Re: [PSUBS-MAILIST] Altimeters as leak indicators

In a message dated 3/28/2012 2:11:35 P.M. Central Daylight Time, hc.fulton@gmail.com writes:

From what I remember Phil’s DW had a gauge that at 2 psi suction went clockwise. I think that he may do the same?? When I came up with the idea I thought “I think I have seen this somewhere before” Til then I was playing around with DP gauges and all sorts of complications. Also I did not want to go for an option of a used gauge such as an altimeter. However that is a great option. Hugh

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of James Frankland
Sent: Wednesday, 28 March 2012 11:20 p.m.
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Altimeters as leak indicators

Hi All,

Thanks for the tips in this thread. I like Hughs idea of reversing the gauge and using the small reference bottle. I think this idea has just saved my "sewage cart" gauge. I'll just use it like this and it will just read in reverse. Its already zero'd in the middle. Lots of options now.

I do have an overpressure valve as well.

Kind Regards

James

On 28 March 2012 02:50, Smyth, Alec <Alec.Smyth@compuware.com> wrote:

Hi Jim,

You are recalling a thread in which I tested Snoopy’s life support on land with the help of Jon’s O2/Co2/cabin pressure meter. My life support is elementary but I found the pressure to be surprisingly stable – so much so that I didn’t need to adjust the flow once in a test that I think ran about half an hour. I’m sure in the archives there are good posts by Cliff Redus, who has taken a PLC based approach that adds O2 based on cabin pressure sensing. And then of course there’s Phil’s invaluable life support paper on the website. That’s a must read.

Thanks,

Alec

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of JimToddPsub@aol.com
Sent: Tuesday, March 27, 2012 5:27 PM

To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Altimeters as leak indicators

Very good point, Alec. If you didn't have an overpressure valve, at least the altimeter would let you know you were about to get your butt kicked when you got to the surface!

I had thought that once I closed the hatch, pulled -2.5 psi (+5,000 feet on the altimeter), and verified no leakage, I would then bleed the air back in s-l-o-w-l-y, close all valves in order to return to 1atm, and dive. However I'm now wondering if it would be better to retain slight negative pressure (maybe one lb) for submerging. Would that complicate any of the equipment such as the O2 system?

What are the thoughts of all you experienced guys? What have I not considered?

Thanks,

Jim

In a message dated 3/27/2012 3:43:19 P.M. Central Daylight Time, Alec.Smyth@compuware.com writes:

Just an aside related to this thread… remember Kittredge’s one accident as described in his memoir? He had a slow air leak into the cabin during the dive, and upon surfacing blew out the K-250 hatch dome and found himself outside the sub having been blown out of the opening. That story was the original reason I installed two things in Snoopy, an altimeter and an overpressure valve. I would point out the two go together.

Alec

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From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jon Wallace
Sent: Tuesday, March 27, 2012 4:06 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Altimeters as leak indicators

Probably somewhere around 2-3psi I would think. Not sure about the rest of you but I have to start clearing my ears at around 6-8 feet of water pressure. If you need to clear your ears in a 1ATM during operations, that indicates a problem of some kind which should send you to the surface. The two main issues I can think of that you want to avoid is an internal pressure/dive duration that ends up requiring decompression; a high enough pressure level that introduces O2 toxicity. Both of those situations would be difficult to get to without the pilot knowing something was wrong since even without any gas monitoring you'd be clearing your ears plenty of times. Unless you are drawing a vacuum as part of the pre-dive systems check (like DW-2000 does) there should be no clearing of ears unless there's a problem maintaining 1ATM within the cabin.

Jon

On 3/27/2012 1:35 PM, JimToddPsub@aol.com wrote:

I think I'll add an onboard checklist for possible causes if the alarm goes off. This brings up the question: What level of cabin pressure increase should activate the alarm?

I'd like to hear some answers on that one.

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