no sump alarms fitted to auxy gens on cross channel RORO

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boatymcboatface
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no sump alarms fitted to auxy gens on cross channel RORO

Post by boatymcboatface »

firstly hi im new

Im a new 3rd engineer on an aging cross channel 30000 GRT RORO that for obvious reasons shall stay nameless and one of the first things that has stuck me that kind of beggars belief is that none of the 4 sulzer 1500kw auxy generators have low level sump alarms fitted.

I asked the chief about it and apparently it isnt required by class, only low lub oil pressure and sure enough i checked and that is correct.

I mean your car will pass an MOT without a sump alarm, but would you drive round without one??

wondering in my head now what the MCA would have to say about this lol
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The Dieselduck
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Re: no sump alarms fitted to auxy gens on cross channel RORO

Post by The Dieselduck »

Level and pressure are two different things.

Pressure is certainly a critical alarm, hence most have a shut down attached to it. While Level is more of a convenience. I find level sensors / alarms to be somewhat unreliable, and i hate it that my BMW doesn't have a dipstick. I personally like to see the level, feel the oil, smell it; it can tell you lots.

But I think its important to make sure this alarm is set as a convenience, not as a protective device. The Viking Sky incident comes to mind, the cruise ship off Norway, where this became a major issue, in rough seas in combination with established onboard protocols, all main engines shut down to low
level, and could not be restarted, massive evacuation was undertaken. Now it wasn't for low level per se, but I can imagine a layer of complexity is not desirable.

https://safety4sea.com/engine-lubricati ... ujcnBszQg9
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popeye62
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Re: no sump alarms fitted to auxy gens on cross channel RORO

Post by popeye62 »

Hello 3rd
I am familiar with the Sulzer ZA(?) which had calibrated dipsticks in the bed plate and no level alarms. The problem with sump level alarms is that they only really work when the vessel is in still water plus, their setting is arbitrary. Where do you set the level, 100, 200, 300mm above the pump suction? The calibrated dipstick is the only reference to a 'normal' level I have ever seen. Things get more complicated with dry sumps when the sump tank is a yard part not an engine part, the engine builder may give a minimum volume but is more likely to just give a minimum flow (the pump does not determine the pressure it is the resistance to flow through a given cross sectional area). What you must be cognisant of, alluded to by dieselduck, is weather. Most of the time crossing the Channel you don't see any and some engineers believe that running a sump (trunk piston engine) at a lower level reduces LO consumption, it doesn't.
The answer is good watchkeeping; accurate dipping at least once a watch. It is highly unlikely that a sudden loss of oil will occur, the only real chance of this is if you are purifying a small volume of oil in the sumps/tanks in service and this would make me nervous (make sure the sludge tank level alarm is working and dip the sumps hourly) if you have an assistant on watch train him up to dip the tanks and explain that making a turn will affect the level etc.) Do you purify the sump of a 1.5MW engine or just change the oil? What volume of oil are you operating with?
If you really want to know the factor of safety for the level then get out the drawings of the sump/tank, take the cross-section and incline it to SOLAS/IACS rules (15 degrees either way static and 22.5 degrees either way dynamic, you will rarely, if ever, roll that far) at what level is the pump suction uncovered? Same longitudinally for trim (7 degrees). Regarding pressure, the low-low pressure is an immediate shutdown in my experience there is no time to do anything between the low pressure alarm warning (set half a bar above the low-low s/d) and the shutdown because there is usually something else wrong like the pump.
Keep the oil as clean as you can, all the time, without exception. Good luck.
boatymcboatface
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Re: no sump alarms fitted to auxy gens on cross channel RORO

Post by boatymcboatface »

hi thanks for your replys

interesting about the viking sky... low level wernt triggered? any money they were inhibited

yes on our ship they are purified, 1 puri between the gens and it is alternated, as you say popeye this makes me nervous.

what makes me even more nervous is the sump puri suction and return/filling valves are ball v/vs... I would have thought SDNR would be more sensible


so say a sump v/v starts passing or the puri dumps oil, the first indication you would have would be low oil pressure and by then it would be too late!!
popeye62
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Re: no sump alarms fitted to auxy gens on cross channel RORO

Post by popeye62 »

The Viking Sky recorded 18 low level alarms (on all three engines?) which were acknowledged and "...cleared within a few seconds" This is clearly a sump level maintained too low for the conditions. There were no more alarms triggered between 09:04 and 13:37 which suggests two possibilities; the weather abated or the level alarms were inhibited (the sumps were not topped up until after the blackout). The interim report does not answer this and I haven't seen the full report. After the blackout, while the EMG was running the crew transferred 10 tons of oil to the three sumps (bingo!). MAN reported that the volume of oil in the sumps was maintained between 28% and 40%; they recommend 68% to 75%. If you know the volume of the tank then maintaining the minimum volume of oil is easy, you can mark the dip stick or dedicated sounding tape. The report states that one engine was restarted after an hour and was connected in "manual load sharing mode" which is an odd comment as one engine connected to the mswb doesn't have to be in phase or share with another unless it was possible to load share with the EMG, however, the issue with the power management system continued, the report says that over the next hour the other two engines were started in "automatic load sharing mode" but "the engineers had to continually balance the electrical load manually" this is not automatic load sharing and they may have been referring to automatic synchronizing and the report does not say how well they managed the balance (no report of overload, overspeed or reverse power).

Can you run a genny for 12 hours, change over generators and then purify the sump of the stand-by? That would ease your nerves. If you must purify the running engine just make sure the LO purifier sludge tank high level alarm is working, even better if you have a flow alarm to the sludge tank (similar to a bunker overflow alarm so you don’t have to wait for a high level in the sludge tank but warned that oil is flowing to it immediately)
I can’t see a problem with ball v/v’s, the system is sump to sump so the oil will just run back to it. Is there a problem picking up suction from the sump? A non-return valve would keep some oil in the suction line for priming the puri pump.
“A sump valve starts passing” Possible, but unlikely; which valve? Unless you have a plug in the bottom of the pan which is leaking, the oil must be pumped out of the sump so you would see a leak (make sure the tank top and pit bilge are clean so that leaks are more noticeable and also good check of clear crankcase vents and flame arrestors to keep the pressure down in the CC) What would happen if the LO cooler was damaged, would the sump level rise or fall? Why?
“The puri dumps oil, the first indication…is low LO press.” No, definitely not, the first indication is The Puri Is Dumping Oil. How long would it take for the puri to empty the sump to the point where the main pump lost suction?

Would you know what to do? There is an old adage that goes: what the watchkeeper does in the first 10 seconds can determine what the rest of the ship does in the next 10 hours, days or weeks. Open your ERO (emergency response organisation)file and look at the emergency preparedness for ‘Blackout’. There is no such thing as a stupid question so ask anything and everything and you will become a great 3rd. Best of luck
John
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