A portable Venturi Vac system?

  • #1
Hello,
We make a Venturi vacuum system for recovering CNC coolant from the swarf trolley. It is a simple arrangement consisting of a venturi tube tee'd off the coolant pump and a stand-off placed at the bottom of the swarf trolley with a filter disc.

Now the problem with this system is that it is dedicated to each machine, where pressurized coolant passes through the venturi from the pump (motive) and creates a suction through which coolant is sucked from the swarf trolley. Coolant that passes through the venturi is returned to the sump. A schematic is attached for reference.

Now, I have had multiple clients ask for a similar portable system. But I can't for the life of me figure out how! I could use compressed air or even a Turbine Blower to generate the vacuum in the venturi, but the sucked coolant will mix with this air on the outlet of the venturi. How do I avoid this?

Thanks,
KV
 

Attachments

  • Schematic.jpg
    Schematic.jpg
    45.5 KB · Views: 28

Answers and Replies

  • #2
sophiecentaur
Science Advisor
Gold Member
2020 Award
26,162
5,372
How do I avoid this?
No doubt you've been thinking this through and I'm only here five minutes so forgive my 'obvious' suggestion. If the "to machine" feeds several machines and the yellow line is fed by all the vacuum cups then, as long as it's all balanced with appropriate valves to control all the different flows then coolant would be fed to and fed from all the machines.

It could be a lot quieter than a pneumatic system and no 'oily air' to get rid of.
Or did I just mis read the situation?
 
  • #3
jrmichler
Mentor
1,549
1,752
How about a pump? Search pump rubber impeller to find about a type of pump that will pump dirty oil up out of a tank. You would need to make sure that the impeller will not be damaged by your coolant.
 
  • #4
sophiecentaur
Science Advisor
Gold Member
2020 Award
26,162
5,372
How about a pump?
Doesn't he already have a pump and one that's suitable for the job? I'm not sure why the OP wants a shared system but perhaps he plans a totally static arrangement.
It may be that economies of scale could mean that a single pump could produce enough 'suck' for several work stations.
But I would (again) suggest that a system of high speed air could prove to be very noisy. And isn't this all Known art? You can buy systems for home workshops on eBay!
 
  • #5
jrmichler
Mentor
1,549
1,752
The OP strongly implies that a portable system will need to suck the oil up from the sump. This will require a self priming pump.

The volume of oil sucked up from the swarf will be far too small for a self priming trash pump. A gear pump might self prime, but metal chips do not go well with the tight metal to metal clearances in a gear pump. Same for piston pumps. A small diaphragm pump will work until a metal chip wedges under one of the check valves. That pretty much leaves a rubber impeller pump.

The OP could also add a venturi to the client's system, but that would require system specific engineering to size the venturi to the clients system. Assuming, of course, that the client's system had coolant flow rate sufficient to drive a venturi. A standalone self priming pump needs no engineering - just place the suction line in the swarf trolley, the discharge line in the sump, and turn it on.
 
  • #6
Tom.G
Science Advisor
3,952
2,646
There are pneumatic devices that create a vacuum using compressed air. There are no moving parts, they work by entrainment.

It was decades ago that I ran across them so I don't remember what they were called. But the construction was a 3-layer sheet of clear plastic with the two outer sheets being solid. The middle layer had many channels and Air In, Vacuum In, and Exhaust connections.

Think of a tree with the trunk being the vacuum channel and the branches being fed the compressed air. The compressed air, on its way to the exhaust, entrains the air in the trunk.

They were used to scavenge excess cleaner or glue from a machine assembling medical devices. But the company that built the machine was a bit late in delivering it, they couldn't keep the vacuum process working, They blamed the machine designers and then the controls engineer. Turned out the material that was being vacuumed up was dissolving the plastic. After that discovery the vacuum generator was changed to a metal one that could be easily disassembled and cleaned!

Cheers,
Tom
 
  • #7
sophiecentaur
Science Advisor
Gold Member
2020 Award
26,162
5,372
However it's done, it should not be necessary for the sharp bits of swarf to get into any pump. It's common to pass the dirty coolant through a trap first with a low entrance and high exit to the pump and let the heavy particles fall to the bottom. Graded filters can also remove various sized particles. Alternatively, if the coolant is relatively low viscosity, a centrifugal system can remove particles ('Dyson').
 
  • #8
No doubt you've been thinking this through and I'm only here five minutes so forgive my 'obvious' suggestion. If the "to machine" feeds several machines and the yellow line is fed by all the vacuum cups then, as long as it's all balanced with appropriate valves to control all the different flows then coolant would be fed to and fed from all the machines.

It could be a lot quieter than a pneumatic system and no 'oily air' to get rid of.
Or did I just mis read the situation?
Sorry. I'll make it clearer. The diagram shows the coolant tank and plumbing of 'one' machine. The venturi is installed on the discharge end of the pump and the vacuum cup is placed in the swarf trolley of that particular machine. The 'To machine' is the hose that supplies coolant to the spindle of that machine. This is the basic arrangement i have now.
The requirement is to replicate this in a portable setup. The venturi needs coolant pressure to generate the vacuum. This coolant which passes through the venturi is returned to the tank through a pipe connected to the outlet of the venturi ('Coolant returned to tank' in the pic)

Maybe I can use a AODD pump in a portable trolley. Suction piping that will simply drop into the coolant sump, my venturi connected to the discharge end of the pump with a tee connection. Outlet of venturi will again have a pipe that is dropped into the sump (to return the coolant that is tee'd off). Finally the third port of the Tee will also have a pipe that returns coolant into the sump (three pipes enter the sump.. the suction pipe and two lines from the Tee.. pic enclosed for reference).

Is it too simplistic? Meaning.. it basically consists of a pump, venturi, tee and some pipes. Does it make sense as a buyer to get this as opposed to a dedicated system on each machine? As this portable one will require a guy to continuously drag the trolley around from one machine to the next, probably in each shift to recover the coolant from each respective swarf bin.
 

Attachments

  • WhatsApp Image 2021-06-25 at 18.20.20.jpeg
    WhatsApp Image 2021-06-25 at 18.20.20.jpeg
    41 KB · Views: 19
  • #9
Also my present system uses zero resources to make it happen, as we simply use the coolant from the pump. No air or electricity is required.

The portable setup might require one of the two.
 
  • #10
rbelli1
Gold Member
1,001
381
...zero resources...
...coolant from the pump...
Except for the extra electricity to pump the coolant through the recovery device. Plus whatever it costs to purchase and maintain the many recovery systems.

Nothing is free. If it looks free you are not looking hard enough.

BoB
 
  • #11
sophiecentaur
Science Advisor
Gold Member
2020 Award
26,162
5,372
I can't quite see how using the pump on each machine isn't the best option. The gear needn't take up much room - just a T and a jar to catch the grot should be there anyway, imo.

But the customer is always right so, if you offer it, they will come.
 
  • #12
4
1
Well, I don't know the solution but what I have seen at my uncle's shop is,

There where machine for wood working not a CNC, and already attached dust collection of 4". but it's not enough so they added second layer of vacuum. When I checked for it on one article they using vacmaster vacuum cleaner as a secondary vacuum.
 
  • #13
sophiecentaur
Science Advisor
Gold Member
2020 Award
26,162
5,372
When I checked for it on one article they using vacmaster vacuum cleaner as a secondary vacuum.
Wood dust can be 'sucked up' with air but coolant plus metal swarf is less amenable. Has to be pumped out somehow.
 
  • #14
Tom.G
Science Advisor
3,952
2,646
Wood dust can be 'sucked up' with air but coolant plus metal swarf is less amenable. Has to be pumped out somehow.
Kinda depends on the details. Have you heard of a Wet-or-Dry (also Wet/Dry) vac, by Shop-Vac, DeWalt, Craftsman, Vacmaster, for instance? My small Shop-Vac does a decent job on spills that would otherwise be quite a pain.

[edit]
I've even used it to clear a garbage disposal that a neighbor accidentally dumped a flower pot of gravel into. (tip: first blow the water thru, including from the trap, THEN vacuum out the gravel!)
[/edeit]
 
Last edited:
  • #15
sophiecentaur
Science Advisor
Gold Member
2020 Award
26,162
5,372
Kinda depends on the details. Have you heard of a Wet-or-Dry (also Wet/Dry) vac, by Shop-Vac, DeWalt, Craftsman, Vacmaster, for instance? My small Shop-Vac does a decent job on spills that would otherwise be quite a pain.
Yes. Very much the details. It’s essentially pumping a sometimes pretty viscous liquid and a quantity of heavy particles of various shapes and sizes. I use a Vax and it works ok to get chips out of the lathe bed and all over but it’s essentially a dry process with oil coated chips but not much coolant. (It needs help with a brush).
If this is to be an automatic system, there needs to be a lot of liquid. Would a vac be matched to the job? You still couldn't do without manual cleaning, of course but please not a continuously running vacuum cleaner. Machine shops are noisy but we can do without the sorts of noise that you get in a joinery shop (ear defenders necessary always).
 
  • #16
Sorry for the delay in response. But here's what I've done this week :-

Took a simple AODD pump and dropped its suction flexible pipe straight into the machine sump, discharge pipe from the pump connected to my Venturi, outlet of which is returned to the sump with another flexible pipe. Took trials and the system works!

Some queries :-
1. Used an AODD pump since no flooded suction can be provided (pump mounted higher than the tank). But this has led to a pulsating flow at the outlet of the venturi that goes back into the sump. Can this be turned into a continuous flow? Pulsation Dampener / Centrifugal pump perhaps?

2. We took this trial with only water. I am worried that the pulsating flow will cause some atomization of the coolant or maybe foaming might happen? Not sure.

Any tips?
 
  • #17
Any help would be appreciated guys!
Questions :
1. Pulsating flow out of the venturi might lead to foaming or atomization of the coolant? Or not?
2. For cases with a suction lift of less than a meter, are AODD pumps advisable or can I work with a centrifugal pump as well (for coolants..). If I must use an AODD pump and in case pulsations are not desirable, I need a pulsation dampener. Please correct me if i am wrong here.

But then I would much rather use an AODD pump since I do not want to introduce any electrical connections to the trolley. A simple air line shall be used. So I guess, centrifugal pumps are out.
 

Related Threads on A portable Venturi Vac system?

  • Last Post
2
Replies
31
Views
11K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
1
Views
2K
Replies
2
Views
2K
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
1
Views
6K
  • Last Post
Replies
1
Views
800
Replies
18
Views
358
  • Last Post
Replies
3
Views
2K
Replies
1
Views
3K
Top