Hi All,

I've been infusing for a few years now and recently I've purchased a Greisinger GDH absolute gauge. My question is, when everyone says they get a perfect leak proof bag - is it really? Is there an acceptable tolerance for a leak to still be considered perfect?

Obviously the volume/size of the part being infused is relevant so after multiple tests envelope bagging a 1m2 glass mould with about 1mm thick laminate + flow media. I've had leaks ranging from 1mbar/hour to 10mbar/hour.

I've been under the impression that a perfect seal means it should keep the same vacuum for days on end. Is this asking too much?

The parts I'm infusing are cosmetic carbon so avoiding any pin holes or bubbles is the goal.

Thank you.

Welcome  to the digital gauge club. For me, one of the best tools you can get for vacuum infusion.
No, it's impossible to get a 100% perfect seal. Especially not with typical resin infusion equipment.
Most people use analogue gauges, wich aren't suitable to detect small losses, so when they speak of a perfect seal, this only means that there are no detectable leaks.
1mbar/h is a good seal, 10mbar/h could be ok if you are not using slow curing resins.
I aim for an end pressure during evacuation, and don't do a drop test at all. First I connect the gauge directly to the pump, to see what is able to achieve at the moment (wich changes with temperature and humidity). Then I work on the vacuum setup until I get within 2mbar to that. For really big moulds, 5mbar is ok for me.

I've got a digital gauge, but haven't used it in years. I still find the quickest and most reliable leak indicator is the tone of the pump - I know if my bag is sealed well before my gauge ever settles on a number. That said, mine is not a Greisinger GDH and I understand these are very good, so perhaps mine just isn't as useful as yours. 

I do every now and then leave a part under vacuum for days before infusing it, sometimes because I'm waiting for warmer weather, sometimes I just get distracted with other work. Generally, a slight leak will still be present. After 2-3 days, when you reconnect the part to the pump, you will probably hear a slight change of tone for a brief second as that air is evacuated again. If you tug on the bag, it should take 4-5 days to notice any slacking of the bag. This degree of leak is fine, and won't make a difference to the infusion. 

Since I got the Dvp pumps, the sound of the pump isn't as useful as before anymore. This works only with oil bath pumps. But the far superior performance and the abstinence of this slight oil mist around the pump are worth it.
I found that the gauge is more accurate than the pump tone of my older pumps. Additionally, it tells me where the leaks are. I can work my way along the seal, and the pressure immediately reacts if I am working on a leak.

Yeh I'll admit it is harder with the DVP pumps, i tend to use my DVP for pre-preg and my older pumps for infusion, just for this reason.

I should get a Greisinger, I do only hear great things about them. 

I've got a "vac checker" made by dd compound. I can't complain about this one. It shows the boiling point of water at the current pressure, wich is usefull when working with aramid.

Thank you, Oekmont and Hanaldo.

I can highly recommend the Greisinger, one of the most useful tools I've ever purchased.

I did not realise just how hard it was to get a bag to

Hi guys, ive struggled alot when it comes to making a perfectly sealed bag. ive been recommened to use a digital gauge, but i havent understood why/how a digital gauge would help getting a sealed bag? 
from what i undertand, the analogue gauge will tell you if the theres a vac leak, wouldnt a digital gauge do essentially the same thing?

thanks

I have described the procedure in my first post of this thread. An analogue gauge is simply not nearly accurate enough for this method. Analogue gauges can help you determine if your bag is tight after a drop test, but they can't give you live feedback while you are working on the bag. With a digital gauge you can work your way around the sealing (while the pump is running) and keep an eye on the pressure and you will see an immediate reaction of the pressure once you come across a leaking area.

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