Any advice on building a vapor phase cleaning system? - Page 1
Forum section: electronics / projects

author: TerraHertz
author_rank: Super Contributor
timestamp: January 02, 2016, 12:30:58 am
content: For a vacuum system I'm building, I've realized that I really need a better cleaning method than 'scrubbing in a tub.' The major problem with hand washing things, is contamination and loss of the fairly expensive solvent. If just used as a liquid, it can only be used once.Reading up on vapor phase solvent cleaning methods, it seems like it wouldn't be too hard to make one from scratch for fairly low cost. Starting with a stainless steel laundry tub, and adding heating elements around the bottom and a cooling coil around the desired upper limit of the solvent gas. Lots of other details too, like needing two separate sumps; one heated, the other to catch and recycle condensed (and hence clean distilled solvent.) Temperature control and safety limits on the heating sump and cooling coils, facility to run a final distillation cycle and drain-off when done... what else is needed?I'm not yet certain if water separation would be needed, or how it's done if it is needed.I'd be using IPA as primary solvent for cleaning. Because it's easily available, not too poisonous, works reasonably well, and is suited to vapor phase cleaning. Possibly other solvents, and mixes as I learn more.It also occurs to me, that if I build the thing to handle higher temperatures, it could also serve for vapor phase solder reflow work.Has anyone here ever attempted to build either (or both) such things?Any advice?I haven't been able to find any online texts specifically about IPA vapor phase cleaners and their operation, other than that they work, and are commercially available (at costs far beyond my means.)Anyone know of something useful on that topic?Here are some sources relevant to vacuum systems cleaning in general:http://vacuumcursus.nl/casussen/Cleaning_Chapter.pdfCLEANING FOR VACUUM SERVICEHow to choose a cleaning solutionSolvent selection and effectiveness:http://www.productionmachining.com/articles/selecting-solvents-for-precision-cleaningDan Gelbart on coatings and surface cleaning:https://en.wikipedia.org/wiki/Kauri-butanol_valuehttp://cool.conservation-us.org/coolaic/sg/bpg/annual/v03/bp03-04.htmlhttp://infohouse.p2ric.org/ref/05/04280.htmThe Precision Cleaning for Advanced Technologies Technology Handbookhttp://www.inventec.dehon.com/uploads/cms/pdf/Inventec_S24_03.pdfCleaning PCBs in Electronics: Understanding today’s Needs (mostly a slideshow)http://www.google.com.au/patents/US5054210Isopropyl alcohol vapor dryer system (patent)http://www.baronblakeslee.net/vapor-degreasers/Sell vapor degreasers. FAQs

author: plesa
author_rank: Frequent Contributor
timestamp: January 02, 2016, 12:47:28 am
content: What about ultrasonic with various cleaners, like IPA, citric acid and etc? For home use I suppose it is better than vapor cleaning ( without chiller it is complicated).

author: TerraHertz
author_rank: Super Contributor
timestamp: January 02, 2016, 01:37:40 am
content: Quote from: plesa on January 02, 2016, 12:47:28 amThe #1 problem is that any cleaning system in which the solvent is not continuously re-distilled, results in the solvent rapidly becoming too contaminated to use.IPA isn't cheap. 4L was about $34 I recall. And it's not something you can buy in Woolworths.http://www.matthewmcdonald.com/238/purchasing-isopropyl-alcohol-in-australia-aka-ipa-rubbing-alcohol-propan-2-ol-2-propanol-and-isopropanolIt's just not affordable, practical or environmentally acceptable to be using IPA in bulk, single use only. Then how to dispose of it? And even 'single use' isn't good enough, cleaning-wise. Hence the idea to build a vapor phase system.I do have an industrial chiller (actually a pub beverages chiller.) Needs a small plumbing repair and regassing, but I can do that. Though I'm hoping that for a smallish vapor phase setup, circulating water with forced air cooling may be good enough. Could be wrong about that, but it's not a show stopper if it does need chilling.Besides, it's looking like I'll have to install chilling for an oil diffusion vacuum pump anyway.I have a small ultrasonic cleaner, but the tank is only about 8cm deep by 8cm dia.Lots of vacuum system parts are much larger, and oil contamination is the primary issue.

author: apelly
author_rank: Unknown
timestamp: January 02, 2016, 03:19:56 am
content: Try some searches related to home distilling.A reflux still can be operated in such a way that all the condensate runs back onto the boiler, or can be tapped off into a container for later use.A pot still is simpler, and all of the distillate ends up in your collection vessel, although less pure.Effectiveness obviously depends on IPA being the most volatile thing in your boiler. More volatile compounds can be somewhat effectively tapped off in batches from a reflux still, but it's slow and boring.Placing your dirty item in the boiler, above the liquid, and allowing hot condensate to drip from your reflux column onto it seems like a fairly sound way to go.Obviously boiling IPA makes a bomb. Safety glasses may not be enough. I suggest hearing protection too.

author: SeanB
author_rank: Super Contributor
timestamp: January 02, 2016, 09:17:20 am
content: 2 stainless steel deep wall pots. Cut the bottom out of the one, and roll up to form a lip to collect the condensate. That is the upper condenser, and the lip collects the condensate to funnel out through a pipe to the outside. Excess drips back down to the sump. Other one is the sump, left intact and brazed to the upper one.Take 1/4in stainless steel ( or plain steel here) tube and wind around the bottom of the lower one, up to around half way. That is both the condensing coil and your heater. Silver solder to the stainless steel, and bring out the ends so you can connect to the rest of the refrigerant circuit. Take the ends and braze on some 1/4 copper refrigerant pipe to use for the rest. Will probably be around 10m of tubing. Braze a thermowell so you can sense the coil and pot temperature.Wrap the lower pot with some insulating wool on the outside and under, and some polyamide sheet to keep in place, so it will only heat the inner vessel.Upper vessel similar, but the same length of pipe brazed over the outside from top to bottom, so the entire wall is chilled. Then insulate again, so it will only get heat from the inner side, and a thermowell to sense temperature. then you simply use a half HP or larger ( up to around 3/4HP) freezer compressor, a pencil drier and around a half meter of capillary tube, and then fill with R600A as refrigerant. Would be nicer to use R12 or R134A, but no longer sold in AUS/NZ to the public, though you can probably get a refill can of R134A at the auto parts store for AC refill. R600 is flammable though, it is propane. Usual things about vacuum out before filling, and fill the lower pot half way with water before trying out to have a cheap load, then adjust gas fill to get condensing temperature to under 5C.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 04, 2016, 05:09:21 am
content: Thanks SeanB, very detailed. A few problems though: Construction will depend on what I can find, so I'll be improvising. And I know I can't braze tubing to thin-walled stainless without making a mess. Maybe you can, I can't.Also not sure attaching the cooler condenser coil to the boil-pot is a good idea, since it entangles two separate control loops - the IPA vapor chiller, and the boil-pot rate of boil. I know it's theoretically more efficient that way, but I'll probably just use an electric heater for the boil pot. Not like I'd be using it all the time.What I was more hoping to find, is tales from someone who has used such a thing. And operating advice, like what are the best temps for the boiler, and the chiller. How to ensure there's no vapor overflow into the room, what anti-fire/explosion measures are needed, how to minimize & remove water contamination, and any other surprises I may not see before they happen.Does anyone bother with an inert gas layer over the IPA vapor?Photographs inside and out of a working vapor phase cleaning setup would be nice.

author: LukeW
author_rank: Frequent Contributor
timestamp: January 04, 2016, 06:15:22 am
content: Maybe something like a giant Soxhlet extractor, presumably fabricated out of metal instead of glass, with the apparatus to be cleaned in the extraction cup, so that it's constantly washed with refluxing solvent?Boiling flammable solvents is everyday bread and butter business for organic chemists... it's a matter of having a well constructed apparatus where the flammable vapors aren't able to escape (an almost completely closed apparatus but not completely closed - you need to equalise the pressure at a point somewhere), working inside a fume hood, using something like a heating mantle to heat it and not a naked flame, and keeping any other ignition sources away.

author: plesa
author_rank: Frequent Contributor
timestamp: January 04, 2016, 06:12:15 pm
content: Quote from: TerraHertz on January 02, 2016, 01:37:40 amOK, there are other cleaning agents on water basis which can clean almost all stuff for your vacuum, you do not needs IPA.Also there are way how to clean used and contaminated solvent ( re-destination for example).By the way by the diffusion pump the cleanliness of vacuum chamber or what you want to build will be affected more than by using with not properly cleaned parts. And even more if system will be not pumped continuously. Rather invest into the turbo molecular pump.