Nitrox production guideline - Continuous blending

[iain/hsm]

SNIP,


And to IAIN/HSM , this is very much in line with the European Standard BS8478:2006 Breathing Gases Component Concentration. Is US Navy and the British or EN somehow sharing information Iain ?

Thanks & Later,

IYA

Hey, We taught them everything they know, The rest we (Royal Navy) gave away for free, so no surprised there.

With Nitrox, just three simple points in a nutshell.

1. Any gas with a percentage of oxygen greater than 23% shall be classed as oxygen
2. Oxygen is USE NO OIL
3. Filters by there very nature fail
4. Learn of Burn

Thats it.

Just to add on the point of double filtration, mixing blending yada yada from one of the US founders of nitrox for recreational sports divers came the following "pearls of wisdom" If we go down the oil free route it will kill the advancement of nitrox to scuba divers as no dive shop will make the investment to change there compressors to oil free...............Solution.... a green and yellow sticker label and trademark the term "Safe AIR"

Iain Middlebrook

---------- Post Merged on September 11th, 2012 at 02:10 PM ---------- Previous Post was on September 10th, 2012 at 03:50 PM ----------

Pretty much in a nutshell nitrox for the scuba diver, but for a couple of points.

It is interesting in that the "set up" for nitrox production for dive shops both in the USA and UK for sports divers there are some glaring omissions.

1. The omission of any of the current gas industry guidelines for compressing gas at elevated oxygen concentrations .
2. The total omission of any industrial oxygen supplier as adviser, BOC, Linde, Praxair, Air Products, all conveniently "forgotten"
3. The total lack of practical safety procedure for operators when filling by partial pressure.
4. The total lack of differential between oxygen compression by reciprocating gas compressor to 2200psi against liquid "developed gas" compression to <3500psi for example

One other header for my last post
Learn of Burn

Iain Middlebrook

 

[frogman62]

Documents for review

All,

There should be no confusion in the U.S. about this issue. Attached are two documents that seem to define the issues very clearly. Draw you own conclusions from the research and records. A third document is too large for inclusion in this post. It is a Dept of the Navy Technical letter approving the Lawrence Factor filter system M-A64 filtration system for use in NITROX blending, and supplementing the US Navy diving manual to include this information. It is the approval to use oil lubricated compressor in NITROX applications. I have listed this in the "files" section for anyone's review on the < compressor_team > site. You can PM me and I'll send you a full copy of the technical letter and test results
Jim Shelden

View attachment NASA.PDFView attachment HyperbariUnerseaMedicine.pdf

 

[iain/hsm]

All,

There should be no confusion in the U.S. about this issue. Attached are two documents that seem to define the issues very clearly. Draw you own conclusions from the research and records. A third document is too large for inclusion in this post. It is a Dept of the Navy Technical letter approving the Lawrence Factor filter system M-A64 filtration system for use in NITROX blending, and supplementing the US Navy diving manual to include this information. It is the approval to use oil lubricated compressor in NITROX applications. I have listed this in the "files" section for anyone's review on the < compressor_team > site. You can PM me and I'll send you a full copy of the technical letter and test results
Jim Shelden

View attachment 135221View attachment 135222

Be afraid be very afraid, there is confusuion in your post already Frogman

But if you are seriously putting up these two frankly amateur reports appertaining to nitrox percentage as being in any way relevant to nitrox production and that either of the two reports you quote are in any way to be taken as being any way relevant to the subject post you are either very much misleading or very much mislead.

The two articles are in themselves are at best "lightweight" enough, using the NASA 50% regulator "bomb" test is just a poor example but citing these articles as a basis for using even a similar percentage for entraining oxygen into a oil lubricated composer is totally misleading and frankly shows a total ignorance of the principle involved.

Look test yourself at 30 40 and 50% oxygen in your oil lubricated compressor do yourself a favour try it and see, then do a full gas spectrographic analysis of the composition gas. (not just CO CO2 water, oxygen and oil) a full gas spec of the total gas composition at each of these percentages and wake up to the reality of what you are implying.

Depressing 50% even 60% pure dry cold and clean nitrox already at pressure out of a cold clean cylinder even at velocity is nothing.

Try using it with the heat, oil particulate and at gas discharge valve velocities and temperatures of a old oily designed for AIR reciprocation air compressor and then come back tell us what nasties you just created and are "off gassing" from the lubricant and if they are OK to breathe let alone the adiabatic loads, oil oxidation, breakdown and subsequent piston rod and bearing premature damage with the resultant higher service and repair costs.

Again I ask you similar questions to those to Coltri:


1. What are the maximum rod loads for each stage on these Kiddie compressors
2. What are the compression ratios for each stage?
3. What is the gas temperature for each stage?


By Gas temperature I mean the calculated gas factor temperature and NOT the head temperature or the physical surface temperature of the head discharge tube.

Then we can really put nitrox blending safely into perspective. Iain Middlebrook

 

[frogman62]

Iain, This has nothing to do with my compressors. It has nothing to do with Jim Shelden.
This is the US Navy, NASA and Hyperbarics International documents on NITROX issues.I only listed these because no one seems to have the published documentation
JS

 

[iain/hsm]

Iain, This has nothing to do with my compressors. It has nothing to do with Jim Shelden.
This is the US Navy, NASA and Hyperbarics International documents on NITROX issues.I only listed these because no one seems to have the published documentation
JS

Frogman

Im sorry but I don't see the relevance of your examples to the subject post in hand.

"Nitrox production guidelines - Continuous Blending"

From my point It's like posting a page out the Swagelok catalogue of a bunch of fittings and saying "Look" because they are all oxygen cleaned we can make up an neat oxygen compressor with them. LIke some oxy Hackmaster stunt built comtraption.

It just don't add up, The Rutkowski article with his Myth and Mayhem nonsense or the NASA article, both are about cold gas dispensing.

Look no one is worried about 40% in your cylinder or squirting a lung full out once a breathe through the mouthpiece.

Its the hot oily gas during compression, the rapid "oxidation" of the lubricant and the micro flashpoints within the compressor during continuous blending thats the question.

Further my three questions regarding these Kiddie pumps still stand. Iain Middlebrook

 

[frogman62]

Iain,
This isn't about Kidde pumps. It has nothing to do with my compressors. This is simply a difference between what you think and what the U S Navy , NASA and Published results of air quality testing for oil lubricated compressors.
Jim Shelden

 

[IyaDiver]

Peace and peace and no war please.

I read the link Frogman, it is about regulators for use up to 40% 02, and not about cont-blend of Nitrox using oil lubricated compressor.

I have zero fear of using Nitrox up to 40% but I am worried if I am to be the one making them by doing cont-blend on my Bauer, that is the question I need to get the answer for.

I have no doubt LF MA64 is approved for Nitrox blending, but surely it is partial blending and not cont-blend.
Exactly why I raised this question about CONT-BLEND and not partial blending.

Hyper Filters are for downstream of all stages of compressions, it then clean the air to Super Clean Air nearly oil-free.
My question is, my Bauer needs ambient air, even though I feed super clean air ( assumed it is possible ), my Bauer introduces the oil mist at stage 1, and some minor natural design leak of floating piston oil in stage 3. That reality of oil-in-air..... I can not escape no matter what. So I am violating the very clean rule of nearly oil-free air when I mix say Nitrox 32%. The output of my compressor probably can deliver Nitrox approved air by any world standard when it is tested at the scuba tank, but I can't comply while making that Nitrox mix. So where is the safety for me , the Nitrox maker ?

So won't it be fair, as to not confuse us compressor owners, filter manufacturers who have Nitrox approved/legal or whatever Hyper filtration system it is called, should warned us that it is for PARTIAL BLENDING ONLY and not for continuous blending in an oil lubricated compressor.

Isn't it an irony, that the dive industry set Nitrox's air oil level so very low, because they know it has to be that clean due to the involved danger ( nothing to do with our lungs being scattered with X amount of oil mist or Y amount fine dirt particles a CGA Grade D/E air still allows ) of higher oxygen level in the Nitrox mix. If it weren't for that danger, we would be pumping 50-70% oxygen with our Bauer. Yet some compressor manufacturer advertised that it is OK to cont-blend up to 40% oxgyen in their oil lubricated compressor ???

Where is the logic in that ? That is what I was dying to know and created this post.

Now simple logic.
Let say I want 40% Nitrox/EAN mix in my tank. Industry standard said my tank must super clean of oil traces because of safety. OK, I clean my tank super clean. DONE.
And then compressor manufacturer said, I can pump up to 40% oxygen using cont-blend devices on their oil-lubricated compressor. OK, I buy the mixing stick and etc etc. DONE
I then must buy special Hyper Filters because I must not mix air having oil trace higher than 0.1 mg/L when making Nitrox, its wrong and dangerous. OK me buy hyper filter. DONE

I then want to start making 40% Nitrox using cont-blend and I must use the mixing stick. OK.
I inject 99% oxygen into my a mixing stick and its metered to produce 40% Nitrox and it goes to my 1st stage. OK.
When my compressor starts running......I will ask myself, what am I doing injecting high 40% oxygen level to a super dirty 1st stage compression, which has breather running to crankcase and sucking oil mist into the 1st stage
If I can be safe pumping dirty oil air with high oxygen level in my compressor stages, why do I need a hyper filter then ?
What extra safety do I get from hyper filters, for cont-blend ? Nothing, no added safety, just added cost.

That was why I asked , how do I cont-blend with my Bauer ?

Tanks with 40% nitrox is OK, me not scared because even in the hottest of my climate, my tanks will not exceed 60C for sure being under the sun, me do not use black color tanks. However, I am scared to have 40% oxygen in my compressor because I have cylinder head temperature sensors on all 3 heads. I can read easy 133C 2nd stage exhaust pipe exterior temperature within 20 minutes of a Mariner 200 running at 32 ambient temperature, God knows what is the real compression air temperature peak inside all 3 compression chambers. Bauer electronics will shut comp down when it hits 135C at 3rd stage, little do they realized or care to realize that K 120 II block is hottest at 2nd stage. Mine has no Bauer electronics, so I install my own and a more accurate one with data logging capability.

I also know oil auto ignition temperature ( AIT ) at elevated ambient pressure like inside the 2nd and 3rd stage, can burn well below its AIT which is tested at 1 ATM. A 365 Celcius AIT ( 1 ATM ) of a good compressor oil, at mere 30BAR (this is refrigeration compressor, thus low pressure ) drops to down to 215 Celcius.
Auto-ignition of lubricating oil working at h... [J Hazard Mater. 2011] - PubMed - NCBI

This is the scarry bit :
"They are close to flash point temperature and the lubricating oil can be hazardous when it works for high-pressure operating condition and abundant air flows into a compressor."



I seen lower oil AIT figures at elevated pressure from a study of a Mine accident involving higher pressure compressor to feed a Mine working tools. See attachment.



Got another one and interesting :
Mitigating Explosion Risks in High Pressure Air Injection Compressors

Using an Accelerating Rate Calorimeter (ARC), samples of fresh and used synthetic lubricants were heated in the presence of air at initial pressures up to 34.5 MPa (5,000 psi). Self-heating rates and pressure responses were measured.

The results highlighted the significant effect of pressure on auto-ignition temperature. Most significantly, the auto-ignition temperature of the diester-based lubricant dropped from the manufacturer's reported level of 410 °C (770 °F) at atmospheric pressure to 180 °C (365 °F) at pressures in the range of 17.2 to 34.5 MPa (2,500 to 5,000 psi). Also, the auto-ignition temperature of used (oxidized) synthetic lubricant was further reduced to values close to the operating temperature levels of the compressors. Finally, it was noted that the auto-ignition temperatures for different brands of diester-based lubricants were all very similar.

The significance of this study is not only in the temperature data, but also in the discussion of several significant changes that Encore made to the design and operation of their high pressure air compressors as a result of this study. This information will assist future HPAI operators in designing safe and reliable air compression systems.


Chemlube 800 AIT is 391 Celcius and flash point is 279 Celcius.
http://www.ultracheminc.com/productimages/thumb/CMS/Files/CHEMLUBE_800.pdf

Attached Bauer's synthetic oil AIT


The heat of compression with 21% oxygen scares me, because I have a digital temp logger and permanent install the sensors on all 3 cylinder head temp. Me don't have the one which can read compressed air temp, but probably I am one of the rare person to actually logged a compressor cylinder heat temp for the sake of learning. I mean the 1st year of installation I have hundreds hours worth of temp data logging. Now I know the temp profile and use the digital temp logger as meter only. The answer is obvious, me need 3000ish CFM ( 80 M3 per minute ) blower with good static pressure to cool my Marine 200. Without it, compressor can not be operated, PERIOD. That blower has power of approx 200% of the Bauer original pulley fan, probably more. The total amount of heat sink surface area on Bauer cylinder heads is not enough to cool by Bauer slow pulley fan in 30C ambient temperature. The only way I can improve cooling is to exceed Bauer's pulley fan air velocity so that I move more heat away by speeding the airflow.
See the temperature rise graphs attached.


PHOTO
My own compressor. In a compressor cubicle.
The two yellow digital temp data logger legend :
T = Tower, which is the final water separator of a Bauer P41
1 = Cylinder Head 1
2 = Cylinder Head 2
3 = Cylinder Head 3


PHOTO
My friend's compressor. Totally open air, meaning open air car park.
The single digital temp 4 channel data logger legend
T 4 = PZero as final water separator, skin temperature.
T1 to T3 are the cylinder heads temp respectively


I know extra heat will be generated when doing cont-blending up to 40% mix, that is the scariest bit because of known oil AIT decreasing at high ambient pressure. The reason I dare not cont-blend until today , even though I am seeing people doing it for years and years and no explosion.

I attached a Mariner 200 with a burnt out 2nd stage pipe fitting. Nope, no Nitrox making on this. I just want to show you guys the potential heat generated by our dive compressor, in 30 - 32 Celcius ambient temp and long running hours, plus probably not 100% open air kind of proper ventilation.

The brown residue is burnt oil. Go figure how hot did the oil get to be burned or how low the actual oil AIT at a mere 50 BAR or +-750 psi inside a 2nd stage. How did the oil leaked out ? The oil could leak out because that fitting and only that fitting on Bauer K120 II block, uses o-ring for easy installation of that elbow. Its o-ring is 200 celcius rating, so how did the o-ring leak.........? Because it was burned by the heat and maybe by the oil. I dont know. All I know is, HELL that is real hot to have happened that way.


With all this I am seeing, I then asked HOW DO I CONT-BLEND USING OIL-LUBRICATED COMPRESSOR ??
Good that the US Navy Manual answered my question once and for all.
There is no way US Navy does not know oil reduced AIT at high pressure. They even have their own Mil Spec oil standard.

Thanks Gentlemen.
IYA
.

 

[frogman62]

IYA,
Good points, but the one attachment I could not post because the file is larger than the web site allows, clarifies the US Navy's acceptance of "oil lubricated compressors" producing oil free air with the hyperfilter.
The testing was done using the worst possible condition of oil lubricated compressors by using an old Ingersol 15T4 compressor which had broken piston rings and considerable blow-by.
My experience with the Navy included only partial pressure blending. However the Hyperbarics International study confirms the 21 to 40% rule for for continouus blending of nitrox.
While this is for commercial purposes of selling more nitrox at a reasonable cost. Testing of nitrox blended through surplus military compressors ( and tested to NFPA standards by TRI" with a dew point requirement of -65 degrees F) confirm the air/nitrox as one grade higher than "E' requirements and accepted by fire department in the U.S. as meeting all safety requirements. These compressors have only standard filters on them Not Hyperfilters
I believe all this discussion will never be resolved because of the "difference in standards" between the US and Europe on the % of O2 being treated as air vs oxygen.
I will be glad to forward to anyone the study conclusion and test documents but I will need an email address to send them.
Jim Shelden

 

[IyaDiver]

Hi Jim,

Thanks for the reply.

What I still can not accept is, the risk of me injecting 40% oxygen into 1st>>2nd>>3rd stage of my oil lubricated compressor in a cont-blend scenario.

What comes out or upstream of my filter tower is no worry, the downstream part I am worried because of heavily oil laden air during production of EAN mix is what is happening prior to filter tower. I am speaking of CONT BLEND.

The logic of the whole safety of OIL FREE air when having more than 23% of oxygen mix in the air is what drives me nuts but I know I have to believe and respect that.

You can place the mentioned US navy file at depository like RapidShare or something, so that everyone can study them......I think that is more wise.

" the US Navy's acceptance of "oil lubricated compressors" producing oil free air with the hyperfilter."

I am asking of cont-blend situation, not about air cleanliness level of what my compressor can produce as final production air output. I do not need US Navy data on production air quality. What I want to see the Making-Of-Nitrox in Cont-Blend situation with oil lubricated compressor. We are speaking on different frequency here. I don't think US Navy will make that Diving Manual with OIL-FREE COMPRESSOR as requirement ( as I linked ), if oil lubricated compressor is approved for cont-blend as what you want to make me believe. All we got to see is the issue date of the document , if indeed US Navy produced another contradicting document stating it is OK to cont-blend up to 40% with oil lubricated compressor.

I don't value Hyperbarics International data as much as I would value a USA Navy one.
Why ?...... because they are profit oriented , they are a business unit . Unlike US Navy which I am sure is safety oriented and we know how advance US Navy is , in terms of hardware and database.


I know I will not die using my P41 filter system even at 40% EAN/Nitrox , a P41 is not hyperfilter grade. What I want to be sure is, will my oil lubricated compressor has the potential to explode if I do cont-blend up to 40% oxygen, where I know so very well from the water condensate produced by the 2 water and oil separators.......that my air in that 3 stages are so oil laden and totally way off the oil limit when oxygen in the mix is 23% or higher.

Please focus on stage 1>>stage 2 >>>Stage 3 oil laden air during cont-blend, and not final production air after filter tower.


Thanks again Jim.
.

 

[Doc Harry]

What I still can not accept is, the risk of me injecting 40% oxygen into 1st>>2nd>>3rd stage of my oil lubricated compressor in a cont-blend scenario.

Then don't.

Working with high-pressures gasses is a risky business, we all have to decide what risk we are, and are not, willing to take.

You can never be sure that your compressor will not blow while blending 40%. No one can guarantee you anything.

You have done your research and you know the risks. Now decide for yourself what risks you are willing to take, and decide upon your liimits.

If you aren't willing to blend 40% through your first stage - then don't.

I have bank cylinders that I regularly pump up to 4,500 p.s.i. with 32%.

Banking 40% would give me more options than banking 32%, but I am not willing to pump 40% up to 4,5000 p.s.i.

So I don't.