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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

CHM 605

Compressed Gas and Cryogen Safety

contents
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
compressed

“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.

cryogen definition
Cryogen definition…

See handout

bp < -160ºC and used as ….

N2 and He most common here

gas under high pressure
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/

acetylene toyota
Acetylene + Toyota

This was a combination chemical hazard PLUS pressure issue…

pressurized gas hazards
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
nomenclature
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
see compressed gas safety handout
See Compressed Gas Safety Handout
  • label
  • secure
  • cap
  • move with cart
  • leaks?
  • temperatures?
  • protection from damage
  • hydrostat test date
regulators
Regulators
  • Not optional
  • No substitutions
  • No grease

See also

Aldrich Tech Bulletin AL-151

teflon tape
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.)
gas tight lines
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

leaking cylinders
Leaking Cylinders?
  • THINK FAST!?
  • (Be prepared.)
empty cylinders
Empty Cylinders?
  • (Do not “empty” cylinders!)
  • See page 4 of handout.
particularly hazardous gases
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

cryogen safety
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….)

the most commonly reported injury associated with cryogen use is
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

liquefied gas hazards
Liquefied Gas Hazards
  • Extreme Cold
  • Asphyxiation
  • Toxic Hazards (sometimes)
  • Obscured Vision
  • High Pressure (if system sealed)
  • High Magnetic Fields
  • Liquid Oxygen…..
condensing o 2
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.
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