Zero Leak Vacuum Infusion

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Zero Leak Vacuum Infusion

Author	Message
leeks	l leeks posted 5 Years Ago Post Details
l Group: Forum Members Posts: 7, Visits: 3.7K	+x 8900120dd - 10/17/2019 8:45:33 AM hi guys, ive purchased a digital gauge (gersinger GDH 200) its very useful for finding leaks by watching the gauge while the pump is running. however as soon as i switch the pump off, the vacuum drops dramatically, but the bag is still extremely tight, this leads me to believe i am using the gauge wrong! i did a quick test, by connecting the gauge directly to the pump, and then block the line when it hits zero psi. but then the gauge reading kept creeping up by 0.1 psi every 2 minutes. am i doing something wrong, should i be setting the absolute (zero) before pumping vacuum? thanks I had the same issue with mine when I first purchased a GDH. You will find the issue being you require more volume for the gauge to read accurately without the 'creep'. If you do not have a catch pot/vacuum chamber to gain additional volume, try doing the same test with a lot longer vinyl hose - atleast 3+ meters.
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Designbikes	Designbikes posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 4, Visits: 14	I have been working with the GDH 200 and the Vac Checker for a few years now and would never ever do an infusion job without a digital pressure gauge. I always connect the gauge to the resin inlet line during the evacuation process to see what is going on in the bagged system. These gauges are so precise that you see in an instant if you found a leak which saves time during the process setup. With an analog gauge I am not able to see the difference between 10mbar and 100mbar. An absolute bag pressure of 100mbar leaves 10% air in the system which is the origin for voids in the laminate whereas 10mbar leaves only 1% air. I always try to reach a value below 10mbar, the lower the better as well as I always do a vacuum integrity check which allows not more than 3mbar/3 min pressure rise. https://german-advanced-composites.com/vacuum-resin-infusion-process leads to an article from German Advanced Composites and might help to understand the physics behind. Edited 5 Years Ago by Designbikes
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Chris Rogers	C Chris Rogers posted 5 Years Ago HOT Post Details
C Group: Forum Members Posts: 120, Visits: 933	I totally agree that digital gauges are a huge help with infusion but an important thing to consider when pulling really high vacuum levels is that you get into the problem of volatile materials - mostly water - boiling off in your bag. A lot of the problems you see on a drop test are moisture related once you have a really good bag. If you drop test an almost perfect bag (sub 15-20 mbar) and then let it sit under high vacuum for a few hours you should notice that your drop test results look a lot better if you drop test again after time to evacuate the moisture. In the sub 50 mbar range most high vacuum pumps can only move a very small volume compared to their rated free-flow capacity so it takes a long time for moisture (because when something becomes a gas it gets huge!) to get sucked out. Last week I wrote a post about troubleshooting infusion which goes all over this: https://explorecomposites.com/2019/11/19/troubleshootin-vacuum-infusion/ and you should check out this info from Vacmobiles which explains moisture issues really well: https://www.vacmobiles.com/vapour_pressure.html
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Warren (Staff)	Warren (Staff) posted 5 Years Ago Post Details
Group: Administrators Posts: 2.5K, Visits: 7.9K	Some great information on those links. Should be of good use to anyone struggling with infusion. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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Designbikes	Designbikes posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 4, Visits: 14	+x Chris Rogers - 11/25/2019 7:25:37 PM I totally agree that digital gauges are a huge help with infusion but an important thing to consider when pulling really high vacuum levels is that you get into the problem of volatile materials - mostly water - boiling off in your bag. A lot of the problems you see on a drop test are moisture related once you have a really good bag. If you drop test an almost perfect bag (sub 15-20 mbar) and then let it sit under high vacuum for a few hours you should notice that your drop test results look a lot better if you drop test again after time to evacuate the moisture. In the sub 50 mbar range most high vacuum pumps can only move a very small volume compared to their rated free-flow capacity so it takes a long time for moisture (because when something becomes a gas it gets huge!) to get sucked out. Last week I wrote a post about troubleshooting infusion which goes all over this: https://explorecomposites.com/2019/11/19/troubleshootin-vacuum-infusion/ and you should check out this info from Vacmobiles which explains moisture issues really well: https://www.vacmobiles.com/vapour_pressure.html Absolutely correct and the Vac Checker indicates when the moisture in the bagged system starts boiling and the volume to be evacuated is increased by the generated vapour. You come to a halt with the evacuation process when this happens, with room temperature at around 30mbar absolute pressure. Depending on the amount of moisture and the performance of the vacuum pump it can take a while until all vapour is drawn out of the the bagged system. Edited 5 Years Ago by Designbikes
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Hanaldo	Hanaldo posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Good post Chris, lots of good info. All though for the record, I do this for a living and I ALWAYS clamp the vac pump and shut it off after the infusion has completed 🤠
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