Looking for 100% O2 Pressure Gauge

I'm setting up a 100% O2 deco bottle and I have everything but a pressure gauge. A dive shop told me that I could just use a regular pressure gauge because there are no "true" O2 pressure gauges; but I'm second guessing that opinion. The tank was 100% O2 cleaned by another shop and I had them replace the tank valve o-rings with viton rings. I'm using a 100% O2 compatible regulator. I'm thinking the pressure gauge should have viton rings, too. Suggestions on this?

If you are running an 100% O2 bottle. What pressure gauge are you using? I'm looking for a 1.5" face gauge...maybe I'm just being picky!

Use oxygen compatible o-rings, and get a standard brass & glass SPG (or one of the newer plastic models that isn't as heavy). DiveRiteExpress has them for $58 each right now, which is a screaming deal.

Most of the standard 'brass & glass" SPGs from DiveRite, Halcyon, Salvo, etc, all come from the same place in Italy.

SparticleBrane:

Use oxygen compatible o-rings, and get a standard brass & glass SPG (or one of the newer plastic models that isn't as heavy). DiveRiteExpress has them for $58 each right now, which is a screaming deal.

Most of the standard 'brass & glass" SPGs from DiveRite, Halcyon, Salvo, etc, all come from the same place in Italy.

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That + oxygen compatible lube, such as Christo Lube 111.

Bourdon-tube gauges, of which the standard "brass & glass" SPGs are an example, have no moving parts or O-rings that come into contact with the gas. They consist of a flat tube curved into an arc which tries to straighten when presurized - like those party favors that unroll when you blow into them. Linkages attached to the tip of the tube transmit the deflection to the needle giving you the pressure. Since the inside is simply a closed end tube, it requires no lubrication there.

Any gauge of this type can be prepared for oxygen service by properly cleaning the air tube with acetone, or a solvent that evaporates completely to gaurrantee that there's no oil residue, which would flash if exposed to oxygen at high pressure.

In commercial use the only difference between a standard gauge and an oxygen gauge is the reminder on the face to "use no oil".

toddr:

I'm setting up a 100% O2 deco bottle and I have everything but a pressure gauge.

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OK. Go on...

A dive shop told me that I could just use a regular pressure gauge because there are no "true" O2 pressure gauges; but I'm second guessing that opinion.

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Why? For one of the few times in history an LDS is correct.

The tank was 100% O2 cleaned by another shop and I had them replace the tank valve o-rings with viton rings.

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Why viton? Why not EPDM?

I'm using a 100% O2 compatible regulator. I'm thinking the pressure gauge should have viton rings, too. Suggestions on this?

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I use EPDM. Or Buna. Doesn't really matter.

If you are running an 100% O2 bottle. What pressure gauge are you using?

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Whatever one I pick off the shelf. I prefer the plastic gauges as they are lighter.

EPDM o-rings are a little more durable and less prone to growing feathers so they are better in dynamic applications.

However viton o-rings have a higher ignition temp and maybe more importantly, more shops seem to stock them in the 03 size you need.

Also, EPDM o-rings are usually identified by a white ring around them and on a small o-ring the ring can get hard to see or result in marking a large portion of the o-ring surface.

Buna/nitrile rubber o-rings have been a standard in aircraft O2 system service for years and they are quite durable. However they have a much lower ignition temp than EPDM or Viton and do degrade over time with O2 exposure - but in an O2 system that is designed to pressurize fairly slowly with no compression heating, sharp bends in the flow path that may generate heat or entrained particles that may spark, the fuel issue is minimal as ignition sources are absent and annual service takes care of the O2 exposure issue. In an SPG long term O2 exposure is a moot issue as it is only presurized and exposued to very high PPO2's for a small percentage of the time.

However, unlike Nad, I would not go so far as to say they are ok in an SPG. The bleeder hole in most regs and the flow path in most HP hoses is quite small, but they are not designed for O2 service and gas in the bourdon tube does go from zero to 2400-3600 psi fairly quickly and any gas initially moving through the hose does come to a sudden stop at the end creating the potential for compression heating.

My first choice would be EDPM, but Viton are probably more available at the average dive shop and as long as you properly lubricate them with Christolube or Tribolube, they will hold up fine on the HP spool used in the SPG as it is only semi-dynamic with fairly few rotation cycles per dive.

I am not a real fan of plastic SPG's. They get beat around a bit if clipped to a D-ring with stage /deco bottles, etc and I prefer the durability of brass and glass - especially when I am a half mile back in a cave.

Aquamaster-- Why are you carrying your o2 with you that far back in the cave??

Toddr-- Why do you need a pressure guage on your o2? Some people leave it off altogether and I'm not a fan of that-- then you have to get a pressure checker or hook up another reg to your o2 to check the pressure in it if you forget, or are bad at guesstimating your usage, and I hesitate to put things on my o2 bottle that get used on other bottles and are not treated with that same caution that I treat my o2 regs with. However, I also have no need to be able to know my o2 pressure extremely precisely. Generally speaking, I look at the guage to know if I'll have enough for my stop, and when I get out I check it again to see if it's over a "minimum fill" amount. Therefore, I have no need for a large face pressure guage, and use one of those larger button gauges instead. Much easier to read then the tiny button guages, and I can read it underwater if I want to. Also, only one oring in a static position. Several companies sell them, but PiranhaMFG seems to have a very good price on them...for whatever reason, screenprinting "Salvo" on the face makes them much more expensive... Nothing special was done to clean the one I've got on my reg and it hasn't blown up after over half a year of use and approximately 75 deco dives. Of course, your mileage may vary, and you should not hesitate to get things cleaned, because o2 fires do happen. This is my my experience, take it for what you paid for it!

don Francisco:

Bourdon-tube gauges, of which the standard "brass & glass" SPGs are an example, have no moving parts or O-rings that come into contact with the gas. They consist of a flat tube curved into an arc which tries to straighten when presurized - like those party favors that unroll when you blow into them. Linkages attached to the tip of the tube transmit the deflection to the needle giving you the pressure. Since the inside is simply a closed end tube, it requires no lubrication there.

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The little rod that sticks into the end of the high pressure hose has an o-ring on it. That doesn't contact gas?

Blackwood:

The little rod that sticks into the end of the high pressure hose has an o-ring on it. That doesn't contact gas?

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You are talking about the spool, I assume. This does come into contact with gas and was not included in the description of a Bourdon tube guage by the poster, who was only talking about cleaning the gauge, not the spool or hose. DA Aquamaster did discuss the spool and the usage of various types of orings on the spool in his very informative post.

Blackwood:

That + oxygen compatible lube, such as Christo Lube 111.

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Phil also has Tribolube 71

Aerospace Lubricants TRIBOLUBE 71 - 2oz