How to close off holes in a overflow tube.

[Qmavam]

I have two concentric aluminum tubes, a 4" and an 8". The 4" will have two sets of overflow holes, that I want to be able to shut off or open one or the other.
The drawing gives all the details. On the right I added one Idea I do have. Two additional bits of info, the two tubes are electrodes,
so must be continuous and insulated at the bottom and the temperature is 90*C.
I'm looking for other simple to implement ideas about how to close off or open these holes. It will be a somewhat rare event, but the over flow will need to be adjusted on occasion.
Thanks for your input, Mikek

 

[ttabbal]

I had a similar setup in an aquarium. It didn't use the holes though. It used a valve on the outlet to adjust flow to match the intake. The idea was to maintain a full siphon without air for increased flow and decreased sound. Perhaps an adaptation of that idea would be useful.

Your o-ring tube looks like it would work as well. Perhaps a threaded setup for easier adjustments?

If you have restrictions other than temperature, you might want to include them. Material availability could be an issue for corrosives or other reactions.

 

[gard]

I think the O ring fitted slug should work. If the fluid is clean, it can be a close sliding fit with no o-rings as is common in hydraulic valves.
If its easy to disassemble, a couple of wraps of electrical tape or plugs for each hole

 

[Dave Smith]

what size are the holes you want to plug ?

 

[Qmavam]

I think the O ring fitted slug should work. If the fluid is clean, it can be a close sliding fit with no o-rings as is common in hydraulic valves.
If its easy to disassemble, a couple of wraps of electrical tape or plugs for each hole

It will be a hot oily fluid, so electrical tape is out, even PVC is out as it softens at the 90*C we will be at.
Disassembly is still up in the air, I have one design that epoxies the parts together, so can not be disassembled,
another design that uses O-Rings to seal the tubes together, That one should be able to be disassembled.
I'm thinking both the bottom seal and the sliding tube may be nylon.
Thanks, Mikek

 

[Qmavam]

what size are the holes you want to plug ?

That hasn't been finalized but the inlet only flows 400mL per minute, I think it is a 1/4" pipe at low pressure.
So the overflow doesn't need to be large, but I would desire an even flow from around the 4" tube, so maybe
eight--3/16" holes spaced every 1.62" around the 4" I.D. pipe. But, probably 4--1/4" would work. I'm not sure if
the number of holes around the circumference is critical to the way the oil flows in from the =edges of the 8" tube.
The fluid is pretty clean so I don't expect the holes to plug with any debris.
Thank you for your time and input, Mikek

 

[Asm109]

When you are asking for open flow ie, not under any pressure but gravity, you need large holes so that air and water can flow freely. Thing about how large waste lines are in a house.
A small hole can get an air bubble and choke off the flow. Next thing you know you have a spill out the top.
I learned this from study of first principles and NOT bitter messy experience /s

 

[Dave Smith]

so maybe eight--3/16" holes spaced every 1.62" around the 4" I.D. pipe, Mikek

I would get some stainless spring shim in a roll and cut some pieces approx 1/2 inch wide strips that would work like internal snap rings. then you could just slide them down to cover the holes. they could be easily removed when needed, and could be coated with a film of silicone if needed
for sealing.---I will include some examples of some bands I have so you can understand what I mean.
Dave

 

[Qmavam]

I would get some stainless spring shim in a roll and cut some pieces approx 1/2 inch wide strips that would work like internal snap rings. then you could just slide them down to cover the holes. they could be easily removed when needed, and could be coated with a film of silicone if needed
for sealing.---I will include some examples of some bands I have so you can understand what I mean.
Dave

That's an idea I have not seen!
The scenario, we change the type of oil being treated, some require longer treatment, that would necessitate flowing higher in the tube, so closing lower holes. But this is only an occasional change, this may work well. Simple to implement, cheap and no machining required. All I need are 4" internal clip rings. Great Idea!!
I appreciate your time and thinking on this, Mikek

 

[rabler]

Another option that you might consider, make the intersection of the pipes at the bottom of the larger pipe a slip joint. Raise or lower the inner pipe as needed, rather than trying to seal holes. You could use an o-ring or a nylon seal like the finish plumbing slip joints under your sink to seal that connection.