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Vac Pump Cruelty

aga - 28-4-2016 at 12:34

My single-stage, single-vane vac pump failed to pump today, so i pulled it apart.

Here's the Innards with just the oil resevoir removed:

This is some goop that was in there (it started as a clear oil) :

It feels lumpy and a bit rubbery, similar to broken up bits of the factice i made some time ago.

Hardly surprising seeing as no end of nasty liquids and gasses have gone into it.

Disassembly is dirty and oily, as will be the cleanup and fixing.

Lesson learned : always use a crap-trap in line with the vac pump or it will get broken.

The real shame is that i had already integrated it into my new fume hood.

The shiny new (and illuminated!) button got pressed for Vacuum and just a distressed buzzing sound happened, no vacuum

Thinking of vinegar or dilute phosphoric acid to rip all the rust out.

Magpie - 28-4-2016 at 12:39

Vacuum pump abuse is one of society's most heinous crimes.

aga - 28-4-2016 at 12:45

I was thinking of posting in 'The Cops Showed Up' thread, but they didn't.

Vac pump abuse like this goes on behind closed doors all the time.

If any pumps are affected by this post, please visit www.pumpline.com for help and advice.

Loptr - 28-4-2016 at 13:25

I freaked out a while back when hose full of solvent made a straight-shot from the vacuum-take off adapter (not sure exactly how it happened) and into the pump. I pulled the pump apart shortly afterwards to clean the innards and the pump ended up being alright after that. The damage that it did incur was to a filter can that sits in between the hose barbs and the pump itself--a corrosion took place that caused it to grow a beard on the bottom of the can. It looked like a little gnome without a body, and a little similar the nitric acid gnomes I saw back at school.

aga - 28-4-2016 at 13:41

LOL.

Brilliant description Loptr, just brilliant.

Detonationology - 28-4-2016 at 13:57

I was running a nitric vacuum distillation today, using the double trap method. I had my pump open a few weeks ago for cleaning, but for some reason, all 4 of the vanes were seized when I went to start it up-- not a single mm of Hg. Not happy when I took it apart to realize that some black goop plastered the vanes into place. A washed with acetone and wiped with a rag, then used the air compressor to blow out any dry crud. Not sure if it was caused by my choice of oil or simple from neglect.

aga - 28-4-2016 at 14:00

The choice of oil seems quite important.

Currently all i have that appears suitable is 'baby oil' (some slightly watered mineral oil).

I;ve heated it before and it gives off vapours and goes a bit brown : i expect that it's better boiled for a while before sticking in a vac pump.

Chemist_Cup_Noodles - 28-4-2016 at 15:23

Hm, what about a silicon based oil? Similar to one that you might use for a lab oil bath and also a lubricant? They seem kind of pricy, but idk if they would work or not. Surely they are quite inert though, so it shouldn't f*ck up your pump like baby oil did. But tbh it looks like you skipped the oil part of baby oil and flung baby shit all in there.

NedsHead - 28-4-2016 at 16:35

When the local heating/cooling supply store is out of vacuum pump oil I use pneumatic tool oil, it works just fine

Magpie - 28-4-2016 at 17:44

Quote: Originally posted by aga

Vac pump abuse like this goes on behind closed doors all the time.

This is also one of the most under-reported crimes because of the stigma. Thank you for having the courage to report this.

j_sum1 - 28-4-2016 at 18:43

Hey. I don't feel so bad now.
I inadvertently did violence to my diaphragm pump a few months ago.
I put some iodine vapours through it which I don't think helped the aluminium parts very much. I also flooded it by not looking how full my filter flask was getting. And, like an idiot, I did not disassemble and clean it right away. I did not appreciate the damage until the next day when I turned it on and there was no suck at all.

But the gaskets were still intact. It responded well to the cleaning out of crap. The inside does not look so pretty but it is still functional. And I have made a solemn promise with a boy scout salute to never suck nasties without a trap.

You could probably call me a reformed pump abuser. But the truth is that I still have not constructed or purchased a decent trap.

XeonTheMGPony - 29-4-2016 at 08:55

Quote: Originally posted by NedsHead

When the local heating/cooling supply store is out of vacuum pump oil I use pneumatic tool oil, it works just fine

Won't for too long though.

Hydroshocked Dry Mineral oil or a synthetic Silicon rated for vacuum pumps. Synthetic silicon ones are the best IMO.

Very good scrubber then mechanical filter, better would be Wet scrubber> Drying scrubber > Mechanical 1uM filter.

Trick is preheat the pump (Let run blanked off till at operating temp)

This will maximize the health and life of your pump, in refrigeration we can't do as all of that but I all ways use a large filter dryer on mine to help protect from contaminants

To flush a pump out drain off half the oil, measure out a fresh bit of oil matching the drained portion, slowly feed it into the intake so it flows through the vans, drain all oil from pump, pulse on for a second and no longer, refill with fresh oil, and run till at operating temp, continue for 10 minutes then shut down and release the vacuum.

Filters and oil are much cheaper then a new pump! and to make a solid scrubber filter system is very easy! 2 - 1L Erlenmeyer flasks and a water cartridge filter would do the job impeccably.

1l wet scrubber, 1L drying scrubber then the 1micron water filter to remove any particles that made it through

aga - 29-4-2016 at 09:04

Currently this poor pump is undergoing emergency surgery.

Amazing how well phosphoric acid rips the rust off, especially with a toothpick to scratch off the sludge.

Most of the bits are now rust-free under mineral oil, awaiting re-assembly.

Doing the big casting part at the mo.

XeonTheMGPony - 29-4-2016 at 09:13

inspect the bore care fully the finest of scratches will obliterate its vac capability

[Edited on 29-4-2016 by XeonTheMGPony]

aga - 29-4-2016 at 10:11

I did wonder about stuff like that, hence using a wooden toothpick rather than a metal scraper (e.g. screwdriver).

aga - 29-4-2016 at 11:19

Wow ! I'm impressed !

Here's how it looks after a few hours in ~50% phosphoric acid with some gentle scraping.

The shine is due to some mineral oil coating to keep the air out.

[Edited on 29-4-2016 by aga]

XeonTheMGPony - 29-4-2016 at 12:55

If the bore has been gouged or has pits in it and they are not too deep you can recover it by care full honing with a brake cylinder hone with a constant slow flow of mineral oil in a cross thatch pattern, but you'll probably need to get new blades.

Once that is don run for 30 minutes with fresh mineral oil, power purge (Dribble oil into the intake port while running) then drain refill with fresh oil and let run for an hour. Both runs are don with a tiny bit of air allowed to run through.

After this it should pull a good vacuum again, not like new, but use full.

aga - 29-4-2016 at 13:13

The 'bore' by which i assume you mean the hole that the vanes spin in, that part is clean and scratch-free.

We'll see if it works when the cleanup/reassembly is done, so try not to lose too much sleep.

XeonTheMGPony - 29-4-2016 at 13:22

that's a good thing then!

Puzzle Pump

aga - 30-4-2016 at 01:42

Well, these are all the actual pump Bits.

They all came Out, so i guess they all go back In somehow ...

aga - 30-4-2016 at 04:27

Success !

Thanks to the support of all the VPAA people out there.

(vac pump abusers anonymous)

Edit:

Rigged up to the 'hood it reads at about 20 mbar (15 torr) which i think is roughly what it has always shown as it's best vacuum.

[Edited on 30-4-2016 by aga]

Dr.Bob - 30-4-2016 at 06:15

Just changing the oil occasionally will do wonders, but I will admit that we often only change it every 6-12 months, but we do have a trap or two for most pumps, and try to keep them cold with dry ice at all times. But the Welch I mostly use (at work) has been in use for 5 years without any issues, and it was old when I got it. The other one I use now, another old Welch, looks even older, if too small for the number of things on it, and barely restarts if turned off, but still pulls a decent vacuum. But I know it is on borrowed time, it looks older than I do, and sounds worse. We did just change the oil, but the sight glass is so old and filthy, that it is barely even possible to see the fill line, have to use a strong flashlight.

aga - 5-5-2016 at 12:14

Today i got some 'proper' vac pump oil, so changed out the Baby Oil that i'd used as a stop-gap.

With the Baby oil i got 20 mbar.

With 'Proper' oil i get 100 !!!

Edit:

That's 80 mbar WORSE in case anyone was wondering.

[Edited on 5-5-2016 by aga]

Loptr - 5-5-2016 at 12:39

Quote: Originally posted by aga

Success !

Thanks to the support of all the VPAA people out there.

(vac pump abusers anonymous)

Edit:

Rigged up to the 'hood it reads at about 20 mbar (15 torr) which i think is roughly what it has always shown as it's best vacuum.

[Edited on 30-4-2016 by aga]

aga, got an extra room? I think I might come to stay with you for a while. The background in your photo is gorgeous!

My backyard is a graveyard and a university. Kind of strange.

[Edited on 5-5-2016 by Loptr]

aga - 5-5-2016 at 14:02

There is one extra room, although that's reserved for the kids if/when they want to come home for a while.

Basically No, and you can't come and live in my new fume hood either.

Yeah, i do kind of live in paradise.

'Paradise' all depends on your state of mind.

Most places are Paradise, just takes the Eyes to See.

If you do not like where you live then you can Move to somewhere Different.

I did 10 years ago, and do not regret it at all, quite the opposite.

careysub - 6-5-2016 at 11:15

A question about pump strategy:

I have an aspirator set-up (5 gallon bucket, pump, aspirator) for stripping off solvent, and distillations down to 20 torr or so.

I also have a Harbor Freight two stage pump (good to 22.5 microns) which I am setting up as a dual purpose vacuum bagging pump for composite construction, and also for doing low pressure distillation (below 20 torr) of what I expect would be relatively small batches.

The vacuum bagging system design:
http://www.joewoodworker.com/veneering/EVS/concept.htm
has PVC vacuum reservoirs totaling about 6 L in volume that will act also as particle settling chambers.

How much additional pump protection do I need to add? Options include a particle filter (perhaps just a SS mesh screen?), activated charcoal, an acid remover (sodium carbonate?), a drying agent and a cold trap (would ice plus calcium chloride? suffice).

I am thinking that a drying agent is not really necessary, as the pump would typically encounter atmospheric moisture anyway in normal use. I would guess that an acid remover and activated charcoal should be provided since some reactive chemicals would be coming across, even if not in large amounts. Note though that the HF pump is not terribly expensive (currently $160) so heroic protection measures are not called for.

I also just learned of the Savant Gel pump which is acid resistant, and good to about 20-30 torr, and can be had for not too much on eBay (~$100). I did not know about this pump, but it seems to fill the same role as the aspirator. Is there some justification for acquiring one? Does it have significant advantages over an aspirator?