Hello all
I watched Sal’s latest video a couple of times where he provides updates from the VDR along with the vessel track from the AIS. Some interesting observations that was not noticed earlier, such as there were 3 blackouts and the vessel bow moving to port seconds before the impact. Timeline from the video. Not sure if the time between the AIS/VDR/CCTV are sync’d – so will provide the times below on the vessel issues
01:24:33 First blackout. Course/speed 141/8.5 (On another video we observe the lights flickering before complete blackout)
01:25:31 Lights comes on. 58 seconds. Quite a few deck lights and not likely these are fed from the ESB, so probably from the MSB. A slight wisp of smoke can be observed around this time (auto or manual start of another engine). Cannot make out if running lights came on before this. Let’s also remember that the exhaust from the EDG will not be in the funnel. Actual location and capacity of EDG is unknown at this time – definitely not a truck engine – more like 400-500 kW.
At some point in between lights on above and blackout below, thick black smoke observed from the stack. I think this is the main engine running astern.
01:26:37 Second Blackout. 65 seconds after lights come on – more on significance of this below
01:27:04 Anchor drop order from the Wheelhouse.
01:27:11 Lights on again. Main engine started again shortly after (within a few seconds)
01:28:30 Vessel starts swinging to port (left)
01:28:45 Impact. Black out looks like a few seconds before Key Bridge collapse. (Approx 70-80 seconds after lights on)
In port information: Reports of ‘blackout’ from reefer containers loading team. Was this complete blackouts with DGs tripping or was it only reefer circuits tripping? Information to be confirmed.
NTSB advises ‘circuit breaker’ faults are the primary cause and have requested Hyundai engineer to assist with the investigation.
Considered opinion:
With the vessel info we have so far that was mostly noted from this forum with people digging up information,
While it is not a 100% confirmed, I think this vessel (similar to many of the large container vessels) is equipped with a high voltage (HV) system. Could be standard voltages of 3.3 or 6.6 or 11 kV (Kilo Volts).
On a HV design system, Diesel generators are producing HV and connected to a HV board. The HV board will provide power through transformers to the MSB (main switchboard) and several transformers to power the reefers. Vessel is equipped with 1400 reefer plug outlets. So possibly 10 – 14 transformers with each transformer feeding 100 – 140 outlets. Then there is the Bow Thruster rated at 3000kW. Makes most sense that the motor will match the HV bus voltage. Power to each of the reefer transformers will be through a separate circuit breaker on the HV board. In the case of the BT, the circuit breaker will actually feed a motor controller that in turn is connected to the BT motor with cables running all the way to the BT space. I am assuming this BT is single speed motor and a CPP (as opposed to VFD and FPP).
After a blackout, the reefer loads (feeder circuit breakers) on the HV be designed to be switched on sequentially such that the generators are progressively loaded. The duration for this sequence could be about 2 minutes or so. The feeder to the MSB most likely will have no time delay and come on immediately as the MSB may have a sequential program as well built into the design.
So, after the lights come on after the first blackout, we have a second blackout about 65 seconds later. Is this during sequential loading of the HV board with the reefer feeders coming on and we have a bad actor that trips the board? Possible. Note that it happens again. Lights on again and what looks like about 70-80 seconds later blackout again possibly due to the same defective breaker.
What about the first blackout? What could have caused this if everything was in steady state operation? What about the lights flickering … does not happen on the subsequent blackouts? I had earlier theorized that the timing of the first blackout could be coincidental to the Wheelhouse advising they are done with the BT. Is it possible that while securing the BT, either the motor contactor or the circuit breaker does not open as designed and ‘chatters’ and creates fault leading to the blackout? Does this ‘chatter’ manifest in light flickering? Possible.
I had earlier speculated that the wheelhouse had requested the BT again close to impact and possibly this was the cause of the second blackout. But I now think BT came on and the last bit of the vessel bow turning to port is indicative of this.
So then, what about the steering? During a blackout, the steering will fail in ‘last position’. Was the rudder a few degrees to stbd? Or was this the Curtis bay water pushing the stern. Both are possible. But I think the blackout damaged the steering gear and was hydraulically locked. Position unknown.
Assuming there was no human error, the concurrent and consequential cascading failure can only be termed as a freak accident. Would be good for the NTSB to release some findings shortly such that responsible operators revise their standard operating procedures.
