^^
If methane is vented into the atmosphere for whatever reason, do you have to file an environmental report?
Regards
Sutripta

No. Because under normal circumstances, methane is never vented into the atmosphere. LNG terminals have a continuous flare stack burning all the time to burn excess gas. But they have realised that they are wasting so much of energy and now all major terminals are trying to minimise the burning and almost every ounce of gas is reliquefied and put back into the tanks or pumped into the gas grid. Flares are lit only during an emergency to avoid imminent pressure build up and consequent disasters.

On a ship, methane is almost never vented, unless it is an absolute emergency. Small leaks may occur from valve glands, flanges and pipelines which are quickly arrested or the operation suspended due to safety reasons. Methane is heavier than air at temperatures less than -130 degC. If at all they are vented at that temperature, they sink down quickly from the vents and flow down over the deck and down the ship side until they warm up and start becoming lighter than air and starts going up. The cold vapour causes immediate condensation of the atmosphere in contact with the it and the entire path of movement becomes a large visible cloud painting a nasty picture around the ship. Other air intakes nearby, for instance, the ships very own ventilation systems, nearby IC engines, flare stacks etc can suck in this LNG and cause a disaster and for this reason, it has to be immediately reported for safety reasons. But if such a thing does happen, and that too in port, you can rest assured that the vessel will never see that port or any other port in that country ever again.

Trivia: LNG expands roughly 600 times when it changes from liquid to gas at ambient temperature!

However, methane is a very nasty greenhouse gas, as bad as CO2 and now steps are bring taken to control emission of methane into the atmosphere, however small the quantity may be.

Originally Posted by shashanka

One somewhat unusual aside in my case has to do with my very first voyage

That is some experience Shashankaji, and that too on your maiden voyage. You have lived through every seaman's nightmare. Thanks for sharing the story.

In my 20 years at sea, I have seen all kinds of whales, dolphins, seals, sea gulls, flying fish and many other sea creatures, but never a shark. Not once, although we do sometimes keep wishing you can see that terror inducing dorsal fin in all its wildness, from the safety of your ship's deck. I think they only show up if and when you are on their menu. The only sharks I have seen are whale sharks, which are more like gentle giants. I am posting a picture below where one whale shark came visiting to check if our lifeboat is in good condition. Every 3 months the lifeboat is lowered into the sea and manoeuvred just to make sure the people are familiar with the process and to ensure the launcing gear is in good condition. As soon as this guy approached, the boat was quickly pulled up. Luckily, the hooks were still connected.

[vibbs]

Originally Posted by Ithaca

Here is what I was able to source online.



Source: Fuel Grades


Also attached is the BP Updated technical guide

I was refering actually to uncertainities in VLSFO with just 3 months to go for the mayhem to begin.

What we have, is only speculations on where they are expected to slot in. What exactly will be available post 1 st january 2020, only time will tell.

Originally Posted by SCORPION

Attachment 1916883

Wow!!! That's one great pic

[Sutripta]

Originally Posted by SCORPION

However, methane is a very nasty greenhouse gas, as bad as CO2 and now steps are bring taken to control emission of methane into the atmosphere, however small the quantity may be.

Actually far far worse. The reason for my asking. Only saving grace is that it is not as long-lasting as CO2

The only sharks I have seen are whale sharks, which are more like gentle giants. I am posting a picture below where one whale shark came visiting to check if our lifeboat is in good condition.

Gentle giants is right. Vegetarian to boot.
Indian Western coast is on their migratory path. Far too many are getting caught in fishing nets and drowning.

Regards
Sutripta

[shashanka]

Originally Posted by SCORPION

...That is some experience Shashankaji, and that too on your maiden voyage. You have lived through every seaman's nightmare. Thanks for sharing the story....The only sharks I have seen are whale sharks, which are more like gentle giants. I am posting a picture below where one whale shark came visiting to check if our lifeboat is in good condition. Every 3 months the lifeboat is lowered into the sea and manoeuvred just to make sure the people are familiar with the process and to ensure the launcing gear is in good condition. As soon as this guy approached, the boat was quickly pulled up. Luckily, the hooks were still connected.

That is a great capture of the whale shark, SCORPION! I remember the fist time I came across mention of this gentle creature was while reading "Kon Tiki" as a school boy - Thor Heyerdahl's account of his crossing the Pacific from Peru to the Polynesian atoll of Raroia in a raft made from "balsa logs lashed together with hemp ropes". Crossing 4300 nautical miles of open ocean in a balsa raft in order to prove a point, adds weight to that old adage - when the ships were made of wood and the men were made of iron

[Thad E Ginathom]

Originally Posted by shashanka

Thanks Jeroen and you are right of course - safety & survival training has assumed huge importance in the past couple of decades. I too went through the training a few years back while serving on off-shore vessels.

A long time back I did a Basic Sea Survival course. It was a pro course at a seafaring college, but they did a special day for sailors on the yachtmaster course. The content was only slightly tailored. We still learnt, eg, how to step off the side of a ship. As the master-mariner instructor put it, we might have a lifetime of safe small-boat sailing, but find ourselves on a sinking cross-Channel ferry!

I am a non swimmer, and actually really dislike being in water... but the practical (ie wet) part of the day was amazing. I am absolutely certain, for instance, that nobody who has not been taught how would be able to get an unconscious person out of the water and into a liferaft. Another great hands-on experience was setting off flares. This is something that one can simply not do except in genuine emergency, without causing, and getting into, a lot of trouble. And one experience can't be matched by any amount of reading.

I haven't sailed for decades now, and have probably forgotten most of that stuff, along with the majority of my small-boat seamanship, but I was proud of that certificate, however lowly, as being a real-seaman's qualification. Actually, if I remember correctly, it would have been one of the things needed to get anywhere near, let alone on, an oil rig. If only as a visitor.

I'm in awe of the skills of big-ship mariners! This is another great thread about ships, the machines that power them, and the guys that make it happen

[Sutripta]

Originally Posted by shashanka

One somewhat unusual aside in my case has to do with my very first voyage - the M.V. "Sonavati",
...

I remained on leave for a few months after the disaster and joined back sometime in March '74. So I can say that my sea carrier proper started in '74, since my first voyage (on the "Sonavati") lasted barely 2 weeks.

This is truly amazing. An ordeal which did not traumatise you. And an experience which will top any normal dinner table tale!

Just wanted to know is there a 'club' for such shipwrecked people. (Like crossing the equator, circumnavigating the globe). What are they called.

Regards
Sutripta

[Ithaca]

Originally Posted by SCORPION

Now to answer your questions. Again, a reminder, I am talking about steam turbine engines, mostly:

1. The boilers are designed to burn either gas only, HFO (Heavy Fuel Oil) only , or both simultaneously.
2. LNG vessels have this written into the charter party. Older LNG ships had a guaranteed boil off rate (from the maker) of not more than 0.15%/day of the total cargo capacity of the vessel. Normal maximum consumption of gas in the 100 bar boiler ships is about 6.5 tons/hour at full sea speed of about 18~20 knots.
3. There is only one grade of LNG.

Thank you @SCORPION for that long and detailed reply to my query. My doubts have been cleared.
For me as an engineer to get into LNG ships, I will have to take two demotions and rebuild my career which at this stage is not something I would like to do.

Originally Posted by SCORPION

In my 20 years at sea, I have seen all kinds of whales, dolphins, seals, sea gulls, flying fish and many other sea creatures, but never a shark.

What a photo, beautiful.
Reminded me of this picture that was shared on one Whatsapp group.

Boat over a whale.

Originally Posted by vibbs

I was refering actually to uncertainities in VLSFO with just 3 months to go for the mayhem to begin.
What we have, is only speculations on where they are expected to slot in. What exactly will be available post 1 st january 2020, only time will tell.

@Vibbs, As you would expect, no ship owner or charterer is ever going to allow a vessel to burn LSMGO for an ocean voyage due to the exorbitant costs involved. ULSFO & VLSFO are the only viable options so far.
Let's see how the industry adapts since there is not grace period provided to vessels as of now.

[Thad E Ginathom]

Originally Posted by shashanka

One somewhat unusual aside in my case has to do with my very first voyage - the M.V. "Sonavati", Scindia's small coastal vessel which sank in a cyclone off the coast of Vizag on 8th Dec 1973. I was the 5th Engr on board at the time and the youngest crew member by a couple of decades - I was 21 and the others were veterans in their 40's. The other youngster was the wireman (D'Silva if I remember correctly) who was my age & also making his first voyage. To cut to the chase - there were 38 crew members, out of which 33 survived. I was in the life boat with 22 others and all of us survived and were picked by the "Jala Moti" (also Scindia's vessel) on the 10th of Dec'73, 44 hours after "Sonavati" went down, some 300 miles off Vizag.

The other 15 crew members chose the life-raft - and 10 survived. The radio officer, Mr. Billimoria, had the most tragic death. On the second day - 9th Dec'73 - after the cyclone had passed, sharks attacked the L\raft. It is difficult to visualise the horror of the incident - suffice it to say that Billimoria was taken first & two others who apparently suffered heart attacks, were dragged away subsequently. One has to acknowledge the immense will to survive & the courage of the remaining 10 crew members on the L/raft. They were also rescued up by "Jala Moti" a few hours after she had rescued us.

An amazing and gruelling story. It's too easy for small-boat sailors to think that ships, the big ones, at least, can survive almost anything. Plainly, that is not true. In fact, a master-mariner friend has told me that there were two occasions in his life where he seriously wondered if his ship would survive.

[shashanka]

Originally Posted by Thad E Ginathom

A long time back I did a Basic Sea Survival course. It was a pro course at a seafaring college, but they did a special day for sailors on the yachtmaster course. The content was only slightly tailored. We still learnt, eg, how to step off the side of a ship. As the master-mariner instructor put it, we might have a lifetime of safe small-boat sailing, but find ourselves on a sinking cross-Channel ferry!

I am a non swimmer, and actually really dislike being in water... but the practical (ie wet) part of the day was amazing. I am absolutely certain, for instance, that nobody who has not been taught how would be able to get an unconscious person out of the water and into a liferaft. Another great hands-on experience was setting off flares. This is something that one can simply not do except in genuine emergency, without causing, and getting into, a lot of trouble. And one experience can't be matched by any amount of reading.

I haven't sailed for decades now, and have probably forgotten most of that stuff, along with the majority of my small-boat seamanship, but I was proud of that certificate, however lowly, as being a real-seaman's qualification. Actually, if I remember correctly, it would have been one of the things needed to get anywhere near, let alone on, an oil rig. If only as a visitor.

I'm in awe of the skills of big-ship mariners! This is another great thread about ships, the machines that power them, and the guys that make it happen

Originally Posted by Thad E Ginathom

An amazing and gruelling story. It's too easy for small-boat sailors to think that ships, the big ones, at least, can survive almost anything. Plainly, that is not true. In fact, a master-mariner friend has told me that there were two occasions in his life where he seriously wondered if his ship would survive.

Thanks, Thad - you've raised two pertinent points. It is difficult to get an unconscious person into a raft under the best of conditions even in calm seas - in anything above mill-pond conditions (moderate seas and above) it might prove impossible without help & support from others already in the raft.

The other point you have put the finger on is hands-on experience of flares. In the life-boat, the 2nd Off (nominally in-charge of safety equipment at the time) tried to set off flares to signal a ship on the horizon on the second day of our ordeal, and finally succeeded in dropping the the flare into the water next to the lifeboat. On the subsequent tries he did alright. The ship in the meantime continued sailing on over the horizon.

[shashanka]

Originally Posted by Sutripta

This is truly amazing. An ordeal which did not traumatise you. And an experience which will top any normal dinner table tale!
Just wanted to know is there a 'club' for such shipwrecked people. (Like crossing the equator, circumnavigating the globe). What are they called.
Regards
Sutripta

Thanks Sutripta - I now feel that at that age (21), and if you are reasonably healthy & fit, one's resilience is really high. And one's ability to forget the past & dive into the present. I'll confess that I enjoyed the momentary 'minor celebrity' status that Sonavati conferred. And in Kolkata, which was my home port at the time (having passed out of DMET recently) I certainly basked in the attention. But all good things must pass & I was soon back to the grind.

Your point about the "shipwrecked survivor's club" is something I too toyed with for a while - to no avail! I found that most of those I was able to get in touch with (ex-Sonavati & other incidents) were keen to get on with their lives & forget the dark episode in their past as quickly as they could. Ans frankly I don't blame them.
Regards,
Shashanka