I agree with every part of this that i actully understand.
Where do you see this - locked at midships?
Don’t understand what you mean … overpressure valves are safety valves set at the MAWP of the system and will relieve pressure to the header tank if there is a situation with rudder slap or similar to create the overpressure in the SG hydraulics.
There should be no such ‘remain locked’ condition. Regulation requires that the emergency SG pump to come on line as soon as the EDG power is available. No manual start needed. When the power was restored though SG pumps 1 and 2 most likely would require a start from the steering stand in the wheelhouse. Engineers are not monitoring this.
I’ll submit yet another reference: lecky jake, He is an electrician. He has some good videos and one in particular where he tests start up from a black out and the first ship generator didn’t respond. It wound up being bad backup batteries (low voltage). Just seems to have some similarities to the Dali. Look up "lecy jake “blackout test” and see what you guys think.
Do the gensets start off air or the batteries? Is it the same 24 volt bank everything else uses?
The four generators are of a size where they would be started with compressed air. The EG should start with its own dedicated 24 volt battery.
I suggest a transit of the Houston Ship Canal in a large ship will see you reaching for the cape and magicians baton rather than your slide rule.
@retdmarineengineer:
Referring to the rudder angle, if I read the PR correctly the rudder was midship (0°) as the 1st blackout happened. From that moment until the Emergency Generator (EG) came online, probably not later than 45 seconds after the first blackout had begun, the rudder remained inoperable and therefore stayed in that position, also there was no reason for an overload which would have to be higher as the highest reachable torque when powered (the reachable torque does not depend on how many hydraulic pumps are runnig, a higher number of sultaneously running pumps allow only higher angular speeds but the maximum possible torque is not increased).
In case of overpressure the plunger cylinder facing the one which faces the maximum pressure must be fed with oil in order to avoid a negative cavitation caused by air entering the hydraulic system pushed by the atmospheric pressure against a too low oil pressure and also bubbles of no more sufficiently dissolved gas can appear in the depressurized oil volume.
Typically there are two unidirectional overpressure safety valves which “short circuit” two opposite plunger cylinders in order to allow the hydraulic oil to flow from the chamber of the overloaded cylinder directly to the chamber to the opposite cylinder.
This works passively (i.e. without any electric or hydraulic power), leakage losses are compensated when the corresponding pump(s) is/are running.
How exactly the displacement of the hydraulic pump is controlled depends on details which require the complete hydraulic diagram and sometimes it’s only a simplified representation, in such case the diagram must be checked in the manufacturer documentation of the pump.
As long as the pressure in any hydraulic cylinder remains below the preset pressure of the safety valves the rudder works normally, if the steering gear is overloaded the rudder can move in either direction as long as the overload lasts and until either hard stop is reached. Of course it won’t affect the rudder angle indicators but as long as the torque overload lasts the helm or tiller remain ineffective.
Thanks for the clarification about the automatic switch-over in case of main power failure, it also seems logical.
Some ME Control Room consoles feature steering gear pump start/stop controls, probably in parallel (i.e. function-wise, not referring to the hardware wiring of the contacts) with the bridge console start/stop controls.
One of my replies ended misplaced.
The Emergency Generator (EG) must meet some formal requirements, they’ve been listed in this or the more technical discussion about the incident.
The EG is typically a small high-speed (here 1800 RPM for 60 Hz) 4-stroke diesel engine driving a synchronous low voltage generator (here 440 V 3-phase). The power is typically small, my guess always changes but I’d say around 400 kVA, first I thought it would be rather around 500 kVA or so.
Two independent starting methods are required, the main one is usually a regular starter powered by very common dedicated lead-acid batteries (usually 24 V), the secondary one is mostly either hydraulic (with a hand pump, regardless of a possible electric pump) or, for smaller engines, with a spring-loaded starter where the spring is charged manually with a crank or a lever.
The large DG’s are started by the common starting air reserve (around 25 to 30 bar (barg)).
The EG batteries are only used to start de EG but interestingly SOLAS requirements are very low as only 3 consecutive starts are mandatory.
Other SOLAS requirements are also surprising but I’d have to find them again.
As secondary starting system SOLAS seems to allow pneumatic starters, which I consider as not admissible (not to be confused with the use of starting air). Explosive starters are also liste though I’ve never seen any. When it comes to air starter, they’re not considered as highly reliable, they’re either based on a compressed air motor or an air turbine. Good hydraulic ones are reliable. The spring-based types I don’t know well enough.
Also the secondary starting system only needs to allow 3 consecutive starts within 30 minutes.
Ventilation, cooling, lubrication and fuel tank must be dedicated strictly to the DG.
Here I just mention what I found online.
I’m possibly wrong as I mentioned that the emergency swichtgear panel can be in a separated room (I meant accessible from the EG room). I must try to find the original SOLAS texts.
I’ve been involved in the design of emergency power systems but not related to ships.
The main air-started DG’s are indeed very large compared to usual land-based gensets but their controls are not always that advanced compared to the power but it depends on the ship.
Negative Sir. It will see me relaying on pilot skills , my sea time experience, which is not 5 decades like yours but close to it and will see me taping into the knowledge of experts who authored the literature I quoted in one of above comments.
Suggest You Sir look it up to find some titles from well known training and ship handling centers. You have to get familiar there with science first before they let you touch their toys.
Compare what you had at your disposal 50 years ago and what you have now . Slide rules?? Oh my God You really must be ancient 
or “vintage” . ,
May be Houston Channel is for eagles only but from my “experience” i have never met a pilot who would say his area of ops is the easiest in the world. Last but not least pls do not forget , that even if You employ some magic , the moment You screw up the science steps in including forensic to explain and find answers of Your magic failure.
Cheers
Indeed you need to make sure that the charger allows the battery to be removed while running.
The design of the switchboard in lekckyjake’s very good video is absolutely dreadful, not even insulated separators betwen both fuses, cable lugs which should never be used for such wire gauges, fuse holder contacts without additional clip to increase contact pressure and the list goes on.
Also the non-protected (i.e. non-fused) conductors between the battery and the corresponding fuse should be run separately in individual flexible non-metallic protection tubes or insulated fiberglass textile tubes. A good practice is to install battery fuses as close as reasonably possible to the respective battery connections and use less antique fuses and fuseholders.
And after loosening the battery connections, the wrench shouldn’t be hold when removing the screw (at 8:24), I’m very surprised he did that as he’s very highly experienced. It’s also possible to use shrink tubing to cover unused parts of the wrench or ratchet.
In the video leckyjake mentions that the batteries are 200 Ah (here 12x 2 V cells), which is surprisngly low, it corresponds to 2 large truck starter batteries. It’s even questionable if two 12 V industrial batteries would not be wiser as 6 internal elements witihin the same 12 V battery will be better matched as 12 individual 2 V cells. For large capacities only single cells can be used though, they’re very reliable if well maintained and from reputable manufacturers. The ambient temperature is very important.
Also if 24 V batteries (mostly two 12 V batteries in series or twelve 2 V single lead-acid cells in series, some can reach several thousand Ah for large batteries), the voltage can reach around 28.8 V DC which is higher than the usual tolerance for non-automotive 24 V industrial devices like e.g. PLCs, relays, contactors,…
To fully comply, in many case DC/DC converters would be required to ensure a stable enough voltage-regulated 24 VDC, typically with parallel DC/DC converters and highly selective distribution.
A crude way to supply uninterrupted DC power than using redundant DC/DC converters is to simply monitor the battery voltage and shed the loads once the set cut-off voltage is reached (hopefully with enough hystheresis to allow a pumping effect wich can damage powered devices if the battery voltage recovers afthe the load shedding, leading to load reconnection which against decreases the voltage so the load gets shed again).
Many 24 V DC industrial equipment will not run around 18.5 V DC, 24 V DC powered genset related devices are designed for a wider voltage range to not shutdown when the starter battery voltage drops (though here the batteries are used to as backup batteries not to start any engine) and also allow around 30 V as 28.8 V is around the highest regular charging voltage for 24 V lead-acid batteries.
The other generator-related devices didn’t shut down due to randomly more favorable undervoltage tolerances.
If there had been a blackout, most supplied electronic equipment would have stopped working as the usual limit is 24 V DC -10 % = 0.9 x 24 V = 21.6 V DC, i.e. below 21.6 V DC a device specified for 24 V DC +/- 10% will no longer necessarily reliably work. The cut-off limit may be lower but it is not guaranteed. The maximum voltage can be +10 % (26.4 V DC) or sometimes higher, especially for devices which are likely to be powered by 24 V batteries.
In the case of the video, most 24 V DC supplied devices would probaly have been shut down, including most electronic bridge equipment.
24 V DC supplies should be redundant and monitored, automatic battery testing should also be performed. Very reliable are redundant modular systems without any single point of failure.
Of course this is absolutely not leckyjake’s fault, it’s not even that old a vessel, it’s just that the electrical design was already outdated as it was built.
I quicly watched a very few of leckyjake’s videos and I highly respect him for his experience and work attitude if the term is correct in English. He’s the type of person who’d be able to improve a lot electrical equipment of ships because those who know best what is reliable or not are those who must troubleshoot day after day and keep things running.
Referring to the PR (Preliminary Report) there’s something odd: The NTSB implicitly mentions (page 11) that, among other devices, navigation, radio, and “other emergency equipment” would have lost power during the 1st blackout (the VDR Recording Control Unit features a integrated battery providing power for 2 hours, it’s formally unknown if at any time it was powered by its internal battery).
This would be surprising as some equipment is powered by AC UPS power and also some is powered 24 V DC with centralized battery backup (DC UPS).
I’d rather expect that both AC UPS power and battery 24 DC didn’t fail, as if there would have been issues it should have been mentioned in the report.
Also I don’t expect the simultaneous failure of both the 24 V DC battery power and AC UPS. Unless large central batteries (typically 48, 110 or 220 V DC for land-based systems) are used, it’s likely that the DC UPS and AC UPS batteries are separated. But the exact UPS configuration is not known.
Critical bridge (wheelhouse) equipment is powered without interruption for a limited time even without emergency 440 V AC power from the EG.
From page 10 of the report:
The loss of electrical power stopped all three steering pumps, and, therefore, the rudder was unable to be moved. At the time, the ship was on a heading of 141.7°, a course over ground of 140.8°, and speed over ground of 9.0 knots, with the rudder amidships (0°).
If there was something wrong with the steering gear in addition to all three pumps being stopped I didn’t see it in the report.
Also this on page 11
When the emergency bus was powered, emergency lighting, navigation and radio equipment, alarms, and other emergency equipment would have been available, and the designated emergency steering pump (no. 3) would have been available to turn the rudder…
While just pump 3 is on, are the rams not connected to that pump bypassed in some way to allow the rudder to move?
Are these valves a potential source of trouble?
Air entering the system? Cavitation? Dissolved gas? Don’t understand any of this or rest of the explanation of the hydraulics.
The steering gear pumps are variable delivery (volume of oil) pumps at the rated pressure. These pressures are usually around 40-50 barg. It is a closed loop. For any rudder command 2 cylinders are pressurized (usually diagonally opposite) and the oil from other 2 cylinders are bled to the suction side of the pumps.
High pressure can be experienced when the rudder ‘slaps’ acting against the hydraulic oil pressure during bad weather. Safety valves are provided for this.
Hydraulic lock can also occur if the 2 cylinders that are supposed to bleed does not or bleeds too slowly due to faulty solenoids. Hydraulic locks are required to be alarmed. No indication from the PR that this occurred.
Yacht Sailor
Usually the system is designed to operate all 4 rams with the 2 systems (hydraulic power units). Means are to be provided to isolate one set in case of emergency such as a pipe failure.
And yes, potentially the solenoid valves could be a source of trouble.
The pumps I dealt with were pretty simple, they ran either way so they were always pushing fluid in one hose and sucking from the other one at the same time.
No engineer would, because it is pure nonsense. That post and his others sound like the ramblings of a small boat mechanic and wannabe electrician with access to Wikipedia. Typical internet me too stuff.
I think it is an AI. It’s got a pretty good stream going. It’s like the Dali brood of cicadas has come out.
???
Last time I set up hydraulic steering I bled all the air out of it and that was that. It wasn’t like a scuba diver getting the bends later.
We are not talking about a toyboat steering system.
So…how DOES air get in? Hydraulics are kind of all the same. I don’t get it???