A brief discussion of anaesthesia cylinders and the medical gas pipeline system

1. DR UNNIKRISHNAN P
SENIOR RESIDENT
NEUROANAESTHESIA
SCTIMST,TRIVANDRUM

2. Mr Cylinder
I am a supply tank containing high pressure gas or
gas mixture @ a pressure that can be in excess of
2000psig

3. We should know how we measure
pressure
Psi = pounds per square inch
Psig = pounds per square inch gauge
Difference between measured pressure and surrounding atm
pressure
Psia = pounds per square inch absolute
Based on a reference point of ‘0’ pressure=perfect vacuum
Psia = psig + local atm pressure

4. What does the cylinder contain?
[1]nonliquefied compressed gas.it doesnt liquify @
ordinary temp & pressures <2500psig
E.g. O2,N2,air,Helium
[2]liquefied compressed gas becomes liquid in
ordinary temp & pressures from 25-2500psig
E.g. nitrous oxide,CO2

5. Also note that…
100 kPa=1000mbar=760mm of Hg=1030cm of
H2O=14.7psi=1atmosphere

6. What is Critical Temperature?
It is the temperature above which a gas cant be
liquified, no matter how much pressure is applied;
O2--119 C [so it is a gas in room temp]
N2O36.5 C [so it is a gas+liquid mixture@room
temp;if temp >36.5,then it exist only as gas]

7. SIZES

8. Parts of a cylinder

9. Parts
BODY-VALVE-PRESSURE RELIEF DEVICE
BODY--Made of steel-molybdenum alloy
MRI compatible:aluminium
VALVE—bronze/brass
HANDLE WHEEL—turned counter clockwise to
open

10. Valve-Port /Stem/Seat
Point of exit of gas
Take care
Im not the conical depression and I dont like the
retaining screw.
Stem closes the valve by sealing against the seat

11. Packed Valve
Stem sealed by Teflon
Turning the stem causes the seat to turn
So called Direct acting
Withstand high pressures
Opened by 2-3 full turnes

12. Diaphragm valve
Stem is separated from seat
Turning the stem moves a metal diaphragm against
the opposing force of a spring acting on seat
Can be opened by 1/2 to 3/4 turns
Less likely to leak

13. Pressure Relief Device
Vent the contents into atmosphere if pressure
inside increases to dangerous level
RUPTURE DISC: when pressure increases above
a specific level due to high temperature or
overfilling ;it rupturesrelease contents
FUSIBLE PLUG:when temperature increases
above ‘Yield temperature’ it melts

14. Pressure Relief Valve
Dont confuse with others
I am a reclosing device and prevent discharge of
contents after normal pressures have been restored
More susceptible to leakage

15. Conical Depression
Situated above the safety relief device
Receives retaining screw of the yolk

16. PIN INDEX SAFETY SYSTEM
Used on cylinders AE
Holes on the valve positioned in an arc below the
outlet port
Pins on the yoke or regulator are positione to fit
these holes
If both are not aligned, port wont seat

17. PIN INDEX SAFETY SYSTEM
.

18. PRECAUTIONS
Must be tested at least every 5 years
Pressure in a filled cylinder @ 70⁰F cylinder may
not exceed the service pressure marked on the
cylinder [O2,He,He-O2,CO2-O2 are allowed
additional 10%]

19. COLOUR CODING
L
Oxygen White shoulder/Black
body
Nitrous oxide Light blue
Medical air Black and white
Suction Yellow
Nitrogen Black
Carbon dioxide Grey
Helium Brown

20. MARKINGS
DOT/TC specification number
Service pressure in psi
Serial number
Identifying symbol of the purchaser,user or
manufacturer
Initial qualifying test date
Retest date
5 pointed star after last test date=may be retested every
10 instead of 5 years
‘+’ after test date = cylinder can be charged upto 10%
in excess

21. LABELING
L

22. Tags

23. RULES FOR SAFE USE OF
CYLINDERS
Handled only by trained staff
Keep away oils,rubber and other combustible
substances
Never expose to >52⁰C
keep all connections tight
Take care to avoid obstructions to discharge ports

24. RULES FOR SAFE USE OF
CYLINDERS
Never interchange parts of cylinder used for one
gas with other
No adapters please…
Keep the valve closed when not in use
Valve is most prone for damage
No alterations
Dont use as a roller
Avoid electric contact

25. RULES FOR SAFE USE OF
CYLINDERS
Dont drag me..
Take precautions to prevent falling
Remove wrappings before taking into OT
Storage:cool,clean room with adequate ventilation
Secure,safe place. Protect against all extreme
things!

26. RULES FOR SAFE USE OF
CYLINDERS
NO SMOKING
NO OPEN FLAMES
NO OIL OR GREASE

27. RULES FOR SAFE USE OF
CYLINDERS
Small cylinders best stored upright
Dont drape with any material during storage
Should be grouped by contents or sizes
Good segregation between empty and full
Flammable gases should not be stored in an
enclosure containing oxidizing gases

28. RULES FOR SAFE USE OF
CYLINDERS
Identify contents by label; Check for DOT
Immediately before fitting, remove the protective
cover
Pressure reducing regulators always used; inspect
them for any damage before connecting
Remove dust and foreign bodies

29. RULES FOR SAFE USE OF
CYLINDERS
CRACKING—reduces possibility of flash fire
A sealing washer in good condition should be used
Valve should be opened before bringing the
apparatus to the patient. Flow control valve should
be closed before the cylinder valve is opened
While opening, stand to the side; not in front or
back
Quick opening can generate heatflame

30. RULES FOR SAFE USE OF
CYLINDERS
After opening the cylinder, check the pressure
Hissing sound= leak tightenstill leak replace
washer. Localize leak with soap water.
If leak in valve itself,tighten the packing nut by
turning it in a clockwise direction
Even if no hissing sound, check for loss of
pressure when no gas is being used
Valve should be fully open when in use

31. RULES FOR SAFE USE OF
CYLINDERS
An empty or near empty cylinder shouldnt be left
on anaesthesia machine
Valve should be closed before removing from a
regulator or yoke
Lower part of the tag removed when cylinder is
empty
Caps replaced before shipment

32. HAZARDS
Incorrect cylinder,contents
Incorrect valve
Incorrect color,labelling
Inoperable valve, damaged valve
Suffocation,fires,explosion,thermal injury
Contamination of contents
Overfilling, theft of Nitrous oxide cylinders

33. MEDICAL GAS PIPELINE
SYSTEMS
Central supply
Pipings extending to target locations
Terminal units

34. RULES FOR SAFE USE OF
CYLINDERS
The maximum amount of oxygen that can be
stored inside a health care facility is 20000 cubic ft

35. Design
2 banks of cylinders
Each have its on pressure reducing regulator
Must contain a min of two cylinders
Connected to a common manifold[header]
Check valve in between each cylinder lead &
header

36. Design
N

37. PRIMARY/SECONDARY
SUPPLY
Primary supply [duty/running] actually is the
portion supplying the system
Secondary supply automatically becomes the
primary, when the latter fails [switch over done by
manifold change over device]
Operating supply is the portion which normally
supplies the piping system [ consists either a
primary OR primary+secondary supply ]

38. Reserve Supply
For larger systems
When operating supply fails /emergencies
/maintenance
Activating switch is there for activating reserve
supply

39. Pressures
Gases other than Nitrogen @50-55 psig
Nitrogen @160 psig

40. Oxygen
Stored as liquid @ low pressures & < --148⁰C[when
large amounts are required] OR
as compressed gas in G or H cylinders

41. Nitrous oxide
Be careful against leaks; its an asphyxiant
Regulator can become cold and can freeze
theft

42. Medical Air
Air that has no detectable liquid
hydrocarbons, less than 25 ppm gaseous
hydrocarbons,less than 5 mg/m3 of particulates of
1 micron size or greater @ normal atmospheric
pressure and a dew point @ 50 psig of less than
4⁰C
Low levels of nitric oxide found in ambient air may
improve oxygenation in ventilated patients

43. PIPED AIR SYSTEM
Employ 2 or more compressors

44. INTAKE
Intake location should be free of dirt/fumes
Quality checked periodically
Water content reduced with after cooler/dryer
Monitored for carbon monoxide
N.B. Other gases: CO2, Nitrogen

45. PIPED DISTRIBUTION
SYSTEM
MAIN LINES: pipes connecting the source to
risers or branch lines or both
RISERS: vertical pipes connecting the main line
with branch lines on various levels of the facility
BRANCH LINES: they service a room or group
of rooms on the same level of the facility
Flexible hoses used only in exposed areas..Why?

46. PIPED DISTRIBUTION
SYSTEM
Pressure relief valves set @50% above the normal
line pressure. Close automatically when excess
pressure relieved
Shut off valves isolate areas of the system in the
event of a problem and allows for repair.
[1]Manual @ accessible areas installed in boxes
[2]Service: only for authorized personnel
Emergency Oxygen Supply Connector: T fitting
for connecting auxiliary source of O2

47. PIPED DISTRIBUTION
SYSTEM
Master Alarm System: monitor the pressure in the
main line
When switch over from primary to secondary
supply
When reserve supply is reduced to a certain level
When reserve is below that is required to function
When pressure in main line increase or decrease
Area Alarm Systems: e.g. PACU,ICUs

48. TERMINAL UNITS
BASE BLOCK
PRIMARY VALVE: open when male probe
connected & close when detached
SECONDARY VALVE: shut off flow when
primary valve is removed
GAS SPECIFIC CONNECTION POINT /
SOCKET ASSEMBLY

49. TERMINAL UNITS
GAS SPECIFIC CONNECTION POINT /
SOCKET ASSEMBLY
Connecter may be DISS/ Quick Connector
Equipped with a backflow check valve
Quick Connector easy to use; but leak more

50. TERMINAL UNITS-types
Wall outlets
Ceiling mounted hoses
Ceiling mounted pendants
Ceiling mounted columns

51. HOSES
connect anaesthesia machine to terminal units
each have a permanaent non interchangable
connector
Inlet & outlet connectors
Braid adds to strength

52. TESTING OF MEDICAL GAS
DISTRIBUTION SYSTEM -INITIAL
blow down
Initial pressure testing
Standing pressure test
Piping purge test
Test for cross connections

53. TESTING OF MEDICAL GAS
DISTRIBUTION SYSTEM-SYSTEM
VERIFICATION
Cross connection test
Test of values
Outlet flow test
Alarm testing
Piping purge test
Piping purity test
Final Tie-in test
Operational pressure test
Medical gas concentration/air purity test
Source equipment verification

54. Problems
Inadequate pressure
Leaks
Excessive pressures
Alarm problems
Cross connection of gases
Contamination of gases
Fires
Depletion
Theft

55. THANK YOU

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