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Pipe Bursting Demonstration

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Pipe Bursting Demonstration

Unread postAuthor: SpudStuff » Mon Sep 04, 2006 12:41 am

So for all of you people who say " Ohh your pipe is gonna blow up and your really gonna be fucked then look at this. This 3/4" Pvc pipe birst at 1608 PSI and at didn't grenade. Yes i know air pressure will act somewhat different but common people.
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Unread postAuthor: MrCrowley » Mon Sep 04, 2006 12:57 am

and thats 3/4", so that would make a difference as well.
not sure how but it will :wink: :lol: jkz
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Unread postAuthor: ProfessorAmadeus » Mon Sep 04, 2006 1:02 am

OMG that was so INTENCE!!! :shock: that sucked but i thought flowguard was cpvc or at least some is
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Unread postAuthor: frankrede » Mon Sep 04, 2006 1:17 am

Thats alot of pressure. Makes me feel safe.
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Unread postAuthor: CS » Mon Sep 04, 2006 3:28 am

This is where a the bell curve and 3 sigma standard come into play. Below I made a rough assumption of what one would look like for the bursting pressure of PVC pipe by simply adding some numbers to a already existing graph I found on the net, shown below.

Image

Basically the height of the curve denotes the percentage of a given event occurring. In our case, the possibility of the pipe bursting. The most common percentage is listed in each 8 portions the curve has been divided into. And the further 'right' you move on the graph the higher results the given situation produces. In our case, a higher burst pressure. As you can see I went ahead and listed some numbers to give a idea on what the bursting pressures would roughly look like. Pretend as if I went out and tested 10,000 pipes for there bursting pressure and what I got is what is listed on the graph.

Since the height of the wave occurs at 250PSI, that also means that the median bursting pressure is 250PSI. Although a major fluke in production that produces weak chemical bonds in the PVC occurs .13% of the time resulting a low bursting pressure [0-40PSI], and another .13% of the time a uber-strong bond is formed by the PVC resulting in pressure withstanding capabilities of 500+PSI. Both these instances are rarely accounted since of there rarity. The other 6 portions are more plausible, and increase with there likeliness as there height in the curve increases.

So if you were to go test a section of pipe according to this data the pipe would most likely burst at around 250PSI. But you dont want to approach anywhere close to that median in fear of failure. So to accommodate for this fear they will rate the item at a negative deviation of the median. Something such as pipe is held to high negative deviations since failures of such can result in serious injuries or death. While something such as rubber band is not, since what happens when a rubber band snaps? Nothing, so it doesnt need that high of standards. Problem being some companies will get greedy and rate a product at a lower deviation to make there product appear better. But most industries can venture into -4 deviation on a 3 sigma standard since in the pipe industry that would require you to make a 1" thick pipe rated for 10PSI to be absolutely sure it will not fail.

Chances are that pipe companies have tested huge amounts of pipe for there failure point and had a few fail under there claimed safety figure, but the chances of someone having such fail on them is so low, its accepted. I mean there wouldnt be a pharmaceutical drug on the market if they were held to a -4 deviation on a 3 sigma standard.

This is why we avoid even approaching the stated pressure rating of pipes since as we can conclude that there is proven flukes that may end in our possession. The results of a failure in our instance is not acceptable, hence why its held to such high standards. Damn I hate when I have to sit here and cover something so extensively before someone understands...

[Ill admit the bell curve actually graphed for our situation would be steeper, but you get the idea ;-) ]

EDIT- Ive edited the post a billion times in a attempt to get the picture to work, and finally got it working. Its now working, and not a worry. MrCrowley, thanks for the heads and now I will delete your post since it has no matter in this discussion.
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Last edited by CS on Mon Sep 04, 2006 3:38 am, edited 2 times in total.
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Unread postAuthor: MrCrowley » Mon Sep 04, 2006 3:53 am

wouldnt the diameter of the pipe have an influence as well as i doubt you could get a piece of 2"PVC up to 1600psi, or did i read your post wrong and it is possible?
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Unread postAuthor: CS » Mon Sep 04, 2006 4:05 am

Bah! Kinda like a airplane to whale dung [Way over your head]

The pressure ratings I stated were completly factual, but were attempted to be somewhere close to reality so they could be easier understand in the whole new concept for most. The factual testing results I provided would obviously need to be tested on all possiblie standards, which would included the same 'diameter' of piping. The whole point of the testing is to exploit 'flukes' occuring from manufacturing defects resulting in either positive and/ or negative results.

I would highly doubt even under the most perfect of 'normal' conditions for a 2" sch 40 pipe to withstand 1600PSI. Dont stick me to it since producing actual numbers isnt my thing, more concepts and creativeness are my thing.
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Unread postAuthor: MrCrowley » Mon Sep 04, 2006 4:26 am

Do what gort does and pull numbers outta your ass :wink:
anywho if there was a defect and the pipe rated for 250psi blew at 50psi and your finger went with it could you sue(sp?) the pipe manufactur(sp?)

p.s you can only sue people on very special occasions in NZ so im not sure if thats how you spell it :D

btw is it true that some guy in America(ofcourse) sued someone for steeping on his roses then the guy counter-sued cos he got "pricked" by a rose and he won the court case?
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Unread postAuthor: CS » Mon Sep 04, 2006 4:53 am

Pipes are not rated for gaseous pressure, only water. Which is a whole safety issue in itself since most places water pressure only reaches ~40PSI.

Not sure about that one in particular, but ya many o' dumb lawsuits have been won. Frick' were getting off-topic.
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Unread postAuthor: mark.f » Mon Sep 04, 2006 8:03 am

SpudStuff, gas pressure is a lot different than hydraulic pressure. Liquids don't compress near as much, which is why we use them to hydrotest things before we fill them with gases.
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Unread postAuthor: sgort87 » Mon Sep 04, 2006 10:35 am

HEY! I only pull numbers out of my ass (*reaches in ass*) 13% of the time!

Seriously though, 3/4" PCV can hold a CRAP LOAD more pressure than something like 4 and 3" PVC. Notice that the pressure rating is about twice as high on 3/4" than 4". This being said, the burst pressure of 4" is probably half or less than that of 3/4".

You also need to understand that this test was done under ideal circumstances. The pipe had not been previously used/damaged, the temperature was right, and correct solvent welding methods were used. Also, this was only one pipe. (I didn't actually watch the video, but I assume these things are true.

Now onto the next section of my rant. 4" PVC is a lot more dangerous to have burst on you than 3/4" PVC. Why? Because there is more of it and it's wall thickness to ID ratio is a lot smaller. Think about this: Inside a foot of a 1000 psi-charged 3/4" pipe, there is how many moles of air? I'm not gonna do the math on that part, but my point is that there is that in 4" PCV, there is over 28 times thaqt amount of air, meaning once the pipe bursts, there is a lot more air pushing chunks of PVC at your face.

Never assue you are safe when pressurizing these chambers. I have had pipes burst apart on me before. Just remember that you aren't always safe. Take precautions.
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Unread postAuthor: noname » Mon Sep 04, 2006 11:18 am

I'm not saying anyone will believe me (no one has before) but I have had 3/4" Sch 40 PVC explode in my basement at 140 psi. It was rated to 480. And yes, it sent shrapnel all over and into my friend's leg (the dumbass who pumped it that high after I told him max 80 psi).
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Unread postAuthor: SpudStuff » Mon Sep 04, 2006 12:26 pm

Water pressure and air pressuer are exactly the same thing. they only act differently when they burst. That pipe is CPVC but it is pretty much the same thing. Also yes the video was done under perfect curcumtances but real life wouldn't be too much different.
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Unread postAuthor: sgort87 » Mon Sep 04, 2006 1:46 pm

Okay, I watched the video. That is using water pressure meaning there is a lot less actual compression in the pipe than with air. When water is compressed, there is not much compression. When air is compressed and released, it results in a violent expansion causing shards of PVC to be thrown about.

This video is not only inaccurate because it shows a safe hydropressure test, but it also shows it with CPVC which is NOT PVC.

Don't ever try to convince anyone that rupturing pipe is safe.
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Unread postAuthor: SpudStuff » Mon Sep 04, 2006 6:26 pm

Im not saying that it is safe by any means im just saying that it dosn't grenade.
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