From: Alan James <alanjames@xtra.co.nz>
Sent: Jan 18, 2011 8:25 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Pressure testing with a vacuum pump
Hi Jim,
I was more concerned with structural integrity than air leaks with my posting.
I'm building a small sub out of fiberglass / epoxy & will be needing to thoroughly
test it.
From what I gather you can't pull more than an absolute vacuum because there's
no air for your pump to push out.
I'm wondering if you filled your hull up with water whether a high pressure water pump
could create a negative pressure in the hull. Or am I barking up the same tree.
Alan
----- Original Message -----
From: JimToddPsub@aol.com
To: personal_submersibles@psubs.org
Sent: Wednesday, January 19, 2011 4:04 PM
Subject: Re: [PSUBS-MAILIST] Pressure testing with a vacuum pump
Alan,
Still you can take it down to about 30 feet without ever leaving your shop. If it doesn't leak air at that pressure
differential
that's good. If it does leak, you've only got air (or a leak detector) instead of dirty water or salt water into the defect.
So this begs two questions:
1. What's the best product and/or procedure for locating a small leak flowing from the outside of a vessel to the inside?
2. Would it be better to try to seal the hatch and pressurize the vessel on the inside to detect air leaking to the outside?
That's putting the higher pressure on the "wrong" side of the hatch/canopy.
Jim T
In a message dated 1/18/2011 8:20:05 P.M. Central Standard Time, alanjames@xtra.co.nz writes:
Thanks everyone for clearing that up,
I was thinking that if you had a pump that could produce 250 psi & it's sucking
from somewhere, that you could attach it's intake to a hull & produce a negative
250 psi pressure. Have done a bit of "Googling" with your direction & have sought
of got my head round it.
Darn! it seemed a lot easier option than dropping my hull down a deep lake on a long rope.
Regards Alan
----- Original Message -----
From: "Jens Laland" <laland@artematrix.org>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, January 19, 2011 1:19 PM
Subject: Re: [PSUBS-MAILIST] Pressure testing with a vacuum pump
> This one I find quite useful with regards to measuring vacuum, ref
>
> http://traktoria.org/files/instrumentation/vacuum/Pressure_Conversion_Table1.pdf
>
> Best regards,
> Jens Laland
>
>
>
>
>
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