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  1. Prometheus21

    Size andtemperature of compressed gas slug.

    Good catch! I will be honest and say I assumed the Z-factor would be < 1.0 as I usually operate in that area - shows you what I now of the subject... I only have charts up to a 1000K available so time to start searching for extended charts
  2. Prometheus21

    Size andtemperature of compressed gas slug.

    Snickster: Correct; the Z factor is important. Yet to estimate T2 the Z factor is usually omitted so that a conservative result is used as basis for design (like you say). That brings up another question; is there any official diagrams for the compressibility factors given different gases? I...
  3. Prometheus21

    Size andtemperature of compressed gas slug.

    LittleInch: in this setting (filling station) the definition of ambient will be standard condition, 15.00 °C; 59.00 °F) and 101.325 kPa. Having talked to a test engineer at Air Liquide CTE they recommend designing the system to contain 1/8th of the volume Vh+ VDVP; as a rather conservative...
  4. Prometheus21

    Size andtemperature of compressed gas slug.

    To clarify: the system is simple compared to the systems actually seen in active filling stations for cylinders. As for the sketch (rapid, simplified one): A simple single-ended DPV - distance/volume piece is shown, connected to a hose. Vu is the volume upstream of the flex hose including...
  5. Prometheus21

    Size andtemperature of compressed gas slug.

    Hello everyone, As my knowledge on this topic is lacking, and I'm heavily in need of a refresher course; some input from you as well will likely be very helpful. For the sake of discussion I am looking at simple system; a DN6 flexible polymer-lined flex-hose with a distance/volume piece...
  6. Prometheus21

    Left vs right thread

    Denial: I work in a company that design and manufacture such torches; albeit fewer and fewer these days due to cheaper products entering the market. Anyway I had the great pleasure and privilege to be taught by one of the original design engineers of such a product back in the day; he was at the...
  7. Prometheus21

    Left vs right thread

    LH threads are also a great way to make Joe the Homeowner think twice before using the equipment. Oxygen is not flammable; just an oxidizer. Cutting torches are supposed to be ignited using pure acetylen; possibly with a very small amount of oxygen to avoid bothersome soot. You then adjust the...
  8. Prometheus21

    Left vs right thread

    Like dtimberlake mentioned; fuel gas fittings often have LH threads; like most cylinder valves meant for flammable mixtures. But I have also seen a M19x1.5 LH thread on a nitrous oxide cylinder at an offshore facility once; wheras the rest of the industry uses RH threads...
  9. Prometheus21

    Compression Ignition in Pneumatics

    Having designed and manufactured equipment intended for both low and high pressure (industrial) gas service, including oxygen, the general risk of ignition in compressed air systems is always something to consider; however briefly. Note that there are a multitude of possible ignition mechanisms...
  10. Prometheus21

    Reduced-Noise Gas Flow Design Guide and spreadsheet by Nelson and NASA

    And the worksheet(s)https://files.engineering.com/getfile.aspx?folder=415a7522-be42-47bd-b480-c2396bce6658&file=Gas_Flow_Noise_Estimation_Update_230503.xls
  11. Prometheus21

    Reduced-Noise Gas Flow Design Guide and spreadsheet by Nelson and NASA

    I came across this thread and got curious on the topic; so I reached out to Nelson as well. He was very forthcoming with the documents, sending me a copy with his personal updates - in the spirit that NASA intended as a public service. With that in mind - see attached documents for the Design...
  12. Prometheus21

    What Challenges do you face with Detailers as Fabricators?

    As a small private-owned company that designs a multitude of equipment and systems for (mostly) the industrial gas sector (or any industry that might use this industrial gases in their production), I can relate to your struggle. We have a large project going on with a German supplier that also...
  13. Prometheus21

    Fraction in Decimals within drawing.

    "Or are you telling me that the machine doesn't see the difference" - It depends on the machine. Most of them does differentiate between nominal and actual tolerances(Not older models, you would be surprised how many manufacturers uses equipment from the 40's, 50's and 60's still in some part of...
  14. Prometheus21

    Fraction in Decimals within drawing.

    "2. I suppose, for a machinist, the tolerance band would be the one dictating the machining hours required, machine capability and subsequently cost, rather than the number of decimals. Haven't myself worked directly with a machine, I am assuming that keying in 5 decimals into their programming...
  15. Prometheus21

    Experience with determining the cleanliness of parts

    Hello everyone, Our production is intended for oxygen service (industrial and medical), meaning everything has to be cleaned for oxygen service in accordance with strict standards. We have a range of inspection methods employed to qualify the cleanliness of the final product; including Direct...
  16. Prometheus21

    Fraction in Decimals within drawing.

    I second what ctopher states; most of the European manufacturers I have worked with also demands hard dimensions and tolerances, and will measure to those tolerances. I work with older machinists from eastern Europe; I can't tell you how much I learned from those guys over the years - and it...
  17. Prometheus21

    Distance pieces in hose assemblies for oxygen service

    LittleInch - Its always fun when the customer insists on 6 mm and 10 mm sizes, and you explain that when it comes to flexible hoses its 1/4'' and 3/8''. The real fun begins when the customers demand 6.35 mm hose, calls it a 6 mm hose and refuse to accept the term 1/4''; demanding all drawings...
  18. Prometheus21

    Distance pieces in hose assemblies for oxygen service

    Hello everyone, Rubber and plastic (flexible) hoses in oxygen system often incorporate what is a called a distance piece, and is described in ISO 14113. In short it is there to lessen the effect of adiabatic compression. Now the standard describes that the distance piece should have a volume of...
  19. Prometheus21

    Industrial practices in CAD modeling of machined parts

    My experience is from the industrial gas industry, mostly regarding the design of high pressure oxygen systems. Form follows function. If I need a part to be made in a particular way, it's for a reason. If the part can't be made with existing tools and methods, we make new tools that allows it...
  20. Prometheus21

    O-ring permeability in vacuum

    Hi, It is a nice formula, but what are you trying to accomplish? Sealing against vacuum is tricky depending on the sealing configuration. Static, dynamic, face seal? Dovetail configuration? Half-dovetail? If it is hot water then an EPDM material should be considered as a material. Further I...

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