Transocean - Tyranny of Depth - Does It Matter?

? "Atmosphere"...? "...desalinated water to wash down the equipment?"...

Who needs an atmosphere? Why wash-down the equipment? Engineer it for the environment it'll be in.

Nothing is out of reach, if your *budget* can handle it.

Your dream/vision isn't thinking in terms of Cost-vs-Benefit yet.

What would you be doing with this "garage" on the sea floor? Harvesting manganese nodules...?

Generally speaking hydrostatic pressure is not a big deal. It is the difference between the hydrostatic and the wellbore pressure that is the issue.

There are no humans at that depth. it is all done with ROV's which don't need much in the way of pressure containment (except for the control systems which are in a pressure vessel and are often pressure compensated with dielectric oil.)

Actually we use closed cell foams at depth all the time. They just happen to have a very high concentration of glass microspheres. Google or Wiki syntactic foam.

Yes, syntactic foam does work well up to the pressure limitations of the glass microsphere collapse rating.

The atmosphere could be non-oxidizing such as nitrogen, helium or ??? That would potentially open the possibility of applying the vast majority of surface equipment for use within the enclosure.

The exotic materials currently in use for immersion are expensive and there just are not very good alternatives for expedibles such as cutting or impact tools. This is where the DI water or RO water wash down would come into play. Since they could be washed down and stored in the garage free of oxygen they would last longer.

The ROV and anything venturing out could potentially be made of less costly materials since they wouldn't be coming back to an oxygen environment. You would still need to consider galvanic corrosion.

You could also enclose the BOP or other equipment and place a maintenance robot in the enclosure.

a little cross-fertilization... Anything that works on a submarine, at 5000 feet, ought to be applicable, as it has been field tested, and proven successful.

If something is being tried, and hasn't been done before, you have to consider it an experiment.

Great question though, and one that is on every thoughtful person's mind.

Chris

Let's stretch the depth and consider the following thought experiment. What would happen to the functionality of the following equipment if exposed to a 2500 up to 40,000 psi nitrogen or helium atmosphere? Consider they would be in their own little environment such as the surface of a gas giant planet. The rate of pressure increase would simulate the rate of descent.

Desktop PC

Pump/motor (Electric or hydraulic)

Industrial robot

Industrial CNC equipment

Batteries

Light sources

Video equipment

Now consider the trip time to and from those equivalant depths and whether you are able to launch at all due to sea state.

Regarding the thruster motors on ROV's. Are the motors fluid immersed or are they using something like a magnetic drive with a sealed motor case?

Most electronics cannot handle much in the way of pressure unless they are specifically designed for the environment. batteries, Aluminum electrolytic capacitors, metal can semiconductors and crystals, all would be crushed and unusable. Further hard drives are designed for their heads to fly above the disk surface in the disk surface's "ground effect". if you change the gas that it operates in, you change the fluid dynamics of that airfoil and your hard drive doesn't work.

What if you changed to solid state hard drives?

Any way around the crush issue for the batteries, capacitors, metal can semiconductors and crystals? If you left them vented and vacuum impregnated with a compatible material similar to the process of impregnating aluminum die castings would that be a potential solution? If that wouldn't work could you pot everything in a structurally sound potting solution? You would have a great heat sink just outside to cool everything down.

unless they are specifically designed for the environment. !

The cost just sky rocketed.

GA Rorschach

Yep, that is why electronics for space environments are so expensive, the semiconductor wafers are the same, but they go through special screening and packaging and testing and the cost goes through the roof, same with Mil Spec electronics, again the testing and screening and the packaging is what makes a mil spec 555 timer cost 100 times what a commercial one does. Add in the fact that the lot sizes are relatively small and you throw out any possibility of bringing the prices down through the economies of scale either.

".whether you are able to launch at all due to sea state" . I know for a fact this is a genuine issue in the north atlantic - where there are plans for a 2.5 km deep drilling operation.

I believe I heard it on the news after the Sikorsky helicopter crash - rescue crews were unable to use ROV to search for survivors because it was unfit to launch them.

The need for specific conditions to launch the vehicles sort of defeats the purpose of using them in emergencies - most likely to occur in the worst conditions afaict. Severe wind and wave conditions are, after all, a risk factor for accidents and failures.

I have no clue about the subsea garage idea, but a subsea presence of the ROV at all times seems pretty damn necessary to me if it's going to be any use. They can practice their emergency functions down there, come up on a rotation basis for maintenance when necessary and when conditions are good for it.

most fixed platforms have ROV's launched and operating 24/7. for ships, the problem is that the sea state is constantly tugging on the tethers.

I guess the question for fixed platforms would be, if "most" then perhaps it should be a rule to have ROV engaged for all such operations. I'm not sure what regs are followed here - maybe it is a rule already.

The ROV's I've seen into use hydraulic motors, big pump with its own inverter running at about 3000 volts 3 phase, all determined by the cable length and weight of the copper verse the added diameter for insulation. Electronics mostly in armored fluid filled boxes to isolate them from the pressure.

If the electrical components can't be vented or encapsulated readily in potting compound, how much could be relocated topside since all of the operator interfaces would be there anyway? I assume this same question applies to current ROV's. How much do you really need to enclose in the pressure vessel on the ROV?

Batteries could likely be taken out of the problem category since pressure compensated batteries are already available for ROV's. This would potentially eliminate issues with use of lithium batteries since a substiture would be available.

If vented electronics components were availabe, how would they function immersed in a cooling liquid or gel bath similar to the manner some high end PC's are now available?

I found some interesting information on the Siemens Subsea Power Grid. They are claiming large scale subsea processing at 3000 meters depth by late 2012:

http://www.ordons.com/201005044502/siemens-presents-subsea-power-grid.html

Capacitor arranged in a high pressure environment (Sounds expensive)

http://www.wipo.int/pctdb/ja/wo.jsp?WO=2008145639&IA=EP2008056435&DISPLAY=DESC

The effects of space environments on Electronic Components (Nasa):

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/7193/1/03-0863.pdf

It doesn't appear to say much regarding pressure effects compared to other factors.

Failure Mechanisms in Electronic Products at High Altitudes:

http://www.dfrsolutions.com/uploads/publications/2004_HighAltitude_Hillman-Blattau.pdf

ROV World - Which electronics are pressure sensitive?

http://www.rovworld.com/modules.php?name=Forums&file=viewtopic&p=16431

Containment of downhole electronic systems:

http://www.freepatentsonline.com/5647435.html

Power Electronic Conversion Systems for Deepwater Applications:

http://www.elkraft.ntnu.no/eno/Papers2007/Jacobo-Korea.pdf

Permanent downhole monitoring for extreme temperature and pressure environments:

http://www.onepetro.org/mslib/servlet/onepetropreview?id=00071593&soc=SPE

Magna-Tech Electronics Components Sealing Division:

http://www.magnatechmfg.com/services/electronic.asp