Is a robinair coolmax 15600 vacuum pump intended to be used to evacuate a tank/vessel at atmospheric pressure repeatedly?
I don’t see anything specifying usage range in the manual.
No, generally not. These pumps are used for extracting airco systems, and they are happy with very deep vacuums, or they will smoke the **** out of you.
I’ve noticed the vapor coming out at certain times.
What’s a better pump design for drawing down from atmospheric pressure?
Snocutt,
I’ve been using a Gast Rotary Vane Oilless 1023 series pump for years now, and it’s totally fine drawing down from atmo. It’s a 10 cfm pump that will do 26"Hg. It’s a bit loud, but you can get them used for $150-$175 on ebay. Rebuild kits are available at reasonable prices, IIRC…
oilless pumps like gast work well. Then it comes down to choosing how much cfm and macsimum vacuum pressure. some will only pull 24hg while others will get 29hg.
The coolmacs robinair will get 29hg at close to sealevel… i’m 650ft above sealevel and got 29 every time with it and it evacuates a vac bag quickly… so cfm is of importance… i wouldn’t go lower than 3cfm or it just takes long to reach full vacuum. Robinairs work well for composite work but it will smoke a lot. and the more you use them for composites the more they smoke, and mine did not like being ran for more than 8 hours.
i ordered a thomas piston pump … once i have used it i will report back… it’s a model 2660. it’s around 3cfm. One composite shop i saw in Cali was using two gast rocking piston pumps.
A bit off the subject, sorry. Fastrr, are there times where the physical effect between pulling 26" and 29" is really noticable, especially during vacuum-bag layups?
Drawing down from athmospheric fast is a typical job for a side channel blower. These contact-less fans extract a lot of air fast, but do not reach deep vacuums.
After the air is out a rotary vane pump (oil lubricated) can be used to draw vacuum to the desired level. The industrial types have self regenerating exhaust filters, which are capable of running for some 10 minutes or so outside of specs. (as in: above -0,5 bar)