Need to seal steel pipe with PVC pipe inside, How?

[cavitate]

I have as an example, an 8" pipe 6 feet tall, I want an inner 4" plastic pipe down the center with the plastic pipe out the bottom of the steel pipe.
There will be a another steel pipe inside the plastic pipe. The seal must be electrically insulated for High Voltage. (10kV?) I'm using the generic plastic, because whatever the tube is, it has to hold up to oils and 90*C heat, PVC won't work. The only pressure is gravity, so less than 3 PSI on the seal. I have a drawing to help understand what I want.
Thanks, Mikek

 

[LittleInch]

A thermo plastic resin plug might do.

Look up monolithic isolation joints and the same sort of system applies.

What's the 10kV between? the steel tube and ??? You'll need a big insulator on the outer pipe to avoid shocks and killing someone.

10kV is pretty big so the spark gap is more than 2" I think.

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[cavitate]

> A thermo plastic resin plug might do.

I have attached a drawing of what I think you might be suggesting. Your thoughts?

Look up monolithic isolation joints and the same sort of system applies.

Will do.

What's the 10kV between? the steel tube and ??? You'll need a big insulator on the outer pipe to avoid shocks and killing someone.

There is another steel tube in the 4" plastic. Both 8" and 4" steel tubes are electrodes. Yes, probably build a plexiglass enclosure around it for safety.


10kV is pretty big so the spark gap is more than 2" I think.

Our first test vessel has 2-1/2" spacing and we have had 20kV on it without any problem. After looking it up I see 10kV-1/2" at sea level
Thanks Mikek

 

[LittleInch]

That looks feasible.

You might want some little legs on both the 4"and 8" inner pipe to give the resin something to grip on.

The IJ resin is good for at least 10kV.

Curious as to what this is though?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cavitate]

That looks feasible.

Good

You might want some little legs on both the 4"and 8" inner pipe to give the resin something to grip on.

Thanks for that!

The IJ resin is good for at least 10kV.

I'm not getting any hits on IJ Resin, can you give me a better search or link or explanation?

Curious as to what this is though?

Small scale oil / water separator.

Thanks, Mikek

 

[LittleInch]

Or try epoxy resin they use in cable joints.

Like this stuff

https://www.3m.co.uk/3M/en_GB/p/d/b5005197007/#

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

There is a big difference in CTE between steel and plastic. There are rubber sleeves that can adapt the pipes together. The joint needs to be flexible.

 

[cavitate]

There is a big difference in CTE between steel and plastic. There are rubber sleeves that can adapt the pipes together. The joint needs to be flexible.

Good point I hadn't considered. It will cycle from room temp to 90*C when in use.
Thank, Mikek

 

[EdStainless]

You might consider a flexible resin for the potting.
You will likely need a different primer/activator for each of the materials.

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P.E. Metallurgy, consulting work welcomed

 

[cavitate]

I have made another drawing with an Oring seal.
Sorry for my drawing skills, I hope it gets the point across.
I would not be able to engineer a proper Oring seal, so that
would need to be farmed out. But, I want to get a concept that
would do the job.
This is ignoring how The 4" pipe will be insulated, but we'll get there.
Thanks for any input you can provide,
Mikek

 

[LittleInch]

The outer tube and plug will slide down when the weight of the fluid is added.

Your welded ring looks to be in the wrong place.

You only need O rings on one face or the other not both. The outer face looks better as they will be held in under tension.

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Also: If you get a response it's polite to respond to it.

 

[cavitate]

The outer tube and plug will slide down when the weight of the fluid is added.
Your welded ring looks to be in the wrong place.

Probably should add more info. I expect a tripod will be welded to the outside of 8" pipe support it standing upright.
Then the 4" pipe could slid down, thus the welded support ring.

You only need O rings on one face or the other not both. The outer face looks better as they will be held in under tension.

Hmm... The 8" tube is filled with liquid it would leak between the Nylon and 4" pipe without a good seal. Am I missing something?
Thank you for your response,
Mikek
PS I'm thinking threaded pipe, then use a pipe couple to do the machining on rather than a 6 foot 8in diameter pipe.
Quick drawing.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cavitate]

I think I found an easy solution. Just need to find what the material is, and pipe that is 4.5" and 8.5" O.D.
Mikek

 

[LittleInch]

Good for 10kV?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cavitate]

Good for 10kV?

I expect so, but will have to spend the $24 to get one and test. The flat bottom is a good design for us, it will
be easier to drain. I think I can put a drain on the flat part.
The previous test vessel we built had a resistance over 200MΩ,with emulsion in vessel, the limit of my test equipment.
Thanks, Mikek

 

[cavitate]

There is a big difference in CTE between steel and plastic. There are rubber sleeves that can adapt the pipes together. The joint needs to be flexible.

After finding the price of Stainless steel pipe, I already bit the bullet on 30"
piece of 4.5" stainless pipe at $60, from the scrapyard. I found several pieces of 8.5" O.D. pipe, but it was all bent,
out of round, or dented. When I put the 4" on the scale I was glad I didn't find any 8.5".
So, now I have thought it will be much cheaper to use 8.5" O.D, aluminum pipe and
coat the inside with an epoxy, that will insulate and hold up to oils @ 90*C.
We will test the Por-15 and ask the company how it works with aluminum.
Any recommendations for an Epoxy that will be a good candidate for aluminum, be flexible enough to handle the differing CTE,
and handle oils at 90*C.
Thanks, Mike

 

[cavitate]

The rubber boot I was so happy to find may not be the right material. I find it is called Elastomeric Polyvinyl Chloride.
I can't find and specifications for Elastomeric Polyvinyl Chloride, all I get are hits for PVC.
Would there be any difference in max temp before deforming between Elastomeric Polyvinyl Chloride and PVC?
Thanks, Mikek

 

[LittleInch]

Is it solid or flexible?

Looks to me a bit like a domestic plumbing adaptor so could easily get VERY flexible at 90C

Stick it in a bath of hot water and find out!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cavitate]

Is it solid or flexible?

Yes, it is flexible, I would have called it rubber until I researched and found it is an Elastomeric Polyvinyl Chloride.

Looks to me a bit like a domestic plumbing adapter so could easily get VERY flexible at 90C

Even more flexible at 90*C, than room temp, to the point I'm concerned it might deform under the heat. Also it is not good with acetone, has a rating of, 'severe affect' which could be avoided, as the preferred cleaning agent is hexane, where as Polyvinyl Chloride has a Satisfactory to 72°F (22°C) rating.

Stick it in a bath of hot water and find out!

I'm tempted to make a double boiler, water in the bottom a motor oil in the top, drop a sample in and run it near 100*C for several hours. However, I think I'll call Fernco and ask their technical dept for more info, it's a lot easier.
Thanks, Mikek

 

[LittleInch]

Jesus,

Acetone, Hexane, bits made from plumbing parts, 90C operation, 10kV electricity....

Hope you have
A) Life insurance
B) Your garage is a long way from your house
C) A video recorder running so that investigators can see what the big bang was...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.