[PSUBS-MAILIST] Fw: O2 cleaning

Thu Jan 16 11:58:22 EST 2020

Thanks Sean.

I think im ok then.  I made sure that the tape didnt go into the path of
the O2 flow.  Also im at low pressure at that point.

The only particulate filter I have is part of the final flowmeter and is
built into the unit.

Thanks for the advice.
regards
James

On Tue, 14 Jan 2020 at 13:24, Sean T. Stevenson via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> PTFE is fine to use. There are some liquid / paste thread sealants out
> there which may not be O2 compatible. Sometimes, the liquids have the
> advantage of being less likely to introduce fouling particles / debris into
> the system than a tape sealant, but this is largely dependent on technique.
> If you're careful to avoid wrapping over the end of the fitting with tape,
> and don't do too many wraps, you'll be fine. Keep in mind that the primary
> purpose of a PTFE sealant is actually to act as a lubricant, in order to
> allow greater engagement of the interfering tapered threads at lesser
> torque. Gap filling the spiral leak path is secondary. There may also be
> liquid sealants which are okay for oxygen use, but you need to check.
>
> On a slight tangent, particulate filters are always a good idea upstream
> of any critical components, and certainly where you don't have easily
> actuated manual shutdowns/ overrides. Where I employ certain electronic
> regulators in gas pressure control systems, I make a point of filtering at
> 40 microns maximum, and finer is better, though more maintenance intensive.
> There's nothing more frustrating than breaking down a failed regulator to
> discover that it failed because it was fouled by a bit of sand, or a bit of
> PTFE tape.
>
> Sean
>
> -------- Original Message --------
> On Jan. 14, 2020, 05:07, James Frankland via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
> Hi Sean
> You said here.
> "Finally, if you're assembling any tapered thread connections (NPT), use a
> PTFE or other thread sealant suitable for oxygen systems".
>
> You got me slightly worried now.  I used ptfe tape on two BSPT joints I
> have on my O2 system.  I was careful to keep the ptfe tape only on the
> tread, but still.  It was just ordinary ptfe tape.  They are downstream of
> an outside mounted O2 clean regulator set to relieve at 14bar max, so its
> only low pressure in the pipe.
>
> Do you think i need to re seal them with something else?
>
> Thanks
> James
>
>
>
> On Tue, 14 Jan 2020 at 02:50, Sean T. Stevenson via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Barring the presence of obvious open sources of ignition, fires in oxygen
>> systems can also occur as a result of localized heating due to adiabatic
>> compression, and to flow phase transitions (I.e. laminar to turbulent). If
>> you, for example, have a dead headed volume downstream of a 1/4" ball valve
>> at zero gauge pressure, and high pressure oxygen upstream, and you open
>> that valve suddenly, the compression of the gas within the downstream
>> volume will generate a lot of heat, which can conceivably cause the
>> spontaneous ignition of any fuels present. Such fuels can include not only
>> residual hydrocarbons from insufficiently cleaned systems, but also the
>> system fittings themselves. Often machined fittings can have thin-walled
>> features (e.g. intersections of drilled holes in elbow fittings), and these
>> locations are at risk of localized heating to the point at which the metal
>> itself begins to burn, which can be catastrophic in the presence of high
>> pressure pure oxygen. Using needle valves allows you much finer control
>> over the rate of pressurization - the idea being that by avoiding fast
>> pressurization rates, the heat from adiabatic compression has time to
>> dissipate from the system plumbing, and the ultimate maximum temperature of
>> the compressing volume is kept lower, reducing the risk of a spontaneous
>> fire.
>>
>> Sean
>>
>> -------- Original Message --------
>> On Jan. 13, 2020, 19:25, Ian Juby via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>
>> Hey Sean,
>> I'm new to the group, but you said in your reply "You also want to avoid
>> the use of any fast acting valves in oxygen systems. Use needle valves
>> where possible."
>> Why do you suggest avoiding fast acting valves?
>> Tanks eh!
>> Ian
>>
>>
>> On Mon, Jan 13, 2020 at 9:07 PM Sean T. Stevenson via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>>
>>> If you don't already own a copy, pick up a copy of the Oxygen Hacker's
>>> Companion, by Vance Harlow:
>>>
>>> http://www.airspeedpress.com/newoxyhacker.html
>>>
>>> That said, plain carbon steel is a less ideal material for O2 use than
>>> is brass or stainless. You also want to avoid the use of any fast acting
>>> valves in oxygen systems. Use needle valves where possible.
>>>
>>> To clean parts for O2 use, just avoid the use of solvents and use a
>>> hydrocarbon free cleaner. My preference is Orange TKO, but there are many
>>> others. Simple Green also seems to be popular. Use as directed, and check
>>> both your cleaning brushes and the rinse water with a UV light to ensure
>>> that it is coming away clean. Just repeat the cleaning / rinse until it
>>> does. To dry, small parts and fittings can dry in ambient air, but tubing,
>>> hoses, and more complicated parts with dead spaces will have to be blown
>>> dry. This must be done with hydrocarbon-free air (I.e. nitrox quality) or
>>> e.g. pure nitrogen, to avoid recontaminating the parts.
>>>
>>> You want to replace any soft parts in your oxygen system with oxygen
>>> compatible materials where necessary (I.e. Viton O-rings and oxygen
>>> compatible valve seats), and then use O2 compatible lubricants exclusively.
>>> The gold standard for this is CHRISTO-LUBE MCG 111.
>>>
>>> Finally, if you're assembling any tapered thread connections (NPT), use
>>> a PTFE or other thread sealant suitable for oxygen systems.
>>>
>>> Sean
>>>
>>> -------- Original Message --------
>>> On Jan. 13, 2020, 15:53, hank pronk < hanker_20032000 at yahoo.ca> wrote:
>>>
>>> Hi Sean,
>>> I am installing the O2 paediatric regulator in E3000 now.  I have a
>>> tower valve that accepts the regulator, and the valve screws directly into
>>> the hull penetrator.  The hull penetrator is a steel nipple.  How do you
>>> recommend I clean the nipple and fittings?  I have an O2 braided ss hose to
>>> the tank.  The hose is actually from my O2 cascading set up.
>>> Hank
>>> _______________________________________________
>>> Personal_Submersibles mailing list
>>> Personal_Submersibles at psubs.org
>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>
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