Scubapro O-ring Sizes

[Timmyjane]

Deleted

 

[passedoutwookie]

I am late to the party here but this thread is a GREAT resource. Many thanks to all who contributed. Can someone tell me what the N and D stand for in the o ring chart and sheet?

 

[buddhasummer]

N likely Nitrile (material)
D likely Duro (hardness)

 

[passedoutwookie]

N likely Nitrile (material)
D likely Duro (hardness)

I assumed that as well, but there is already another column for material and hardness. Check out the mk20 column on this chart. It has “N” for o rings that are marked as viton in the material column.

 

[buddhasummer]

Nitrox

 

[passedoutwookie]

Nitrox

So those are required only when servicing for nitrox use, otherwise they do not need to be replaced? I am planning on going back with all viton anyway (I don't see any reason not to based on price). Any reason not to just replace them all with viton that I am not aware of?

 

[rsingler]

Any reason not to just replace them all with viton that I am not aware of?

Yeah. Viton is just not the best seal. It has lower tensile strength and most important, it permanently deforms much more quickly than either Nitrile or EPDM. That results in a failure to seal much earlier than an oring that retains its "springiness". IMO, this factor essentially eliminates the value of the extended lifetime of the compound, unless you're just storing them on the shelf for a decade.

After a decade of riding on the FKM bandwagon, if you are not using high pressure oxygen I no longer see much advantage in the o-ring. And even then, the benefit is present primarily where adiabatic heating is of concern. If you have red hot particulates impacting your oring, ANY of the compounds can burn.