The Case Of The Tongues Of Fire

 

When words are a burning issue,
you’d better know how to put out the flame

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We’ll call them Dak-Ho, Alexei, Dmitri and Bogdan not their real names but they were real people.

Dak Ho was from Korea. He’d been a chief engineer for twelve years. He seems to have understood English, but the others found his spoken English was difficult. He had a gentle demeanor, was hard working and popular.

Bogdan, Alexei and Dmitri were first, second and third engineers. Bogdan and Dmitri were Romanian and recently promoted, and Alexei was Ukrainian and new to the vessel.

The Ship

Maersk Doha

The Maersk Doha was a 12 year old containership of 4,507 TEU , with a crew of 23 on a regular run between the Far East and the East Coast of the United States and had a service speed of 23 knots.

She was equipped with an Aarlborg auxiliary boiler and in her funnel was an Aarlborg exhaust gas economiser, or EGE, which exposed pipes to the engine exhaust to make steam to heat the bunker fuel and various other onboard needs.

The Voyage

On 1 October 2006 the Maersk Doha was in Norfolk, Virgina loading and unloading containers. She was scheduled to depart at 2100 but was delayed until midnight. The engineers took the opportunity to do maintenance work on the main engine and the auxiliary boiler was kept running with its feedwater circulating through the exhaust gas economiser to keep it warm and ready for sailing.

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The auxiliary boiler keeps the EGE warm and ready for sailing

Just after midnight on 2nd October the Maersk Doha left her berth bound for Miami. Problems had already begun. One of the generators proved hard to start and a faulty reversing mechanism on the main engine left one cylindre stuck in the reverse position restricting her speed to 16 knots.

About half an hour later a low pressure alarm went off in the machinery control room. Sometimes it happened because the auxiliary boiler flame hadn’t ignited but other indicators seemed to show that the boiler was alight. Steam pressure continued to fall so Dmitri telephoned Bogdan for help.

Auxiliary Boiler
The MaerskDoha’s auxiliary Boiler – why did the alarm go off?

Bogdan, Dmitri and Alexei checked the auxiliary boiler. It was still alight, the water level looked normal but steam was escaping from the furnace air inlet. Dmitri turned off the fuel pump to extinguish the flame and opened the boiler door.

Inside, the furnace tube was bulging inwards and had cracked.

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Through the steam, Dmitri could see the damage in
the boiler tube

Noise from the nearby Number One generator was distracting so Alexei started the Number two and 3 generators on the other side of the engine room and shut down number one. He knew that without steam the bunker fuel wouldn’t be warm enough to run the generators so Alexei switched them to diesel.

Diesel leaked from several joints so Alexei began to fix them while Bogdan and Dmitri went to the engine control room to talk with Dak-ho and plan repairs. The auxiliary boiler’s main steam valve was left open to let steam from the EGE supply the steam system and heat the bunker fuel.

A second feed water pump was started to replace the water being lost as steam and prevent the EGE from overheating, but it had a faulty seal.

Dak-Ho talked to the master and asked for the speed to be reduced. The Master asked if he should stop and anchor or if he could continue until they’d cleared the port channel. Dak-Ho said he could continue at low speed, he didn’t say what the limit was and the master did not ask.

The Master seemed to think the problem was minor. The pilot offered to take the ship to an anchorage and stay onboard until it was fixed but the master declined.

Dak-Ho, Bogdan and Dmitri discussed the repair plan. Over the next half hour the ship’s speed increased until, at 1.36 she reached her full manouvering speed of 70 rpm, 16 knots.

In the engine control, high temperature alarms went off. Oil carried over from the engine with soot catches fire at 240 degrees, the exhaust gas temperature at the EGE was already 350 degrees Celsius Over the next five minutes it rose beyond the temperature sensor limit of 600 degrees. The bridge was alerted and speed was reduced speed until, by 2.19 it was at dead slow, 20 rpm.

Dak-Ho climbed up the funnel intakes to the EGE. The casing was hot and there was a hissing noise. He rushed back to the engine control room, shouting “fire!”.

Light fittings and cables around the EGE casing caught fire, paintwork charred.

Dmitri and a motorman attacked the fire with portable extinguishers and a fire hose but the heat and smoke beat them back.

Dak-Ho telephoned the master, who sounded the emergency alarm.

Still working on the fuel leaks in the generator compartment, Alexei thought there was a false alarm. Then came announcements over the public address system, crew were called to muster stations and told it was not a drill. He went out of the compartment to see smoke and burning debris falling from the funnel uptakes in and rushed to the engine control room.

There he found Dak-Ho and a maintenance worker trying to open an emergency door. Dak-Ho ordered Alexei to shut down the pump circulating water through the EGE but he didn’t.

Finally, the three men evacuated the engine control room down an emergency ladder through a hatch in the deck head.

At the muster station, Bogdan ordered Alexei to start the emergency diesel generator but the engine stopped due to high cooling temperatures and wouldn’t restart. It had seized.

At 2.39, the main engine was shut down. Two men in fire fighting suits and breathing apparatus entered the funnel uptake and turned their fire hoses on the engine exhaust and the EGE casing, directed by the Chief engineer by the door.

Radiant heat from the EGE casing continued to rise. Bits of lagging feel away revealing cherry-red metal beneath. As the firefighters worked, a large section of lagging dropped, it looked as if the whole structure was collapsing so the Chief Officer ordered the men out of the compartment.

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It seemed as if the whole structure was collapsing

It was 2.48 and the run of bad luck hadn’t finished. Dak-Ho suggested using the CO2 fire smothering system. Bogdan and the third officer activated the quick closure valves on the fuel and lubricating tanks in the engine room and shut the engine room fire dampers. The fire pumps were shut down.

At 2.52 the remote operating valve in the Fire Safety Control Centre was fired. Frost gathered on the pipework and the cold cracked the paintwork as the Maersk Doha’s anchor was dropped.

Strangely, the number three generator kept running, the CO2 should have smothered it and stopped it. The CO2 system hadn’t worked. Only seven out of 230 gas bottles had worked.

After talking to the master about contacting the US Coast Guard and whether assistance was needed, the pilot left the bridge. They hadn’t communicated well: the master thought the pilot was going to notify the Coast Guard, but the master thought the pilot would do so.

For 40 minutes the pilot monitored VHF radio, expecting to hear a report from the vessel. When he heard nothing he notified his control tower which contacted the port authorities and the Coast Guard.

Two tugs with fire fighters and equipment set out for the Maersk Doha.

Meanwhile, Dak-Ho spoke with Zodiac Maritime Agency, the ship’s manger in London. They couldn’t understand what he was describing so they asked him to write it down and email it. Zodiac’s technical personnel then advised the master to attack the fire directly through access doors in the EGE casing. To do that it was necessary to cool the casing enough to open the doors.

At about 4 o clock the emergency fire pump was started so that boundary cooling could be resumed, but nothing came out of the fire hose. The pump didn’t have suction pressure and wouldn’t prime. The seawater valve was closed and couldn’t be opened from the fire station.

If the CO2 system hadn’t worked then the main fire pump in the engine room could be used to get water into the fire main. Bogdan and an AB donned breathing gear, went to the engine control room, pushed the start button and the No. 1 fire pump came to life.

By 6am, boundary cooling had resumed an the two tugs with fire teams arrived. The master believed the situation was under control so let the fire chief and a marine chemist to board. With them they bought a thermal imaging camera which the fire captain used to tell the team the hottest areas on the EGE casing.

A fire hose was led across the bridge roof to pour water into the main engine exhaust uptake in the funnel. It didn’t cool the fire, it made it hotter.

For a few moments the fire hoses were turned off to let the water in the main engine room bilge drop. Without the fire hoses, the fire got cooler.

As the dawn light glimmered on the horizon, the EGE casing was finally cool enough for the doors toi be opened and water to be sprayed onto the EGE tubes inside. First the lower doors, then the middle doors and finally the upper doors.

At 12.30 in the afternoon, about eleven hours after the fire began it was declared out. The Maersk Doha was safe. Her auxiliary boiler had a one metre long and a half metre high with a crack about a third of a metre long.

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Molten metal,ash and slag solidified at the bottom of the
exhaust trunking

In the Exhaust Gas Economiser more than half its tubes were destroyed and the structure and casing were buckled. Molten metal, ash and slag had solidified at the bottom of the exhaust trunking. Around the area, paintwork, light fittings and even fire detectors had been burned. Debris and water from firefighting had fallen down the engine exhaust into the forward turbocharger. Water gathering in the bilge had leaked into the main engine oil tank and, like the fire fighting water, had to be pumped into an empty ballast tank to avoid pollution.

All in all it wasn’t a pretty sight. And it was all down to poor maintenance and the wrong fire fighting techniques.

Fire requires three elements, something to burn, a source of ignition, and oxygen. It’s called the fire triangle. Remove one element and there can be no fire. In this case the ‘something to burn’ was soot. No soot, no fire.

Diesel engines produce a lot of soot and exhaust gas economisers are very good at collecting it. When an engine is operating at reduced power it’s less efficient and puts out more soot. The Maersk Doha’s entry and exit from Norfolk and the problem with the engine’s reversing mechanism increased the build up of soot in the EGE and the threat of a soot fire.

There were three EGE soot cleaning systems on the Maersk Doha – an ultra sonic system that triggered every 30 minutes, compressed air blowers and a water washing system. The water washing system should have been used once a month but the last record of it being carried out was August 31, a little more than a month before the incident. There’s confusion over how often the compressed air blowers were used. They could be set to operate automatically or manually. A note on the controls gave instructions not to operate them automatically and the last record of them being used was on September 30, shortly before the incident.

Soot had gathered on the EGE. It was just waiting for enough heat to burn, all that took was a failure of the auxiliary boiler and time.

In this case the source of ignition, the next element in the fire triangle, was heat from the main engine. During the 50 minutes it took to advise the bridge of the auxiliary boiler failure that heat was increasing the temperature of the EGE. Dak-Ho’s report to the master was unclear regarding what he meant by low power and what limits the master had to work with. By the time the fire was discovered at 2.19, an hour an 45 minutes after the low pressure alarm, it was already well established.

Nobody knows exactly why the auxiliary boiler failed. Shortly before the incident it operated with low water levels, a situation that should have been detected automatically, triggered an alarm and extinguished the boiler flame, but it didn’t.

Insufficient feedwater got through the system to absorb heat in the EGE, the EGE overheated and the soot ignited. That event, according to the official report, was attributable to poor operational and maintenance routines.

Soot fires aren’t unusual. In fact, there had been a soot fire in an EGE on another Zodiac Maritime Agency managed vessel in May 2003. Advice about cleaning and fire response was put out by the company shortly afterwards but once it was circulated it wasn’t absorbed into the onboard quality management system.

That advice, like the previous owner’s papers in the engine control room, advised attacking an EGE soot fire directly by using water from the fire main that had been used for cleaning it. That isn’t what happened.

The firefighters didn’t know enough about what they were dealing with. The first two attacks did not reach the seat of the fire. The main engine was still running so the fire inside the EGE casing was still growing,

 Posted by at 17:58

  8 Responses to “The Case Of The Tongues Of Fire”

  1. Whatever we do on training; if panic strikes, we tend to go the wrong 50%
    Despite all the STCW, ISM and more to come, it still remains a pure human reaction on un-expected situations.
    All the other extra ‘tits&bits’ may only aggravate things.
    Such as complexity of ship’s design, automation, cargo and combination of cargoes stowed, port calls at not-so-modern ports.
    Language barriers and tiredness after (regulated) hours on duty.
    A (traditional) boat-drill and fire-drill are just as such.
    I started seafaring in 1959 and stopped end of 1995.
    Even the weather pattern has changed so much, necessitating added vigilance.
    Wish all colleagues (at sea and ashore) safe working.

  2. Certificates, of course, don’t stop people panicking (They don’t even mean that they’re competent to do the job!) but regular training and good leadership can certainly reduce the tendency to panic to manageable proportions.

  3. Very nice article, Bob. But I’m a little bit dubious about your saying: “… At those temperatures the water already inside the casing was breaking up into hydrogen, a fuel, and the oxygen that fuel needed to burn, in what is called a hydrogen fire….” I don’t think that was the case.

    My guess is the water reacted with the soot inside the economizer. Would you check this detail?

  4. The two phenomenae considered as likely by the Maritime Accident Investigation Branch were an iron fire, which occurs when steam reacts with iron producing an exothermic reaction in which, in effect, iron will burn, and a hydrogen fire, which occurs when water dissociates into its two constituents, oxygen and hydrogen, at high temperatures. The latter case provides two sides of the fire triangle, oxygen and a fuel (hydrogen). which would explained the observed phenomena.

    Prehaps you can clarify the reaction you’re suggesting, prehaps with a reference, and we’ll check it out.

  5. I fully agree with the Iron Fire phenomenon at 1100 degrees C as per your description above. I just doubt that the water decomposed into hydrogen and oxygen in this case. Thermal decomposition of water happens at temperature above 2000 degrees C, while the whole EGE structure will melt down before it reached 1600 degrees.

    Here is a reference about carbon(soot)-water reaction in which it produces hydrogen (fuel): http://www.webelements.com/webelements/elements/text/C/chem.html
    C + H20 –> CO + H2
    Combining H2 from the reaction and O2 pushed down into EGE by the water spray, we complete the fire triangle.

    To be perfectly honest, I don’t know details (pressure, temperature, etc.) for this reaction to happen. So, this is only a rough guess.

  6. Let’s just cycle back a little.
    A soot fire can occur a temperatures from 120 celcius (Under extreme condition) to 300-400 celcius. This will depend on the dryness of the soot.
    Hydrogen fires, which involve the dissociation of water (H20) into oxygen and hydrogen occurs at temperatures above 1,000 celcius. It is self sustaining and exothermic, ie., the reaction gives out heat.
    The reactions are:
    2H20> 2H2 + 02
    and
    H20 + C> H2+C

    Both hydrogen (H2) and Carbon Monoxide (CO) are flammable.

    At above 1,100 celcius two reactions occur, the rapid oxidation of iron and, when present, a reaction between iron ans steam, again this is exothermic, ie., temperature increases. These are usually lumped together as ‘iron fires’.

    2Fe+O2>FeO + heat
    Fe + H2O>FeO + H2 + heat

    Note that hydrogen fires and iron fires can co-exist.

    You might like to check out this article: http://www.manbw.com/article_004063.html

    The reaction you mention, which involves pushing steam (H2O) through coke (Carbon) goes:

    C+H2O>CO + H2

    Both resulting gases are flammable. However, the reaction is endothermic, ie, it cools down the coke. Adding water would, therefore, cause the temperature to go down, not up, as observed on the Maersk Doha. One would then have to introduce dry air to reheat the coke before applying more water. The engine room fire dampers were closed so I’m not sure where the dry air would come from, it doesn’t seem to me that the water initially being sprayed in would have introduced air forcefully enough to reheat the soot.

    Certainly, neither the MAIB, nor the engine manufacturer or the manufacturers association seem to have considered that reaction.

  7. Fires like this are indeed rather “normal”, not only on two stroke engines.
    My experience is with medium speed 4 stroke engines without boiler.
    Once a fire in the exhaust starts, one way of dealing with it is to keep running high power on the main engine. The result is namely that the exhaust gas contains much less oxygen then on low power. In this case also the fire really started burning when the engine was slowed down and stopped. Keep running high power, and the fire will eventually burn itself out, because of lack of fuel (soot), and at rather low temperatures because of lack of oxygen.
    Just cool down surroundings as applicable.
    When it is decided to stop the engine, then I would imagine that stopping the oxygen supply can be attained by closing the air intakes of the turbo charger with a tarpaulin to prevent air drafting through the engine supplying the fire with oxygen. Never tried this though.

    The fact that spraying water on white hot metals is tricky business is well known, you learn that on any good fire training course.

    One thing I missed in this case: it is normally the bridge who calls the engine room that there is a fire in the exhaust; they are the first to notice by the smoke.

    • Actually, that’s something worth putting into the forum. My impression is that the accepted wisdom is using a deluge. Of course, in this case, the one guy who was possibly in a position to give that advice was put on the bench because he was difficult to understand