Compression fittings - have I overtightened them?

Odai · 10-26-2009, 08:33 PM

hello,

I recently finished a water cooling setup. However, at first I got a leak. I therefore had to drain the system to sort it out.

In doing so, I had to take the tubing off the fittings. I noticed at the time that there were indentations on the tubing from where the "screwy bit" makes contact. First time round, once I had tightened as much as possible, there was a small gap between the screw bit, and the base of the fitting. However, second time round, after fixing the leak problem (caused by Swiftech design, standard third party o-rings don't create a seal), the screw bit went much further. I had the fitting screwed into the block, put the tubing on, and screwed the "screwy bit" down. Without using pliers, the screw bit went almost all the way, leaving practically no gap at all. It was easier to tighten too. Could I have overtightened it?

And should I be worried it was a lot easier to tighten the second time round? I'm afraid the tubing could be cut into.

I'm using Tygon 7/16" ID 5/8" OD tubing and bitspower compression fittings (same size, 7/16, 5/8)

I've included some photo's, incase my barely understandable description doesn't make any sense

EDIT: The extent to which I tightened the fittings on the blocks is pretty much the same as how much I've tightened the one shown above, at the bottom. (reservoir).

EDIT 2: First post by the way on a great forum.

cstkl1 · 10-26-2009, 08:39 PM

holy crap

yes u have if thats bits compression.
and u might have torn the tubing at the top

suppose to leave that non threaded area on the compression empty.

Hondacity · 10-26-2009, 08:47 PM

its good

Fafeifa · 10-26-2009, 10:02 PM

You need some rotary adapters or an extender because the base of the 3/4"OD compression fittings are wider than the machined spot for the fittings. It will leak no matter how tight you go.

Odai · 10-27-2009, 04:22 AM

hello,

Fafeifa, sorry I wasn't clear, but the fittings are 5/8" OD, not 3/4".

I've leak tested it randomly for about 12 hours, I haven't had any leaks so far. I'll assume the tubing hasn't been torn then. So would that mean it will stay that way?

ChielScape · 10-27-2009, 05:42 AM

you cant overtighten compression fittings..

jim0ne · 10-27-2009, 06:41 AM

Quote:

Originally Posted by ChielScape

you cant overtighten compression fittings..

Thats what i thought also.

pwolfe · 10-27-2009, 07:46 AM

I was under the impression if you over tightened CP's you could actually cut into the tubing. At least on my tfc compressions, I could see the tubing being cut into when I over torqued them.

Baulten · 10-27-2009, 07:50 AM

I did some tests on spare tubing (PrimoFlex 1/2" ID 3/4" OD) and I was unable to cut or tear the tubing by tightening the compressions all the way down. I don't do it in the computer case simply because it's HARD to get the compressions that tight, but even if I did, it wouldn't sheer the tubing.

quattro_ · 10-27-2009, 08:47 AM

^^ +1 there is no way a comp. fitting can do any harm to tubing, tested on 7/16 and 1/2, it will only leave a mark on the tube .
i also will not recommend doing this simply because by tightening the compression you are also forcing/screwing the fitting itself into block/res/pump etc etc .

shazza · 10-27-2009, 08:56 AM

I've experienced the same thing where the fittings went on much easier after undoing them a time or two and using the same tubing. Haven't had any issues so far, and a number of mine have been running for months.

Wolf132 · 10-27-2009, 12:51 PM

Looks like to me that the o-ring under the horizontal compression fitting isnt even being compressed.

NaeKuh · 10-27-2009, 02:18 PM

Quote:

Originally Posted by quattro_

^^ +1 there is no way a comp. fitting can do any harm to tubing, tested on 7/16 and 1/2, it will only leave a mark on the tube .
i also will not recommend doing this simply because by tightening the compression you are also forcing/screwing the fitting itself into block/res/pump etc etc .

no ur never suposed to overtighten compressions on both the threads and the actually tube compression.

Quote:

Originally Posted by pwolfe

I was under the impression if you over tightened CP's you could actually cut into the tubing. At least on my tfc compressions, I could see the tubing being cut into when I over torqued them.

yup.

The pinch eventually cuts into the tubing, and leads to the barb failing.
Waterlogged showed us a great cut view on how and why.

millertime359 · 10-27-2009, 03:51 PM

Quote:

Originally Posted by ChielScape

you cant overtighten compression fittings..

Quote:

Originally Posted by NaeKuh

no ur never suposed to overtighten compressions on both the threads and the actually tube compression.

yup.

The pinch eventually cuts into the tubing, and leads to the barb failing.
Waterlogged showed us a great cut view on how and why.

You just tighten the ring down enough to put pressure onto the tubing so it can't be pulled off. There is no reason to tighten the nut all the way down. (Well outside of it looking a little better.)

Maybe Waterlogged can post those photos again as i forgot where they are.

ChielScape · 10-27-2009, 03:57 PM

its practically impossible to tighten it all the way down anyway...

millertime359 · 10-27-2009, 03:59 PM

Quote:

Originally Posted by ChielScape

its practically impossible to tighten it all the way down anyway...

Wrenches?

yea, 1/2" 3/4" by hand is impossible to tight all the way down. 7/16" 5/8" is much easier.

ChielScape · 10-27-2009, 04:50 PM

wrench... dude.. seriously? you use a wrench?

millertime359 · 10-27-2009, 05:01 PM

I don't, but it has happened, I think it has happened too much actually.

I've read a few threads on here and even Dean from Koolance has commented about how many RMA requests are due to overtightening fittings with wrenches.

dengyong · 10-27-2009, 05:15 PM

Quote:

Originally Posted by millertime359

I don't, but it has happened, I think it has happened too much actually.

I've read a few threads on here and even Dean from Koolance has commented about how many RMA requests are due to overtightening fittings with wrenches.

How does one put a wrench on a knurled fitting with no flats ?

millertime359 · 10-27-2009, 05:22 PM

Quote:

Originally Posted by dengyong

How does one put a wrench on a knurled fitting with no flats ?

Vise grips or pliers if we want to get specific.

A box-end wrench can be used on a few different barbs as there is a hex shape there.

Noisy · 10-27-2009, 05:58 PM

Instead of risking over tighten, I just use this.
http://www.sidewindercomputers.com/bishsimatoma1.html
works great

ChielScape · 10-27-2009, 06:34 PM

Quote:

Originally Posted by Noisy

Instead of risking over tighten, I just use this.
http://www.sidewindercomputers.com/bishsimatoma1.html
works great

and exactly how does that prevent you from overtightening anything?

Waterlogged · 10-27-2009, 06:46 PM

Quote:

Originally Posted by millertime359

You just tighten the ring down enough to put pressure onto the tubing so it can't be pulled off. There is no reason to tighten the nut all the way down. (Well outside of it looking a little better.)

Maybe Waterlogged can post those photos again as i forgot where they are.

Ask and ye shall receive.

millertime359 · 10-27-2009, 07:02 PM

Quote:

Originally Posted by ChielScape

and exactly how does that prevent you from overtightening anything?

+1

I'm a bit lost on that too.

Thanks Waterlogged.

dengyong · 10-27-2009, 07:42 PM

Quote:

Originally Posted by Noisy

Instead of risking over tighten, I just use this.
http://www.sidewindercomputers.com/bishsimatoma1.html
works great

???