Standard for Assessment of O-Ring Appearance 2

[rneill]

I'm going to be having some o-rings pulled out of a valve to be assessed for how well they have performed after several years of service. I'm asking to have the valve manufacturer prepare a report including detailed pictures of the O-rings but I'd also like an "objective" evaluation of O-ring condition in regards to visual appearance (blisters, cracks, residue).

I've seen such reports in the past that use references such as "ASTM #6 blisters" found on the O-ring but I'm at a loss as to what ASTM standard these criteria come out of.

I've reviewed NACE TM0187 (didn't find anything), NORSOK M701 (a scale for RGD damage from cracks but nothing on blisters) and I looked at a variety of ASTM standards but didn't find anything that seemed to provide objective criteria for assessing visual appearance.

Can anyone point me in the right direction ?

 

[TVP]

ASTM D 810 is a common standard for evaluating blistering of coatings, which uses a numeral designation like 6 (medium size), 8 (small), 10 (no blisters).

 

[rneill]

I did a search on ASTM D810 and came up with "Methods of Test for Sulfated Residue, Lead, Iron and Copper in Lubricating Oils" that was withdrawn in 1962.

There does not appear to be a current document D810 ?

 

[thgirw]

Have a look to SAE AIR1707, revision A Patterns of O-Ring Failures, maybe it may help?

 

[TVP]

rneill,

I apologize for the error, the correct standard is ASTM D 714 Standard Test Method for Evaluating Degree of Blistering of Paints. That's what I get for working from memory rather than double checking the exact number. Ugh.

 

[rneill]

Thanks, I'll take a look

 

[dgallup]

There is a MIL-STD-413C that specifies allowable sizes of o-ring defects in new parts. The RMA has a similar document, I don't know the number off the top of my head. I don't think a paint spec would be relevant to o-rings.

One of the most important parameters you want to inspect is the amount of compression set in the o-rings. This can be measured quantitatively.

 

[rneill]

There was a significant amount of compression set in the dynamic o-rings, not so much in the static. Bad enough that I don't think that is the material we should be using.