Not entirely sure whether TR2 should have been automatically connected. If in-case TR2 did get connected automatically, wouldn’t the same fault that took out HR1/LR1, cause TR2 to get disconnected as well eventually?
Conventional St-by machinery for A1 Class ships, one in service another stars automatically in case of failure
From report: The bus was designed to be normally operated with the LV bus tie closed, which was the configuration during the accident voyage. With the LV bus tie closed, one transformer (TR1 or TR2) is designed to be used, with its associated HR and LR breakers (see figure 5).
Assuming that was indeed the intention of the designers, there is no redundancy, the system is one failure away from a blackout. On other type of vessels, the system is operated with the high voltage bus tie closed, but with the low voltage bus tie open, using both step down transformers, TR1 and TR2. In case one transformer trips, only one low voltage switchboard would be lost and the standby auxiliaries from the other side would be started automatically, therefore keeping the propulsion running and avoiding a total blackout.
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AV2013,
Many thanks for this.
This is what I could not understand as the switchboard setup in Fig. 5 appears to destroy any available redundancy particularly being mindful of essential pumps required to maintain ME running integrity being fed off the LV BUS.
Just like the Key Bridge, the “Dali” switchboard setup, on departure, appears to represent a single point of failure.
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Fig.5 is simplified elec drawing. EG supplies power to the EBUS(ESBD) and i.e. to critical consumers(SG3) connected. EG Power is limited abt 200 kW. EBUS is connected with LV Bus via two ACB. But EG does not supply any power to LV Bus
If so how come Class approved it ?? Or as sometimes happens they simply rubberstamped it.
I can understand a single HV feed through a single transformer into the LV Bus with a closed bus tie……in open waters. One would assume that during periods of UMS the Power Management System would instantaneously changeover to another transformer/feed circuit in the event of failure.
Yet, in enclosed Pilotage waters, one would assume that the HV feed would be fed via multiple transformers/circuits with an open bus tie negating reliance on the PMS changeover. Time critical.
In the case of “Dali”, when feed 1 failed, the PMS did not automatically changeover and the feed 2 circuit breakers were closed manually.
Interesting.
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spowiednick,
Perhaps this was an operational issue and not a design issue.
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Wonder if they got ETO on board or only electrician as there is a hell of a difference between the two as far as grasping of ship’s automation is concerned. But I was also on ships (coasters) where there was no even electrician on board but it was in 1988-1992 .
Had a case in Nava Sheva on a small 1700 teu ship( 15 years old) . Agent was on board pilot and one tug was ordered for high tide and vessel was prepped for departure. ( weekend ). I was informed by duty mate the engine can not be tested on dsalh/dsastrn prior departure.
Called the ECR and asked the Cheng what the hell was going on and when the problem could be solved .In some vague terms he explained they had some electrical propblems and were working on it.
We had to leave at high tide otherwise next sailing is 12 hrs later., It turned out after some time of nervous waiting they had no clue what was the problem let alone how to solve it. Informed frustrated agent to cancell pilot and tug arranging by doing so 12 hrs offhire . Informed tech superintendent( German) about the situation who told me to do everything to solve the situation ASAP. Did niot even talk to my Filippino Cheng.
During weekend it was a nightmare to find and/or arrange any service but Agent told me they have shipyard there and suggested calling some shipyard electricians to assist Engine crew( cheng, 2nd eng, 3rd eng , 4th eng , electrician) .
Two guys showed up after 3 hrs of waiting and fixed the problem in 30 minutes . I was informed there would be a blackout and after system recovery all functionalities were restored . When i asked them in the presence of Agent what the hell was the problem they said it would be explained in their work and time sheet description attached to the invoice for service and suggested to change the whole complement of engine crew ASAP.
I am not suggesting it was the case here with Dali as even if the Dali engine crew new the system like the back of their hand , the time given to THINK and problem solving was nonexistent .
Cheers
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Is that so?? Shackles (links) are painted white and marked by sezing wire. If divers go down to examine the rubble on the pottom what is the problem in sending one to check the first marking nearest the hose pipe . Beats me .
The transformers feeding the LV board are 2x100% with one in service and other on MANUAL stby. This is not ‘running’ machinery requiring ‘hot’ stby, but rather static equipment. Operating with the LV bus tie open even for short periods introduces complexities. For example lights, ventilation fans, etc are not redundant. What about the bus tie to the ESB? Which side should this be from? Some of the life saving eqpt (fire protection, detection, Oil mist detectors, etc), battery chargers, etc also needs to considered.
Not easy to meet regulatory requirements to operate the LV bus open.
Where do you get this? SG pump on this vessel itself will be around 150kW. Not to mention the other big consumer - fire pump. EDG will be around 400 - 500 kW.
So my read on the diagram is that electrical distribution was set up for many single points which could fail. Tripping HVR, HR1 or LR1 would blackout the ship so why on earth would not either DGR1 or 2 be running with HVR open and also HR2 and LR2 closed with two separated independent paths of current to the low voltage buss. Why also was the bowthruster still connected after dropping the tugs?
Retdmarineengineer,
Thanks for that.
If the service transformer fails on that feed, how is it detected and how is the HV feed changed to the standby unit?
100% correct. And yet we see not even the slightest change in heading - except more to stbd coinciding with the black smoke. The SG pump connected to the ESB also has to meet the SOLAS requirement of 35-30 in 28 seconds. Its just that with 2 pumps in operation the rudder movements will be much faster.
So either the SG was rendered inoperative due to the blackout or God forbid it was not switched on! Remember the SG pumps are generally started/stopped from the Wheelhouse. The helmsman presumably is still on the stand where the switches are located. Wonder if he is aware … the mates for sure would, but with confusion it could be possible it was not switched on.
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Hello Aus
As soon as the feed fails you have a blackout and start initiation for the EDG sequence. Changing over to the standby unit is a manual process - and will begin after the crew confirms it is safe to do so.
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Hi Old School
What you describe is the setup on DP drill semis and ships. Many other features need to be incorporated into the design to operate as so. Ships are simple and rightfully so. On vessels where you do not have HV generation, there is only main switchboard. All DGs supply this board and all consumers are off this board. No ‘LVR’ or means to split the bus by a breaker. There are bolted connections on the actual copper to isolate sections in case of damage/fire – nothing to introduce more ‘redundancy’.
Just imagine HVR and LVR does not exist and think of them as one HV and LV board. Thanks
I may be wrong of course but given data above and : 1 kt= 0.514444 m/s , 1 shackle =27.5 m , time 01:29:10 - 01:27:01 = 129 sec ( note conversion to SI system ) out of curiosity have calculated as follows:
Anybody here who had more then 12/13 shackles of anchor chain on a cargo vessel??
If not , then it means their chain :
a) stretched
b) broke someplace
c) port anchor dragged
d) did other magic
Cheers
That graphic shows the resultant of both rudder position and all other factors including environmental forces We don’t know what the path would be without the other forces.
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My logic - if the ship was not carrying rudder on the bridge approch ( reported rudder was amidships) - I am having a hard time believing there was any significant bank cushion going on then - and the lights going out don’t change that.
Also - at least in my experiance - folks are putting way to much emphisis with the loss of rudder impact do to the engine being stopped. Of course when ship speed is greater than engine speed it opens up the turning diameter - but with 8 kts of water going past the rudder it has to have an impact on your heading that we have not seen so far anyway.
To me this is the piece of the puzzle that is missing so far.
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