Originally Posted by
Old Farang
Arh, I know that I should just read what is here and then just move on. However, it is supposed to be General Discussion, so here goes!
Grandpa me has been both chief electrician and chief engineer on small ****s, medium ****s, big ****s, and then REALLY BIG ****s. Usually not at the same time, although on diesel electric ****s the chief electrician gets blamed for all the **** that goes wrong, including if the engines stop! I have worked on ****s that are completely DC, ****s that are only AC, and worst of all, ****s that have both AC and DC electrical systems. I have worked on ****s from one small **** where the main generator was shaft driven, to a REALLY big dynamically positioned drillship that had a 15 megawatt power system generating at 6 kV via 4 or 5 horrible French engines.
That particular **** did not have any main diesel propulsion engine, although there was a similar drillship in the fleet that did have a big diesel propulsion engine in addition to a multitude of electric powered thrusters, having been converted from a cargo ship, rather than being built as a drillship.
The container ship that wanted to mate with the bridge (MV Dali) is much more modern to most of those that I worked on, so it will have much more up to date electronic systems and controls.
However, the basic main engine is just a later model to those that I have encountered. It is a 9 cylinder, two stroke, direct reversing slow speed diesel marine engine as found in hundreds of similar vessels. It is direct coupled to a fixed pitch propellor at the stern of the ship, placed just ahead of the rudder. It does not have a clutch, it does not have a gearbox, it does not have a brake. It is started using high pressure air (30 to 40 bar), via direct injection to probably 5 of the 9 cylinders. It is rated at 41,480 kW at 82 rpm. (55,630 hp).
To reverse such an engine, in my experience, there are interlocks to ensure that the engine is stopped, or very near so, before it can be started in the reverse rotation It has been reported that when whatever happened that led to the main engine stopping, the ship was making around 8 knots through the water. The inertia of around 100,000 tons of still moving ship will cause the prop to keep rotating, and therefore the main engine, until such time as the drag slows it down and reducers the shaft speed enough to attempt to restart it.
Clouds of black smoke from the stack, were visible on one of the videos. However, it is not known yet, or not reported, if an attempt was made to restart the engine, OR which direction if it was a restart attempt. Most modern ships like this one have bridge control, but that can be transferred to the engine room and that has also not been reported. However, good practice would be that the engineers would be on standby in the engine room while the ship was under pilotage regardless of where the control was set. By regulation a reversing engine is required to have a starting air reserve to enable 12 attempts without replenishment.
As known, and as can be seen, the lights went out! In the specs published for this ship show there are listed a total of 4 auxiliary generators, plus there will be an emergency generator with limited power installed well above the water line, and not in the main engine room. That generator will start automatically and MAY have been the source of the lights returning, but that is highly unlikely as it is only big enough to feed essential circuits such as nav equipment and a few escape lights. It is self contained, starting, fuel, cooling all separate to the rest of the systems. It has an automatic transfer switch and its own switchboard.
Now what I find really unusual with this ship is that it has a bow thruster! And that then explains why it has 4 auxiliary generators. As the 2 gen sets are of slightly different size
(3,840 kW & 4,400 kW), I would say that the two 3,840 kW generators are probably just for the bow thruster, which is rated at 3,000 kW. I would also suspect that the gens are mounted somewhere near the bow in a separate compartment, completely remote to the engine room.
Cargo ships of this size usually have two auxiliary generators, with each one being of sufficient capacity to provide the ships running load alone. The gens can be run in parallel to the main switchboard, and it is again good practice to run both of together when in a situation such as this ship was, maneuvering in a harbour. In fact, it may even be mandatory. Right now, unknown, and may never be known!
The other requirement in such a situation is that the forward anchor is to be made ready to drop, and a crew is to be stationed there to do so at a moment’s notice. It has been reported that it was dropped, but probably too late to be of any use. It will also be interesting to find out just how long the deck crew stayed at their position when it was obvious that the ship was going to hit the bridge! Power is not needed to drop an anchor, but it needs to be set just hanging on the brake, which can be released by hand.
The sequence of just why the main engine stopped is yet to be determined. But in can be said that the most obvious reason is that the power blackout occurred first. Although it is a diesel engine, and is quite happy to run without any power ignition, all of its auxiliaries require electrical power. The main cooling circulating pump, always just shortened to “main circ”, is an electrically powered pump. The engine requires large volumes of air, which has to be supplied to the engine room by big fans. There will be a multitude of electrically powered sensors and control that rely on power, many of which will shut down the engine to prevent any damage, such as lube oil pressure, cooling temperature and flow. The sea water cooling system will also be part of the monitoring of engine parameters, and has an electrically powered pump.
Modern systems for sure will have better monitoring and alarm systems, but I always recall a ship that I was on as electrician around the time that I first worked on ships. It had a couple of small diesel generators; in fact, they were Rolls Royce engines. They each had a basic 24 volt powered alarm system, protected by a 15 amp fuse. At sea only one gen was needed, so when that 15 amp fuse blew for whatever reason, the engine stopped as the fuel rack solenoid needed power! Everything then rapidly became very quiet!
ps. I have not looked at that YouTube post, having only just open this thread.
