I once watched an "impossible" pumping operation on a tanker. > > The deck gang was cleaning tanks and were pumping the last bits of water > from the bottom of the 50' deep tanks. They used air operated diaphragm > pumps sitting on deck with the water spewing from the pumps and running > across the deck and overboard. > > >From what I understood of physics what was happening was impossible. One > cannot suck water from any deeper than about 30' since one makes a vacuum > with the pump and air pressure (about 15psi) pushes the water (about a half > a pound per foot) column up. If the column is heavier than 15psi it won't > go up. > > Turns out that the bottom end of the suction hose had a section of pipe on > it with a small hole drilled in the pipe above the water level. This > allowed air in to form bubbles and make the water lighter allowing the > water/air mixture to be sucked up to the deck. I regret not remembering > what size the drilled hole was. >
Speculating the air injection should be high at the start and zero after the suction hose is fully primed. A tube strapped to the suction hose might allow the priming and then it could be plugged. One could even push compressed air into the tube to super aerate the fluid and maximize the height. This should be convenient since the pump is air operated. Alternately a big check valve at the bottom might allow the suction hose to be primed with water from top? I remember the P250 centrifigual pumps required an air tight suction hose to operate at full capacity without sucking air. That brings the question; "air operated diaphragm pump"? I understand using air or water to drive the pump in a flammable environment but why use a diaphragm pump for a high capacity application? Maybe it wasn't "high" capacity? Just curious. Cheers. > From: [email protected] > To: [email protected] > Date: Fri, 21 Jan 2011 13:25:54 -0500 > Subject: Re: [Liveaboard] Thanks Bob, Ben, and Norm > > > There was (at one time at least) a method of coating big ship tanks called > Flote Cote. > > The tank would be filled with water, paint poured on top of the water, then > the water slowly pumped out of the tank. The paint would cling to the > steel as the water level descended. > > I have no idea how well it worked. > > > > I once watched an "impossible" pumping operation on a tanker. > > The deck gang was cleaning tanks and were pumping the last bits of water > from the bottom of the 50' deep tanks. They used air operated diaphragm > pumps sitting on deck with the water spewing from the pumps and running > across the deck and overboard. > > >From what I understood of physics what was happening was impossible. One > cannot suck water from any deeper than about 30' since one makes a vacuum > with the pump and air pressure (about 15psi) pushes the water (about a half > a pound per foot) column up. If the column is heavier than 15psi it won't > go up. > > Turns out that the bottom end of the suction hose had a section of pipe on > it with a small hole drilled in the pipe above the water level. This > allowed air in to form bubbles and make the water lighter allowing the > water/air mixture to be sucked up to the deck. I regret not remembering > what size the drilled hole was. > > > > Norm > S/V Bandersnatch > Lying Julington Creek FL > N30 07.68 W081 38.47 > > > > > Actually, I did the reverse of the usual method: fed a wire down the > > pipe, attached a rag to it at the top, and pulled it down a bit; then, > > while having a helper slowly pull it, I poured a whole lot of paint down > > after it (that way, I had a tall "stack" of liquid paint following the > > rag - and it wasn't being wiped off.) When the rag got to the bottom, I > > climbed down, stuck the paint bucket under the pipe, pulled out the rag, > > and caught (most of) the paint. Then we repeated the drill a couple of > > hours later, and again later still. Messy, but certainly better than the > > usual. > > > > _______________________________________________ > Liveaboard mailing list > [email protected] > To adjust your membership settings over the web > http://liveaboardonline.com/mailman/listinfo/liveaboard > To subscribe send an email to [email protected] > > To unsubscribe send an email to [email protected] > The archives are at http://www.liveaboardonline.com/pipermail/liveaboard/ > > To search the archives > http://www.mail-archive.com/[email protected] > > The Mailman Users Guide can be found here > http://www.gnu.org/software/mailman/mailman-member/index.html
_______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://liveaboardonline.com/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardonline.com/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
