|
After Cliff's post I thought I had it all figured out. Then Carsten is trying to confuse me. ;} Some have said I live in a vacuum, and that would make since, since the brain can't fire on all cylinders in a vacuum. So 50 millibar is close to a complete vacuum, but if you use 1000 millibars as sea level, then pulling a light under pressure down 50 millibars would come to 950 millibars. Simulating the subs pressure hull being 2 feet below sea level. Pulling a 0 millibars vacuum in a sub, simulates the external water pressure at close to 34 ft /10 m depth in freshwater. I remember a tour guide for the diesel sub with the designation USS Blueback, that is a museum in Portland, Oregon, tell me that when they were snorkeling, that if a wave shut off the snorkel valve, that the twin diesels would quickly suck a lot of air out of the subs hull, and every one on board would feel it. I was thinking that a small bicycle air pump used inside ones sub, could pull a partial vacuum as well. If one takes into account of all the internal components of a particular sub, would you guys think it would be a worth while test to pull a hard vacuum in the subs hull after light vacuum testing was completed successfully for a new sub, and/or newly refitted sub? Regards, Szybowski > Subject: Re: [PSUBS-MAILIST] Vacum test > From: MerlinSub@t-online.de > To: personal_submersibles@psubs.org > Date: Mon, 1 Jun 2009 21:50:00 +0000 > > 870- 1090 mbar is the min - max atmosphere pressure count on sealevel. > > The former Spurdog owner told me that he surface that boat that way that he > start the dieselmotor underwater and press the diesel exhaust fumes to the dive tanks. > And if he can not here any voice or sound anymore in the interior the boat surface normaly.. > > But he old me that he was very carefully with the presure compensating ballvale on the hatch > of this 60ts monster after surfacing and before he can open the hatch - > otherwhise it will may damage his ears.. > > Its maybe also a good choise to kill a fire inside the sub.. > just start the diesel or the air compressor and evacuate the interior.. smile.. > > vbr Carsten ----------------------------------------------------------------------- --------------------------------------------------------------------------------- > > > "Cliff Redus" <cliffordredus@sbcglobal.net> schrieb: > > Brent when I did my shop testing with a vacuum pump, I would pull the boat down from 1 atm (14.7 psia or 1015 mbar) down to 12.7 psia ( 875 mbar) while I was in the boat. It was not uncomfortable. Was easy then to squirt some soapy water onto all my through hulls to check for leaks. You wouldn't want to pull a hard vacuum. As a comparison, Mount Everest has an elevation of about 29,000 ft the barametirc pressure is about 300 mbar. > > > > Cliff > > > > > > > > > > Cliff Redus > > Redus Engineering > > USA Office: 830-663-6445 > > USA mobile: 830-931-1280 > > cliffordredus@sbcglobal.com > > > > > > > > > > ________________________________ > > From: Brent Hartwig <brenthartwig@hotmail.com> > > To: PSUBSorg <personal_submersibles@psubs.org> > > Sent: Monday, June 1, 2009 2:07:58 PM > > Subject: RE: [PSUBS-MAILIST] Vacum test > > > > > > > > Thanks Much Carsten, > > > > I see says the blind man as he spits into the wind, it's all coming back to me now. > > > > I thought you meant you were using a aqua lung instead of your own lungs. ;} > > > > I had to check to see if 50 millibars was almost a complete vacuum, or only a slight vacuum, since I'm used to using inches of mercury. > > > > I was talking with a composite fabricator last week, and he was telling me how some folks will use a shop vac to pull the bulk of the air out of a vacuum bagging project, then close the valve for the bag, then turn off the shop vac. Then turn on the vacuum pump, since many of the smaller vacuum pumps are slow to pull the bulk of the air out of a larger space. I can see how this would be useful when vacuum testing a sub unmanned down as far as your vacuum pump would go, after any major changes to items connected to a subs thru hulls. > > > > The other thing that comes to mind is, that all other items in the subs interior need to be able to withstand the amount of vacuum you plan to pull. > > > > Regards, > > Szybowski > > > > > > > > > > > Subject: RE: [PSUBS-MAILIST] Vacum test > > > From: MerlinSub@t-online.de > > > To: personal_submersibles@psubs.org > > > Date: Sun, 31 May 2009 22:54:00 +0000 > > > > > > You need just some millibars underpressure and a barometer. > > > > > > No need for a big vaccum. > > > > > > If the underpressure stays for a minute or so - the boat is tight. > > > > > > If you take to much underpressure you may seal the leaks in the o-rings/hatches configuration etc. > > > > > > Subs are untight normaly only on or near the surface.. Deeper the waterpressure tight everything if proper construction.. > > > > > > The lung is a wounderful very fine vaccum pump.. Cost nothing and waste no space. > > > Just breath out to a snorckel pipe conect to a ballvale - close it before you end - and do it 3-4 times this way. > > > > > > vbr Carsten > > > > > > > > > > > > "Brent Hartwig" <brenthartwig@hotmail.com> schrieb: > > > > > > > > > > > > > > > > Cliff and Carsten, > > > > > > > > Did you use a vacuum pump or shop vac to pull the partial vacuum? Isn't it hard to draw air into your lungs from SCUBA when the vacuum is trying to suck it out of your mouth? I had planned to do a unmanned test using a vacuum pump to do some basic low pressure leak testing on my sub before taking it for actual water testing. Just let the pump go down as far as it can, then turn off the valve and see if the partial vacuum holds. For infusion molding applications they some times use ultrasonic leak detectors and stethoscopes for detecting leaks on the out side of the mold plug layup. Like seen here at Fibre Glast. > > > > > > > > http://www.fibreglast.com/showproducts-category-Vacuum%20Infusion-20.html > > > > > > > > > > > > We used a chalk duster when testing the seal of large concrete CA apple cold storage rooms. > > > > > > > > I've seen a couple of subs that didn't do a vacuum test at the shop before they went and put the subs in the water for there first water test, such as the Alicia sub, and if they had, they would of saved a fair bit of time. Not to mention all the people that came to see the sub do it's first test dive laughing at you for being wet behind the ears. ;} > > > > > > > > I've been using a vacuum on my sub a lot lately. Shop vacing all the rust, paint and copper slag out after blasting that is. > > > > > > > > > > > > Regards, > > > > Szybowski > > > > > > > > > > > > > > > > > > > > > Subject: Re: [PSUBS-MAILIST] Vacum test > > > > > From: MerlinSub@t-online.de > > > > > To: personal_submersibles@psubs.org > > > > > Date: Mon, 25 May 2009 21:01:00 +0000 > > > > > > > > > > I use my lungs, a ballvalve and a snorckel to evacuate the internal of > > > > > Sgt.Peppers some 50 milibars to check for leak as predive procedure. > > > > > > > > > > vbr Carsten > > > > > > > > > > > > > > > > > > > > > > > > I pulled a partial vacuum on my boat to look for leaks. I actually had > > > > someone working the vacuum pump and I climbed in the boat with a bottle > > > > of soapy water which I squirted at each fitting. While this works to > > > > look for leaks, it is not a good test of the structural integrity of > > > > the boat as the max depth you can simulated is 34 ft (10m) of fresh > > > > water. > > > > > > > > Cliff > > > > > > > > > > > > > > > > > > > "glen brown" <glenbrown@vodamail.co.za> schrieb: > > > > > > Hi > > > > > > Can anyone be so kind to tell me if any one has used vacum to test there sub > > > > > > for leaks and the integrity of there hull when i used to dive for diamonds > > > > > > on the west coast of south africa we used to prime our gravel pipes and > > > > > > pumps with vacum either using a venturi ,milkmachine, car airconditioner > > > > > > motor ect I remember one day we had nothing to use so i decided to use a > > > > > > 300hp tractor engine making an adapter to the air intakeof the engine and > > > > > > using a 44gal drum as a safety resivoir to protect the engine from water i > > > > > > clearly remember how the drum was crushed by the pressure differance any > > > > > > coments. > > > > > > All the best > > > > > > Glen S.A > > > > > > |