We use a small shop vac or a battery operated car vac. The over-pressure
relief valve is located externally and has smooth barrel/cylinder casing over it
- the vac hose end has a machined plastic nozzle with an internal o ring groove
and o ring. The vac is slipped onto the pressure relief valve and a light vacuum
quickly sucked - the tech watches the cabin pressure guage through the dome and
the pilot watches it also. At a couple of pounds neg, the vac is stopped
and the gauge watched to make sure it stays steady with no leakage. The nozzle
is easily pulled off and the sub is ready to launch. Prior to pulling the
vacuum, the bellows on the O2 system is backed off so that the neg pressure
doesn't cause the O2 make-up system to function and add oxygen.
Phil
----- Original Message -----
Sent: Tuesday, January 04, 2011 8:14
PM
Subject: Re: [PSUBS-MAILIST] Pre-dive
Vacuum
Phil & Dean,
This is intriguing. What pressure differential do
you pump it to? Do you use the over-pressure relief or another
port? What's the whole procedure?
Best regards,
Jim
Hi
Dean, have you piped the intake to the tyre inflator to use it as a
vacuum pump from the outside of the sub. Or do you sit inside & pump
air out from there. Regards Alan
From: "Recon1st@aol.com"
<Recon1st@aol.com> To:
personal_submersibles@psubs.org Sent: Wed, 5 January, 2011 3:46:33
AM Subject: Re:
[PSUBS-MAILIST] Pre-dive Vacuum
Jim on my sub I installed a small air
pump I made from these small 12v
auto tire inflator.
It works very well.
Dean
In a message dated 1/2/2011 6:14:19 P.M. Central Standard Time,
JimToddPsub@aol.com writes:
Phil,
That's certainly worth putting on a pre-dive
checklist. It will definitely go on mine. How do you go about
it?
Thanks,
Jim
In a message dated 1/2/2011 1:51:25 P.M. Central Standard Time,
phil@philnuytten.com writes:
We never dive any of our subs unless they've held vacuum for
several minutes immediately prior to launch - this procedure tests and
'sets' the o rings and avoids a nasty surprise at the end of a large
air-gap launch!
Phil
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