Wow he simply gave an example of how it works from piecing parts together. Wether those pieces are custom fab or just meticulously ordered to fit perfectly together.
He showed a solution and seemed proud of his work. Why knock a guy trying to show us a way. May not be the only way to do it but it works for him…
I would say the vast majority of us havent. U sound like a miserable teacher who doesnt want his students to ask questions and just read the book. “Did u read the whole book? No? Then we cant talk about it”
I personally have not worked on putting a machine together this elaborate but the way i see it, i would prpbably want to put a ball valve after the gear pump, so that the gear pump isnt feeling any stress?
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Kotk was nice for sharing how he did. I wish we could demystify this once and for all. I want to build these for myself but don’t have the pesos to r&d all these pumps I’m seeing so any true info helps. Moving pictures are a great bonus!
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Gear pumps are made to operate under vacuum flow.
They are used in a variety of industries, plastic injection molding, chemical synthesis as dising/flor pumps, oil and gas as feed pumps, etc…
A similar style pump, lobe pumps, are NOT made for vacuum use, but can handle more chunky consistency products. Lobes are use for food and beverage industries, almost every processed food you eat is produced using lobe pumps.
Gear pumps by their design tolerances are MADE to operate under vacuum.
The tolerance of the head dictates the vacuum level the head is capable of being pulled down to, to feed towards, or pull out of.
Lots of the pump heads @Kingofthekush420 posted he uses are NOT made to withstand high vacuum levels. Like stated, the precision of the gear pump mechanism dictates the level of vacuum ability they can feed from and pull out of, WITHOUT needing check valves.
You don’t necessarily need check valves, or even gear pumps for a WFE.
You can use a needle style PTFE valve to control the I let flow, and use your vacuum levels to control the inlet flow to a WFE.
Most of the stills I used in my organic/Inorganic labs in college did not have checkvalves or gear pumps. They are unnecessary. Unless you start wanting to feed at a very high speed, or work with a substance that is highly viscous even when heated.
Having a ptfe needle valve does not seem that precise…
Why settle for something u have to get in the perfect rotation everytime when u can just press a red button and everything flows the way u want?
If the gear pumps were perfect then yes we wouldnt need a check valve but almost all the times ive seen gear pumps used from summit brand to B&W brand, they all needed a check valve eventually.
So yeah maybe a 50k gear pump would work perfect but i think most of us will settle with an imperfect (sub $3k) gear pump that just needs a check valve or ball valve to function properly
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Just put your check valve in a place that is 1) easy to replace, ideally with a valve upstream so when it needs service its easy to swap. 2) have 2 or 3 checks on hand. you might not see any issues for a yr, or could see issues in 2 weeks. 3) Liquid column with “goose neck” is your friend (although this has been debated) Height of such isnt trivial and i think theres benefit to having a smaller discharge nozzle ID than the tubing. Continuous discharge from high vac is a difficult app and aint nothing wrong with redundancy, im a believer in “the little things add up” (for better or worse )
Def could design your own if ya got the time. the industry needs a check for this app specifically. At the very least it does make for a simpler startup/shutdown i guess. (might could instead use a flow sensor and solenoid thats spec’d to temps)
I think the best check would have the following characteristics - 1) minimal volume and deadspaces. 2) easy to heat uniformly 3) drainable 4)easy to service (seals and mechanism) 5)…thoughts? i know im missing something here
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You have a line to give them feedback on their gear pumps? Because whoever designed their stainless rotating shaft that goes inside not one but two stainless plates, in an environment that withstands tremendous thermal cycles and no bearing/bushing to speak of can suck my ass
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Yeah. Send me a picture of the issue. Document the problem.
They redesigned alot based off my comments months back.
Taking a negative stance towards a manufacturer gets you nowhere.
They have engineers that CAD all their machines.
I have a few chines gear pump MFG’s I can reference them to use too, I haven’t had issues like what you are stating.
Witte gear pumps have steel shafts with no bushings too.
Maybe your pump heads were too tight of tolerances.
I would think for deep vacuum you would want an actuated ball or globe valve. IMO, most check valves don’t seal well enough to hold micron vacuum, regardless of soft seals. I also don’t see gear pumps holding hard vacuum while not running. Especially if they operate at a range of temperatures (if the seal tightly at room temp, wouldn’t they bind at elevated temp?). I’ve personally worked with a ton of deep vacuum equipment but never had a chance to use a gear pump as a positive shutoff
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Companies need their noses rubbed in their own shit until they stop doing stupid stuff and selling it at a premium. Putting a rotating shaft inside a metal plate, both made out of a metal known for galling is a recipe for failure.
Don’t know if I’ve got any pics of the failure but I’ve repaired at least a dozen of these pumps and ones clearly very similar or inspired by the yhchem ones all with the exact same failure, always galls on the stainless shaft inside of the stainless plate. A brass or bronze sacrificial bearing/bushing would keep this from happening if the OEM knew WTF they were doing
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Could be remembering wrong but the witte pump’s gear is a molybdenum alloy specifically for high heat steel shaft contact, not just normal steel(s).
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Hi , great post here. Any chance you can DM me with some of the parts you have had success with. We are trying to build a feed system and two discharge pumps. Happy to pay for your help with this since you already went through the pain of putting it together.
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Could get some ideas from this