The Viking Sky Accident Report Finally Came Out

Low Lube Oil. EL FARO. Diesel or steam, lubrication is pretty basic.

"The low lube oil pressure was due to low levels of lube oil in the sump tanks in combination with the vessel motion, causing the lube oil suction pipe opening to be exposed to air"

The report provides some context.

None of the vessels in the fleet of five sister vessels had been provided with instructions on correct lube oil sump tank filling levels or alarm setpoints. In June 2016, the engineers working on board the sister vessel Viking Sea requested information from MAN regarding the recommended oil levels. MAN was unable to give a clear answer as the tanks were designed by the shipyard and not by them. The shore organisation of the ship management company was made aware of the email exchange between Viking Sea and MAN. However, no guidance on correct filling levels or alarm set points was issued by the ship management company until after the accident on Viking Sky.

Thanks for the info. I operated WWII diesel-electric. Big honking diesel locomotives turning 900V generators creating power to two 5,000 HP electric motors. Used excitation MG sets to kick the motors over.

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I can feeeel the frustration that C/E must have felt.

And reading the report they wouldn’t have been able to correctly calculate it themselves since the tanks weren’t the right size, so the proper ullage level of LO would have been above the OEMs safe height for degassing effect.

But, above half-full sure woulda been a safer bet in a storm!

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Can’t argue with that, “half-full” does sound unambiguously too low.

On the other hand having clear written instructions with the required soundings in centimeters would have been a better bet for both the Viking Sky and her sister ships.

I was also surprised that neither the crew nor the company had a handle on the lube oil consumption.

This was the one that jumped out to me. “Those damned nuisance alarms” is one thing but when the unit actually shed load that should’ve caused a mad scramble to get oil into that engine as a minimum.

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I don’t like to armchair engineer it since I wasn’t there but it did seem odd to me that they were waiting for someone to tell them what the optimal sump level was. My thought would be that “optimal” is enough to run the engines so I am going to fill them up to get my engines running and whether that is “too much” is a detail to be worried about later.

The simplest plausible explanation for the crew’s actions is that they believed the lube oil levels were okay.

The bridge called the E/R and asked how long before propulsion would be restored it was not known because the cause of the shutdown was not known.

The cause of the shutdowns was not immediately apparent to the engineers, and they were therefore unable to estimate when it would be possible to restore power.

That would also explain why they did not immediately start adding lube oil.

Apparently the engineers believed that most likely the problem was with the control system.

Due to the proximity of the vessel to shallow waters and a concern that there might be an issue with the engines’ control system, the engineers did not want to risk another blackout by attempting to switch DG2 to automatic. DG2 was therefore left in manual mode which meant that the electrical load on DG2 had to be manually controlled and did not automatically share load with DG1 and DG4. Only some load was taken by DG1 and DG4, while DG2 was taking most of the load.

Why else would the engine crew, in an emergency, focus scarce resources (time and attention) on possible issues with the control system?

I am literally sitting in an armchair right now. The thing is that it’s not just an engineering question. The other half of the equation is human factors.

Perhaps the most well-known incident of this type was the Three Mile Island partial meltdown. There was a mismatch between the operators’ understanding and the actual state of the system.

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So much could be fixed with the ladder logic from the automation being displayed on screen
Worked on a semi with a fantastic L3 thruster control system, the whole story displayed on screen.
Any issue the operator knew what it was re a failed start.

Back in my armchair.

There’s two parts to this incident; the way the emergency of lost propulsion was handled and secondly how the engine room was managed on a routine basis. The way the lube oil was managed doesn’t seem to follow good engineering practice

Apparently nobody ashore or aboard knew what the correct oil levels in the DG sump tanks should be and apparently no one was concerned about it.

Instead of managing according to oil levels they were going solely by the TBN (Total Base Number).

The cost of exchanging lube oil due to low TBN alone – when oil samples were otherwise ok – was mentioned as a source of annoyance.

The NSIA was also informed that maintaining an oil level higher than strictly necessary would be to run an unnecessary economic risk as there is always a possibility that the complete volume of oil in a tank had to be discarded, e.g. in the case of a water leakage or other contamination.

Lube oil was added based on an assumption about the rate of consumption.

Both engine crew and technical shore staff have reported that this was a concern as the TBN fell below the recommended minimum level faster than expected. This would trigger the exchange of part of the volume of oil in the subject tank to increase the TBN. It was common practice to discard a certain volume of oil and refill a somewhat larger volume to compensate for presumed oil consumption.

Problem was, the rate of consumption was based on an incorrect assumption.

The general impression of both crew and technical shore staff was that the engines – still being new and of a modern design – consumed very little oil, although no one knew or would estimate the actual consumption when asked.

As shown in section 1.8.7.1, the nominal consumption specified by the engine manufacturer was 467 litres/week and 635 litres/week for the small and large engines, respectively. Both on board and shore based technical staff found this surprisingly high when confronted with this number.

The investigation has not been able to establish the exact oil consumption of the engines, but data samples indicate that the actual consumption is likely in the range of the nominal consumption specified by the engine manufacturer.

So what this would imply, if my understanding is correct is that the ship presumably came out of the shipyard with the correct amount of lube oil in the DG lube oil sump tank.

Then over time, with each partial oil change to adjust the TBN, the lube oil levels would become lower

Meanwhile the engineers (somewhat justifiably) ignored the low-level alarms except to compensate by adjusting the low level alarms limits yet lower from time to time.

If that’s correct that having DGs trip out on low lube oil was just a mater of time, and a time would be when the ship hit bad weather.

Hard to understand how an engine room would be managed that way.

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That’s…remarkable.

I don’t understand why levels/consumption rates had to be assumed. The issue of not being able to get accurate sump levels is only present during rough seas. During smooth seas and at the dock, accurate levels could easily be obtained and trends/norms established.

This seems high to me also for modern 4 stroke engines. Maybe that’s based on 100% power for all 168 hours of a week?

By looking at LO ROBs over time, actual consumption could be determined to see if it was anywhere near these figures.

You’d know better than me they didn’t have to. Apparently however, make an assumption is in fact what they did.

Add that to the list of reasons to have clear written procedures.