<div dir="ltr">Oh! Well I suppose it just depends on the volume the valve can handle. This is an interesting calculation, which I have not done but should. In general, these valves should handle pretty huge flow rates. But you're right, its basic to surface very slowly when there's any over-pressure - normally we dive with under-pressure. For a K-boat sized hatch, an over-pressure of 1/4 psi translates to a force of 95lbs trying to pull the dome out of the hatch ring. I know Snoopy's dome stays put at 1/4 psi, but I wouldn't take it any further than that just in case. <div><br></div><div>BTW, on the subject of calculations and changing topics back to the recent thruster compensation thread, you were right about the temperature change. The volume I had to compensate was a combination of thermal contraction and air bubble. The air bubble was of unknown size, but I ran the numbers on the thermal contraction alone and it is enough to cause the problem. The little hose only has a an internal volume of 10ml. The thermal contraction of the oil turned out to be 16ml - add to that the volume of the unknown bubble, and you can see the hose was inadequate even if it squashed to zero internal volume. I am now installing bellows bottles in place of the little hoses, with a capacity of 60ml. And a better filling method that should eliminate the bubble. You'd think I wasn't an engineer, assuming the effect of thermal contraction to be negligible. Its easy to focus the calculations on big items like hull strength or stability and make assumptions about the little stuff.</div><div><br></div><div>Best,</div><div><br>Alec</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jun 19, 2015 at 4:19 PM, hank pronk via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
You have to be experienced to surface slowly and hover while the valve leaks out the air.--------------------------------------------<br>
<span class="">On Fri, 6/19/15, Alec Smyth via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br>
<br>
Subject: Re: [PSUBS-MAILIST] over pressure valve<br>
To: "Personal Submersibles General Discussion" <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
</span> Received: Friday, June 19, 2015, 4:16 PM<br>
<div class="HOEnZb"><div class="h5"><br>
I<br>
don't get the "in the hands" part... its<br>
completely automatic.<br>
On Fri, Jun 19, 2015 at<br>
4:09 PM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
wrote:<br>
<br>
<br>
Agreed,<br>
<br>
In the hands of an experienced submarine operator an over<br>
pressure valve is safe, providing it is large enough. I<br>
have not seen an example of a large enough OPV. A simple<br>
valve in the hatch will do the same job, just need an<br>
umbrella :-)<br>
<br>
The noise of a compressor is a welcome sound if it means<br>
keeping the dome on the sub :-)<br>
<br>
Hank--------------------------------------------<br>
<br>
On Fri, 6/19/15, Carsten Standfuß" via<br>
Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
wrote:<br>
<br>
<br>
<br>
Subject: Re: [PSUBS-MAILIST] over pressure valve<br>
<br>
To: "Personal Submersibles General Discussion"<br>
<<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
Received: Friday, June 19, 2015, 2:47 PM<br>
<br>
<br>
<br>
But a overpressure vale works<br>
<br>
full auto. A compressor<br>
<br>
not. <br>
<br>
<br>
<br>
A OPV needs<br>
<br>
no energy - but a compressor did.<br>
<br>
<br>
<br>
<br>
<br>
A OPV needs no room - but<br>
<br>
a compressor did.<br>
<br>
<br>
<br>
And a<br>
<br>
compressor is<br>
<br>
a noisy solution..<br>
<br>
<br>
<br>
vbr<br>
<br>
Carsten<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
"hank<br>
<br>
pronk via Personal_Submersibles" <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
schrieb:<br>
<br>
> Personally I think an onboard<br>
<br>
compressor is a much safer option than an over pressure<br>
<br>
valve. There are multiple safety benefits to an<br>
onboard<br>
<br>
compressor, over pressure being the biggy. With a<br>
<br>
compressor you can get rid of the pressure without<br>
surfacing<br>
<br>
and trying to control a perfect ascent. With the OPV<br>
you<br>
<br>
have to surface a bit and let air out and wait then<br>
surface<br>
<br>
more and wait and so on. You can't just surface and<br>
hope<br>
<br>
the valve keeps up with the demand. This is more<br>
important<br>
<br>
for subs with large domes.<br>
<br>
> The next<br>
<br>
benefit to a compressor is, if you lost all your air,<br>
you<br>
<br>
surface by dropping your weight. In my case the weight<br>
is<br>
<br>
small and I would also drop the thruster and tail<br>
assembly.<br>
<br>
Still, not much sub out of the water. With the<br>
compressor,<br>
<br>
I can open my vent valve in the hatch and use the<br>
compressor<br>
<br>
to fill the ballast tanks.<br>
<br>
> Hank<br>
<br>
><br>
<br>
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