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Boards: Machines, Physics > Medical Gases > Flashcards

Medical Gases Flashcards

1
Q

1atm = ? psi

A

1atm = 14.7psi

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2
Q

PSI

A

pounds per square inch

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3
Q

psig

A

pounds per square inch gauge
o Difference btw measured pressures and surrounding atmospheric pressure with most gauges constructed to read zero at atmospheric pressure

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4
Q

psia

A

pounds per square inch absolute
o Absolute pressure based on reference point of zero pressure for perfect vacuum
o = psig + local atmospheric pressure

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5
Q

Nonliquefied compressed gas

A

gas that does not liquefy at ordinary ambient temperature regardless of pressure applied
o Oxygen, nitrogen, air, helium

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6
Q

Cryogenic Liquids

A

Nonliquefied gases that become liquids at low temp

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7
Q

Liquefied compressed gases

A

becomes liquid to large extent in containers at ambient temperatures, at pressures 25-1500psig
o Nitrous oxide, carbon dioxide

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8
Q

Which organizations regulate manufacturer, marking, labeling, etc of medical gas cylinders?

A

DOT - Dept of Transport
Transport Canada

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9
Q

Role of Dept of Labor, OSHA?

A

regulates matters affecting safety, health of employees in all industries

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10
Q

Body of Cylinders

A

o Steel +/- various alloys added, steel carbon fiber: “3AA”
o Advantages steel carbon fiber: hold more gas than older steel counterparts, lighter weight
o Aluminum for MRI: “3AL,” “3ALM”
o Flat, concave bases with neck fitting with tapered screw threads attached to valve

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11
Q

Function of valve?

A

Cylinders = Filled, discharged through valve (spindle valve) attached to neck – bronze, brass
–Only removed by cylinder owner

Parts: port, stem, packed or diaphragm valve

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12
Q

Stem of Cylinder Valve

A

rotated during valve opening/closing
 To close valve, stem seals against seat that part of valve body
 When valve opened, stem moves upward, allowing gas to flow through port

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13
Q

Port of Cylinder Valve

A

point of exit for gas, should be protected in transit by covering

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14
Q

Cylinder Packed Valve

A

Most common
 Stem sealed by resilient packing eg Teflon to prevent leaks around thread
 AKA direct acting, bc turning stem causes seat to turn
 Valve capable of withstanding high pressures
 Requires 2-3 full turns to open

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15
Q

Diaphragm Valve

A

–Closure accomplished by metal-to-metal seal, bonnet nut - clamps one or more circular disks in place
–Disks/diaphragms separate upper, lower stems, may be permanently attached to diaphragms
* Upper stem: actuated by manual/automatic means
* Lower stem: shuts/permits flow through valve

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16
Q

Advantages of a diaphragm valve

A

opened fully by using ½-3/4 turn, seat does not turn so less likely to leak, no stem leakage can occur bc of the diaphragm

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17
Q

When is a diaphragm valve preferred?***

A

pressures low, no leaks can be allowed ie flammable gases

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18
Q

Disadvantages of a diaphragm valve?

A

More expensive

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19
Q

Handle/Handwheel

A

o Open (counterclockwise) or close (clockwise) valve
o Variety of shapes
 Ex: hexagonal opening (CUHA)  one end opens tank, other fits hexagonal nut of valve (risk of loosening packing nut instead of opening tank)
o Good practice: handle attached to each AM, check cylinder can be opened before use
o Each large cylinder has permanently attached handwheel that uses a spring and nut to hold firmly in place

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20
Q

Pressure Relief Devices

A
  1. Rupture Disc
  2. Fusible Plug
  3. Combination Rupture Disc/Fusible Plug
  4. Pressure Relief Valve
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21
Q

Pressure relief: rupture disc

A

non-reclosing device with disc held against an orifice
 When predetermined pressure reached, disc ruptures  allows cylinder contents to be discharged
 Pressure opening: orifice against which disc functions
 Used in some air, CO2, CO2-O2, He, N2O, He-O2, N2, O2 cylinders
 Protects against excess pressure DT high temperature or overfilling

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22
Q

Rated Burst Pressure in Rupture Disc

A

Pressure at which disc designed to burst; determined by material, thickness, shape of disc, diameter of pressure opening

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23
Q

Fusible Plug

A

thermally operated, non-reclosing pressure-relief device with plug held against discharge channel

Offers protection from excessive pressure caused by high temperature but not from overfilling

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24
Q

Fusible plug yield temperature

A

temperature at which fusible material becomes sufficiently soft to extrude from its holder so that cylinder contents discharged
* Fusible plug with yield temperature of 212*F sometimes used on certain nitrogen, air cylinders

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25
Q

Combination Rupture Disc/Fusible Plug

A

prevent bursting at predetermined pressures unless temperature high enough to cause fusible material to yield
 Devices with yield temperature of 165F cylinders of: air, oxygen, nitrogen, nitrous oxide, He, He-Ox, CO2, CO2-O2 mix
*Bc function only in presence of excessive heat/pressure, do not offer protection from high pressure DT overfilling

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26
Q

Pressure Relief Valve

A

spring-loaded device designed to reclose, prevent cylinder contents from being discharged after normal pressure has been restored
 Set pressure: pressure at will start to discharge, marked on valve
 Generally more susceptible to leaks
 Found on air, He, O2, nitrogen, He-O2 mix, CO2, CO2-O2 mix cylinders

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27
Q

Conical Depression

A

o Above safety relief valve
o Receives retaining screw of yoke
o Must be distinguished from safety relief device  if retaining screw tightening into safety relieve device by mistake, can be

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28
Q

Where is the noninterchangeable safety system located?

A

Btw cylinder valve, pressure regulator

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29
Q

Pin Index Safety System

A

Holes on valve - port will not seat unless pins/holes aligned

Holes numbered from R to L (clockwise direction)
1 = R, 6 = L when facing valve

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30
Q

PISS: O2?

A

2, 5

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31
Q

PISS: air?

A

1, 5

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32
Q

PISS: N2O

A

3, 5

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33
Q

PISS: Nitrogen

A

1, 4

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34
Q

PISS: Cyclopropane?

A

3, 6

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35
Q

Bull Nose Connections

A

Ensure appropriate connections with large tanks, btw cylinder valve and pressure regulator

Outlet threads mesh with nut, nut may be tightened -> nipple seats against valve outlet
* Gas channel of valve aligns with channel of nipple

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36
Q

What are the bull nose connections indexed by?

A

diameter, thread size, right/left hand treading, external/internal threading, nipple seat design

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37
Q

E Tanks - O2

A

Empty cylinder = 14#, 1900psig, 660L

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38
Q

H Tank - O2

A

Empty cylinder = 119#, 2200psig, 6900L

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39
Q

How measure quantity remaining in a cylinder for non liquefied gas?

A

Pressure gauge

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40
Q

B tank - O2 pressure

A

1900psi, 200L

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41
Q

D tank - O2 pressure

A

1900psi, 400L (D doubles B)

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42
Q

M tank - oxygen

A

3450L, 2200psig

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43
Q

How measure quantity of gas left in cylinder of liquified gas?

A

Weight of cylinder

Why: If the liquid remains when withdrawal stops, cylinder pressure will slowly increase to its original level as temp rises WHY CANNOT USE PRESSURE

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44
Q

Why can’t you use pressure to determine the contents of a cylinder containing N2O?

A

Pressure depends on vapor pressure of liquid -> Pressure remains nearly constant (with constant temperature) until all liquid has evaporated, after which pressure declines until cylinder exhausted

During use: temperature not likely to remain constant
* Evaporation of liquid, expansion of gas requires energy in form of heat, which is supplied by liquid in cylinder = cooling (vaporizers)
* If outer surface of liquefied gas cylinder becomes cold as gas discharged, residual liquid remains in cylinder ie cylinder should feel cold
* As temp falls, vapor pressure of liquid also decreases so have progressive fall in pressure accompanies release of gas from cylinder
* If the liquid remains when withdrawal stops, cylinder pressure will slowly increase to its original level as temp rises

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45
Q

What is a cylinder’s service pressure?

A

max pressure to which cylinder may be filled at 70*F

testing: minimum 1.66x service pressure

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46
Q

Filling of Cylinders

A

Pressure in filled cylinder @ 70*F may not exceed service pressure on cylinder except for some nonliquefied, nonflammable gases, which may be allowed an additional 10%

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47
Q

Filling of cylinders for liquefied gases

A

 Pressure in cylinder at 130F may not exceed 1.25x max filling pressure at 70 except N2O, CO2

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48
Q

How prevent cylinder containing liquefied gas from being overfilled?

A

maximum amount of gas allowed defined by a filling density (filling or fill ratio) for each gas

 Filling density NOT the same as volume of the full cylinder occupied by the liquid phase, N20 = 68% vs in full cylinder liquid phase 90-95% of vol

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49
Q

What is filling density?

A

percent ratio of the weight of gas in a cylinder to the weight of water that the cylinder would hold at 60F

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50
Q

Coloring of Cylinders

A

o Top/shoulder (part sloping up to neck) or entire cylinder with assigned color
 Nonfading, durable, water-insoluble paint
o >1 gas: colors applied so that each seen from top
o Corresponding color on valve protection caps, hoses, connectors, knobs, gauges on medical equipment
o International code: oxygen is white, air black and white (different in US)
o Color standardization not applicable in areas where specialty gases (eg calibration) used
 Ex: calibration of airway gas monitor
o Labels more reliable

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51
Q

Markings on a Cylinder

A

o Permanently stamped on the shoulder, required by DOT and TC
o Ex: DOT-3A2015 
DOT specification = 3A
service pressure is 2015 psig at 70F
8642 - serial number
XYZ -manufacturer
JCN -owner’s symbol
o + sign: authorized to be charged up to 10% excess of marked service pressure
PLUG or SPUN

52
Q

SPUN

A

bottom end closed by spinning

53
Q

PLUG

A

closure produced by spinning, drilling, plugging

54
Q

The following is a label on a cylinder. What is denoted by each set of numbers?
DOT-5B2425
8651
ABC
EMP

A

Top line - DOT specification is 5B, service pressure is 2425 at 70*
Second line - serial number
ABC - manufacturer
EMP - owner’s symbol

55
Q

Labeling

A

abel or decal required on side, ideally on shoulder but not so that covers permanent marking
o Hazard class – oxidizer, nonflammable gas, flammable gas
o Name of gas
o Signal word – DANGER, WARNING, CAUTION
o Statement of hazard: dangers with anticipated use/handling + measures to avoid injury/damage
o Name/address of manufacturer/distributor
o Statement about contents
 Usually volume in L at 70F, +/- cylinder weight when full and empty
o Expiratory date

56
Q

DANGER

A

Immediate Hazard

57
Q

WARNING

A

less than immediate

58
Q

CAUTION

A

no immediate hazard

59
Q

What is the hazard class symbol for an oxidizer?

A

Yellow sign, circle under flames

60
Q

What is the hazard class symbol for a flammable gas?

A

Red sign, flames

61
Q

What is the hazard class symbol for nonflammable gas?

A

Green gas cylinder

62
Q

Tags

A

o Three sections, often same color as cylinder
 FULL: detach when cylinder put into service
 IN USE: remove when empty
 EMPTY
o Goal: amt of cylinder contents, NOT identification

63
Q

What is the most easily damaged part of the gas cylinder?

A

The valve

64
Q

What are the temperature limitations of cylinders?

A

No part of the cylinder subjected to temp >54C (130F), below -7C (20F)
 Avoid proximity to radiators/heat ducts, exposure to extreme cold
 Snow, ice accumulation on cylinder: thaw at room temp or water <130*F

65
Q

What is an adiabatic process?

A

heat neither lost to or gained from environment

66
Q

How is an adiabatic process relevant to gas cylinders?

A

OPEN VALVE SLOWLY

If gas passes quickly into space btw valve, yoke or regulator – rapid recompression in space will generate large amounts of heat
* Particles of duct, grease, etc in space= flash fire, explosion
* Opening valve slowly prolongs time of recompression, permits some of the heat to dissipate

67
Q

What is true about transfilling?

A
  1. May affect purity
  2. When small cylinder transfilled from large cylinder containing gas at high pressure, rapid recompression of gas in small cylinder may cause temperature rise sufficiently= FIRE
  3. Risk charging with gas other than what originally in cylinder - dangerous mixture
  4. Missed inspections of safety devices etc that would be caught by manufacturer
68
Q

What are the requirements of medical grade oxygen?

A

Medical grade oxygen required to be 99% pure

Of remaining 1% (10,000ppm):
* <300ppm CO2
* <10ppm CO
* <5ppm oxides of nitrogen
* No other contaminants specifically excluded from other 9685ppm  potential to have dangerous amts of other compounds, not be in violation of existing standards

69
Q

Liquid Oxygen Tanks

A

Stationary unit refilled by gas supplier as needed

Smaller portable units filled from stationary unit
o Broader, shorter than cylinders – amt of gas determined by weight
o Pressure relief device, means to limit amount of liquid oxygen contained

When not in use pressure in container controlled by venting excess gas to atmosphere

Limits time oxygen can be stored in portable unit

70
Q

What government org oversees liquid oxygen tanks?

A

DOT

71
Q

What are required markings on a liquid oxygen container?

A

Specification number, service pressure for which container designed, identifying mark of original container owner, serial number

Date of manufacture, symbol to identify inspector

72
Q

Storage of liquid oxygen tanks

A

Cool, well-ventilated areas away from heat sources, corrosive atmospheres

Upright position

73
Q

What are three unique risks of liquid oxygen?

A
  1. cryogenic burns
  2. Creation of an oxygen enriched environment, increased fire hazard
  3. Valves may freeze if not kept free of moisture
74
Q

What organizations oversee pipeline systems?

A

o National Fire Protection Association
o Compressed Gas Assoc
o Canadian Standards Assoc
o International Standards Organization
o State/local codes

75
Q

At what PSI are gases other than N2, instrument air pumped?

A

160psi

76
Q

What are the three ways in which a facility can supply oxygen?

A
  1. Gaseous supply
  2. Liquid supply
  3. Oxygen concentrators
77
Q

Liquid Supply

A

Best for systems with constant demand

less expensive, more convenient
* Store at ground level, location where potential ignition sources minimal
* Special insulated vessels to keep <-297*F, prevents evaporation
o Thermos bottle with outer, inner metal jacket
o Metal jackets separated by insulation, layer near vacuum to retard heat transfer from exterior

78
Q

MOA Liquid oxygen storage

A
  • Usually kept cold by latent heat of vaporization as gaseous oxygen removed, temp falls (think vaporizers)
  • Gaseous oxygen drawn off as needed, passed through heater (vaporizer) to bring up to ambient temp, raise pressure
    o Coil, tube, or mesh heated via electricity or hot water
  • Some amt of uncontrolled evaporation DT continuous absorption of heat from surroundings, liquified gas evaporates  if left standing unused for long time, significant amt of oxygen lost
    o Liquid supply best for systems with
79
Q

What is medical air?

A

defined by NFPA as air that meets US Pharmacopoeia (USP) quality standards

80
Q

How medical air made?

A

Manifold cylinders
Oroportioning device that mixes gases from oxygen/N2 cylinders
motor-driven compressors

81
Q

Compressors to create medical air

A

take in ambient air, compresses to above working pressure, supplies to one or more receivers – withdrawn as needed
* Pressure relief valve
* Automatic drain, slight glass to permit visual checking that operating ok
* Pressure gauge

82
Q

Important considerations for air compressors

A

 Intake location for compressors important – air as free of contamination as possible from dirt, fumes, odor

 Water content must be reduced via aftercooler (air cooled, condensed moisture removed) or running air through dryer

83
Q

Instrument Air

A

different than medical air, doesn’t have to meet same requirements

84
Q

Piping systems: main lines

A

pipes coming source to risers, branch lines, or both

85
Q

Piping systems: risers

A

vertical pipes connecting main line with branch lines on various levels of facility

86
Q

Piping systems: branch (lateral) lines

A

piping system that services room, group of rooms on same level of facility

87
Q

What piping diameter is required for oxygen vs other gases?

A

Oxygen = 1/2”
Other gases = 3/8”

88
Q

Where are pressure relief valves located in a piping system?

A

set at 50% above normal line pressure downstream of regulators, upstream of shut off – prevents build up if shutoff closed

89
Q

Shut Off Valves

A

isolation in event of a problem, maintenance, repair, testing, expansion, etc
o Manual: accessible to anyone, visible
o Service: authorized personnel only

90
Q

Placement of shut off valves

A

 Outlet from supply source, isolates entire supply source
 Main supply: manual shut off near entry to building
 Each riser: manual shut off valve adjacent to connection to main supply line
 Each branch line, except in anesthetizing locations/other vital life support
* Critical locations = service shut off valve whether lateral branches off riser
* Manual valve immediately outside each critical location so shutting off supply to one location will not affect others

91
Q

What is a terminal unit?

A

Point in piped gas distribution system at which user normally makes connections, disconnections

92
Q

What are the parts of a terminal unit?

A

base block (attached to pipeline distribution system)
primary valve
secondary valve
gas-specific connection point (socket assembly) face plate

93
Q

Primary Valve on a Terminal Unit

A

o Opens, allows gas to flow when male probe inserted
o Closes automatically when connection broken, prevents gas loss when removal component disconnected
o Not a unidirectional valve – permits flow in either direction
o When in place, secondary valve stays open

94
Q

Secondary Valve on a Terminal Unit

A

o When primary valve removed, gas flow shut off
o Open when primary valve in place

95
Q

Socket Assembly

A

o Receptor for non-interchangeable gas-specific connector part of or attached to base block incorporated into each terminal unit
 Female component = outlet connector
 Male component = inlet connector

DISS, quick connect systems

96
Q

Diameter Index Safety System

A

noninterchangeable connections for medical gas lines at <200psi
 Body, nipple, nut

97
Q

MOA DISS

A

 Body, nipple, nut
 Two concentric, specific bores in body; two on concentric, specific shoulders on nipple
* Small bore mates with small shoulder
* Large bore  large shoulder
 For noninterchangability btw different connectors: two diameters on each part vary in opposite directions so as one diameter increases, other decreases
 ASTM: every AM must have DISS fitting for each pipeline inlet

98
Q

Quick Connectors

A

 Proprietary quick connect systems, allows apparatuses to be connected/disconnected by single action without tools/undue force
 More convenient, leak more than DISS
 Gas-specific male, female components
 Releasable spring mechanisms locks components together – different shapes/spacing of mating portions for different gases

99
Q

Face Plate

A

permanently marked with name +/- symbol of gas that conveys, +/- identifying color

100
Q

Types of Terminal Units

A

Wall outlets
Ceiling mounted hoses
Ceiling mounted pendants
Ceiling Column

101
Q

Wall Outlets

A

small rooms, equipment connected near wall

102
Q

Ceiling mounted hoses

A

I hope this is self explanatory but if not, think PCVRH

103
Q

Ceiling mounted pendants

A

keeps wires, hoses from cluttering floor, easily moved to various positions

104
Q

Ceiling column

A

similar to pendant, less versatile with respect to positioning
 Risk of hitting head, tough to reach if short, difficult to assess hoses inside column

105
Q

Hoses

A

connect AM, other apparatus to terminal units
o Permanently attached, noninterchangeable connector
o Color-coded with name +/- chemical symbol of contained gas on each connector
o Keep away from heat source (OR lights) – potential to cause rupture, keep off floor
o Gentle curve
o Over time, can weaken, swell, or crack – inspect routinely

106
Q

If you need more hose length, is it preferred to have one long hose or multiple short hoses?

A

o One long hose&raquo_space;> several connected to create long hose
 Resistance may interfere with gas flow
 Leaks: most occur in connectors or where connector fits into hose

107
Q

What is the pressure for a gas mixture during a standing pressure test?

A

20psi

108
Q

What is the pressure for nitrogen during a standing pressure test?

A

30psi

109
Q

What is the pressure for a N2O during a standing pressure test?

A

40psi

110
Q

What is the pressure for oxygen during a standing pressure test?

A

50psi

111
Q

What is the pressure for medical area during a standing pressure test?

A

60psi

112
Q

Operational pressure tests for oxygen, N2O, medical air

A

 Oxygen, N2O, medical air: outlets deliver 100L/min with pressure drop <5psi at static pressure of 50-55psi

113
Q

Operational pressure tests for nitrogen, instrument air

A

 Nitrogen outlets, instrument air: 140L/min, pressure drop <5psi at static pressure of 160-185psi

114
Q

Oxygen Concentrators

A

o Pressure swing absorption (PSA) technology, incereases oxygen concentration by adsorbing N2 onto molecular sieve that allows oxygen, trace gases (esp argon) to pass through

115
Q

What is the concentration of oxygen achieved using oxygen concentrator? Product name?

A

 Oxygen concentration 90-96%, name = Oxygen 93% USP

116
Q

Molecular sieve used by oxygen concentrator

A

Inorganic silicate = Zeolites - Belongs to class of crystalline compounds

117
Q

MOA Sieve

A

 System of precisely arrayed cavities, pores that are uniform in size within each granule – molecules readily adsorbed or completely excluded
 Molecular size, polarity of gas determine whether retained by sieve material

118
Q

Zeolite’s affinity for water

A

STRONG
* During use, water in sieve will displace other molecules, reducing capacity to adsorb nitrogen
* Not affected by room humidity during normal operation
 Sieve at entrance to bed or column adsorbs moisture, returned to atmosphere during purge phase
 Beds must be kept sealed from atmosphere to prevent moisture migration into them

119
Q

what is the benefit of pressure swing adsorption?

A

allows for continuous output of oxygen-enriched gas via two sieve beds in sequential adsorption-desorption process
 As one sieve adsorbs N2 under pressure, other is desorbed/purged
 Output depends on size of installation

120
Q

basic MOA of oxygen concentrator

A

o Pressurized air passes through sieve bed: O2 passes through freely; N2, CO2, CO, water vapor, hydrocarbons trapped
 Trapped molecules = desorbed (released) by venting sieve to atmosphere, s adsorptive force
 Regeneration of sieve via purging with some product gas

121
Q

More Thorough Description of Gas Flow through A Concentrator

A

o Filters at inlet remove particles, bacteria; sound reduced by muffler (1)
o Compressor receives filtered air, compresses it to higher pressure (2)
o Heat exchanger (coiled tubing) cools gas (3)
o Some concentrators: compressed gas will enter reservoir (surge tank) (4) – dampens pulsations generated by compressor
o Valves (6) (electrically or pneumatically controlled) direct gas flow through concentration
 Two zeolite beds: continuous oxygen production, sieve regeneration (7)
o Product tank functions as reservoir of product gas (8)
 May also serve as source of purge gas
o Pressure regulator (9): reduce pressure of gas flowing to outlet to lower, more constant pressure
o Check valve btw pressure regulator, outlet prevents room air from being sucked into sieve bed when concentrator off
o Filter near outlet: prevents sieve material, bacteria, other matter from contaminating outflow
o Status indicator required by US – low oxygen concentration in product gas

122
Q

Oxygen Concentrator Operation

A

o 2.5-19min once turned on to reach maximum concentration
o Concentration process becomes less efficient if FR increases above optimum level

123
Q

Applications of an oxygen concentrator

A

o Domicilary use: compact, lightweight – easy delivery, transport
o Remote locations: when pressurized oxygen, liquid oxygen supply unavailable, unreliable or prohibitively expensive
 Field hospitals, disasters, etc
o Source of oxygen supply for pipeline systems
 Large-scale oxygen concentrators – main supply for pipeline systems or pipeline supply during shutdown
* Fill cylinders
 Reservoir usually supplied by number of concentrators in parallel
 Need reservoir supply that automatically supplies system if concentrator malfunctions or falls [O2] below present minimum
 Argon does not alter flow characteristics

124
Q

What are advantages of an oxygen concentrator?

A

o Cost: product gas less expensive; depends on cost of concentrator, other means of supplying oxygen, electricity, maintenance
o Contaminant filtration: airborne contaminants filtered by molecular sieve, released back into atmosphere
o Compatible with IR, galvanic, paramagnetic gas analyzers (not adversely affected by argon)
o Reliable
o Simple: no dependence on compressed/liquified gases and assoc delivery problems

125
Q

What are disadvantages of an oxygen concentrator?

A

o Maintenance: regular servicing required, esp for compressor
 Impt to clean/replace air intake filters
o Max O2 yield ~96%

126
Q

What are the main three hazards with oxygen concentrations?

A

o Fires
Risk of ignition – keep away from heat, flames, overheated electrical connections, loose connections, oil, grease
o Water Contamination
Humidity not problematic under normal conditions
Very high humidity: oxygen concentration in product gas to be lowered
o Contaminated intake air: not likely to be contaminated by fumes, water, atmospheric pollutants -> damage sieve medium, premature sieve exhaustion

Boards: Machines, Physics (9 decks)

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