anaesthesia gas cylinders & pipeline gas supply
DESCRIPTION
A brief discussion of anaesthesia cylinders and the medical gas pipeline systemTRANSCRIPT
ANAESTHESIA GAS CYLINDERS & PIPELINE
GAS SUPPLY
DR UNNIKRISHNAN PSENIOR RESIDENT
NEUROANAESTHESIASCTIMST,TRIVANDRUM
Mr Cylinder
I am a supply tank containing high pressure gas or gas mixture @ a pressure that can be in excess of 2000psig
We should know how we measure pressure
Psi = pounds per square inchPsig = pounds per square inch gaugeDifference between measured pressure and surrounding atm pressure
Psia = pounds per square inch absoluteBased on a reference point of ‘0’ pressure=perfect vacuum
Psia = psig + local atm pressure
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
Also note that…
100 kPa=1000mbar=760mm of Hg=1030cm of H2O=14.7psi=1atmosphere
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]N2O36.5 C [so it is a gas+liquid mixture@room temp;if temp >36.5,then it exist only as gas]
SIZES
Parts of a cylinder
Parts
BODY-VALVE-PRESSURE RELIEF DEVICEBODY--Made of steel-molybdenum alloyMRI compatible:aluminiumVALVE—bronze/brassHANDLE WHEEL—turned counter clockwise to open
Valve-Port /Stem/Seat
Point of exit of gasTake careIm not the conical depression and I dont like the retaining screw.Stem closes the valve by sealing against the seat
Packed Valve
Stem sealed by TeflonTurning the stem causes the seat to turnSo called Direct actingWithstand high pressuresOpened by 2-3 full turnes
Diaphragm valve
Stem is separated from seatTurning the stem moves a metal diaphragm against the opposing force of a spring acting on seatCan be opened by 1/2 to 3/4 turnsLess likely to leak
Pressure Relief Device
Vent the contents into atmosphere if pressure inside increases to dangerous levelRUPTURE DISC: when pressure increases above a specific level due to high temperature or overfilling ;it rupturesrelease contentsFUSIBLE PLUG:when temperature increases above ‘Yield temperature’ it melts
Pressure Relief Valve
Dont confuse with othersI am a reclosing device and prevent discharge of contents after normal pressures have been restoredMore susceptible to leakage
Conical Depression
Situated above the safety relief deviceReceives retaining screw of the yolk
PIN INDEX SAFETY SYSTEM
Used on cylinders AEHoles on the valve positioned in an arc below the outlet portPins on the yoke or regulator are positione to fit these holesIf both are not aligned, port wont seat
PIN INDEX SAFETY SYSTEM
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PRECAUTIONS
Must be tested at least every 5 yearsPressure 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%]
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
MARKINGS
DOT/TC specification numberService pressure in psiSerial numberIdentifying symbol of the purchaser,user or manufacturerInitial qualifying test dateRetest date5 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
LABELING
L
Tags
FULL
IN USE
EMPTY
RULES FOR SAFE USE OF CYLINDERS
Handled only by trained staffKeep away oils,rubber and other combustible substancesNever expose to >52⁰Ckeep all connections tightTake care to avoid obstructions to discharge ports
RULES FOR SAFE USE OF CYLINDERS
Never interchange parts of cylinder used for one gas with otherNo adapters please…Keep the valve closed when not in useValve is most prone for damageNo alterations Dont use as a rollerAvoid electric contact
RULES FOR SAFE USE OF CYLINDERS
Dont drag me..Take precautions to prevent fallingRemove wrappings before taking into OTStorage:cool,clean room with adequate ventilationSecure,safe place. Protect against all extreme things!
RULES FOR SAFE USE OF CYLINDERS
NO SMOKING
NO OPEN FLAMES
NO OIL OR GREASE
RULES FOR SAFE USE OF CYLINDERS
Small cylinders best stored uprightDont drape with any material during storageShould be grouped by contents or sizesGood segregation between empty and fullFlammable gases should not be stored in an enclosure containing oxidizing gases
RULES FOR SAFE USE OF CYLINDERS
Identify contents by label; Check for DOTImmediately before fitting, remove the protective coverPressure reducing regulators always used; inspect them for any damage before connectingRemove dust and foreign bodies
RULES FOR SAFE USE OF CYLINDERS
CRACKING—reduces possibility of flash fireA sealing washer in good condition should be usedValve should be opened before bringing the apparatus to the patient. Flow control valve should be closed before the cylinder valve is openedWhile opening, stand to the side; not in front or backQuick opening can generate heatflame
RULES FOR SAFE USE OF CYLINDERS
After opening the cylinder, check the pressureHissing sound= leak tightenstill leak replace washer. Localize leak with soap water.If leak in valve itself,tighten the packing nut by turning it in a clockwise directionEven if no hissing sound, check for loss of pressure when no gas is being usedValve should be fully open when in use
RULES FOR SAFE USE OF CYLINDERS
An empty or near empty cylinder shouldnt be left on anaesthesia machineValve should be closed before removing from a regulator or yokeLower part of the tag removed when cylinder is emptyCaps replaced before shipment
HAZARDS
Incorrect cylinder,contentsIncorrect valveIncorrect color,labellingInoperable valve, damaged valveSuffocation,fires,explosion,thermal injuryContamination of contentsOverfilling, theft of Nitrous oxide cylinders
MEDICAL GAS PIPELINE SYSTEMS
Central supply
Pipings extending to target locations
Terminal units
RULES FOR SAFE USE OF CYLINDERS
The maximum amount of oxygen that can be stored inside a health care facility is 20000 cubic ft
Design
2 banks of cylindersEach have its on pressure reducing regulatorMust contain a min of two cylindersConnected to a common manifold[header]Check valve in between each cylinder lead & header
Design
N
PRIMARY/SECONDARY SUPPLY
Primary supply [duty/running] actually is the portion supplying the systemSecondary 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 ]
Reserve Supply
For larger systemsWhen operating supply fails /emergencies /maintenanceActivating switch is there for activating reserve supply
Pressures
Gases other than Nitrogen @50-55 psigNitrogen @160 psig
Oxygen
Stored as liquid @ low pressures & < --148⁰C[when large amounts are required] OR as compressed gas in G or H cylinders
Nitrous oxide
Be careful against leaks; its an asphyxiantRegulator can become cold and can freezetheft
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 4⁰CLow levels of nitric oxide found in ambient air may improve oxygenation in ventilated patients
PIPED AIR SYSTEM
Employ 2 or more compressors
Takes in air
Compress it to working pressure
Supplies it to receiversused from here as needed
INTAKE
Intake location should be free of dirt/fumesQuality checked periodicallyWater content reduced with after cooler/dryerMonitored for carbon monoxideN.B. Other gases: CO2, Nitrogen
PIPED DISTRIBUTION SYSTEM
MAIN LINES: pipes connecting the source to risers or branch lines or bothRISERS: vertical pipes connecting the main line with branch lines on various levels of the facilityBRANCH LINES: they service a room or group of rooms on the same level of the facilityFlexible hoses used only in exposed areas..Why?
PIPED DISTRIBUTION SYSTEM
Pressure relief valves set @50% above the normal line pressure. Close automatically when excess pressure relievedShut 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 personnelEmergency Oxygen Supply Connector: T fitting for connecting auxiliary source of O2
PIPED DISTRIBUTION SYSTEM
Master Alarm System: monitor the pressure in the main lineWhen switch over from primary to secondary supplyWhen reserve supply is reduced to a certain levelWhen reserve is below that is required to functionWhen pressure in main line increase or decreaseArea Alarm Systems: e.g. PACU,ICUs
TERMINAL UNITS
BASE BLOCKPRIMARY VALVE: open when male probe connected & close when detachedSECONDARY VALVE: shut off flow when primary valve is removedGAS SPECIFIC CONNECTION POINT / SOCKET ASSEMBLY
TERMINAL UNITS
GAS SPECIFIC CONNECTION POINT / SOCKET ASSEMBLY Connecter may be DISS/ Quick ConnectorEquipped with a backflow check valveQuick Connector easy to use; but leak more
TERMINAL UNITS-types
Wall outletsCeiling mounted hosesCeiling mounted pendantsCeiling mounted columns
HOSES
connect anaesthesia machine to terminal unitseach have a permanaent non interchangable connectorInlet & outlet connectorsBraid adds to strength
TESTING OF MEDICAL GAS DISTRIBUTION SYSTEM -INITIAL
blow downInitial pressure testingStanding pressure testPiping purge testTest for cross connections
TESTING OF MEDICAL GAS DISTRIBUTION SYSTEM-SYSTEM
VERIFICATION
Cross connection testTest of valuesOutlet flow testAlarm testingPiping purge testPiping purity testFinal Tie-in testOperational pressure testMedical gas concentration/air purity testSource equipment verification
Problems
Inadequate pressureLeaksExcessive pressuresAlarm problemsCross connection of gasesContamination of gasesFiresDepletionTheft
THANK YOU
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