AWABS - Gas supplies and cylinders Flashcards
Older cylinders description
Thin walled
Seamless
Molybdenum steel
NOT MRI safe
Newer cylinders description
Aluminium alloy with fibreglass coating
MRI safe
Lighter weight
Information engraved onto cylinder
Information for label around shoulder of cylinder
Information from coloured plastic ring in neck of cylinder
How are cylinders tested
Gas cylinder / valve colour system and how stored
New system is that body of cylinder has to be white but colours on shoulder identify the gas
Note helium is brown and white (looks yellow on picture)
Also note Nitrous is “French blue”
Oxygen cylinder size categories and capacity
Use of knowing oxygen cylinder sizes
To calculate number of cylinders required for transfers etc
Size of oxygen cylinder usually on back of anaesthetic machine
Size E
Size of oxygen cylinder used in cylinder manifolds
Size J
Size of oxygen cylinders found in ambulances
Two size F cylinders are on ambulances
Newer / common oxygen cylinder size in hospital (aluminium alloy and fibreglass cylinder rather than molybdenum steel cylinder)
Size CD -smaller in size than size D but higher capacity as higher pressure
460 L capacity
Stored at 23,000 kPa
“Only” oxygen cylinder not stored at 13,700 kPa
A newer version of the D cylinder with an integrated valve
Capacity of nitrous cylinders compared to oxygen cylinders
Store higher capacity than oxygen
How to calculate cylinder contents
Why Nitrous and CO2 (stored as liquids) need to be measured by weight
Pressure remains constant until all liquids used up as when liquid is at saturated vapour pressure
Critical temperature definition
Temperature ABOVE which a substance cannot be liquified, no matter how much pressure is applied
(will remain in gaseous state)
Critical temp of O2
-118.6 degrees
(often rounded to -119 degrees)
Critical temp if NO
36.5 degrees
Critical temp of CO2
31 degrees
Pseudocritical temperature definition
The temperature BELOW which there is a risk that a gas mixture will separate out into its constituent parts
(Occurs in gas mixtures eg Entonox)
Pseudocritical temperature of Entonox
-5.5 degrees
What happens if a gas mixture falls below pseudocritical temperature and clinical implication
How to reverse gas mixture separation
Re-warming and mixing
How to store Entonox cylinders
Horizontally
Above 5 degrees
Large cylinders have dip tube - ensures delivery is from bottom up, therefore never deliver gas with lower than 20% oxygen
Filling ratios
Pin index system
Safety mechanism
Bodok seal
Piped gas supply
Central supply
Pipelines made of alloyed carbon - bacteriostatic and prevents breakdown of gases
Pipeline supply is 4 bar (400 kPa)
Outlet is colour coded and named with Schrader valve
Schrader valve has gas specific index collar
Non interchangeable screw thread (NIST) on pipework to anaesthetic machine
Schrader valve gas specific index collar picture
Cylinder manifolds
Vacuum Insulated Evaporator (VIE)
Stainless steel outer layer, plain steel inner layer with vacuum between (and ?pearlite)
Superheater made of copper coils
Critical pressure for oxygen
5 bar
Safety features of VIE
Specific fill system refers to not accidentally filling it with NO
Oxygen concentrators
Possible side effects of Argon
Low dose:
Nausea, Vomiting, Headaches
High dose:
Neurological side effects, Seizures, Weakness
Tare weight definition
Weight of an empty cylinder / receptacle
