Experts: HNBR O-Rings verses Nitrile?

[Rock_Hudstone]

I need to replace a regular black Nitrile rubber o-ring oil seal but have had trouble finding the exact metric size I need.

Can I substitute a green HNBR o-ring such as those used on A/C lines and fittings?

Are the HBNR seals as oil resistant and durable as Nitrile?

 

[yonyon]

Call me silly and call me crazy but I was under the impression that HNBR o-rings are nitrile o-rings and are okay with oil. Don't use them for gasoline though.

 

[Rock_Hudstone]

Originally Posted By: yonyon
Call me silly and call me crazy but I was under the impression that HNBR o-rings are nitrile o-rings and are okay with oil. Don't use them for gasoline though.

Yes, they are a form of nitrile, guess I should have been more clear. I was just wondering if someone could explain more on the correct applications.

 

[SnPb]

The Parker O-Ring Handbook has a good description of the different elastomers available and their applications.

Parker

 

[djb]

HNBR is almost always a better substitute for N-Buna (aka nitrile, Buna-N) Rubber ("NBR").

HNBR is NBR with "end caps" on the vulnerable ends of the molecules. Think of it as putting copper caps on pilings to keep them from rotting as quickly.

If you have a specific application in mind, you can often find a better material.

 

[DB_Cooper]

In a pinch I've used the A/C green "O" rings for power steering pumps and engine oil fittings. No problems.

 

[Gotch]

What is the application? I've had in the past, issues with nitrile seals failing on a hydraulic motor application. Changed to viton and they didn't swell as much and failure rates went down substantially.

When we root caused the original issue with the nitrile seals, we found that they were incompatable with the synthetic hyraulic fluid we were using.

 

[Trav]

What size O-Ring do you need? I have hundreds of sizes here all Viton 70.
Don't go by color. While its true most A/C seals are green i have lots of colors and all the same material. Green, blue, red, black, brown all Viton 70.

 

[Rock_Hudstone]

Originally Posted By: Trav
What size O-Ring do you need? I have hundreds of sizes here all Viton 70.

It is 21mm O.D. x 15mm I.D. x 3mm thick, for a washer trans rebuild I'm doing similar to this: http://www.automaticwasher.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?38714

I have all the parts except the drive shaft O-ring seal which is the main reason for the tear down in the first place.

 

[Trav]

I have a 21x15x2.7mm and a 21x14x4.5 Viton O ring if that will help.