Vaccum bag connectors

[mpitfield]

I have just about had it with my vacuum bag connector and ready to either get some tips on how to keep it from leaking or get a better one, if a better one exists.

Currently I am using the following, but for me it is a real hit and miss and right now I have a tip to tip CF layup 1 hour in, the thing is leaking and the pump is cycling every 5 min. I have removed it, re-added it, sealed it with bag sealant tape and 5 min cycling is the best I can do unless I completely un-bag it which I won't do at this stage so I will ride this one out. I have used this attachment maybe 15 times and it has been the same way since day one, some layups the pump might cycle 2 or 3 times and others it cycles more frequently.

Before someone asks, I have already determined with certainty that it's the connector and not the bag or any other part of my system.

Tips on how to use this better or a better attachment are greatly appreciated.

 

[amellrotts]

I'm listening as well....

 

[rharshberger]

Guess I need to read the OP several times before asking a question, it was a duh moment. I use this cheap one from ACP sales https://www.acpsales.com/OnlineStore.php?cat=4901 with no problems, for a vacuum line I use the micro-irrigation line from HomeDepot, and my Food Saver plugs into that via the canister hose. It does what I need it too but probably not near as much vacuum as a real vac pump.

 

[mpitfield]

Guess I need to read the OP several times before asking a question, it was a duh moment. I use this cheap one from ACP sales https://www.acpsales.com/OnlineStore.php?cat=4901 with no problems, for a vacuum line I use the micro-irrigation line from HomeDepot, and my Food Saver plugs into that via the canister hose. It does what I need it too but probably not near as much vacuum as a real vac pump.


View attachment 287847View attachment 287848View attachment 287849

Hey Rich, thanks for the reply.

I was just looking on ACPs site and thought this one was a good candidate https://www.acpsales.com/OnlineStore.php?cat=4902 I also looked at the one you sent a link to and I think it would also be better that what I have. The reason I am looking at the one above is the "high temp" description as I plan on making a heat box. Not that I will be baking over 150 however you never know and I don't want to keep buying these things.

I was also looking at some other ones in the UK as it seems that they have a much greater selection over there.

Bottom line is I don't want to spend any more than I have to however I want something consistently reliable. It is either me and my technique or the connector I have is just a poor design, either way something has to change.

 

[FredA]

I have the same fitting as pictured in the OP -- leaks more often than not.
Leaks so bad, I just leave the pump running.
I too am looking for a good solution.....

 

[dixontj93060]

Have you tried applying grease at the junction point?

 

[mpitfield]

I have the same fitting as pictured in the OP -- leaks more often than not.
Leaks so bad, I just leave the pump running.
I too am looking for a good solution.....

lol well at least I am not the only one having challenges with this one.

Have you tried applying grease at the junction point?

I have not but tried grease, but earlier on this evening I thought about applying some sealant like silicone or latex calking but then it would be a messy clean up and who knows what it would suck into the layup. The issues I see with grease is that there seems to be rubber washer on it and I know some rubber and oil based lubricants don't play nicely together, plus contamination may be a concern. The other thing I don't like about that idea is that it seems more like a work around and for the price of a good one, whatever "good" means in this case then I would rather spend it.

Having said that is the grease or sealant a common technique for sealing these connectors.

Here is one I found in the UK, with a built in check valve https://www.airpress.co.uk/265-alum...-standard--professional--industrial-kits.html

And here is another one which looks pretty serious, both from the UK https://www.hosetechnologies.com/aerospace-product.php?c=94&p=223

 

[FredA]

I've used "official vacuum grease" (don't have it here in front of me to give you the brand, etc...) on the rubber -- still leaks.
Crap design IMHO.

 

[watheyak]

I just have the tube enter the side of the bag through the sealant and add a little extra sealant where the tube enters. fold the end of the tube in a patch of breather cloth so it wont get stopped up by the bag material. Free and zero leaks.

Lately I've been using latex caulk as a sealant, which works even better than the tape and is cheaper as well.

 

[Reinhard]

Our rocket club had some opportunities to work do some composite work in a professional setting and the base of the connectors used ther looks exactly the same as the one pictured in the first post. The only difference is the check valve, which looks like the one in the airpress.co.uk link.

The picture below shows a fin can getting ready for the autoclave.


The work flow used here is roughly described as:
*) Ensure seal on both connectors are clean
*) Tape base of connectors to breather, make sure that tape does not cover the planar surface (a small bit on the periphery is ok)
*) Bag and seal layup
*) Create incision in the bag and connect top of the connector. Pay attention to not introduce any wrinkles, a second person assisting can be helpful here.
*) Connect to vacuum system and to vacuum gauge.
*) Hunt down audible vacuum leaks, if applicable. Wrinkles in the bag are your enemy. In my limited experience, they are more common in tape seals, but I've encountered them in the vacuum connection too.
*) Disconnect from vacuum system and verify that pressure is stable.

No rocket science here, and I assume most folks do more or less the same. My only recommendation would be to be paranoid about wrinkles.

On a side note: Despite the tests above, the layup stays connected to the vacuum system until cured, except for short periods (leak tests, transport between rooms, loading into the autoclave).

Reinhard

 

[GregGleason]

I have just about had it with my vacuum bag connector and ready to either get some tips on how to keep it from leaking or get a better one, if a better one exists.

Currently I am using the following, but for me it is a real hit and miss and right now I have a tip to tip CF layup 1 hour in, the thing is leaking and the pump is cycling every 5 min. I have removed it, re-added it, sealed it with bag sealant tape and 5 min cycling is the best I can do unless I completely un-bag it which I won't do at this stage so I will ride this one out. I have used this attachment maybe 15 times and it has been the same way since day one, some layups the pump might cycle 2 or 3 times and others it cycles more frequently.

Before someone asks, I have already determined with certainty that it's the connector and not the bag or any other part of my system.

Tips on how to use this better or a better attachment are greatly appreciated.

I have the same kind. I usually use Superlube on both sides, and that helps seal it up.



Greg

 

[mpitfield]

Wrinkles in the bag are your enemy

Thank you for the feedback Reinhard

I think the connector is a poor design but I believe my current issue is wrinkles. If I am to work with this connector I need to develop a better method of connecting it. I don't tape the base to the breather, so that is one thing I will change as it makes complete sense. The other issue I have is tightening up the connector, if you see the pic, this is what is currently under vacuum, you can clearly see wrinkles. However it started off as a wrinkle free junction point, but in trying to get rid of the leaks I tightened up the connector and this introduced wrinkles.

I have the same kind. I usually use Superlube on both sides, and that helps seal it up.

Lately I've been using latex caulk as a sealant, which works even better than the tape and is cheaper as well.

Thanks Greg and watheyak, I appreciate the feedback and it is good to know that some sealants have worked for others.

I have some emails out to a couple of VacBag suppliers to see what they have to say.

 

[Pat_B]

I would move your gauge and valve assembly further away from the bag connector. I have a mostly similar connector that I bought from a woodworking supply place and it leaks occasionally too. But by only have the vacuum hose go to the connector, that gets rid of some of the weight that can tug the connector out of place to leak.

 

[Onebadhawk]

I have the same bag connector as well Michael. ..
I haven't gotten to the point of using it yet though. ....
Please keep us abreast if you find a better one....

Teddy

 

[rharshberger]

I would move your gauge and valve assembly further away from the bag connector. I have a mostly similar connector that I bought from a woodworking supply place and it leaks occasionally too. But by only have the vacuum hose go to the connector, that gets rid of some of the weight that can tug the connector out of place to leak.

+1 using a section of hose between the connector and the valve.

 

[mpitfield]

I would move your gauge and valve assembly further away from the bag connector. I have a mostly similar connector that I bought from a woodworking supply place and it leaks occasionally too. But by only have the vacuum hose go to the connector, that gets rid of some of the weight that can tug the connector out of place to leak.

+1 using a section of hose between the connector and the valve.

I have considered putting the gauge on a separate connector like shown in Reinhard's post but then I would have to sources of leaks to deal with.

Here is the logic in the valve and gauge on the connector. The hose is a quick connect so when everything is sealed I can close the valve disconnect the vacuum and move things around, which is a consideration in a work space where I often have to move things around, considering my layups are usually 12 hours. To move the layup attached to the vacuum press, poses more risk to me as my pump assembly is pretty big and not easily moved, both pieces are essentially two hand moves.

I have also thought of using a tee connector and having the hose come off the horizontal point and the gauge on the vertical one. Having said that the hose places very little stress on the connector because I hang it from something where ever I place the layup. One thing, although the picture shows sealant tape around the connector, it does not leak I only put that on while diagnosing the problem last night.

I have the same bag connector as well Michael. ..
I haven't gotten to the point of using it yet though. ....
Please keep us abreast if you find a better one....

Teddy

Hey Teddy, I see you are back from Red Glare, hope you had a great time. I will let you know about the connector, I am leaning towards a different design because I believe that there are better ones to be had and it is a relatively inexpensive part to be mucking around with when the clock is ticking.

 

[mkadams001]

I made something like this https://www.veneersupplies.com/products/Bag-Stem-Assembly.html using a metal valve stem and their connector. It worked ok. I would make a modification where I could use an air line connecter instead of the valve stem.

 

[Onebadhawk]

I have considered putting the gauge on a separate connector like shown in Reinhard's post but then I would have to sources of leaks to deal with.

Here is the logic in the valve and gauge on the connector. The hose is a quick connect so when everything is sealed I can close the valve disconnect the vacuum and move things around, which is a consideration in a work space where I often have to move things around, considering my layups are usually 12 hours. To move the layup attached to the vacuum press, poses more risk to me as my pump assembly is pretty big and not easily moved, both pieces are essentially two hand moves.

I have also thought of using a tee connector and having the hose come off the horizontal point and the gauge on the vertical one. Having said that the hose places very little stress on the connector because I hang it from something where ever I place the layup. One thing, although the picture shows sealant tape around the connector, it does not leak I only put that on while diagnosing the problem last night.



Hey Teddy, I see you are back from Red Glare, hope you had a great time. I will let you know about the connector, I am leaning towards a different design because I believe that there are better ones to be had and it is a relatively inexpensive part to be mucking around with when the clock is ticking.

+1 for that Michael...
And if I know you it'll get jived out...
Let me know what you find....

Yes, thank you, I had a wonderful time in Maryland as I always do...
No kiddin,, if you can make the trip,, it most certainly is a more then worthwhile event,,
though I know it's a haul for you....

Teddy

 

[Screaminhelo]

I have had some experience with these and connector leaks could usually be traced down to wrinkles in the bagging material in these that you are using connector, I never had any trouble with the connector its self. It appears that you have Teflon tape on all of the threads, so I will assume that you have eliminated that as a leak source. Be sure that the rubber seal is not twisting and introducing wrinkles when you lock the puck. The pucks that I have used in the past look identical to the ones that you are using and they proved to be very effective and reliable.

You say that your vacuum pump cycles during the cure. How much vacuum are you trying to pull and what is it dropping to when the pump cycles back on?

 

[Pat_B]

I made something like this https://www.veneersupplies.com/produc...-Assembly.html using a metal valve stem and their connector.

Those are the ones I bought and am overall pleased with them.

 

[pcalvin]

I would also look into your quick disconnect. It appears to be a QD for compressed air. They seal via a spring loaded face seal correct? All of our vacuum QD are an o-ring style.

The twist lock style vacuum chuck you are using is a little tougher to get sealing pressure on, but sealing pressure is not that critical if you have a good smooth bag surface. We make our own threaded collar style vacuum chucks (which have their own issues). When techs call me down to troubleshoot vac leaks the first thing I do is take off the collars on ours and check for smooth bag against the silicone seal, without the collar they still seal from surface area, if the bag isn't wrinkled.

I just tried out some of the twist locks yesterday and I can see how they would introduce wrinkles if your bag isn't tight.

 

[Pat_B]

I've also used some of the gummy bag sealing tape in between the rubber washers and the bag material itself. My valve assembly tends to leak at the metal connection where it disconnects. I find that once I move it around so that it no longer leaks, that it stays that way. That's why my setup would never accommodate having the shut off valve and gage mounted right on top of the disconnect. Mine would leak all the time with that sort of setup.

 

[mpitfield]

I thought I would provide an update.

So I attempted the second T2T layup, same rocket, using my existing connector but connecting it to the bag using another method. I typically oversize my bag to use it multiple times and just trim enough off each time to open it. In this setup, which is only the second time using this bag, I cut a 5x5 square where the existing connector was. I then cut a 8x8 piece of vac bag, applied sealant tape around the edges and pre-installed the connector. I was very careful to tighten it as much as I could without wrinkling or cutting the bag. I then applied this patch/connector to the bag and did a layup.

The result, the connector still leaked, albeit much less but it still leaked. Bottom line my connector does not provide a complete seal, not even close.

So I went on a hunt for a "better" connector and I ordered the one pictured below for $65.00 from ACP Composites. I also ordered a new quick connect (pictured below as well) which has a check valve in it so I can do away with the extra bulky shutoff valve I originally had. Although I was able to prove that my shutoff valve/vacuum gauge were not part of my problem, they were a pain to work with and not really necessary. I have a vacuum gauge on my vac pump that is just as reliable and the integrated check valve allows me to do away with the shutoff valve, which was necessary for my shop setup.

I received a notification that it shipped today so I will be able to use it in the next week or so, at which point I will provide an update.

 

[pcalvin]

Airtech provides a good product, you are on the right track.

 

[Onebadhawk]

I'm waiting with ya Michael, , lol...

Teddy

 

[the random rocketer]

It takes two people to use the first connector. One to spread the bag and hold the base and the other to slit the bag and twist on the top. Then they still leak.

 

[Pat_B]

I built myself sort of a manifold so that I could use two bags at one time. This valve assembly is wall mounted and keeps the weight of the valves off the bag itself.

 

[rharshberger]

I built myself sort of a manifold so that I could use two bags at one time. This valve assembly is wall mounted and keeps the weight of the valves off the bag itself.

I like it!

 

[flynfrog]

The problem you are having is that you are using a pressure quick disconnect not a vacuum quick disconnect. Those fittings are not made to seal in vacuum. They will pull air and kill you pump quick.

The airtech one above is vacuum rated we use them on our autoclaves and pretty much every where else you need a bag passthrough.

 

[Onebadhawk]

The problem you are having is that you are using a pressure quick disconnect not a vacuum quick disconnect. Those fittings are not made to seal in vacuum. They will pull air and kill you pump quick.

The airtech one above is vacuum rated we use them on our autoclaves and pretty much every where else you need a bag passthrough.

uhhh ohhh,,,
I haven't assembled anything yet ,,
but I have all of the stuff for my vacuum set up...
Any quick connect that I've always used on my pressure / compressor stuff
will not work with the vacuum set up ????????????

Teddy