[PSUBS-MAILIST] DNVGL

[Alan via Personal_Submersibles]

Scott, River.
I had a technical advice contract with DNVGL. The reason being so that I
could build to their specifications without going through their $100,000
process. Costs you about the same as an expensive lawyer, but it all
depends on how many questions you have. 
The electrical rules for submarines over-ride the electrical rules for ships..
If you were totally familiar with their electrical rules you could wire up a 
super tanker! A lot in there as they have to cover computerised control. 
Sean is right about no earths in submarines.
The electrical through hulls need to be constructed so that if the cable is
sheared off, no water can ingress. I saw a lot of through-hull fittings at
UI New Orleans & not all had this ability. I guess if you are building for a 
predominantly ROV market it isn't so necessary.
DNVGL normally have reps at UI. I spent quite a bit of time picking their 
brains when I went there. 
They are flexible in some areas & have a golden rule that no one failure
can result in a major event.
What sort of batteries have you got?
Deep Sea Power & Light have an ABS type certification on their oil compensated
battery.
http://www.deepsea.com/?s=sea+battery
South West Electronics have a compensated lithium battery. They were 
looking to get type approval from one or more of the big certifiers but I don't
know if they did, or whether it's in process.
https://www.swe.com/seasafe-subsea-modules/
Alan


Sent from my iPad

> On 22/10/2017, at 6:11 AM, River Dolfi via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Scott and I have been driving ourselves crazy trying to interpret the DNVGL rules on subsea electrical cables. We think that the essence of the problem is that DNVGL lacks rules specific to oil-compensated external battery banks (except being subject to "approval by the society"), and to the best of our knowledge DNVGL has yet to certify any submersible with external ambient batteries.  
>   
> One rule in particular is making us scratch our heads. UWT pt4 ch8 sec2-1.3 states that "All cables in the outer area shall comply with (cargo ship cable rules section). All cables shall have an EARTHED braiding or screen around the conductors and be equipped with an insulating outer sheet." If this is applicable to the main battery cable, damage could potentially create an incredibly dangerous ground fault condition where high voltage is passed to the sphere. While this requirement makes sense for low-voltage electronics who require protection from electromagnetic interference, it appears to be nonsense when applied to a high-voltage DC power cable.
> 
> Thanks,
> 
> -River J. Dolfi
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