[PSUBS-MAILIST] Thruster Reliability

Wed Jul 26 11:00:26 EDT 2023

The glue of the permanent magnets can be affected. 

I use silicone oil with a low ct around 1 after bad expierence wir air 
compensation.
But oil compensation needs also an compensator.bag. 
Siliconeoil is inherend to metal and plastic. (But prevent re-glueing) 

ELBESIL SILIKONÖL B 1 (1 cSt) - 500 g - SILIKON-PROFIS
<https://silikon-profis.de/ELBESIL-SILIKONOEL-B-1-1-cSt-500-g>

vbr Carsten

. 

-----Original-Nachricht-----
Betreff: Re: [PSUBS-MAILIST] Thruster Reliability
Datum: 2023-07-26T14:36:40+0200
Von: "Cliff Redus via Personal_Submersibles" 
<personal_submersibles at psubs.org>
An: "River Dolfi via Personal_Submersibles" 
<personal_submersibles at psubs.org>

These reports look good.  I am in the process of digesting them.  Is this 
the Univolt transformer oil you use?  Kinematic viscosity is low at 2.3 
cSt. <https://www.mobil.com/en-us/industrial/pds/gl-xx-univolt-n-61-b>

Good point compatibly issues and need for testing.  The good news on the MK 
101's is there are only a few parts to evaluate, lips seals, brushes, wire 
insulation and for my case, a Subconn connector.  The other parts are 
metal.  I don't think the permanent magnet would be affected.

Cliff

On Tuesday, July 25, 2023 at 07:07:54 PM CDT, River Dolfi via 
Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Cliff,
Those sound like signs of an incompatible fluid to me. Especially 
considering the length of time that the thrusters were filled with WD40 
compared to the hours they have run in the field.

The US Navy created a bunch of technical reports on various aspects of deep 
submergence systems design, and distributed them among defense companies 
and researchers as part of the "Deep Submergence Systems Project" in the 
60's and 70's. All of the documents are now approved for public release and 
readily available online. This one is particularly interesting and relevant 
to this conversation. I consult it often enough that I have a physical 
hard-copy on my office shelf.
"Handbook of Fluid-Filled, Depth/Pressure-Compensating Systems for Deep 
Ocean Applications"<https://apps.dtic.mil/sti/citations/AD0894795>
There is also:
Handbook of Fluids and Lubricants for Deep Ocean Applications
<https://apps.dtic.mil/sti/citations/AD0866350>

I suspect that the bushing wear is caused by the low viscosity of the WD40 
making it a poor choice for lubrication. I've always been told WD40 is a 
penetrating oil, not a lubricating oil.

I maintain and operate a small fleet of ROV's and AUV's that routinely work 
at a depth of 6000m. All of them use motors that are compensated with 
either univolt transformer oil where high voltages are involved, or a 
silicone oil. The caveat being that all of these are brushless electric 
motors, so don't have the complications of carbon fouling of the fluid.

We have been evaluating fluids that can serve as both a hydraulic system 
oil and an electrical system compensation oil, as we currently run two 
separate oils for each function. The problems we are running into are 
material compatibility with existing components. Things like wiring, heat 
shrink, seals, adhesives, etc. We know what not to do with Silicone and 
Univis, but the only way to determine the compatibility of a particular oil 
with a particular off the shelf or proprietary component, like a Minn Kota 
or any other motor, is testing.

Thanks,

-River J. Dolfi

412-997-2526
rdolfi7 at gmail.com <mailto:rdolfi7 at gmail.com>
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