Need a small vacuum to suck liquid into a reservoir - Page 1
Forum section: electronics / beginners

author: engineheat
author_rank: Frequent Contributor
timestamp: December 27, 2019, 04:23:03 am
content: Hi,We have a machine where a small nest get slowly filled with oil, due to certain process. The nest is roughly 6mm in diameter and 6mm deep. When the oil/grease inside gets too much inside (say, 3mm deep) it causes issues. There are many such nest so cleaning is a time consuming task. They move in a conveyor-like belt.I want to try to build a station where a vacuum can create a suction to suck the excessive oil from the nests into a reservoir, via some kind of tubing. The suction tip cannot reach inside the nest, it can only hover above, because the nests moves in a conveyor like cycle.I don't know what options there are. The suction needs to be strong enough. I can build the reservoir and provide the tubing myself. Ideally we can power it using 24V.What are those things that dentists use to suck the liquid out of patient's mouth when doing dental work?Thanks

author: JustMeHere
author_rank: Frequent Contributor
timestamp: December 27, 2019, 04:42:34 am
content: Maybe blow the oil into a container.

author: DTJ
author_rank: Super Contributor
timestamp: December 27, 2019, 05:50:42 am
content: Grab one of the small sparkfun pumps.https://www.sparkfun.com/products/10398Use small ID tubing and have a catch can between the oil wells and the vac pump.If this does not provide sufficient flow/lift then use your workshop vacuum cleaner as the vac source.

author: Tom45
author_rank: Frequent Contributor
timestamp: December 27, 2019, 06:15:34 am
content: I would be sceptical that a vacuum could suck much, if any, oil without extending into the hole. You do an experiment to see by drilling a hole in a piece of metal and then see if a shop vacuum with a micro vacuum attachment kit would suck out any oil when held above the hole.The suggestion to blow the oil out of the hole should work, but doing it in a way that doesn't create a big mess might take some thinking.

author: tautech
author_rank: Super Contributor
timestamp: December 27, 2019, 07:34:19 am
content: If this is in an industrial setting you might have plenty of compressed air available to use a venturi suction setup.Any mechanical engineer could make one for you.You might have to experiment with nozzle sizes and air pressures in the venturi fitting and hose/nozzles sizes for the suction pickup.If compressed air is available this could be the simplest solution as a venturi has zero moving parts.Squillions of them on Aliexpress to give you an idea of what's available:https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20191226233250&SearchText=venturi+

author: engineheat
author_rank: Frequent Contributor
timestamp: December 27, 2019, 05:44:08 pm
content: Quote from: tautech on December 27, 2019, 07:34:19 amYes, we do have a source of compressed air. Will the venturi create enough suction though? So I guess one side of the venturi is for the input of compressed air, the "middle" portion is for the suction, and then the output side can just be aimed at a reservoir? that simple huh?Thanks

author: Paul Moir
author_rank: Frequent Contributor
timestamp: December 27, 2019, 06:15:02 pm
content: Yeah, and the best part is if some liquid gets sucked into it, it doesn't ruin the pump or contaminate the sump's oil. They make them optimized for volume of flow or maximum ultimate vacuum; I would think you'd be looking for volume of flow. They do use a lot of air so they're pretty inefficient, but they're super-easy to throttle with just a speed control on the supply line. My go-tos are the SMC ZH line.

author: engineheat
author_rank: Frequent Contributor
timestamp: December 27, 2019, 06:26:45 pm
content: I did try to blow it out using compressed air (from the top), there are 2 small side holes that oil came out of, and it made a mess. I wonder if the 2 side holes can be of help when using the Venturi approach?

author: tautech
author_rank: Super Contributor
timestamp: December 27, 2019, 06:59:00 pm
content: Quote from: engineheat on December 27, 2019, 06:26:45 pmPossibly.The considerations will be to maintain a decent vacuum so to throttle it down too much will reduce the vacuum available.Also if this is not a 24/7 installation the vacuum line and venturi needs be below the suction point so there is no flow back when it is turned OFF.The venturi can be placed some distance away even outside with some sort of catch can for the oil.

author: james_s
author_rank: Super Contributor
timestamp: December 27, 2019, 07:49:43 pm
content: Dentists use a regenerative blower to create the suction. That's probably overkill for what you're doing though, I would think an inexpensive diaphragm type vacuum pump would do the trick.

author: engineheat
author_rank: Frequent Contributor
timestamp: December 27, 2019, 11:21:10 pm
content: Can I build a venturi tube using air tubings and a T fitting like this:The compressed air (6 bar) we have come out of a 4mm tubing already. This might be an easy way to try if there is enough suction.I'm thinking:input: 4mmoutput: 4mmsuction: 4mmor would I get better suction if suction tube is smaller in diameter?

author: tautech
author_rank: Super Contributor
timestamp: December 27, 2019, 11:33:03 pm
content: Quote from: engineheat on December 27, 2019, 11:21:10 pmNot really without an inserted nozzle on the compressed air supply side. But yes possible but you'd need to experiment to get good suction.Have a study of the images here of how they are built:https://www.google.com/search?rlz=1C1CHBF_enNZ760NZ760&sxsrf=ACYBGNSvvcWdhKePsxs-J4Vf6z7nJGhbrA:1577489388938&q=venturi+design+principles&tbm=isch&source=univ&sa=X&ved=2ahUKEwimn6j1_dbmAhWbyDgGHYunDH0QsAR6BAgKEAE&biw=1279&bih=673Edit to addWith 6 Bar of available pressure a nozzle of 0.5-1mm would be adequate for what you want to do.It seems you don't need to shift much oil so there's no need to use lots of air.

author: tautech
author_rank: Super Contributor
timestamp: December 28, 2019, 12:01:27 am
content: Further understanding can be had searching for 'eductor'.

author: james_s
author_rank: Super Contributor
timestamp: December 28, 2019, 01:04:14 am
content: A venturi will consume a lot of air, don't forget that compressed air is not free. A small electric pump is likely to be much more efficient.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 07, 2020, 10:22:26 pm
content: If you can not stick the end of your tube into the liquid, but have to hover over it, then a small vacuum or membrane pump probably will not work satisfactory.However, if you use a standard vacuum cleaner, you can such up lots of liquid from several cm away.Of course use a vacuum cleaner that's fit for sucking liquids.Another way is to use some kind of air cylinder or membrane that pushes the end of your tube into the liquid when the pump activates, and a spring to pull it back.Or use a small stepper motor with a lever to move the end of the tube into and out of the liquid compartment. This is probably easier to make reliable then using the vacuum with some actuator, but would need more electronics.