The impact of lubricant on IP

[Zung]

Thanks for the explanations Bro.

For the record, all the o-rings in that reg are stock SP, 2-010 EPDM 85 for the stem, red stripe (ring), and 2-022 EPDM 70 (x 2) for the crown, blue stripe (ring), plus a 2-011 EPDM 85 for the seat, yellow stripe (ring), but this last one doesn't move.

Next time I do the mattmagic, I'll leave the area where the stem o-ring rides rough. It's about 5 mm from the tip and about 10 mm long.

 

[redacted]

Thanks for the explanations Bro.

For the record, all the o-rings in that reg are stock SP, 2-010 EPDM 85 for the stem, red ring, and 2-022 EPDM 70 (x 2) for the crown, blue ring, plus a 2-011 EPDM 85 for the seat, yellow ring, but this last one doesn't move.

Next time I do the mattmagic, I'll leave the area where the stem o-ring rides rough. It's about 5 mm from the tip and about 10 mm long.

The only time I find colored Scubapro o-rings it is either an older regulator that has not been serviced this century or NOS kits (also last century). I was under the impression that those colored scubapro o-rings are nitrile except for the "yellow" ones which I believe are urethane.

 

[Zung]

Sorry about the confusion in wording.
No, I'm not talking about the dyed o-rings of 10-20 years ago.

Currently, SP supplies black o-rings that have a color stripe painted on whenever it's critical. Like this:

 

[Couv]

Thanks for the explanations Bro.

For the record, all the o-rings in that reg are stock SP, 2-010 EPDM 85 for the stem, red stripe (ring), and 2-022 EPDM 70 (x 2) for the crown, blue stripe (ring), plus a 2-011 EPDM 85 for the seat, yellow stripe (ring), but this last one doesn't move.

Next time I do the mattmagic, I'll leave the area where the stem o-ring rides rough. It's about 5 mm from the tip and about 10 mm long.

Sorry I got long winded in the previous post, I should have concluded with something along the lines of: If everything else is exactly the same except the lubricant, then you have found the culprit.

c

 

[knowone]

I saw ABBA in a tree with binoculars. Musicians think they are simplistically technical. Air Supply filled the schlep void. So throw away your guages and fill your regs with grease?

 

[halocline]

I think polishing the stem knife edge that comes into contact with the hp soft seat is a good idea, but IMHO, the area that comes into contact with the stem o-ring should not be polished. In fact, I try to put tiny scratches (preferably a cross-hatched pattern) there. These tiny scratches provide more surface area and nooks and crannies for the lubricant to adhere to.

I thought that "polishing" the piston shaft where it go under the o-ring is putting small scratches in it. I've done this to break up the glaze that seems to accumulate in this area in older pistons. By polishing I mean sanding with micromesh. I wouldn't go all the way to 12000, maybe just to 3600 or so.

Either way I'd be very surprised if silicone vs PTFE grease resulted in a 10 PSI difference in IP.

 

[Zung]

Sorry I got long winded in the previous post, I should have concluded with something along the lines of: If everything else is exactly the same except the lubricant, then you have found the culprit.

c

Yes, all else had been equal. Let me recap:

1. Before: 10 bar/145 PSI, no creep
2. Cleaned everything, reassembled with Christo-Lube 129, no part substitution, cycled about 20x over 6 hours
3. After: 9 bar/130.5 PSI, creeping to 9.2 bar/133 PSI

There're 3 things I'm not sure of:

1. The seat o-ring might not be the same: there're 3 of them 2-011 EP85 with the yellow stripe, 1 on the seat and 2 on the HP port plugs. This should have no effect on the IP, it's a static part.
2. The piston and the seat may have rotated; that could explain the creep, since there's a little scratch at the edge.
3. There's some verdigris inside the cap, where the crown of the piston rides. I soaked it in vinegar for 5 min. and polished it off with Brasso. This MAY affect the IP.