SpudFiles

Biopyro wrote:While PVC becomes more brittle a lower temperatures, it also increases it pressure rating. Hot PVC can handle a LOT less pressure than cold. Brittle just means if you drop it (and in doing so exceed the stress limit) it might explode.

At 60*C the rating of PVC pipe falls to just 22% of its stated rating, so your gun is rated to only 4 bar when you put in the hot water! PVC has the worst temperature-rating decline of all pipe plastics, I think it might be wise to retire this until you can at least get a gauge and thermometer installed.

Failing that, just change your chamber pipe. MDPE or HDPE pipe has a higher rating, and a preferrable failure mechanism, so if you can get hold of some, use that. Even better, use metal!

Interesting that.... I'm using gas rated PVC piping though. And the rating i got from the place i bought it (a professional plumbing supplier) is: 2000kPa with temp range 0C to 60C. Does that suggest that it'll hold 2000kPa at 60C? Either way revision two is going to be metal i think. I'm not much of a plumber, so any ideas as to the easiest way to do this with metal (and cheapest)?

Yep. Go to a hardware store and buy threaded malleable iron or galvanized fittings. If you have any background in electronics you could try copper and solder.

And yes, it's just a safe working range to help prevent lawsuits.

By the way, even though the bv isn't rated that high it should be suitable.

Hmm so I still won't have issues using hot tap water so long as i don't use too much dry ice.

Sounds like the go though (I can fill metal with lots of hot water and shitloads of dry ice XD).... so a few more questions on doing this with metal.
How much is malleable iron gonna cost?
How is the pipe sold? i.e. In metre lengths with threaded ends?
What diameter should i be getting? The bv is 25mm so if I buy say 50mm pipe can i get something to connect them?

evilducky wrote:Hmm so I still won't have issues using hot tap water so long as i don't use too much dry ice.

Sounds like the go though (I can fill metal with lots of hot water and shitloads of dry ice XD).... so a few more questions on doing this with metal.
How much is malleable iron gonna cost?
How is the pipe sold? i.e. In metre lengths with threaded ends?
What diameter should i be getting? The bv is 25mm so if I buy say 50mm pipe can i get something to connect them?

Well it depends.

I think you're in Australia eh? If so then it shouldn't be unreasonable..but it may be cheaper to move to America.

You should just be able to buy pipes with threaded ends, in random lengths. (think 1m, 1 ft/30 cm, 2m) To reduce to your BV simply use a threaded reducer (or buy a malleable iron union).

While you're shopping, remember to pick up a roll of thread tape (teflon/ptfe). The diameter is up to you.

Also, remember there's a big difference in performance between a burst disk and ball valve. But the ball valve gives you a triggerable factor, which is nice.

Yeah I've got teflon tape already for the current one. And yeah when I go steel i will make up for lack of a burst valve with massive pressure.

evilducky wrote:Hmm so I still won't have issues using hot tap water so long as i don't use too much dry ice.

Wrong! The afe working range just means that it can be kept at that temperature and not degrade, it's rating will still be 78% lower. Anything above 60 in industry might cause the pipe to warp and crack etc.

You don't need an electronics background to solder pipe!

Biopyro wrote:

evilducky wrote:Hmm so I still won't have issues using hot tap water so long as i don't use too much dry ice.

Wrong! The afe working range just means that it can be kept at that temperature and not degrade, it's rating will still be 78% lower. Anything above 60 in industry might cause the pipe to warp and crack etc.

You don't need an electronics background to solder pipe!

Alright, you probably wouldn't need to be good with electronics. It would make it quicker, easier and safer though. If you know how to solder, copper is fine but threaded fittings could well be safer.

No, there is NO relation at all. Take me as an example.

I can't solder electronics for toffee (better known as "Teflon soldering" - i.e. completely non-stick), but my copper pipe soldering has been subjected to several hundred pounds per square inch without any problems at all. Even my early pipe soldering still stands up, but my recent electronics soldering is as bad as ever. I've no idea what I'm doing wrong, but...

The only similarity between electronics soldering and pipe soldering is that they both use heat and solder. They use totally different tools, and different styles of solder.

Seriously, if I tried soldering one in the style of the other, I'd end up with either mildly warm copper pipe (a soldering iron does not have the power to solder copper pipe, because the pipe is basically a giant heat sink) or absolutely roasted components in the middle of a solder blob (a blowtorch does not have the precision to solder components without heating them and everything nearby beyond destruction, and pipe soldering uses much heavier gauge solder).

Soldering iron: 10-100 Watts power INPUT (bear in mind some inefficiency)
Blowtorch: 1000-5000 Watts OUTPUT.

Apples and oranges mate.

It's obvious you can't use a soldering iron- but I did try once (very small brass tube) and it worked alright, though rather time intensive.

You're right about that though, pipe soldering is much easier than electronics soldering.

Though consider applying flux, how solder flows, basic things such as heat distribution of 3 elements et cetera..

Look, say it however you want. Anyone can solder pipes together, but if you know how to solder electronics and have an understanding of it then it would probably go easier. Believe it or not.

And if applied correctly, the shear strength of antitomy(sp?) is over 10000 psi.

If you want something quick and easy with minimal fuss go for threaded fittings.

It's obvious you can't use a soldering iron- but I did try once (very small brass tube) and it worked alright, though rather time intensive.

If you insist on not using a blowtorch for such small pipes, I would suggest a using a lighter.


The whole trick about soldering (both types) is that you do not melt the solder and smudge it over the workpieces, but that you heat up your workpieces and let the solder to be sucked in by capillary effect.

psycix wrote:

It's obvious you can't use a soldering iron- but I did try once (very small brass tube) and it worked alright, though rather time intensive.

If you insist on not using a blowtorch for such small pipes, I would suggest a using a lighter.


The whole trick about soldering (both types) is that you do not melt the solder and smudge it over the workpieces, but that you heat up your workpieces and let the solder to be sucked in by capillary effect.

Yes, that's what I was getting at.

I know I could have used a lighter, but I really just wanted to tryit for the sake of it. I normally just use a normal torch or a mini butane torch.

inonickname wrote:Alright, you probably wouldn't need to be good with electronics. It would make it quicker, easier and safer though. If you know how to solder, copper is fine but threaded fittings could well be safer.

Threaded fitting's are heavier, and more likely to leak, but not really any safer as far as handling ressure is concerned.

Dry ice and plastic pipe. It just doesn't sound right. Oh, you know the dry ice will produce pressure at different speeds depending on water temp of course. So how can you know how fast it will evaporate? You mentioned hot water. Did you use cold water before? Theres too many things to pay attention to. Its dangerous. Why can't you use compressed air instead? Go get a bike pump.
How will the frequent and extreme fluctuations in temp effect the PVC? I've played with dry ice before and the water gets cold enough to freeze over completely. I promise you will have an accident sooner or later.

Moonbogg wrote:Dry ice and plastic pipe. It just doesn't sound right. Oh, you know the dry ice will produce pressure at different speeds depending on water temp of course. So how can you know how fast it will evaporate? You mentioned hot water. Did you use cold water before? Theres too many things to pay attention to. Its dangerous. Why can't you use compressed air instead? Go get a bike pump.
How will the frequent and extreme fluctuations in temp effect the PVC? I've played with dry ice before and the water gets cold enough to freeze over completely. I promise you will have an accident sooner or later.

Yes i know that the temperature will affect the rate of sublimation (not evaporation). Dry ice is solid-to-gas not liquid-to-gas). But it is irrelevant. I have worked out the amount of dry ice that will give me 2000kPa through ideal gas law (PV=nRT). Hence the rate of reaction is not relevant as even at 100% completion, the pressure will not exceed 2000kPa. The PVC cracking issue is slightly more complex, but through using warmer water and crushed dry ice (large surface area), the reaction occurs before the ice can cause the PVC to cool rapidly. The issue with warm water derating the pressure is still a problem though and why I will be switching to metal.

Biopyro wrote:

inonickname wrote:Alright, you probably wouldn't need to be good with electronics. It would make it quicker, easier and safer though. If you know how to solder, copper is fine but threaded fittings could well be safer.

Threaded fitting's are heavier, and more likely to leak, but not really any safer as far as handling ressure is concerned.

I meant that threaded fittings would be safer than a bad solder joint. Not much to go wrong. If you can solder or are willing to then consider copper, just make sure you do it properly.