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Post by john b on Feb 7, 2019 11:29:40 GMT -5
Hi everyone,i was wondering if someone might help me out. Im looking to buy a new vacuum pump for degassing some water clear. What im really after is something that can pull near .30 and do it QUICK! for speed of vacuum i keep reading that you need at least 1 horsepower, and that it should be a 2 stage instead of 1 (roatry vane). some say you need higher CFM (like 8) and others say it doesnt matter, the CFM i mean. My last pump was a 1/4 HP zeny and it took almost 3 minutes to get to full vaccumm, which really cuts my working time down.
thanks so much for any help
john b
p.s. im eyeballing a robinair 15800 but im wondering if thats overkill.
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Post by cobra7447 on Feb 7, 2019 13:30:25 GMT -5
Hey John. What you want is a dual or two stage Vacuum pump that can pull at least 6 CFM anything less is too slow. It has to be two stage and maybe 5 CFM but don't go below 5 CFM I'd say 6 CFM is ideal. I use a Mastercool pump. Check on eBay sometimes you can find them used a little cheaper.
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Post by cobra7447 on Feb 7, 2019 13:32:25 GMT -5
When dealing with water clear alumilite I would recommend degassing as well as pressure casting to ensure you get crystal clear bubble free parts.
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Post by john b on Feb 7, 2019 15:03:45 GMT -5
hi all thanks so much for the quick replies. yes i read that 2 stage is much quicker. and yes i do already have a compressor and a pressure chamber which works great. Just wasnt sure what part of the specs is responsible for the "quickness" of achieving vaccuum. heard some people have a 6 CFM but it took over 4 minutes to get to .30. But i think if i go with the one i listed it should be good. also read that its really important to change the oil out, almost after every use.. which is something i neglected to do with my little 1/4 hp zeny. seems like you need a science degree to figure out which rating is responsible for fast vacuum. thanks again yall! hopefully someone else will stumble on this post and get some answers as well. happy day!
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Post by cobra7447 on Feb 7, 2019 15:24:04 GMT -5
Well yeah some say you should change it after every evacuation. Honestly I don't change it after every evacuation. I do change it frequently but not quite that frequently. I would recommend Black Gold vacuum pump oil. Just monitor it. once it starts to look kind of hazy or slightly yellowish go ahead and change it. Sometimes I can get 15 evacuations before I change oil other times less it just depends on what you're degassing and how frequently you're using it. Just make sure you run it a bit before you drain the oil. It'll come out easier when it's warm. You can buy the oil in larger containers on Amazon for a good price. Getting down to 30 will be easier with a two-stage pump. My first pump was a single stage pump and it was slow and not good for what I was doing. Dual stage makes all the difference you will be amazed at how fast that gauge starts moving once you get your new pump.
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Post by john b on Feb 7, 2019 17:38:36 GMT -5
awesome! good news, thank you Cobra!
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