Silicone lube for Nitrox

[Raphus]

I did something stupid and now i need help, so i know how stupid it was..

I dive Nitrox < 40% on holidays.
I know its ok to use silicon up to 40% O2.
Which is no problem, because the silicon us usually used on the inflator hose, which isnt exposed to high pressures.

Now the stupid part:
I used the Silicon lube on the static O-Rings between the hoses and the first stage.
Both Regulator hoses and HP hose for the pressure gauge.
I used very litle, because i know too much is not good.
But i didnt know (at that time) that static Orings do not need any lube.

I used this product:
TIZIP 8g Lubricant, which contains Polydimethylsiloxane, inorganic fillers.
I bought it at my dive shop, but realized that its only for zipties (i guess it has the same ingredients as oring lube?)

In the future i will take no lube, or christolube for sure.
Does it make any differents, that i used it on the HP o-ring which is exposed to 200 bar, or is it still fine for Nitrox with O2<40% ?

 

[johndiver999]

You are going to die!

But not from this.

 

[Luis H]

I only use silicone grease on all my regulators except if they are going to see very high O2 (80% to 100%).

I use silicone spray on the static hose O-rings since they are not actually static during assembly while rotating the fitting.

For the dynamic HP O-ring in the balancing chamber of the diaphragm 1st stages (Conshelf, etc.) I only use silicone grease and I dive Nitrox < 40% a lot.


I have tried and tested the O2 compatible grease and they all separate in a relatively short time. IMO they are not very good as lubricants. They only work when they are brand new (and even then not as well), but they seem to start degrading too fast for my preference. After a while the grease breaks down into a white paste and a runny liquid (not grease anymore).


I have bought many vintage regulator that have not been serviced since around the 70's. When I open them up I have found silicone grease that looked as good as new. If I didn't have to clean the corrosion and replace the seat and O-rings, there would have been no need for service.



I should add: I have used a first stage with silicone lubricant with deco gas Nitrox as high as 50%, which is not recommended and I am not recommending it to anyone, but it was the regulator I had. There is nothing magical about the 40% (line in the sand). My understanding (from what I keep on reading) is that the 40% is not exactly a fixed threshold, but that the risk increases proportionally to the O2 content, and up to about %40 is fairly safe.

I try to always mitigate any risk of using high O2 Nitrox by always opening the tank valve very slowly. Let the pressure build up slowly in the regulator. I like to see my pressure gauge needle rise very slowly.

The risk also increases with other factors, like other contaminants, high velocity gas, particles that could cause sparks, like rust from the cylinder, the design of the valve and regulators, and maybe others.

 

[Raphus]

Thank you!
I was not sure about the effekt of silicone with 200 bar nitrox, because i couldnt find anything about it.

 

[Lostdiver71]

You are fine, the main worry about silicone and Nitrox is in the risk of using it with 100% o2 as in partial pressure filling a tank or using it with a tank of 100% deco gas. As long as you don’t use it on a tank or DIN o-ring you will be good.

 

[Raphus]

You are fine, the main worry about silicone and Nitrox is in the risk of using it with 100% o2 as in partial pressure filling a tank or using it with a tank of 100% deco gas. As long as you don’t use it on a tank or DIN o-ring you will be good.

Just out of interest:
Why should i not use it on a din oring?
I know using it on a tank oring is bad, because if the shop fills it with oxygen first (partialpressure method?) then it will have contact to 100% oxygen, even if its filled for ean 32.

But din orings are placed on the regulator. So they will only have contact to the ean32 right? So why is it bad on them?

 

[Raphus]

I think i can answer my own question :
Because the lube of the din oring can stick to the tank even after removing the reg.

Am i right?

 

[Lostdiver71]

You are correct, if you use it on the DIN o-ring it can contaminate the valve and cause ignition if the tank is filled with pure oxygen to partial pressure fill.

 

[divad]

You are going to die!

But not from this.