Working safely with cryogenic liquids Reyer Jochemsen.
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Transcript of Working safely with cryogenic liquids Reyer Jochemsen.
Working safely with cryogenic liquids
Reyer Jochemsen
Cryogenic liquidsGas Boiling
point
(K)
Latent heat
(kJ/l)
type liq ->gas
volume ratio
N2 77 162 inert 800
He 4.2 2.6 inert 700
H2 20.4 32 explosive 600
O2 90 243 reactive 800
CO2 196 200 inert 900
Working safely
avoid contact
avoid pressure build-up
avoid rapid evaporation (suffocation, elevator)
do not breath in
use safety glasses
use insulating gloves
do not work alone (as much as possible)
Transport
only in metal vessels
not at over-pressure
careful in the elevator
only inert gases
Liquid heliumLiquid heliumWhenever one works with very low temperatures, the safety aspect should play an important roll. There are several hazards to consider.1. The fluids mentioned are extremely cold; as mentioned, helium is the coldest of all fluids. Contact with cold fluids (even cold helium gas!) causes severe frost burns.2. The extremely low temperatures of liquid helium will cause air to condense and freeze. A typical example of this is the occurrence of fluid droplets on helium evaporation pipelines; these are droplets of liquid air, so be careful.3. When working with liquid helium, keep external surfaces clean. In paragraph 2, the occurrence of droplets on the outside of pipelines is mentioned. In case of this kind of condensation, the liquid nitrogen will evaporate out of the liquefied air first, because it has a lower boiling point than oxygen. As a result an oxygen-rich fluid drips from the pipeline; when this happens, spontaneous ignition of grease and oil is not impossible. A clean work area is important.4. NEITHER helium, NOR nitrogen supports life. At high concentrations of helium gas or nitrogen gas an imminent oxygen shortage occurs.Although helium is not toxic, it may cause breathing difficulties in poorly ventilated rooms. High concentrations of helium gas can be noticed by the effect on the vocal cords.
Gasses at high pressurehigh pressure cylinders - do not drop
- use with safety cap- fix to the wall- transport on cart with chain- do not pump on pressure reducer- always close the main valve
What to do if…
there is an accident: phone reception 5678
someone gets severely frozen: phone EHBO through reception 5678
telephone number outside working hours: 4444
someone gets a frozen spot : treat like burning : lots of running water
How to obtain cryogenic liquids
Cryogenic Department (groundfloor)
Hans van Kuijk 5941
Rob van Noort
Wilfred van der Geest
http://www.physics.leidenuniv.nl/institute/cryo/command.asp
Demonstration
Let’s go