Pressure Testing a Boiler Core | Model boiler build, part 9!

this is a perfectly normal thing to be doing on a friday night right right hello internet my name is quinn this is blondie axe i'm back on the fire2 boiler project and i built the core last time and now i want to see if i can pressure test it in isolation before i build it into the final boiler because it's going to be a lot easier to fix any leaks right now so let's go here's where i am right now on this model boiler project you can see i built the core the fire tubes in the two plates and this assembly slides into the shell now before i solder it in there i want to try and figure out if the joints are any good on those tubes because as i learned previously it's nearly impossible to fix them once the boiler is fully assembled real quick since i know not everybody watches every video hydrostatic testing is how you test a pressure vessel safely you pump it full of water and pressurize the water because water doesn't compress and store energy like a gas does so it won't explode if the structure fails before i do the actual hydrostatic pressure test i want to actually test my pump because one thing i noticed when pressure testing my last boiler is that this pump actually has some bleed down in it so i made a blanking plug for the end of the hose here and i'm going to just pressurize the hose and the pump itself with that sealed up i pumped it up to 120 psi and then close the valve and just watch it and see in principle the pump should be able to hold 120 psi essentially indefinitely but it does in fact bleed down very slowly i tried snugging up some of the connections but it does indeed bleed down a little bit and it's not any of my fittings or adapters here there's no moisture on that anywhere so it might be the o-rings inside the pump who knows but it's good to just kind of calibrate what the bleed down of your pump is and then if i get this amount of bleed down on my boiler then i know it's probably not the boiler's fault here's the boiler core that you saw me make in the previous video in this series so the question is can i pressure test this in isolation now my first idea was if there's some way to enclose the core much like the shell would in a way that's easy to do then that would be worth doing now i tried to like buy a piece of steel pipe or something that had the exact right id to go around this core and i couldn't find anything even close that was going to work i could of course use the shell itself but that's very expensive and i'd have to make a new custom piece just to fit the core in the way that i need to to seal the ends so i needed something more like temporary and quick and dirty so the next idea i had was you can buy this high pressure silicone tubing it's used for plumbing turbochargers in cars and it's actually quite good stuff if you get the good stuff be careful because there's a lot of knock offs of this stuff the good stuff is rated to 250 psi the cheap stuff is as low as 40 so make sure you're getting the good stuff but my thought was the four inch diameter might be perfect to wrap around my core and it comes with these nice fully sealing hose clamps and this stuff comes in four inch diameter which i knew was going to be a little too big for the core as you can see but my hope was that maybe it would squish down once i put the clamp on it you know this kit with the hose and the clamps was 15 so for that i figured what the heck i'll give it a try because if it works it's a super easy solution to my problem of pressure testing this core so i tighten the clamp down but as you can see when i got close to the end here it was clear that this was not going to work the tube is buckling there and it's just not going to fit so it was worth a try but on to plan b the next idea actually came from one of my patrons tanda madison you should follow her on instagram because she's awesome she suggested pressure testing this thing inside out just cap the ends and pressure test the inside because the ends are much easier to cap so my first thought was okay let's use an o-ring for this there's a problem with that though and that's these stud holes you can see they're very close to the tops of the flanges by design to try and keep them out of the pressure vessel but that's going to make them difficult to seal with an o-ring an o-ring needs a land which would be probably trapanned into the end plate but then it has to seat down and it's going to be half covering those bolt holes or i have to try and fit some kind of o-ring inside the rim and i also couldn't find an o-ring the right size so it just really wasn't going to work so i think i need to use some kind of flat gasket instead first step is to make some end plates so i have this previously gigantic then large then medium now soon to be small slug of aluminum that you may recognize from many recent projects and i'm going to make a couple of four inch diameter end plates to go on the ends of this core so i need to turn down a fair bit of this diameter and as i've recently learned a good way to do this on a small lathe is to take a very deep depth of cut but a very very fine feed like much finer than your lowest power feed setting so i'm feeding by hand and basically just keeping light pressure on the tool and it makes these very wide very thin chips that are easy to control and that way you don't get giant birds nests that you're constantly having to fish out of the tool but your feed rate has to be just perfect or it does pile up on itself and you have to clear it out while i'm making chips here let me explain one possible catch with pressure testing the core inside out the fire tubes in a fire tube boiler are specifically thinner than they might otherwise need to be and that's because the pressure is on the outsides of the tubes and you can get away with that because of course the outside of a tube is much stronger than the inside think about like an eggshell mom can sit on the egg doesn't break because it's very strong but the chick can still break out from the inside because from the inside an arch shape is very weak or like an arched bridge for example they're very strong from above very weak from below so boilers tend to take advantage of that because you want the tubes to be as thin as possible the thinner the tubes are the more efficient they are transferring the heat into the water and they lose less heat through conduction up out the chimney so just to be sure i looked up the pressure rating of half inch type l copper water pipe which is what my tubes are and even annealed they're rated at 600 psi working pressure and the burst pressure is 4 200 psi so no risk of pressure testing them from the inside with 120 psi with that diameter turned i'll face the front side as is tradition you'll note that i'm not going to be facing both sides of each disc here i just need one side to be machined because it's going to be a gasket sealing surface after a couple of passes i almost got it cleaned up and i actually left it that way for a while thinking oh it's just a fixture that'll be fine and later i remembered no that's a gasket sealing surface it has to be perfect and i went back and fixed it no matter how you turn aluminum you still end up with a giant pile of chips at the end the only one happy about this is swarfy the i've duck the parting blade now and i'm just going to make two grooves where i want to separate the two discs for my end caps i'll have no hope of parting all the way through this giant chunk so i'm just going to make grooves for the band saw and that'll help guide the blade and tell me where to cut woodworker precision is sufficient here i just need to roughly divide this into two plates while i have it set up on the lathe here i'm going to drill a hole all the way through there's already a partial hole there from some previous fixture made with this chunk even though the lower disc doesn't actually need a hole in it i'm going to end up with a hole in it that i'll have to plug later but there's really no choice here because i need a hole to set this up on the band saw as you'll see nice side effect of those starting grooves with the parting blade is it gives me a chance to come in and de-burb both edges of both the discs so after the bandsaw goes through there will already be nice chamfered edges all the way around over to the bandsaw now and this is a setup that i've shown before for cutting thin large diameter pieces with small machine tools and that's that you bolt an angle plate into the vise on your band saw and then i bolt this stock all the way through with some threaded rod and then i just got to line up my starting grooves there with the blade so i just tap tap tap the angle plate into position and depending on how much precision you need here you can either indicate in that angle plate to get it square to the blade or you can just clamp it in the bandsaw vise and that'll square it up approximately pretty well with it lined up i bolt the angle plate down using the vise slot there on the back of the band saw and then i start my cut i'm using wd-40 there to keep the blade from plugging up on this aluminum and away we go now obviously you can't cut this all the way through because you're going to cut through the threaded rod so what i do is i let the saw run until it looks like it's close to the threaded rod and then i'll stop it and rotate the part you can see that there would be no way to clamp this part in that vise it's both too large a diameter for this vise and the stock itself is not long enough for the vice to get a proper grip on it so with the first cut done i loosen the bolt rotate it around to a new area run the saw down again and you can just keep rotating and cutting as many times as you need typically three or four spots is enough to get it to where you're basically right down to the bolt all the way around then normally at this point i take it over to the hacksaw to finish it up but actually this time i realized i could put some small clamps on the extra stock there and just finish the cut this way there was just enough room you got to be careful though and not let the saw drop because it's going to land on the angle plate and the clamps so i've got my hand on the carriage there but be extra careful because the saw not going all the way down means it's not hitting the automatic shut off so that blade is going to keep running i can't say i recommend doing this with your band saw but in a pinch there wasn't room for the clamps on the second chunk so over to the hacksaw and that was easier than i expected i guess you could say i cut it a little close on that center bolt that second disc has bandsaw cuts on both sides now so i got to face one side for the gasket so i dialed it in here on the four jaw and i'm going to face off this side as is tradition i like facing bandsaw cuts in aluminum because the uneven surface breaks the chip for you so you get real nice chips coming off of that now recall that i don't actually want a hole in the bottom plate so i'm going to enlarge it to the tapping drill size for 5 16 32 which is a size of a boiler bushing plug that i have that i normally use for pressure testing so it'll do double duty here for that so bring in the 5 16 32 tap if that sounds like a weird size to you you must not be a model engineer it's actually a very common size in model engineering but not very common size anywhere else model engineers as it turns out use a whole lot of weird threads that nobody else does after you've worked on boilers for a while you end up with handfuls of blanking plugs in a couple of common sizes including 5 16 32 and quarter 40. those are the two that i have lots of the top plate now needs an additional hole for the fill valve and so i'm going to do that on the drill press because it's off center luckily my drill press vice opens up nice and big so i should have no trouble uh get just just i need another like 16th of a imperial fist shake of frustration as i was saying i will of course be using a strap clamp to attach this directly to the table as this standard for a part this size you wouldn't expect a vice to hold something like that i'm drilling and tapping this other hole to match the adapter that i happen to have already made for my pressure testing pump that i use for all of my boiler builds it happens to be quarter 40. there's those model engineer threads again so just tap this by hand no points for straightness here quick deburr and those plates are done so the top needs a fill hole and a vent hole that's why there's two now for gasket i'm going to use this stuff this is a felpro paper gasket material and paper gaskets if you're not aware are extremely high tech these days most of the gaskets in your car are probably paper i've run this stuff up to 60 psi and my steam engine is no problem so i think it'll suffice for this test plus i have a lot of it on hand so i'm going to try it let's mock this up and see if maybe it's going to work so everything is a little bit larger than the end caps on the core so that seems like that should work now those stud holes i mentioned need to be plugged they are the reason i couldn't use an o-ring so i got some screws here and i'll cut some loctite 545 on there make sure to spill that all over the bench that's part of how it works i think this will be sufficient to plug those holes loctite 545 is pretty amazing stuff i've seen it fix leaks much worse than this and i plug the bottom plate and i also need to plug the boiler bushings in the top of the core luckily they're threaded all the way through so it's easy enough to just plug them from behind again using standard 5 16 32 boiler blanking plugs that i have by the handful because i keep making new ones because i keep needing more of them so that looks like that's going to work luckily i had easy access to them from the back okay so i'll clean up the surface here and apply the gasket and let's see if this is going to work so this is the bottom plate here these gaskets apparently work better if you cut an opening in the center of them and not leave them solid like i did there but i'll try this and see if it works so i got out all the small clamps that i have which is not that many i've got just enough for three at each end so i will try that hopefully that'll be enough to clamp these all the way around it's kind of a motley crew here of clamps over on the top now same thing set up the gasket put on the plate and then i realized that this gasket does have to be cut out because of course i need to be able to fill through the fill hole and vent through the vent hole so open up that gasket and let's try that again and more loctite on the adapter here for my hydrostatic test pump thread that into the side hole get that nice and snug and then on goes the hose and let's fill this thing with water so i'm pumping the boiler full now the vent hole is open so the air can escape and i just pump it full of water until the water comes out the top there the goal is to get all the air out of the boiler of course the whole point of hydrostatic testing is that there's no gas to compress inside the boiler we're only pressurizing water so if anything fails it's safe it won't explode so it's water tight that's good now i start building pressure and i'm about 5 or 10 psi up here and the gasket started leaking all over as you can see there i tried tightening up my clamps and i gave it another shot but yeah same deal right around 10 psi that gasket fails i think the clamping of my end plates is not sufficient three points of clamping on a four inch diameter is really not enough for a pressure seal so i thought i might just leave it here and think well the tube joints look good they're probably fine but then i happen to be on amazon and i noticed that crappy c clamps are cheap like borscht for less than a nice dinner for one i can buy a dozen of these things so i did so i figured what the heck i made new gaskets i'll give this one more shot before i give up on the idea so with 12 of them i've now got six points of clamping on each end which is about as many as i can physically fit here so let's see if this is any better i snugged up the clamps as evenly as i could all the way around and then i attached the hose once again snug that down real good fill the boiler with water once again and then put the final blanking plug back in and let's see if this thing will build some pressure right off the bat it cruised past the point where it was leaking before i got all the way up to about 40 psi here it's really actually building pressure quite good no sign of any leaks anywhere so that's encouraging around 40 psi the gasket started to fail again so i went around and snugged up all my clamps i was trying to get them as tight as i dare but if i go too tight i'm just going to shear the paper gasket with the copper edge there so i tightened it up some more and that actually bought me about another 20 psi i was able to get up to 60 psi now before the gasket started to seep again but that's actually very good like that's high enough that i can inspect my tube joints for example there was one tube joint in particular here on the top underneath you can see that i don't have a strong fillet there around that tube there is a ring of solder around it but not a large fillet so i was slightly concerned about that one right now i'm pumping it up to about 100 psi so of course the gasket is seeping a lot but if any of these tube joints were going to leak they would also be seeping right now in addition to the gasket failing so i can pump it up to above 60 psi and it bleeds down to 60 where the gasket starts holding again but i can use that time to inspect the other joints the idea would have been to get the whole set up to 120 psi the final hydrostatic test pressure but this setup does hold 60 very very well as you can see here and the goal with any hydrostatic pressure test is to be able to hold a test pressure for a long period of time with no bleed down so this at least tells me that my tubes are good to 60 psi which is the working pressure if not the final test pressure and that gives me the confidence to finish assembling this boiler i think i can say that these two joints are probably good of course i can't say for sure that tube joints that are good at 60 are going to be good to 120 but i think this exercise was definitely worth doing and i suppose i could try some different gasket material or try to get more clamps in there or make more robust end plates or various other things but at this point i've put quite a bit of time into this and i think i've developed the confidence that i needed to go ahead and finish soldering up this boiler so i hope you enjoyed this little exercise thank you very much for watching if you can swing it throw me a little love there on patreon that's really what keeps this content going and i will see you next time

Channel: Blondihacks

Views: 39,285

Rating: 4.964632 out of 5

Keywords: blondihacks, machining, machinist, abom79, this old tony, vintage machinery, steam, electronics, making, maker, hacking, hacker, lathe, mill, woodworking, workshop, shop, model engineering, engineer, engineering, live steam, machine shop, metal lathe, vertical mill, metalworking, metal shop, jewlery making, diy, home improvement, resin casting, how to, do it yourself, do it yourself (hobby), ASMR, mini mill, mini lathe, tutorial, live steam locomotive, live steam model trains, live steam train

Id: rsN23Q5OzQA

Length: 19min 50sec (1190 seconds)

Published: Sat Oct 02 2021