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What to use to seal pipe?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: ramses » Mon Nov 28, 2011 9:17 pm

I've used copper "anti seize" tape on my hybrid. It's basically thick, wide teflon tape.

You also need to make sure you apply it in the correct direction. You should wrap it in the direction that would make the fitting tend to tighten the tape, rather than catch the edge and unwrap it.
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Unread postAuthor: Woody » Tue Nov 29, 2011 7:18 pm

One more quick question. How do I calculate the pressure needed to rupture burst disks? If I recall correctly, there's a constant unique to the material that is needed to calculate this. What is that constant called?
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Unread postAuthor: SpudBlaster15 » Tue Nov 29, 2011 8:36 pm

Woody wrote:How do I calculate the pressure needed to rupture burst disks?


Try this.
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Unread postAuthor: mobile chernobyl » Tue Nov 29, 2011 9:49 pm

Woody wrote:One more quick question. How do I calculate the pressure needed to rupture burst disks? If I recall correctly, there's a constant unique to the material that is needed to calculate this. What is that constant called?


Yes there is a constant K for determining a standard for when a burst disc of a certain material should rupture. You'll need to experimentally find this constant.

The general form of this equation is well defined in this document

And K can be found experimentally by plugging in your burst pressure to the following equation:

K= (Ultimate Tensile Strength * thickness)/(Burst Pressure * Diameter)
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Unread postAuthor: Woody » Tue Nov 29, 2011 10:10 pm

Thanks for the information.

Funny seems a post of mine got deleted or just disappeared.
I basically said that I found some of the pink teflon tape lying around and used it. Working pretty well. So now I'm leaking less than 1/4psi/sex at 80psi. Not bad.
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Unread postAuthor: Lockednloaded » Tue Nov 29, 2011 10:39 pm

Woody wrote:Thanks for the information.

Funny seems a post of mine got deleted or just disappeared.
I basically said that I found some of the pink teflon tape lying around and used it. Working pretty well. So now I'm leaking less than 1/4psi/sex at 80psi. Not bad.

must ignore hilarious typo...
anyway, 1/4psi/second could be the difference between a combustable mix and too rich of a mix on a hybrid, so you probably need it completely air tight.
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Unread postAuthor: Gun Freak » Tue Nov 29, 2011 10:40 pm

That's way too fast of a leak... You want it 100% airtight for reasons like LnL stated.
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 30, 2011 12:47 am

must ignore hilarious typo...


I won't.

Woody wrote:now I'm leaking less than 1/4psi/sex at 80psi. Not bad.


Image

:D :D :D
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Unread postAuthor: SpudBlaster15 » Wed Dec 07, 2011 4:26 am

Late reply but oh well...

Woody wrote:I basically said that I found some of the pink teflon tape lying around and used it. Working pretty well. So now I'm leaking less than 1/4psi/sex at 80psi. Not bad.


How much tape are you using? I typically use around 8 wraps of double density yellow gas tape on each 2" galvanized joint, press the tape firmly into the threads, then wrench tighten until they're snug. These connections always pass the soap/water leakdown test, and will hold pressure for hours with no noticeable loss.
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Unread postAuthor: velocity3x » Wed Dec 07, 2011 9:18 am

This is what I use. It's rated to 10kpsi.
[youtube]http://www.youtube.com/watch?v=3o4uMq6yQiQ[/youtube][/youtube]
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Unread postAuthor: ArchaneTinker » Sat Mar 10, 2012 9:04 am

LOL, the director of that video should have asked someone how to properly use an adjustable wrench. The movable jaw should lead the fixed one.

edit* Being an HVAC-R serviceman, leak lock is my go to sealer.I do use quite a bit of yellow gas tape when I don't feel like getting messy thoughhttp://www.highsidechem.com/leaklck.html
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Last edited by ArchaneTinker on Sat Mar 10, 2012 11:28 am, edited 1 time in total.
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Unread postAuthor: Petitlu » Sat Mar 10, 2012 10:33 am

Loctite 270 ! good to 4500psi ! :D
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Unread postAuthor: ramses » Sat Mar 10, 2012 1:40 pm

ArchaneTinker wrote:LOL, the director of that video should have asked someone how to properly use an adjustable wrench. The movable jaw should lead the fixed one.



Incorrect. The fixed should lead the movable jaw. Loosen a wrench and pretend to tighten a bolt, and you will see that this way exerts less torque on the movable jaw.
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Unread postAuthor: ArchaneTinker » Tue Mar 13, 2012 6:05 pm

ramses wrote:Incorrect. The fixed should lead the movable jaw. Loosen a wrench and pretend to tighten a bolt, and you will see that this way exerts less torque on the movable jaw.



After some searching and re-searching, followed by trying it for myself, I've come to a conclusion... you're absolutely right. All the old timers dun taught me wrong, donkeys. I figuratively retract my previous statement, but leave it literally for the sake of context.
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