Hello, I want to buy a vacuum gauge for my installation, but I don’t know what range is used in epoxy composites.
What depressure is the correct for composites fabrication?
You need a absolute vac level below 20mbar, better below 10mbar.
Use a digital one like the Greisinger GDH2000
The dial ones in general are relatively useless. OK, they are great to see “if vacuum is on”, but they do not tell you much about the absolute pressure you are working with, as they are in general not built to show pressure against perfect vacuum, and they are too small to be able to read accurately.
There are very, very nice logarithmic vacuum gauges, but utterly expensive.
I usually sell digital vacuum gauges, which are simple and not too costly. (some 300 euro or so)
Don’t you have to have 1013 mbar to reach 1 atmosphere? 10 or 20 mbar isn’t very much vacuum. What am I missing here?
Correct, but I talked about the absolute pressure. I don’t like to say minus 993mbar because the atmospheric pressure is not always the same.
Thats why I prefer the absolute pressure, thats always the same. And never use a gauge that measures relativ, always use one that measures absolute.
I don’t want to spend lot of money on it. If not required an exact depressure measure, I think a cheap vacuum gauge is the best way. I saw this scaled to -30 Hg. what do you think?
A analog one is useless.
Not really useless, you at least can tell you have “a lot of” vacuum. (or not). But indeed it is impossible to tell how much vacuum. These gauges just are not suitable for that.
And they often have inbuilt leaks! The Greisinger costs about 150€ and works perfekt. Nothing is more expansive that material and equipment that dors not work.
For an alternative you can use som digital industry manometers for pneumatic aplications. You can get them at ebay.
What about to use a vacuum regulator like SMC with a digital screen
If digital gauge cost approx 200 euro for the same price you can have both in one
I think this will give the exact reading and permit also to adjust the vacuum if needed
As my old analog gauge died I’m also looking into a new one.
Thanks for all the important information in here!
Had same idea to get a vacuum regulator or switch with a display.
But so far I could only find them giving relative pressure (SMC or PCE industries).
Now I think to use the Greisinger GDH200-14 - any comments on that?
@Herman - what digital vacuum gauges are you using/selling?
For the moment I only buy an analog vacuum pressure (maybe later), so I need the correct range of measure to use? thanks.
You can get the GDH200 from vacmobiles. Works very well
What levels of vacuum do you want for composites? 29.8 or 29.5, is not that different!! An analog gauge, as long as it has good scaling is fine for composites work. They are always cheaper than a digital one. You don’t have to have power for them either. As long as you don’t bang it around, they should always be correct. Your atmospheric pressure will not change so much, that you need to have a perfect reading in your bag.
I’ve used an analog gauge my whole composites career.
digital absolute gauges are a must for composites, if you have never used one I highly suggest you try. After you will never use analog other than for a quick reference of overall vacuum level on your pressure pot. With D.A.P.G. you can read in mbars which gives you great resolution for leak checks. It will tell you exactly how much pressure is in the bagged part, and what the atmospheric pressure is at that moment. I would suggest anyone who is serious about composites to make the investment.
There is a big difference! And the change of the atmospheric pressure is more than you believe. That can make the difference between a perfect part and a not perfect part.
A response from the original poster; “I don’t want to spend lot of money on it.”
I think stating that an analog gauge is “useless” is a little extreme. Like all products, you can buy high and low quality analog vacuum gauges that measure either absolute vacuum or vacuum relative to the local barometric pressure. I can see the benefits of using a digital gauge but if costs are a concern I see no problems using a quality analog gauge with the standard 0-30 inHg range.
Just my $0.02
Are you saying that you don’t infuse on days when the atmospheric pressure is low?
No, I want to say that some pumps create a different vac level depending on the atmospheric pressure, and therefor it is helpfull to controll your absolute vac level. Snd sometimes that makes the difference, also for a leak check. And the GDH200 costs about 200$, that should not be too much.