Viton O'Ring Swells 1

[LuizSouza]

Under request of plant Operators we’re installing new closures to receive the pigs in our gas 8” pipeline (assume our gas is 5% pm and we have some condensate inside pipes that’s why pig procedures) that much more easier to operate than the oldies ones, but some strange phenomenon is taking place, the closure door o’ring, made of Viton, swells and go away from its seat along the spring ring that should fit it in place. My question is:

What could be happening ?

 

[rnd2]

Something is disolving into the Viton to make it swell.
You need to isolate what that substance is.

 

[rnd2]

You need to identify that substance in order to select a O ring that won't swell.

 

[grampi1]

Methanol will swell Viton and Methanol is often used as a hydrate inhibitor in gas pipelines. Some amine corrosion inhibitors will attack Viton as well.

 

[LuizSouza]

Thanks to All

I'll try to identify the substance but it's gonna be a little bit hard. What method to use do you suggest?

 

[corrosionman]

Louizsouza Can you be 100% certain that the material is Viton and not whatever someone found on a shelf to get your job moving ?
Cheers DW

 

[LuizSouza]

Yes, corrosionman, first the closure supplier sent the equipment with buna o'ring that swells faster than viton, we claimed a lot, so they sent us viton's that also swells but slower, the supplier gave us a viton o'ring provision for changing as we operate the closure (once a day), they never has seen it and state their viton o'ring can run up to two years without changing.

We can analyze the gas for one substance each time then it's gonna take a long only with the ones we already know.

 

[monkeydog]

Louizsouza,
Given you change out the o-rings, can you perform a chemical analysis of the o-ring you remove, and compare that to a new "unused" o-ring? That may speed up the process of finding out what is in the pipes.

 

[EdStainless]

You might also want to test o-rings from various suppliers. It may be one of the fillers that is responsable for the dramatic swelling. Not all Viton's will be the same.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[LuizSouza]

Monkeydog, that's exactly what we're doing right now, one of our Chemical Engineer is going thru this.

EdStainless, We cant get other supplier o'ring for testing 'cause we've made an US$180.000 purchase order and this supplier must proof that their viton's is not gonig to fail anymore. I wanna just to be one step ahead learn from you, expert guys.

Thanks to All

Luiz
Brazil
luizhenrique_99@yahoo.com

 

[rmw]

Get them to certify that they are using virgin viton, and not recycle viton. Not all viton is created equal.

rmw

 

[unclesyd]

Make sure you look at Flouraz and Chemraz by Greene Tweed. We have replaced Kalrez and Viton in several areas with these materials.
The website below has some pretty good data that might be of use.

http://www.gtweed.com/85256D3C0038D8DA/vwContentByKey/N25PFPEA943ELETEN

 

[EdStainless]

If push comes to shove and you need an absolute solution...

http://www.sealseastern.com/Aflas.htm

This will not be cheap or easy, but it will work. I would hesitate to suggest that anyone spend the money for Afals, but if you are SE is the only place to go. They know more about formulation than anyone.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[LuizSouza]

Thanks EdStainless

 

[stanweld]

From my days working for a major Gas Utility, some Viton O-rings will swell in natural gas service. At least one Grade does not; unfortunately, I forget the proper grade to use. I would suggest contacting the Gas Research Institute for the proper grade. Also check with the Elastomer & O-ring manufacturers. They had much info on these matters 25 years ago.