Question about Perdix and Transmitter Rubber O-rings

[GF99/99]

Technically yes for if its on the HP side you should use an O2 compatible lube like Christolube or Tribolube but for the last several years to simplify things I just use Molykote 111 on everything. Very very nice for rebreather heads especially if you have a JJ, head pops out like butter.

 

[DiveGearExpress]

Technically yes for if its on the HP side you should use an O2 compatible lube like Christolube or Tribolube but for the last several years to simplify things I just use Molykote 111 on everything. Very very nice for rebreather heads especially if you have a JJ, head pops out like butter.

Just to be clear, most experts would not consider DuPont Molykote 111 (a silicone grease) to be oxygen compatible. And while compatible with most plastics, we definitely do not recommend it in the head of your rebreather because over time it can react with other plastics and contaminates to form insulating films and silicone carbide compounds which can cause intermittent connections in low-current applications such as oxygen sensors. Silicone lubes have been diagnosed as the cause of sensor issues we've seen several times in the past.

Is it safe to use silicone grease with Nitrox? | Dive Gear Express®

www.divegearexpress.com

However, for your Shearwater battery door o-ring, use whatever commonly available scuba lubricant you like... it doesn't matter and Shearwater doesn't specify.

 

[BoatingDave]

The use of oxygen compatible polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE) based lubricants (Tribolube, Christolube, or any other brand such as Krytox or MPT) with either fluorocarbon elastomers (aka FKM, aka FPM, aka Viton o-rings) or acrylonitrile-butadine copolymer elastomers (aka NBR, aka nitrile, aka Buna-N synthetic rubber o-rings) is perfectly acceptable and generally considered best practice within the Scuba industry as they will typically outperform polydimethylsiloxane based lubricants (aka PDMS, aka silicone grease) and are also much less migratory.

Ok very helpful thanks. So are there any typically used o-ring materials (open circuit, not rebreathers) where PTFE or PCTFE lubricants (or silicone grease for that matter) are contraindicated?

 

[DiveGearExpress]

Ok very helpful thanks. So are there any typically used o-ring materials (open circuit, not rebreathers) where PTFE or PCTFE lubricants (or silicone grease for that matter) are contraindicated?

None so far as o-ring materials seen in Scuba applications; they are about as inert as it gets for service in temperatures seen with scuba devices. We've exclusively used oxygen compatible lubricants in scuba open-circuit and closed-circuit applications for 20 years. Most scuba manufacturers have also switched to them as well, if for no other reason than when producing products suitable for use with Nitrox then in practice it is extremely difficult to avoid cross contamination with silicone lubes in manufacturing facilities. The only application in our industry where silicone lubes are still widely seen is underwater lights and cameras.... because it's cheaper.

The only downside to PTFE and PCTFE is if they are exposed to temperatures in excess of about 1200F / 650C; then they release some extremely toxic gases.

For silicone grease, the only o-ring material compatibility concern is VMQ (aka 'silicone' o-rings.) These are occasionally encountered in scuba applications, especially rebreathers for some reason I've never fully understood. The VMQ o-rings are typically orange or red color.

Sizing and Selecting O-Rings for SCUBA | Dive Gear Express®

While it might seem convenient to provide a picture sizing chart, we've never seen an online version that could be reproduced exactly in a Web ...

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[brycejohnson]

Just to be clear, most experts would not consider DuPont Molykote 111 (a silicone grease) to be oxygen compatible. And while compatible with most plastics, we definitely do not recommend it in the head of your rebreather because over time it can react with other plastics and contaminates to form insulating films and silicone carbide compounds which can cause intermittent connections in low-current applications such as oxygen sensors. Silicone lubes have been diagnosed as the cause of sensor issues we've seen several times in the past.

Is it safe to use silicone grease with Nitrox? | Dive Gear Express®

www.divegearexpress.com

However, for your Shearwater battery door o-ring, use whatever commonly available scuba lubricant you like... it doesn't matter and Shearwater doesn't specify.

I am new to Scuba Diving--I started to put together my save-a-dive kit. I went down the rabbit hole of o-rings and lubricant and just thought, how can I trust an US$8.00 160 pack of o-rings? Some or all of this equipment is life sustaining which now makes me want to ask the question. I can assume now based on this article and maybe a little common-sense that not all o-rings and not all lubricants are created equal. Got that. So now, is there a known to work default if I'm in a bind? Does such a lubricant and/or o-rings exist that are safe for all diving related equipment? I should probably refer to my manufacturer documentation first and then ask questions?

Anyway, pleasure to meet all of you and i'm thrilled to be part of this community.

Bryce