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stronger compression joint.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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stronger compression joint.

Unread postAuthor: shud_b_rite » Thu Apr 12, 2007 5:15 am

In my new cannon I have a 20mm diameter copper pipe that is attached to a ball valve using a compression fitting. I know there are several types of compression fittings and that this has kind-of been posted here before but I am asking a slightly different question.

The picture below shows the type of compression fitting I am using. It is the one grips the pipe with a ring rather than making a lip on the pipe. I am not to sure about using this type of fitting at high pressure so I need a way of strengthening it so It wont come apart. Or maybe this type of fitting is strong enough, I don't know.

This is where I got info about the fitting.
http://www.swagelok.com/fittings/tube_f ... _types.htm

So what do you reckon? Will it hold? Or should I strengthen it somehow?
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PROD_TF_Compression.jpg
This is the type of compression fitting I am using.
PROD_TF_Compression.jpg (39.15 KiB) Viewed 604 times
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Unread postAuthor: From_Hamsterdam » Thu Apr 12, 2007 5:44 am

The rubber will deform to producing a strong grip so it should be ok.

You could try gluing the ring down on to the pipe with a glue or epoxy resin.
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Unread postAuthor: shud_b_rite » Thu Apr 12, 2007 5:56 am

The ring is not made of rubber, it is made of coper also. Although you just gave me an idea. I could simply solder the ring to the pipe then tighten the nut. I will try it tomorrow when I get the pipe. Thanks
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Unread postAuthor: From_Hamsterdam » Thu Apr 12, 2007 6:10 am

copper ring? Never would have thought it was that.
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Unread postAuthor: Hotwired » Thu Apr 12, 2007 7:30 am

High pressure?

How high were you thinking? I'm using those fittings on my cannon at 240psi with 22mm copper. So that kinda disproves the 'minimal pressure' that webpage says it can handle.

I did however add my own twist to that - not because I was concerned about it giving way but because there was a leak which wouldn't stop leaking - I fixed the olive on with a copper/brass glue.

In fact I would suggest you fixed the olive on. Solder would be fine.
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Unread postAuthor: Freefall » Thu Apr 12, 2007 10:32 am

For a company like swagelok, 240 psi is "minimal pressure". I'm currently using their "bite-type" fittings on an engineering test part which is intended to see in excess of 1200 psi.
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Unread postAuthor: Hotwired » Thu Apr 12, 2007 11:18 am

Well I'm speaking from my point of view reading it and I read minimal pressure as a bar or so ^_^

The copper pipe compression fittings are rated to 300psi at room temperature when fitted correctly with just sliding the nut, olive and fitting on and tightening it.

Sizes above 35mm are lower and sizes below 12mm are much higher.
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Unread postAuthor: WOW!! » Thu Apr 12, 2007 11:58 am

For code reason, they have to hold at least 90psi of water pressure. Most compression fittings are used for you houses water system, so as long as they are super tight you will be fine.

But if you want to you can all ways just put a pipe clamp right behind it so that it wont come off.

EDIT- After talking to my dad who does this stuff, he said that bite type fittings can hold in a excess of 600PSI, that is the min.
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Unread postAuthor: Hotwired » Thu Apr 12, 2007 12:36 pm

Just in case theres a misunderstanding I was talking about the olive type compression fittings shud_b_rite posted about.
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Unread postAuthor: shud_b_rite » Thu Apr 12, 2007 10:22 pm

I just put some parts together today and I have tested it up to 150 psi and it still feels strong. I also realized that I really really suck at soldering. Thanks for every ones input, I just wanted to check before I spent too much money on something that doesnt work.
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