Fluid that causes fast degridation in O-Ring 1

[sbenzie]

Trying to see if there is anyone out there that is aware of a fluid that will degridate the rubber in an o-ring seal [say NBR].

I`m not looking for the oring to swell, infact the opposite, be eaten !! Thus that the seal provided by the oring will be lost ....

Anyone any ideas ?? I`m told my skydol might do what I`m looking for with a Fluorocarbon oring ???

 

[tbuelna]

A fluorocarbon compound o-ring has very poor resistance to common chemicals such as acetone or ammonia. They will fail the elastomer, but will not dissolve it.

Skydrol, or even brake fluid, will cause swelling with a fluorocarbon elastomer.

Try here:

http://www.parker.com/o-ring/fcg/fcg.asp

 

[MikeHalloran]

Odd question.

Look here:

http://www.efunda.com/designstandards/oring/oring_chemical.cfm?SM=none&SC=Skydrol 500

You should actually test whatever combinations seem promising, because it's not customary to record the degree to which a combination is unsatisfactory in seal/fluid testing.



Mike Halloran
Pembroke Pines, FL, USA

 

[sbenzie]

I tried acetone with a NBR rubber, but I just found it swelled pretty serverly, thus I`m guessing it would just improve the seal [in the short period of time I`m using it] not what I`m looking for.

I could use heat, but I really want to achieve distruction of the seal through chemical means !!

Thanks so far, just hoping someone knows a good combination.

 

[byrdj]

I got bite once by a fluid called "Jet-Lube". It was aviation grade frylquil. However the oring swoll before it desentergrated.

 

[MikeHalloran]

The next thing I'd try is Brakleen.



Mike Halloran
Pembroke Pines, FL, USA

 

[pennpoint]

sbenzie
Iam not sure what it is you are trying to do?
Use a fluid that will deteriorate an O-ring or.
Find an O-ring that will not deteriorate?
Which is it?

pennpoint

 

[diamondjim]

check out the following url and choose
buna n and use all and checkout the results.

http://www.coleparmer.com/techinfo/chemcomp.asp

 

[sbenzie]

To clarify, I have a piece of equipement\assembly I`m testing. I would like to remove a sealing point [Oring] without dis-assembling the equipment.

I think I have three options to stop this seal working -

1. Drill through the steel to the ORing.
2. Use excessive heat to deteriate the ORing.
3. Chemically eat the ORing.

3 seems like the niest option thus I`m trying to find the best combintation of rubber and fluid to achieve this.

I was trying to reduce the amount of guess work to trying different fluids and rubbers, by seeing if anyone out there had done something kind of strange like this before !!

 

[MPENN]

Fatty acids will cause rubber to swell and deteriorate, however, this will happen of time. Perhaps you could select a sealing material known to disolve by a specific solvent.

 

[ornerynorsk]

It all depends on what material the o-ring is. Any maint records to indicate the material? No material is impervious to every chemical, you should be able to contact an o-ring mfr (Wynn's, Parker, etc) once you know the material. Many o-ring handbooks have the compatibility list already prepared.

 

[MikeHalloran]

The question as posed is unusual, because sbenzie seems to be able to choose both the fluid and the o-ring. Further, he wants the o-ring not to swell, the most common failure mode, but to disappear.

A time frame for this failure to happen has not been revealed. If the time frame is 'quickly', that suggests the option of using any arbitrary fluid and simply omitting the o-ring from the assembly.






Mike Halloran
Pembroke Pines, FL, USA

 

[sbenzie]

Glad to see there is humor, I`m wishing the O-Ring came with an ON\OFF switch, but alas !! It is quite an unusual application, I agree, but hey thats what makes engineering fun.

First I need a seal for which the ORing is there doing it`s normal job, then I need to remove this sealing point, thus I was looking for some bright sparkle that might know a combination of ORing [Nitrile, Viton, Aflas etc] and fluids that they have seen being pretty distructive !!!

As you point out I did not really give a good answer for time period, I`m taking a good stab and I think 72hour would be acceptable.

I guess it look like I`m just gonna try some combinations myself.

 

[btrueblood]

Hmmm. If you do have choice of fluids and materials, how about pouring a molten salt to form the seal, then washing it out with a solvent. Or, use molten paradichlorobenzene (mothballs), test with water, and wash it out by baking it (the stuff evaporates fairly quickly at elevated temp's.)

An O-ring compound combination that might work is to use EPDM rings where you want them to stay put, and polyacrylate or polyurethane for the "dissolvable" ring. Test with water, then dissolve/destroy the poly ring using a strong acid or base solution. You will need to test the solvent to make sure you get the right reaction, and may need to use heat to completely destroy the poly ring in 72 hours.

 

[scooter911]

Shot in the dark here but we use a lot of inflatable seals in the vacuum industry. Could even pull a vacuum behind the seal when you want it to open up. Not sure on your size requirements but this works quite well.

Good Luck

 

[ornerynorsk]

What about a low-temp expanding alloy? Cerro-Lo comes to mind. Bismuth is another possibility. Might not highly aggressive chemicals be damaging to other parts of the system? Just a few thoughts.

 

[FIF99]

Hi,

Some fluids do weaken the elastomers like methanol and glycol at a certain pressure/temperature combination. But also water at higher pressure temperature combinations may harm o-ring seals.
Another important matter is the AED (Anti Explosive Decompression) phenomenon. Gasses will integrate in the o-ring material at high pressure over the time, and when the pressure drops the o-ring will crack, due to the extrusion of the gas (CO2 is one of those gasses which easily integrate into the elastomers).
If an application requires as such, you should order O-ring materials with AED, but realize there are a lot of different grades AED within the industry. James Walker have reliable grades.

Regards.

 

[gasketguru]

I don’t think there is an easy answer. Whilst a particular grade of rubber may be unsuitable for a given media, swelling is more likely to be the result than dissolving. Anything that could actually dissolve the rubber would probably be extremely dangerous to handle anyway.

A plastic material might be easier to decompose than a cross-linked elastomer, but then you don’t get the resilience of the rubber. – Introducing some means of imparting mechanical damage seems the only real way to “break” the seal in-situ.

FKE has a point regarding E-D – you might be able to take a mechanically relatively weak rubber compound (silicone for example) and introduce a gas such as CO2 at very high pressure, then suddenly release the pressure causing the entrained gas to burst and split the seal. You might need to repeat this process several times to be sure that the damage has occurred (e.g. it will no-longer hold pressure). This of course depends on what pressure the housing is intended for in the first place.

 

[gasketguru]

Another suggestion from one of my colleagues was why not bypass the seal altogether? If this unit is a test prototype or whatever, then try this:

Fit a plug of a low melting point alloy (bismuth-tin-lead e.g. Rose's alloy etc.)into the body of the unit under the seal position before you machine the O-ring grove. You only need to then heat it to a relatively low temperature, and the plug melts away and leaves a bypass groove beneath the seal.