Agreed. So many little things in the test report that don’t make sense.
They state a loose terminal was found by HHI and then show a picture of a wago(?) spring terminal block. I’ve never seen a wire in one of those TB’s ever get loose(assuming proper initial termination). Their design makes them resistant to it, unlike screw terminals. Link
I agree with you about the cycles on the breaker and relay history. Again, like I stated before, extremely random that they had two 87s in a row while testing considering none had been recorded for the life of the ship.
“Preliminary review of HIMAP-T data extracted on 4/10/2024, suggests that TR1 has not returned this error since the vessel was delivered in March 2015. After about five minutes, we tried to close HR1 VCB, and Differential Current Trip (87T) occurred again.”
As far as what could cause that: improper relay settings, a hard fault experienced prior, an issue with the CT’s. Really though, full testing of the transformer is needed as well as the the relay and it’s associated CT’s and the breakers.
There’s no excuse not to, it’s extremely cheap in comparison to the cost of the accident and the investigation. And it should be an impartial 3rd party with actual experience with this type of stuff which I know NTSB does not have in house. If they were smart that’s what they would do. So far I’m not impressed with the what I’ve seen from them so far but we’ll have to wait until the final report comes out.
When the transformer is energized to the LV SWBD, the load on the xformer is only those consumers that have no delay. Includes mostly lighting (single phase) and some other minor control system stuff that is single phase. Most of these loads are on the 440x220 xformers. Maybe some 440x110 – but unlikely for this vessel. These single phase loads will be balanced as far as possible with the 3 phase supply. Guessing the max power drawn for all this is less than 150 kW - fraction of the xformer capacity. Guessing 2500+ kVA (2000 kW+).
As info (for the non engineers), single phase means 2 of the 3 phases are tapped to provide the voltage/power. Ex: 440 3-phase means you get 440V between any 2 phases. Ships are ungrounded and the power generated is in the ‘delta’ configuration as opposed to shore side where it is a ‘star’ configuration with the require voltage is between a phase and neutral.
All other loads with the largest being the lube pump supplying lube to the bearings (main, crosshead and conrod) and cooling oil to the piston, guessing no more than 250kW, are offline and come on or start on a sequential start basis. Lube pump generally the first one with a 2 sec delay.
So load side fault to trip on differential is unlikely. Actually I also think none of the loads on the LV side are so large to trip the xformer on fault. Single phasing of the lube pump should trip the pump before it cascades up to the transformer.
So agree with the thought of potential CT calibration or minor issue with the xformer. And yes, 3rd party should have been engaged to test the xformers.
Maybe I’m not understanding your scenario. I would also conclude load side condition is unlikely but for a different reason. Differential trip senses current into and out of an apparatus (per phase) and actuates when that differential exceeds the set point (a percentage of phase current). Simplistically, any fault or load condition downstream of the transformer would affect current but not cause a differential across the transformer. My gut feeling is that an odd differential trip on energization is not necessarily a key to understanding the plant condition/reaction for this incident. After reset they demonstrated manual shifting from TR1 to TR2 and vice versa. And it seems later they demonstrated an auto transfer when they lifted the lead with the loose connection, 440 was back in 10 sec. If only the standby transformer was in auto that night.
It does not appear differential trip caused the black outs during the incident and I wouldn’t see why NTSB would need to test transformer more than the extensive power parameter recordings / analysis they made which presumably show a reliable power source to the LV bus. On the other hand one might think the ship owner would want to arrange for further transformer testing to satisfy themselves its was a odd ball transient fluke. Or change the protective device for a “known good” one.
I, not being an engineer, thought that the cleaning and checking of the wiring inside the switchboard occurs in shipyard. Sometimes at night with the ship blacked out.
I didn’t think it was routine to have access inside it while in service.
I hope for this too. And I hope their recommendations in this area are backed up with evidentiary information. Like interviews with shoreside technical staff, emails and main mgt work orders, requests, machinery history entires etc.
Many ships in the world may be in similar material condition and ship management situation but due to the consequences in this case how does this not trigger a flag state pulling the SMC for the ship and getting all in the shoreside staff faces and pulling some kind of extraordinary DOC spot check of Synergy or Grace? Will Singapore flag dig this deep or not look beyond a loose wire?
This may be beyond the realm of NTSB recommendations but maybe it is time for port states to step up what is acceptable. Many commenters on the original Dali threads seemed to have clear ideas of how it “should” have worked, that “surely this cannot be as designed”, with regard to redundancy. This plant seems 100% according to Hoyle to me for the class notations it has.
ACCU or UMS type notations do not speak to propulsion and steering redundancy of the type many seemed to have thought it would. ABS (and I have to assume other IACS societies have similar) has the “R” notation available and the requirements are in the Steel Vessel Rules, Part 4-3-7.
Those rules require an ACCU notation as a prerequisite and application of the 4-3-7 rules are optional. It states: The objective of this section is to provide requirements which reduce the risk to personnel, the vessel, other vessels or structures, the environment and the economic consequences due to a single failure causing loss of propulsion or steering capability. This is achieved through varying degrees of redundancy based upon the vessel’s Classification Notations.
It appears the mismatch between port infrastructure and this size ship presents very real “consequences” of the nature anticipated by the rules above. Is it time to require appropriate R notation for ships of a certain size to enter certain ports? There would be a great wailing and gnashing of teeth from ship owners I’m sure but cost of doing business and all that?
If I am understanding this correctly the indication is that the Class position makes the application of this rule “optional” which astounds me. Why then are managers and owners not addressing this via their respective SMS and vessel audits? Vessel crews do not stand a chance under this umbrella of stupidity. Please correct me if I have misunderstood this.
I may be simplifying but continuing to use ABS as an example, a shipowner is not going to do much above the minimum without motivation.
For example maybe he goes for A1 hull and AMS for machinery. This would indicate to insurers and flag states they have built and classed their ship to Steel Vessel Rules (SVR).
What’s an example of above the minimum? An owner decides to go for ACCU. These rules are also in the SVR. This describes the level of automation to allow periodically or minimally attended machinery spaces and some related notations for bridge control. What’s the motivation? Less crew.
It’s no different for the various R notations that are defined by rules for propulsion and steering redundancy. However, that ship would cost more and without apparent immediate pay back for an owner.
What I’m saying is given the mass and dimensions of this type of ship can a nation require a certain class notation to reduce risk to the ports infrastructure. Have ports done a risk assessment when they started letting these things in?
Wasn’t there a class of tanker or trade in Alaska that required redundant propulsion? Or was that an owner being proactive after OPA 90?
Don’t get hung up on optional. Some class notations are within the rules proper some are the subject of separate “guides”. That is just a document organization thing.
There are class notations for ice classing hulls and operations in polar regions. Presumably an owner would comply with those rules in order to participate in that trade. There are rules for high speed vessels. So should nations with port and highway infrastructure risks require a class notation to reduce those risks? Is the US demand for cheap plastic crap and other things enough leverage to require it and have ship owners comply?
Would it be fair to say that, in the case of the “Dali”, with four generators, two transformers, two bus ties, two separate feeds off the HVSB plus a Power Management System that Class would designate an R notation for propulsion and steering redundancy?
This is extracted from the NTSB preliminary report…
“ As part of the investigative process, the NTSB invited qualified parties to participate in the investigation. While they are not part of the analysis, parties are crucial in helping the NTSB develop the facts around an investigation. The following entities have agreed to serve as party to the Dali investigation:
• Synergy Marine Group
• Grace Ocean Private Limited
• Maryland Transportation Authority (MDTA)
• Federal Highway Administration
• Association of Maryland Pilots
• Nippon Kaiji Kyokai (ClassNK)
• HD Hyundai Heavy Industries Co., Ltd
• Maritime & Port Authority of Singapore
The parties were formed into specialized investigative groups led by NTSB group chairs in the areas of nautical operations (ship handling, cargo, and navigation), engineering (propulsion and electrical), survival factors (search and rescue), bridge structures (design and protection), and recorders (electronic evidence). The Chair of the NTSB traveled with the investigative team and acted as the agency spokesperson.”
So, the owners, managers and class are on the various investigative groups overseen by NTSB group chairs. I certainly trust that this arrangement does not stymie the organisational incident investigation. They need to look outside the “Dali”.
Hogsnort
You are correct in the sense that during the DD the fasteners on the bus bar links are checked with the MSB dead. But not for loose wires and such.
For the normal SVR. And further pardon me as the Steel Vessel Rules became the Marine Vessel Rules but I’m too old to make that click.
Definitely DOA with that assumption. That’s my point. You have to have two steerable propulsion devices. Just thinking out loud, but if you want to drive something that massive into certain ports maybe you need to demonstrate risk has been reduced to as low as reasonably practical. The consequences of a loose wire (and these things happen) are much different depending on size of ship as we all witnessed.
We can reduce risks with engineering controls (usually the best way in my opinion) or concentrate on administrative controls like procedures and things like SMS. So how did that work for the Dali? I’m not that naive that I think this idea would take hold just now (maybe after the Bayone Bridge gets hit or another Seawitch type fire?). Just pointing out there are other ways to look at solutions. FWE.
KP - not sure what the gist is. We agree that the differential did not cause the blackout - a recordable event. We also agree the trip was random. Guess the only item where we differ is not require testing. Maybe right … but I have no issue if they do.
Agree … and Dali is just mid size. Some of the others are true monsters.
I also think the Dali had a double whammy situation with the SG. The blackout may not have had the same disastrous consequences if the SG managed to position the rudder - and in a timely manner.
Guess I thought you were speculating some kind of imbalance in load (that stuff about lighting circuits) could cause a diff trip upstream at the transformer breaker. But my understanding is that diff trips are sensing current into and out of the transformer and looking for a differential in that value (Ph A in to Ph A out etc., not between phases) as an indication of a problem inside the boundaries of the sensing points, in this case the transformer. This is becoming a bit esoteric. Maybe this point best left as is.
What do you make of the steering tests in the supplemental report? All moved according to design as far as times and arc of movement. Wouldn’t you have expected something in the report by now if the investigators were thinking there was something wrong with steeering system, other than loss of power?
First I would have expected some info/statements/possible VDR info on rudder position at blackout and movements when the emerg SG came on line. So far nothing.
Next, on the tests itself where every thing as you say checks out, they should have included a few blackout tests. Run all the 3 as per SOP for maneuvering, keep operating the SG with small movements, simulate BL and see if the emerg steering is functional after the EDG comes on line. And at least one of these tests for the emerg SG to be conducted at 10kts as per the rules.
PS: I think if there any doubt on the maneuverability of these large vessels on the ‘aux steering’, IMO should discuss the validity of their rule that was in place for decades and it looks like only recently these large vessels have taken advantage of this rule.
Some after thoughts:
Is it possible that the emerg SG managed to position the rudder at or close to 15 deg. And without the prop it made no difference to the heading without the prop?
Is it possible the emerg SG struggled to get it to close to 15 deg and could not make any further movement at the required speed (pump worn out – assuming the functionality was demonstrated at sea trials at the reqd speed)?
Is it possible that a hard port rudder with the emerg SG and without the main engine would have made a difference?
I bring this up as in normal operations (as with the testing performed in the report) is at the dock. Wonder if ever they tried or tested in open water at speed.
Many experienced mates/masters/pilots have expressed opinions on rudder authority with and without the prop wash. Would be good if NTSB provides some updates on this. Thanks.