Looking for seal with minimum friction 4

[MH500]

Hi everyone
I have a cylinder with about 20 bar pressure inside. This cylinder designed by me. on top of this cylinder there is a shaft that should have able Longitudinal movement in the cylinder with minimum friction and no leak. in fact this shaft putting something under mechanical pressure while a hydraulic pressure surround it.
I'm looking for a sealing mechanism that do this for me.

Thank u

 

[MikeHalloran]

I've had good luck with Bal-Seals.


Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

Rolling diaphragm cylinders have very low friction and have zero leakage. Bellowfram is one supplier.

Airpel air cylinders have even lower friction but do leak some air.

 

[MH500]

Thanks for your answers.
But I cant provide this products.
Do you know more general seals ?

 

[MikeHalloran]

See the Parker O-ring Handbook.


Mike Halloran
Pembroke Pines, FL, USA

 

[AFG03082015]

Is your shaft essentially a piston?
You could have a look at profile seals as an alternative to 'O' Rings.
For both 'O' Rings & Profile Seals speak to a few different suppliers as many do manufacture low friction back up rings which for use in low pressure situations like you describe.

 

[MH500]

Actually this cylinder uses for a mechanical pressure test on a kind of stone sample in laboratory condition.
our cylinder fills with water under 20 bar pressure and at the same time our stone sample is under mechanical pressure in the cylinder. It means that stone sample is inside the cylinder and water with 20 bar pressure surround around it
This is a university test.
its important that water doesn't leak and cylinder shaft can move smoothly. in this test we should can pass up friction factor.
I designed cylinder by myself and only problem is this seal part.
O rings have a good sealing but also have friction.
I used cup seal. that had good leak prevention but high friction.

 

[AFG03082015]

Have you considered the use of a rod seal?

http://hallite.com/products/rod-seals/

 

[MH500]

Yes.
as I said I had a good experience with cup seal ( Rod seal) , but with unwanted friction.

 

[AFG03082015]

Hi MH500,

Unfortunately I cannot think of a suitable alternative to a Rod seal but hopefully another on this forum will...

My last suggestion would be to consider the seal material if you haven't already? what was the material of the rod seal you have a good experience with?

Maybe consider a material such as PTFE and try and find something with the lowest friction co-efficient possible?

 

[btrueblood]

Is your test pressure a static condition?

Pressure dead-weight calibrators use a simple o-ring, with its attendant friction, and yet achieve near zero pressure offset (zero friction force, and thus no friction effect on the pressure calibration) by spinning the weight that loads the piston rod. Can you do similar, i.e. allow the rod or cylinder to rotate during testing to allow the friction force to "zero out" due to slip?

 

[MH500]

this is a static pressure test. and I cant rotate the shaft during apply pressure .
couple days ago I saw in a similar cylinder , they used a simple PTFE seal thing (I guess !)
It was working with minimum friction and zero leak. but unfortunately I cant contact with manufacturer. because its not identifiable.
Do u see something like this ?

 

[MikeHalloran]

I've never seen an object like that identified as a seal.


Mike Halloran
Pembroke Pines, FL, USA

 

[MH500]

Mr. MikeHalloran
anyway thanks for your attention and your help.
and I hope other friends can help me

 

[MikeHalloran]

But I cant provide this products.

I don't understand what you meant.

If you mean you can't find them, look here:

http://www.balseal.com/reciprocating

I have used Bal-Seals in low velocity reciprocating applications at low pressures, and found nothing that worked better. Use the standard gland dimensions from Bal-Seals' catalog. Many will fit in standard Parker glands.



Mike Halloran
Pembroke Pines, FL, USA

 

[MH500]

Im sure that is usefull for me but actually I dont live in usa and this manufaturer havent any distributor in my country.
So I need replace this good seal with other thing that I can buy.

 

[gruntguru]

Your system sounds a lot like a dead weight tester. I am imagining a plunger being used to pressurise water including a pressurised sample. Add a thrust bearing at the top of the plunger and a handwheel/flywheel so you can rotate the plunger while loaded.

je suis charlie

 

[MH500]

This cylinder putted under a penumatic jack and the jack push the cylinder rod down .. so it cant rotate.and while test the sample should not rotate.
But your idea is intresting and inspiring.

 

[gruntguru]

So put a sleeve between the shaft and cylinder. Two seals - one sealing between shaft and sleeve, one sealing sleeve to cylinder. Rotate the sleeve. (The sleeve will also need radial and thrust bearings between it and the cylinder.)

je suis charlie