Blue harbor freight vacuum pumps

[Coop]

I have tried 2 of the blue Harbor Freight vacuum pumps with the R134A fitting and can not get them to work correctly. One left in the blue box and one not. Ball values in right spots and no leaks are to be found on the pot/chamber. Great Pressure but no Vacuum! When I tried to open the lid with vacuum on nothing was noted relating to any release of suction. When I place vac side fitting on face I can't feel hardly anything when it was pumping. I can't get anything to register on vacuum gauge. But the gauge may be OK just not enough vacuum to make it move the needle. Any ideas folks? My ole brain is puzzled!!COOP

 

[stevers]

Been working with Coop and am sort of puzzled as well. We are curious if the smaller pancake type compressor is to small to properly operate the vac pump. Maybe not enough volume. He means he tried the cheek test and felt no vacuum.
Come on guys, I know one of you has an answer.

 

[dfurlano]

I use a pancake and the HF venturi but you need a shut off to quickly capture the vacuum.

 

[gketell]

I know on mine it will very very slowly pull a vacuum at 70psi but will very quickly pull a vacuum with 90+psi. Mine is a 4.5HP, 30 gallon air compressor and it will kick on from full pressure before I get that full vacuum. So a pancake at 45psi might not cut it.

GK

 

[Firefyter-emt]

Interesting.. I think if you bump up the preasure it might work for you.

Steve, do you think my compressor will be able to handle it?? [}]

btw, that's really a 60 gallon tank. Note the gauge, it's a 3" gauge.... that motor is freaking huge!!

 

[stevers]

uuuuhhhhh, let me think, maybe.

 

[leehljp]

I have a 3 gallon size 3/4 hp air compressor and finagled the Air INTAKE of the compressor to act as the vac side - hooked to my HF vac tank. It works well. Turn it on for about 1 minute and I have 22 - 24 on Vac gauge. I really need a filter to go between the tank and the pump but can't find one here. I might make one or pick one up the next time I am in the States (March '08).

It is HARD and EXPENSIVE finding a vac pump here in Japan.

 

[Coop]

I'm going to take the pot to someone with a larger compressor and see what happens! My 3 gallon pancake may not be enough for the Vacuum side.

 

[DocRon]

I expect that the compressor size is the problem. These little vacuum pumps are actually venturi devices, and as such are sensitive to flowrather than to pressure as such, even tho the two are related. A 90 psi compressor operating with the outlet valve turned down so that flow is low won't genrate much vacuum. My experience comes from using water venturi pumps in the chem lab, for vacuum filtration, and if the water flow is too low, the vacuum does not happen.
Hank, that is a neat idea, to use the input to the compressor as a vacuum. You really should get the filter, tho.

 

[leehljp]

Originally posted by DocRon
<br /> &lt;snip&gt;
Hank, that is a neat idea, to use the input to the compressor as a vacuum. You really should get the filter, tho.

You just triggered a thought - and I think I can make one. I will have to give it a try.

 

[armchi]

I just set mine up myself but have not really done anything with it. Mine will hold the pressure with very mnimal leak for about 24 hours, but I find it will leak when under vacuum. I also have a very small pump. If I just hook up the pump to the venturi device and turn it on, I can pull almost 20 Hg but not any higher. The pump itself does not go up to nearly it's maximum pressure. What I've done is turn the pump on until it reaches it's 20 Hg maximum vacuum then shut the valve off and disconnect the hose so the tank fills up to it's maximum of 90 PSI (the regulator is setup to 90). I then quickly hook the hose up and turn the valve back on. This causes the gauge to reach almost 30 Hg. I shut the valve back off before it starts to go down. Maybe I should install a second valve before the venturi connection. That was just my tests. It held the vaccuum for a while but I think after 12 hours it was all gone.

Since I've not done anything, I don't know how long I should hold the material under vacuum. But from reading some of the posts, an hour or two would be enough. If this is the case, I don't have to worry too much about my slow vacuum leak.

 

[gketell]

Actually you only need vacuum for a very short time. Just long enough to expand/pop the bubbles. What you don't want to do is hold the vacuum so long that the resin starts to set with the air bubbles expanded. If you mix a slow-set batch (a few hours to set) then pulling the vacuum for 20-30 minutes is ok. But if you have a fast set batch you basically want to pull the vacuum, hold it for a few seconds, release and then apply pressure.

Or, as others do, vacuum the resin after mixing in the colors but before mixing in the activator then mix carefully to not add any new bubbles, pour and go straight to pressure.

GK

 

[Coop]

Stevers design is great! Steve and others were right! nothing wrong with my pots vacuum. My 3 gallon pancake was not enough to run the vacuum. I went to a friends house who has a 220 volt 4 hpr compressor. We hooked it up and in 4 seconds we were at minus 29 and it has been hours now and still holding vacuum. I GOT IT! ole Coop sends his Thanks to all my friends at IAP. The Mrs. said "go to Sears and get a bigger compressor" god love that woman!

 

[stevers]

Congrats Coop. I new you could do it!