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CHM 605

CHM 605. Compressed Gas and Cryogen Safety. compressed gases hazards storage, handling & transportation using gas line assembly leaking cylinders empty cylinders special: flammable, toxic, and highly toxic gases cryogenic liquids storage and handling PPE cool traps and baths.

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CHM 605

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  1. CHM 605 Compressed Gas and Cryogen Safety

  2. compressed gases hazards storage, handling & transportation using gas line assembly leaking cylinders empty cylinders special: flammable, toxic, and highly toxic gases cryogenic liquids storage and handling PPE cool traps and baths Contents

  3. “Liquefied” “Compressed” vs “Compressed gas” is defined as a gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 21.1°C (70°F) Liquid nitrogen and liquid helium at or near their b.p. are not “compressed gases.” Even if there’s a little pressure.

  4. Cryogen definition… See handout bp < -160ºC and used as …. N2 and He most common here

  5. Gas under high pressure • is an energy hazard • there are often chemical hazards too, but the energy hazard is NONTRIVIAL. Most of the “normal” size cylinders everywhere around here (N2, Ar, H2, He, air, O2, CO2….) are at 2200 - 2600 psig. http://www.disastercity.com/n2cylder/

  6. Acetylene + Toyota This was a combination chemical hazard PLUS pressure issue…

  7. physical force -- “gas propelled rocket” (if the valve becomes damaged). simple asphyxiation (oxygen displaced) chemical hazards, e.g. flammability, reactivity, burns health hazards, e.g., toxicity, mutagenicity… Pressurized Gas Hazards

  8. Nomenclature • “cylinder” and “bottle” both used to describe many gas containers. • “valve” commonly means the main handwheel (which is an ON-OFF switch really) • “cap” screws onto threads at base of valve • “regulator”… attachment (essential) allows careful delivery of gas

  9. diagram

  10. See Compressed Gas Safety Handout • label • secure • cap • move with cart • leaks? • temperatures? • protection from damage • hydrostat test date

  11. Regulators • Not optional • No substitutions • No grease See also Aldrich Tech Bulletin AL-151

  12. Teflon tape? • read the handout • know WHY things are done the way they are done…. • (Know what is making the seal. It’s not always in the threadsmaking the seal.)

  13. Gas-tight lines • Gas delivery at > 1 atm must be via metal tubing put together correctly. • Swagelok Installers’ Manual gives good info about gas tight lines (also vacuum tight). http://www.swagelok.com/ http://www.chem.purdue.edu/chemsafety/Chem/SwageLokPocketInstallerGuide.pdf

  14. Leaking Cylinders? • THINK FAST!? • (Be prepared.)

  15. Empty Cylinders? • (Do not “empty” cylinders!) • See page 4 of handout.

  16. Particularly Hazardous Gases Acetylene, Arsine, Diborane, Fluorine, Hydrogen Cyanide, Germane, Hydrogen fluoride, Nitrogen dioxide, Oxygen, Phosgene, Silane This is a partial list. See Approval Form

  17. Cryogen safety • High strength magnets in NMR and MRI use helium, which presents quench hazard. • "Quench" = rapid and violentboil-off of gas • Be readyto evacuate to avoid asphyxiation and/or frostbite. (Asphyxiation is forever….)

  18. The most commonly reported injury associated with cryogen use is: (a) broken bone(s) (b) back sprain/strain (c) tissue damage (“cold burn”) (d) hearing loss (e) asphyxiation

  19. Liquefied Gas Hazards • Extreme Cold • Asphyxiation • Toxic Hazards (sometimes) • Obscured Vision • High Pressure (if system sealed) • High Magnetic Fields • Liquid Oxygen…..

  20. Condensing O2 • If liquid nitrogen is left in cold trap overnight…. And system is open to allow air in….. O2 will condense into the coldfinger.

  21. THANK YOU

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