Making a metal wool foreline trap, looking for advice :)

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Albert Mery
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Joined: Fri May 03, 2019 5:53 pm
Real name: Albert Mery

Making a metal wool foreline trap, looking for advice :)

Post by Albert Mery »

Hello all,
I am planning on making a simple foreline trap to prevent oil vapor from the foreline pump from reaching my turbo. I was planning on using metal wool (probably stainless wool because of availability) in a KF25 elbow. A holder would be used to easily replace the metal wool frequently.
A rough diagram of the trap
A rough diagram of the trap
I was wondering if anyone here had any experience building such traps and I would be very grateful is such a person could give me some tips. I have seen activated carbon also being used, would that work? Also, I've read that Lesker's MICROMAZE traps are able to reduce the foreline pressure by an order of magnitude, I was wondering how that worked and whether a simple metal wool trap would be able to achieve the same effect?
Cheers!
Albert
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Richard Hull
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Real name: Richard Hull

Re: Making a metal wool foreline trap, looking for advice :)

Post by Richard Hull »

I did not know that the micro maze was still sold by Lesker. I have used the micro maze trap back in the 90's it was great as long as you kept it well baked out. (heater is included internally) It will, indeed, get one decade deeper than the pump. However, it should never be used in a system that is leaky or one that will be opened to air repeatedly.

Issues with the micro maze.... it collects all manner of nasties! If you have a dirty system, it will scavenge all the filth. Great, right? ...Well....yes, but.... At bake out all that garbage will go into your pump oil. (pump must be run all during bake out). Likewise, the pump must have its bypass valve wide open to let the garbage water vapor and fouled oil vapor out of the pump to cleanse the oil. This process can take a full two hours or more. Quality valving is demanded on both sides of the micro maze for obvious reasons. You better vent the pumps exhaust as over the two hour cleansing, the shop or lab will fill with oil and water mist plus whatever nasties belch out of the micro maze. I still have the maze in my separate experimental line on the fusor table. It does allow for submicron pressures on a mechanical pump when freshly baked out.

I did my first fusion using a micro maze and no secondary pump. I would not recommend it to a dedicated fusioneer. It is not a secondary pump nor will it replace one!

Under no circumstances will any wool oil trap in the pump line equal the abilities of the micro maze to make a mechanical pump go low. The micro maze must be micro managed to do what is claimed of it. Most newbies do not understand vacuum system dynamics to use it wisely. I didn't....at first, but learned to use it well until I got tired of baking it out and got a diff pump on fusor IV back in 2003.

Attached an image of my micro maze in use on fusor III in 2001. The valves must be of high quality and attached directly to the maze!!! I also attach an image of the transfer to the fusor IV bench in 2003.

Richard Hull
Attachments
2001 micromaze pix.jpg
IV const micro maze arm.jpg
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John Futter
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Re: Making a metal wool foreline trap, looking for advice :)

Post by John Futter »

Albert yes you can make your own
the oil vapor condenses out on the extended surface area that you are presenting so it pays to have a reservoir to collect the condensate.
Commercial ones i have taken apart have used copper mesh while a lot of others use alumina beads that also trap water vapor due to the correct pore size
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