Why Did Dali Lose Power in Baltimore? | NTSB Releases Preliminary Report

Comments · 2.4K

• SA

  @sambrown8224 · 2 years ago (edited)

  Afternoon Sal, Retired USCG Marine Engineer Investigator here. Having investigated a similar occurrence on board an LNG ship headed into port back several years ago, there are some similarities here. That ship, an all steam propulsion system, lost steam pressure which shut down all electrical and propulsion systems. During the crews attempt to restore power, the ships high voltage and low voltage buses kept tripping off after being reset. The ship was dead except for the emergency bus for 5 days offshore while being towed around in a circle. What we found after downloading the automation data, was that all the main breakers and bus ties are connected by a PLC (Computer) that tells it the position of all the other breakers and will prevent you from closing the wrong one. The engineers realized that each time the breaker tripped, the PLC had to be reset  for every  breaker every time it tripped. So if it trips 6 times, you had to press the reset 6 times to clear it on all the breakers. The engineers did not know this since they had never operated these manually before. Once that was found, the systems operated normally. A 100k ton ship dead due to something so small is what I'm expecting them to find.

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• WI

  @williamcarl4200 · 2 years ago

  I respect your dedication to your audience. Bet it means a lot to your fans out there as well. Thank you sir.

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• CA

  @cagramer · 2 years ago

  Excellent job going through the NTSB report.

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• JO

  @johntrottier1162 · 2 years ago

  Sal -- Ex Navy electrician mate and retired automation controls designer here. <br>After reading many of the comments and rereading the report, I&apos;d like to add my 2 cents.<br><br>Why was the normal lineup to have 1 transformer in used and the other powered down? <br>I would have expected that both transformers would have their high voltage breakers closed at all times and that there would be a schedule to switch the transformer in use on a regular basis.<br>The way electrical system was actually being operated, one transformer was completely disconnected, often for extended periods of time. <br>Leaving electrical equipment sitting unused and unpowered for long periods of time in a ship at sea is a recipe for disaster. Changing temperature and humidity levels on a ship plays h*ll with electrical connections and insulation. In addition equipment sitting idle will always manage to gather dust bunnies from somewhere. <br>The end result is usually a short circuit or a ground when the equipment is turned back on, always occurring at the worst possible time.<br><br>With this in mind, the following sequence of events may have occurred.<br>1. Until the day before, TR1 had not been used for months. Until the MV Dali pulled away from the pier, it had been lightly loaded as no large motors were in use. Once underway TR1 experienced normal at sea loads, the conditions in the transformer start to change. I suspect this caused a fault in the transformer.<br>2. The electrical control automation system detects the fault on TR1 and trips both HR1 AND LR1 breakers to isolate the fault. This is the 1st power failure.<br>3. The crew overrides the automation and closes TR1 and LR1 to restore power. <br>4. The fault in TR1 is still there, but the first level of automation trips for HR1 and LR1 have been overridden. The automation system most likely tries to alert the crew to the problem (by setting off more alarms), but they are too busy trying to get propulsion back. This is indicated by the heavy black smoke seen after the first power restoration.<br>5. After some programmed time delay (and not nearly long enough from the crews viewpoint), when no action has been taken, the automation safety program proceeds to it&apos;s next level of protective measures, and trips the DGR3 and DGR4 breakers, shutting down power to the High Voltage bus to protect the generators as well as tripping HR1 and LR1 for a second time to isolate the fault.<br>6. With the fault isolated, the automation now connects DG2 to the High Voltage bus by closing DGR2.<br>7. Now forced to deal with the problem, the crew leaves TR1 deenergized and manually close HR2 and LR2 to bring TR2 on line and power the low voltage bus.<br>They have power back, but by now it&apos;s too late, and MV Dali hits the bridge.<br><br>I understand that ship owners want to cut costs, and automation is cheaper than trained people. But I have never seen or designed a piece of automated equipment that was smarter than a well trained operator.

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• SN

  @snwboardr9876 · 2 years ago

  Hey there Sal, great video! I was highly anticipating it! There is a CORRECTION to be made though. The second blackout was NOT caused by HR1 and LR1 breakers tripping again. According to the report it was actually caused by breakers DGR3 and DGR4 both tripping (the main breakers for Gen3 and Gen4). <br><br>This is why DGR2 closed to provide power to the HV Bus which was lost this time. GEN2 was in standby mode so it had spun up. <br><br>I’m a bit confused at this point because the report then states that the crew closes HR2 and LR2, but there’s no mention of HR1 and LR1 being opened or tripped. Not sure why they decided to energize the TR2 side if TR1 was already in operation. <br><br>Regardless, the main correction I wanted to point out is that the Main Breakers for DG3 and DG4 did indeed trip, which is what caused the second outtage. According to the report at least 🤷‍♂️🤷‍♂️<br><br>Thank you again Sal!

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• AN

  @andrewschliewe6392 · 2 years ago

  Great breakdown of the NTSB report. Thanks, Sal.

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• LO

  @loneranger515 · 2 years ago

  Fantastic, clear explanation. I&apos;ve conducted many safety investigations and it&apos;s always difficult to present results in a way that folks (who are not familiar with the system) can understand. Well done!

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• EL

  @EliteMacFreak · 2 years ago (edited)

  Electrical engineer specializing in a relevant field. &nbsp;Obviously there&apos;s a lot of detail missing from that electric plant one-line diagram, and I&apos;m not familiar with CONOPS on container vessels, but it looks like Dali was running an unprotected vital bus lineup, where both port and starboard buses are powered by a single source. &nbsp;For the purposes of the lineup, DG3 and DG4 form a single logical source. &nbsp;This is a dangerous lineup in restricted waters. &nbsp;I suspect what&apos;s going on here is operators were trying to &quot;wear level&quot; their equipment by running one side of the plant (port or starboard) for X months at a time before switching to the other side. &nbsp;The problem is, you can&apos;t do that in restricted waters, because <b>by tying the port and starboard buses together, any single casualty will result in a complete loss of power.</b> &nbsp;You&apos;re always supposed to be operating in a split plant lineup, with 1 port and 1 starboard source energized (HVR and LVR breakers open) unless a casualty prevents you from doing that. &nbsp;This is where I might be wrong for container ships out at sea; when they&apos;re in deep water they have tons of time to recover propulsion in the event of a casualty. &nbsp;However, this should NEVER be the lineup in port. &nbsp;Changing subject slightly, it&apos;s clear that whoever was operating the electric plant didn&apos;t have a clue what they were doing. &nbsp;If HR2 and LR2 trip, it&apos;s not a problem with TR2--there&apos;s either an overload or fault on the LV bus. &nbsp;When they closed the EG output breaker into the LV bus and the EG stayed up, it indicates that an overload tripped HR2/LR2. The source of that overload should&apos;ve been identified and isolated before closing the HR1/LR1 breakers. &nbsp;The fact that HR1/LR1 tripped after 30+ seconds indicates the trip was on long time delay protection. &nbsp;This means that somebody or something (like an automatic relay) turned on a huge load that the forward feeder cabling or transformer wasn&apos;t rated to handle. &nbsp;That&apos;s why I say they don&apos;t have a clue. &nbsp;Excessive/bad automation could also be a contributing factor like Sam Brown said.

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• PO

  @PObermanns · 2 years ago (edited)

  Fascinating report. As a retired USN officer, who served on the USS Lexington and was qualified as OOD-Underway, I listened to your descriptions attentively and stopped the video so that I could peruse the electrical diagram in detail. Same for the text excerpts from the NTSB report. What I was surprised by was the seemingly inherent fragility of that electrical system, and the fact that the emergency generator could only power some of the critical systems. Sure, a warship like mine is designed to take a lot of abuse and keep going - but any ship should have multiple ways of restoring engine propulsion, steering (the Lex had 5 ways to steer her), and full electrical supply from emergency generators to all critical systems. Sounds like the designers never anticipated that the high-volt bus would ever be unpowered. // Since this is not the first collision of a large vessel with a bridge and associated loss-of-life, I think that perhaps there should be the requirement for the tugs to stay close aboard until the ship is thru the bridge. Expensive and inconvenient - but that&apos;s exactly what we have now after this collision.

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• FR

  @FrederickRH1 · 2 years ago

  Thank you for the education. &nbsp;Your point on the Pilot and pilot dispatcher is well taken on the lives saved. &nbsp; Very respectful to those who lost their lives and their families left behind.

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• MI

  @michaelscully4983 · 2 years ago

  Sal, you are a treasure! Not only do you give us the clearest explanations, but you point us to the issues we should be focused on and not the diversive, paranoid drivel that so many try to feed us.

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• GE

  @GetSmart-v9b · 2 years ago (edited)

  As an Industrial electrician I am very familiar with the switch panels in your diagram. I can tell you that in a land based factory, during normal operation, the Tie Breakers are left &nbsp;open. Normally, one even numbered generator and one odd number generator is used on both sides of the bus. Both transformers are used as well. This way, if there is a fault , only half of the loads lose power. It also makes it quicker to isolate the faulty circuit. The purpose of a Tie Breaker is to feed the entire bus if there is a problem with one of the transformers or the feeds. Your diagram may show the position of the breakers as they were found on the Dali , But I can tell you this is not the way these panels are designed to be operated under normal conditions. One more additional point. Usually an overload will trip the branch Breaker and the feed breakers will not trip, however if there is a low resistance short in a branch circuit then all of the breakers in series can trip.

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