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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