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Casting & Stabilization Making your own blanks & stabilizing wood blanks.

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Old 05-19-2018, 02:06 PM   #1 (permalink)
Join Date: Feb 2018
Location: Seattle
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Default Vacuum pump oil in hose

I did my first real stabilization the other day. After about an hour when I came out to check the progress I noticed that the hose running to the tank had some of the oil from the pump backing up into the hose and some had actually gotten into the tank and mixed with the cactus juice. Any ideas on what could cause this, especially since it was holding about -30 pressure? I'm thinking that the oil was actually boiling as the pump housing was very hot. The only reason I knew some had backed up into the chamber was because the pump oil has a slight blue color to it. The oil level is below the MAX line but not by much. Should I pour some out?

Should I not leave the pump running when I am stabilizing after achieving full vacuum? The pump still seems to be working fine. I'm thinking I should put the pump on the floor with the chamber up on the bench? Should I turn the pump off after the fine bubbles are greatly diminished and just let it hold vacuum and maybe turn on the pump for a minute or two during the process? The chamber does a good job of holding pressure.

After watching it I see rather large bubbles coming up from under the piece being stabilized. I think I read somewhere that that is not coming from the wood but from the liquid boiling because of the reduced pressure?

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Old 05-19-2018, 11:21 PM   #2 (permalink)
Join Date: Jan 2015
Location: Centennial, CO
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Change the oil in your pump ASAP. I reduce vacuum if I see the bubbles getting close to the top of my chamber, then reapply full vacuum as the bubbles go down. Some time it takes three or four cycles until the bubbles stay away from the top of the chamber. I have left my pump running for hours w/o problems.

Last edited by tomtedesco; 05-19-2018 at 11:24 PM.
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Old 05-20-2018, 01:19 PM   #3 (permalink)
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Location: Bloomington, MN
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I'm a little puzzled by your setup. You have what looks to me like a metal stabilizing chamber attached to your pump. Maybe it's a clear chamber, but I can't tell from the photo. Your second picture looks to me like a clear chamber in which the blank is soaking in stabilizing resin.

Are you pulling the vacuum in one chamber, and then transferring the blank into a second chamber for soaking? That's not advisable. If I'm misunderstanding your setup, then ignore the previous comment.

I don't know what caused the oil to backflow into the chamber; I'm just speculating. After you achieved full vacuum, did you shut off the pump without closing the valve, causing the oil to be pulled into the hose and the chamber?

If you're going to shut off the pump, you should close the valve first to hold the vacuum in the chamber to avoid equalization of the vacuum, which I understand (and could be wrong) could cause oil to pull into the chamber from the pump reservoir.

You should run the pump continuously until you've achieved what you believe is complete evacuation of air. Once you get to that point, open the valve, shut off the pump, and allow the resin to infiltrate the blanks. Typically, the time for that should be about at least as long, if not longer, than the time you pulled full vacuum.

I put my pump on the floor and the chamber on a bench. I only do that because the vibration noise from the pump running is less annoying than if I place the pump on a the bench.

I let my pump run overnight. That's probably longer than necessary, but I'm not under a time crunch.

Last edited by Brian G; 05-20-2018 at 01:23 PM.
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Old 05-21-2018, 01:33 PM   #4 (permalink)
Join Date: Feb 2018
Location: Seattle
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Brian G - The clear plastic container just sits inside the metal one to cut down on the amount of cactus juice needed when I'm doing small pieces.

The strange thing about this is that the pump was running and pulling vacuum when the oil backed up into the hose with valve open. Don't know how it could possibly do that. Then I close the valve and turn off the pump. Pot holds vacuum well.

After a few hours the pump seemed to get hotter than I think it should have so running overnight probably isn't a good idea.

I got the pump and chamber on CList so maybe the oil is contaminated and shouldn't have that blue/green tint to it. It just seemed strange that oil could work it's way up the tube against the direction of the vacuum whilst the chamber vacuum was holding steady at -30.
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