Rubber in Acidic Enviroment 2

[ghamsa]

We are evaluating the use of "un-restrained coupling" joint in under ground oily waste water piping.
This coupling joint is equipped with internal rubber gasket, which should seal the external of piping end.

My Questions are:

1) Is this type of joint reliable in under ground oily waste water system?

2) The rubber gasket will get in tough with oily waste water, which may contain acidic solution such H2S. Can this rubber gasket withstand this acidic environment?

Thanks all

 

[JimCasey]

"rubber" is not very specific.Neither is "oil". Neoprene or Buna-N are pretty good with acids and oils but EPDM would be attacked by the Oil. Viton tolerates hydrocarbons and acids but is attacked if there is any ammonia or anything with an acetate radical in the molecular structure (acetic acid, vinegar, some paints, etc. Silicone rubber is chemically resistant but if the oil is a silicone-based oil it will attack the SIlicone rubber. Consult with the coupling manufacturer and find out what the specific elastomer is. It would be best if you could identify the oil in question to him, and the concentration of H2S, and ask for his rating for the compatibility. Otherwise look in a standard industry reference such as Corrosion's Handbook, or at least ask somebody knowledgeable about what works at your plant about what elastomers are attacked and which ones tolerate the components of the stream in question.

 

[tothepoint]

There are newer Viton compounds that have enhanced chemical resistance to ammonia and the acetate radical. Chek out the chemcical compatility guide on the DuPontElastomers website. Select the best grade of viton (A, B, F or Extreme), and specify "100% genuine Viton grade_" . There are a lot of lower grade fluoroelastomer materials out there that contain very little fluoroelastomer.

 

[STYMIEDPIPER]

as JimCasey pointed out that "rubber" is too general of a description.Tothepoint is correct as to check with a chemical resistance guide.
Another source to consider---Red Valve Company has a very informative 'Chemical to Elastomer Guide' which I have used for reference purposes for many years.