[PSUBS-MAILIST] Dive report: Snoopy at Seneca

[Alec Smyth via Personal_Submersibles]

Wow. If there is no mistake that is really counter intuitive, because the
hose feels super pliable in your fingers - almost like those yellowish
rubber lab hoses if you know what I mean. The size I'm using is half the
wall thickness of what you calculated with, if that makes a difference.
It's 1/4" ID X 3/8" OD X 1/16" thickness.

Alec

On Tue, Jun 9, 2015 at 6:46 PM, Alan James via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Alec,
> I had a look at the specs on that link. Thanks.
> The 3/8" ID x 5/8" OD X 1/8" tube is rated for 40psi internal pressure.
> As this is for fuel there could be a safety margin of 4x, so 160 psi burst
> pressure.
> I ran a couple of plastics I have in my pressure program through internal
> and then
> external pressure, & the maximum external pressure was 2/3rds the internal
> in both cases.
> This could mean that it would take 106 psi before the hose would equalize
> significantly.
> The diameter would maybe shrink a bit before collapsing.
> Cheers Alan
>
>
>   ------------------------------
>  *From:* Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org>
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Sent:* Wednesday, June 10, 2015 10:11 AM
>
> *Subject:* Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>
> The stuff I'm using is really flexible, and has a wall thickness of only
> 1/16". I'm having trouble imagining that the seal could offer less
> resistance than this, it's very soft. See McMaster item #5552K25.
>
> Best,
>
> Alec
>
> On Tue, Jun 9, 2015 at 5:29 PM, Alan James via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
>
> Does anyone (Sean) have the material specifications in their
> pressure programs for the soft pvc that we would be using in
> our flexible compensation hoses?
> The nearest I had was nylon, & that had a crush depth of 8,000ft
> for a 1 meter long tube, 10mm diameter & 2mm wall thickness.
> I was thinking of using oil filled light housings with the wiring
> running through flexible hose as compensation, but are having second
> thoughts.
> Alan
>
>   ------------------------------
>  *From:* Sean T. Stevenson via Personal_Submersibles <
> personal_submersibles at psubs.org>
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Sent:* Wednesday, June 10, 2015 6:11 AM
> *Subject:* Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>
> I have always been a fan of oil compensation at higher than ambient
> pressure, for a variety of reasons. The only real downside is the
> environmental impact of potentially losing oil to the surrounding water in
> the event of a leak, but that impact can be mitigated with oil selection.
> Positive pressure allows you to compensate for volumetric changes in your
> compensated volumes due to the exterior pressure, as well as for thermal
> expansion of the oil, and if you have any leakage at all, you leak oil out,
> rather than water in, which can be an expensive lesson. Additionally, if
> you provide the bias with something like a spring loaded cylinder or
> elastomeric bladder, you can instrument its displacement for accurate
> monitoring of demanded compensation volume, and potentially detect leaks
> well in advance of when they actually become a problem.  Ambient-only
> compensation has the disadvantage of not compensating for boundary-layer
> viscosity effects on rotating shafts,! density differences (gravity induced
> exchange and/or centripetally accelerated fluid) and other small but
> cumulative effects that can contribute to water ingress.
>
>
>
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