Scuba Tech Tips: Hydrostatic Testing A Scuba Tank - S10E17

[Music] hi guys Alec Pierce tech tips and today we're going to do what we've been promising for some time and that is watch a hydro test now we've talked quite a bit about visual tests and other things you have to do thanks but the hydro test in many people's mind anyway is the real test there's some debate on that but anyway those exactly that make a hydro test has to be done every five years and every scuba tank that's the law very simple now let me explain once again and we've touched on this in previous video and previous episodes not the hydro test is a test of the metal specifically of the elasticity and I've explained and like I demonstrated one time that when you have your good old scuba tank empty you take to the doctor and they fill that skipper tank it stretches a little bit yeah a measure ibly if you put a tape around it before and after you choose bigger and then when you let the air out it shrinks down a little bit so that constant stretching or shrinking constant stretching and stretching and strength and shrinking it will actually cause the metal to crystallize over time many many many times scuba tanks are tested for hundreds of thousands of fills but anyway and that's what the hydro test does it tests the mettle so in a hydro test essentially just to describe quickly what happens your hydro test operator takes your favorite scuba tank and fills it to 5,000 psi that's right stretches a whole lot and then he lets the pressure off it shrinks back down but because the pressure was much higher than normal it doesn't always shrink right back to its original size there's a little bit of permanent stretch permanent expansion as where it's called and the hydro tester operator will then compare that permanent expansion which he can measure to what it indicates in the government regulations as to what's allowed for that type of cylinder and there's the permanent expansion falls within the limits your tank is fine if for some reason the metal has gone bad crystallizer has some other problem it may not go back to that size that proper size and we'll fail the hydro test it doesn't happen very often most tanks feel visual examination it's not hydro test but anyway there's a brief idea you've seen me do this before I've talked about it before let's watch what happens so we have Chris from Simcoe diving it's right around here somewhere and he's going to come out just a minute and he's going to start filling a scuba tank and I'll explain step-by-step what's going on oh here he is right here okay Chris so we're gonna fill up your scuba tank first so again is this a scuba tank that we're not going to test here and they just filled it up with water and he has a special adapter it goes into that tank oh yeah this is spilling out there so the scuba tank has to be completely filled with water one of the things that many divers will last is what happens if the tank fails during the test well you know what to be perfect Frank nothing nothing else you may not even know that it failed and the reason is that the scuba tank is completely filled with water there's no air spaces and the test chamber this big jacket here is called a jacket it's completely filled with the water so there's nothing to expend if it can't expand it can't explode no expansion no explosion so here we go now he's gonna [Applause] pick the scuba tank up like that I put it down inside the Hydra test chamber oh you see I told you it's full of water too so right down in there see the big old wing there's a big oil ring around that that goes down firmly in place and then we clamp it tightly in place so it can't get out of there you could build one of these you know you had some sheet metal around you know you're good for with with a bit of soldering just like that just that simple now this is all stabilized right the water's all the same temperature everything's all sitting there just properly that's why in this particular case Chris of course is a government licensed hydro test operator and the water in the tank and then the jacket has to be the same room temperature has to be the same and stable he actually has a big a big tank upstairs full of water that stays at room temperature all the time because the water comes from the water main is this too cold and he have to wait for it to wait how are we doing good good so we're we're ready to squeeze some of the air out of this tank by pressurizing it we've got our measuring scale here so this measures are displaced water okay you see what are you talking about with this space water the scuba tank is inside the hydro test chamber when he pressure rises the scuba tank I see you this Kevin and he starts to pressurize the scuba tank here regard eyes the pressure and the scuba tank is starting to climb 1,000 and so on I see it pressurizes the scuba tank the scuba tank expands it starts to grow well does the scuba tank starts to grow the water that's in the hydro test chamber has to go somewhere it comes out and it goes into here and Chris is weighing that water so he knows exactly how much water has been displaced 2,000 3,000 this is a steel tank a short 3750 you see test pressure yeah actually on this one it's going to be just over 4,000 boys at 2,400 2,400 huh I knew that 22 50s were always 3750 I remember that from the old days yeah so it's we test it to one point six seven times it's working pressure right which brings it to just over 4,000 psi okay so this is our first cycle toilet this is basically to stretch the tank a little bit and just to get a little bit of the air out right ah we hold it for 30 seconds and then I'll release the pressure so this one was gonna be our this is the test we had a little ink oh we've had a little stretch you might say huh just like doing exercises or stretch versus cylinder up oh yeah this is the real test guys here we go mr. Haskell booster user under booster yep now that boosters capable of testing pressures up to 10,000 psi and you see you can see everything happening the pressure gauge is going up and and the water that's being displaced from the hydro test chamber is going into here so that Chris can delay it and know exactly how much water was displaced otherwise kind of boring actually yeah you got a good book I can look at you should have a video in here with a leaf your tech tips on right all right here we go now we're getting serious 3000 both 4000 psi you say yeah that's what you want okay oh boy your tank is stretched now so we're gonna hold that pressure for 30 seconds and this will drop slightly over 30 seconds what no it shouldn't yeah it shouldn't drop too much if it's holding pressure and you have we have a good seal in the system yeah so at the moment it's displacing seventy six point six cc's of water right which represents the read the number re which is the rejection right I say nanchang let me put that into English the scuba tank is expanded with 4000 psi in it and has pushed water out of the hydro test jacket Chris has trapped the water that water that has pushed out and now he can measure that water so he knows exactly how much water was pushed out now pressure gauges going back down he held it there for 30 seconds going back down and now that water that was pushed up withdrawn back in that's drawn back in sucked back in so now we take a look down here and we can see how much water is left in here not all of it got sucked back in because your tanks a little bit bigger than it used to be yeah how much is left over so we have a 0.8 C C's 0.8 CC so not quite one CC so their tank may I my right here the tank now it's basically a cubic centimeter bigger than it was so we have to use a formula to calculate that it's within specs yeah the permanent expansion which is this number here the 0.8 can't represent more than 10% with this particular cylinder which oh my gosh oh yeah yeah what not even one CC yeah so if if somebody came in with an 80 cubic foot tank when they leave did they have like an 80 point one cubic foot tank is that right can they keep doing that can they keep doing that until I have a nice maybe maybe for some people in their minds yeah yeah yeah so so we using a formula we calculate the permanent expansion in terms of a percentage which can't be more than 10% with this particular cylinder so just let me calculate that so the permanent expansion on this particular tank is 1.04 percent one point zero four and up to 10 percent is permissible only flaw so thanks good and that didn't look like a new tank at all no this is a quite a fight an old soldier steel cylinder a PS PS yep pressured stress steel well that's it this is just like a good car dealership after you get your tank service they wash it that's so simple ideas now this particular setup is very sophisticated there's modern and it's all electronic Chris is very very good at doing his job so it makes it look quick and simple I've seen a lot of old systems where they used the glass tubes and they and the barrettes and so on took a lot longer probably just as good a job but that was very simple there you go hydro testing real simple it's somewhere around you a dive store or a hydro test station it will allow you to watch it's kind of fun to watch just as we've not here but sometimes it's hard to arrange so I thought we'd do this for you how a hydro test is done now you'll know next time you go in Ali appears tech gets catch you soon bye-bye

Channel: Alec Peirce Scuba

Views: 6,309

Rating: 4.9835391 out of 5

Keywords: alec, peirce, pierce, scuba, tech, tips, tip, underwater, dive, diving, vintage, sea, hunt, remembered, skin, salt, water, fresh, At, The, Ranch, service, professional, fun, safe, safety, gear, air, hydro, static, test, steel, aluminum, hydrostatic, testing, vis, visual, interval, elasticity, crystallize, expansion, simcoe, chris, transport, canada, facility, displacement, scale, displaced, 1.67, working, pressure, cycle, rejection, equivalent, ree, Chris, Sproule

Id: lVYeFPhX1OE

Length: 11min 57sec (717 seconds)

Published: Thu Mar 05 2020