[PSUBS-MAILIST] right side up compensator

[Øystein Skarholm via Personal_Submersibles]

Oil Expansion

Since I am from Europe I have to use celsius to not confuse myself.

Let's say Alan fills his motor AND compensator with 8,2 gallons of oil. The
oil and surrounding temp is 20deg C.

He then brings it out in the sun and it warms up to 40deg C

During the dive it cools down to 6 degrees C

Expansion during heating to 40 deg C = 8,31Gallon Total Volume
negative expansion during diving 6 deg C = 8,12 Gallon  Total volume

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lør. 28. mar. 2020 kl. 20:35 skrev Alan via Personal_Submersibles <
personal_submersibles at psubs.org>:

> I like the ROV Oystein, well done.
> That compensator would work well for Brian.
> Brian's problem is that he made his own thruster & housing which is a bit
> of a beast in that it needs gallons of fluid to compensate it.
> His concern is to have enough room for oil expansion which is an unknown
> quantity. Personally I think he will get more expansion with it sitting
> out of
> water in the sun than running underwater where oil circulating against the
> large housing will keep it cool.
> Alan
>
>
> On 29/03/2020, at 7:57 AM, Øystein Skarholm via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Again, NEVER open the oil to contact the seawater. You WILL get water into
> the oil! Have the oil closed. Unless you have a piston in your riser tube,
> the air will flow straight out and water will come i.
> <image.png>
> The idea to the left.....and the result to the right. Just trust me on
> this.
> The below picture shows one of the ROV I have built. The canister in the
> center contains computers and power supply ++ 600Volt DC
> The whole canister is filled with Shell Diala S4 oil (In the progress of
> changing to MIDEL ( Not so aggressive to the rubber and plastic parts.
> I use a small bladder compensator for this (its far too big really, but
> came cheap off the shelve from an auto dealer shop) The little tee lets me
> inject oil through a check valve
> until I get 0,2bar overpressure. The red cap in the end lid is the main
> filling bulkhead.
>
>
>
>
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>
> lør. 28. mar. 2020 kl. 15:14 skrev Jon Wallace via Personal_Submersibles <
> personal_submersibles at psubs.org>:
>
>> I'm thinking we need someone to give a technical talk on this at our next
>> convention.  I'm not only confused but I guessing others are as well.  I
>> thought the simplest approach, from previous discussions, was just to use a
>> length of hose connected to the oil filled motor on one end and open to
>> water on the other end.  See attachment.  This allows expansion of oil into
>> the hose (blue), but traps a gap of air (white) as water (green) enters the
>> hose during a dive.  Water compresses the trapped air the deeper you go, so
>> designing a large enough gap is important because that air gap can get
>> quite small and potentially result in mixing of the oil and water.  At 300
>> feet for example, the air gap is only .652 inches (16.5mm) when using a 30
>> foot (9 meter) hose.
>>
>> My understanding for the need of a bladder is in a closed system, meaning
>> no hose open to the water, to have an expansion point (the bladder) for any
>> increased oil volume due to heat whether it be motor operation or just
>> sitting in the sun while out of the water.
>>
>> Jon
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>>
>
>
> --
> Vennlig hilsen
> Øystein Skarholm
> 91369599
>
> <Compensator.jpeg>
>
> <SDI ROV.jpg>
>
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-- 
Vennlig hilsen
Øystein Skarholm
91369599
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