cooling water seals 2

[RobertHasty]

Hi,

Does anybody have any experience regarding cooling water (glycol + water) compatibility with FKM and NBR seals?
I am referring to the O-rings which can be found on hydraulic hose fittings.

I found this compatibility table from Parker:

https://www.parker.com/literature/O-Ring%20Division%20Literature/Section%20VII.pdf

Page 7-26 states that FKM & NBR are satisfactory in combination with Glycols.

Page 7-27 has an example for Houghto-Safe 620 Water/Glycol and states FAir for FKM and Satisfactory for NBR.

Any experience from board members?
Thank you in advance.

 

[EdStainless]

Temperature will be the controlling variable.
We used NBR for this service.
But we specified the compound as we found that some worked better than others.

 

[btrueblood]

EPDM will be superior to either of those above about 200 deg. F.

FKM aka Viton is variable - the base polymer is not well controlled by that specification, and varying types of Viton have been developed to get better hydrolysis resistance. NBR is ok up to 180F, and HNBR is good to about 210-220F. EPDM is good to 250F in pressurized water/glycol systems.

 

[RobertHasty]

Temperature will be the controlling variable.
We used NBR for this service.
But we specified the compound as we found that some worked better than others.

Thanks for the answer.

I don not know the exact compound yet.
Since the temperature is the main issue, I am afraid the NBR will not do the job for me.

 

[RobertHasty]

EPDM will be superior to either of those above about 200 deg. F.

FKM aka Viton is variable - the base polymer is not well controlled by that specification, and varying types of Viton have been developed to get better hydrolysis resistance. NBR is ok up to 180F, and HNBR is good to about 210-220F. EPDM is good to 250F in pressurized water/glycol systems.

Thanks for the reply.
The problem with EPDM is that is not available in various sizes.

 

[btrueblood]

What type of fitting exactly?

McMaster sells EPDM orings in all of the SAE Oring boss fitting standard sizes, if you are in the USA. There are other shops that will sell them cheaper if you ask. I've been able to find shops with all of the ISO metric sizes as well, but typically you need to buy a reasonable quantity (hundreds)

 

[TugboatEng]

FKM's compatibility with water depends heavily on the type of cure.

NBR is terrible with water above 120°F and also is challenged by chlorinated tap waters.

EPDM works exceptionally well with most types of water over an extremely wide range of temperatures at a very low cost provided it's never exposed to hydrocarbon oils.

Silicone o-rings can work but I find that they're sensitive to damage during installation. Fluorosilicone has better mechanical properties but the cost is very high.

 

[RobertHasty]

What type of fitting exactly?

McMaster sells EPDM orings in all of the SAE Oring boss fitting standard sizes, if you are in the USA. There are other shops that will sell them cheaper if you ask. I've been able to find shops with all of the ISO metric sizes as well, but typically you need to buy a reasonable quantity (hundreds)

I am not in USA.

 

[RobertHasty]

FKM's compatibility with water depends heavily on the type of cure.

NBR is terrible with water above 120°F and also is challenged by chlorinated tap waters.

EPDM works exceptionally well with most types of water over an extremely wide range of temperatures at a very low cost provided it's never exposed to hydrocarbon oils.

Silicone o-rings can work but I find that they're sensitive to damage during installation. Fluorosilicone has better mechanical properties but the cost is very high.

EPDM is the way to go.

120°F is less than 49 °C which is terribly low.

 

[Dynamics_Eng]

Both of them will work fine as long as temperature is below 250F. Goodluck!

 

[btrueblood]

Ed has good advice - your materials may vary from what we get, your best answer is to order some and test it. We've "perfected" a seal test for our valve seals. Simple rig with a thermostat and heater (sometimes a cooler), pumped loop, valve cycling on/off 24-7, and safety pressure switch for shutoff and simple data recorder. We find reputable suppliers and ask for the material identification for repeat orders.