O-ring Chemical Incompatibility - What does it mean?

[Potcarb]

I recently found out that one of my process chemicals may be incompatible with an o-ring based on general chemical compatibility charts. What exactly does this mean? Could it cause a reaction, or does it just mean the o-ring could swell/rupture, etc.?

 

[Compositepro]

I could be both, but the latter is much more common.

 

[Latexman]

If the process chemical is a minor component it could mean no change in o-ring is required. If it is a major component, a change may be required. I’d recommend a risk based approach to guide the decision.

Good Luck,
Latexman

 

[MJCronin]

When you called the research department of one of the major vendors of these O-rings to discuss elastomers, what did they tell you ?

If the line of O-ring materials are anything like that of gaskets, there is probably only one --"best of breed" material that is used under many extreme chemical service.

Would it be possible and is there enough time for you to develop a test block where samples of various materials are placed within the stream of your existing process ? .... Perhaps there is an ASTM standard already developed for this purpose.????

Parker has lots of good information here:

https://www.parker.com/Literature/O-Ring Division Literature/ORD 5700.pdf

TEll us more about your specific problem. What chemicals exactly are you concerned about ????.... Has there been actual material degradation or are you a "nervous nellie" and worried about possible failure ?

MJCronin
Sr. Process Engineer

 

[moltenmetal]

Incompatibility can mean anything from swelling (which might affect whether your o-ring joint will work properly, or last durably- or, if it's a static o-ring joint, might actually make your joint seal tighter!), to embrittlement/loss of elasticity, to being totally destroyed and being washed out of the joint.

Depends which o-ring material and which "chemical". And whether or not it's a problem depends on exposure time, temperature, service life and the nature of your o-ring joint.

Note also that a generic material such as "viton" (FKM) or "kalrez" (FFKM) has many different grades associated with it. Some grades are designed for extraordinarily good service life in hot, dry conditions, but can be destroyed by just adding some steam. Others offer extraordinarily good resistance to some chemical compounds, but might not be good to high temperatures even under dry conditions...The various grades of FFKM available are so different in what they're good for (and not good for!) that they really should be distinguished as different materials entirely.