compressed gas safety (2)

7/27/2019 Compressed Gas Safety (2)

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Topics

PPT-043-01 2

RegulationsUses

Properties and examples

Compressed gas

Liquefied gasCryogenics

Terms and behavior

Containers and markings

Pressure relief valvesViolent reactions

Handling and storage

Inspections

Emergency responseAssist standards

Bibliography


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Regulations

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Regulations for use, storageand handling will be accordingto the authority havingjurisdiction, or AHJ

In the absence of codes, the

following may provideguidance:

Compressed Gas Association

National Fire ProtectionAssociation (NFPA)

Safety Data Sheet (formerlyMaterial Safety Data Sheet)


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Other Sources

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For determining hazardsand for planning purposes:

NIOSH Pocket Guide to

Chemical Hazards

2012 Emergency

Response Guidebook


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Uses

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Industrial uses include:processes, heating,forklifts; industrial gasesmay also have othergases added for processpurity

Medical gases are blendsof several gases

Vehicles converted fromgasoline or diesel

Citizen use for heating


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Gas Properties

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Gases can be: Flammable

Non-flammable

Oxidizers

Corrosive

Asphyxiants

Poison

Inert Or a mixture


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Physical States

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Gas In Cylinder Temperature

Compressed Gas +70 to +32 F in gaseous state

Liquefied Gas +32 to -130 F in liquefied

state

Cryogenic Liquid -130 to -432 F refrigeratedliquefied gas

Storage temperatures are gas-dependent


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Compressed Gas Examples

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Vapor

Types Hazard Class Density LEL/UEL Flashpoint (F)

Methane 2.1 Fl 0.55 5-15% -306

Ethane 2.1 Fl 1.04 3-12.4% -211

Propane 2.1 Fl 1.52 2.2-9.5% -56

Butane 2.1 Fl 2.0 1.8-8.4% -101

Nitrogen 2.2 Non-Fl 0.96 Inert ------

Oxygen 5.1 Ox 1.1 NF/Oxidizer ------

Arsine 2.1 FL/2.3 poison gas 2.69 4.5-64% ------

Chlorine 2.2 NFl/2.3 poison gas 2.48 Oxidizer ------

Fl=Flammable

NFl=Non-Flammable


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Definitions

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Gas: State of matter in which material has a very

low density and viscosity

Can expand and contract in response to

temperature and pressure changes Easily diffuses into other gases; distributes

itself inside a container

If the temperature is dropped and pressure

increased, the gas can be changed to a liquidor semi-solid state


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Compressed Gas

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Material or mixture having in the container anabsolute pressure exceeding 40 psi at 70oF or,regardless of pressure at 70oF, having anabsolute pressure exceeding 104 psi at 130oFor any liquid material having a vapor pressureexceeding 40 psi absolute at 100oF asdetermined by ASTM Test D-323

page 597, CGA Handbook, 3rd Edition


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Liquefied Petroleum Gas

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LP Gas or LPG

Any material with a vapor pressurenot exceeding that allowed forcommercial propane

Composed predominantly of thefollowing hydrocarbons, either bythemselves or as mixtures:propane, propylene, butane

(normal butane or isobutene) andbutylenes


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Liquefied Natural Gas

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Also called LNG

A fluid in the cryogenicliquid state that iscomposed predominantlyof methane


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Cryogenic Liquid

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Cryogenic liquid:Refrigerated liquefiedgas with normalboiling point below -

130oF Hazards include those

of the gas, frostbiteand asphyxiation if

breathable oxygen inair is displaced


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Terms

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Boiling Point:Temperature when a gas converts from itsliquefied state to vaporous state

Critical Pressure:

Temperature above which a gas cannot beliquefied by pressure alone


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Triple Point

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The only temperatureand pressure at whichthree phases (gas,

liquid and solid) in aone-componentsystem can exist inequilibrium


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Compressed Gas Terms

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Vapor Density (Gas Specific Gravity):A comparison of the weight of the gas to air(1.0); heavier-than-air gases will have a vapordensity greater than 1.0; lighter gases will have

a vapor density less than 1.0


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TLV-TWA

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TLV-TWA (threshold limit value - time weighted

average):

Given in ppm (parts per million); exposure amountwhich most people can work in for an eight hour daywithout suffering harmful effects


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IDLH

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IDLH: Immediately Dangerous to Life and Health

Amounts to which persons should not be exposed

due to their harmful effects; sources fordetermining these limits will be found on the SDS,as well in various guides, i.e. NIOSH Pocket Guideto Chemical Hazards


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LEL

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Lower Explosive Limits(LEL) also known as lowerflammable limits (LFL):least percentage of a gas,

mixed with the properproportions of air,whereby having thenecessary heat applied,combustion may result


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UEL

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Upper Explosive Limits(UEL), also known asupper flammable limits(UFL): greatest

percentage of a gas,that when proportionedwith air, may permitsustained combustion


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Flammable Limits

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Flammable Limits, alsoknown as the flammablerange: percentage of gaswithin the LEL and UELwhere combustion may

occur and be sustained

Shown: Hydrogenapproximated (4-75percent)


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Ignition Temperature

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Ignition temperature: Unique to various solids,vapors and gases, the requisite heat from anopen flame source required to ignite materials

Autoignition temperature: The temperaturerequired to ignite materials absent an openflame source


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Expansion Rate (or ratio)

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Conversion of cubic feet ofliquid to cubic feet of gas

Can result in achievingthe LEL or flammablelimits in an inside

environment

Can also result in thetoxic levels or IDLH for agas expressed as

percentage by volume orppm (parts per million)


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Expansion Rate

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Gas Expansion Rate

Methane 625:1

Propane 270:1

Butane 284:1Nitrogen 696:1

Oxygen 860:1

Chlorine 444:1


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Gas Laws of Gas Behavior

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Boyles Law:

Decrease a containersvolume by one half

Temperature andamount of gas remainconstant

Pressure will double


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Gas Laws

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Charles Law:

When the temperatureincreases, the volume

increases

Perhaps the containerwill not be able tohandle the volume

increase


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PVT Relationship

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If temperature of a gasincreases in cylinder,volume of cylinder cannot be increased

Pressure increases andmay activate relief valve

If pressures increase toorapidly, cylinder may

rupture


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Rule of Thumb

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Increase gas temperature 500 degrees = double

pressure

Increase gas temperature 1,000 degrees = triplepressure

Increase gas temperature 1,500 degrees =

quadruple pressure

(Some gas cylinders do NOT have

a pressure relief valve, could

be catastrophic rupture!)


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Cryogenic

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Heat expands a gas

If we pressurize a gas whilecooling it, we can turn a gasinto a liquefied gas

Further cooling and pressuremay convert it to a cryogenicgas

This increases the amount of

product that can be put in acylinder


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Gas Containers

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Lecture Bottles

Cylinders

Tank Trucks


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Gas Containers

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Railroad Tank Cars

Portable Tanks

Fixed Storage

Pipelines


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Cylinders

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ConstructionMust be compatible

with the material

contained

Markings

Labeling required to

identify the gas in storage

and during shipment


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Markings

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Nomenclature relatedto the cylinder and itscontents will assist inthe safety process

Low pressure: Below900 psi

High pressure: 900psi or greater


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Storage Pressure

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Storage Ignition

Types Pressure (PSI) Temperature

Methane up to 6000psi 999 F

Ethane 544 959 F

Propane 109.7 871 F

Butane 31 761 F

Nitrogen 2,000/below 200 as cryogen Inert

Oxygen 2,000/below 200 as cryogen Inert

Arsine 219.7 (*see note)

*Note: Arsine has no given Ignition Temperature but decomposes into arsenic

and hydrogen between 446 F to 464 F


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Color Codes

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Cylinder shells can also

be color coded to betteridentify the contentspermitted into thespecific type of cylinder

This eliminates cross-contamination byintroducing non-

compatible gases intonon-specificationcylinders


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Medical Gas Color Codes

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Medical gases willoften be a blend of aparent gas withfractions of othergases introduced forpurity and stability


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Labels

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FTSC CodeStandard numerical code

for a gas indicating:

Flammability Toxicity

State of the gas

Corrosiveness

CGA V-7 pamphlet provides more in-depth information


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Diaphragm Valve

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Diaphragm valve betterretains the cylindercontents

Not as prone to leakage

as the packed valve Note the diaphragms

location

Note also the relief

valves location in theproduct line


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Packed Valve

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The packed valve haspacking between theupper stem andbonnet

This type is knownfor leaking throughthe packing

Often the leak maybe secured by

tightening the bonnet


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Pressure Relief Valve (PRV)

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May be activated bypressure, temperatureor spring to permitcontainer contents to

escape, therebyaverting a containerrupture

The PRV is in the

product line


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Fusible Plug/Combination

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Fusible plug melts at adesignated temperatureand permits the productof a cylinder to be

released to avert acatastrophic rupture

Combination relief: Onewith a rupture disk andfusible plug

Both are non-resealing


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Rupture Disk

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Rupture disk (frangible

disk) - Operating part ofa PRV: ruptures at apredetermined pressureallowing cylinder

contents to escape Non-resealing

Poison gas cylinders donot have a PRV

depending on theirclassification (PRVs areprohibited)


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Cylinder Hazards

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Material Hazards

Flammability

Spontaneously

flammable (arsine, silane

and phosphine) Corrosivity

Reactivity

Poison

Carcinogenic

Container Behavior

Frostbite

Rupture

Rocketing

Boiling liquidexpanding vaporexplosion (BLEVE)


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BLEVE (Boiling Liquid Expanding Vapor Explosion)

PPT-043-01 45

A cylinder or tank is heated

Contents absorb heat and convert to pressurized vapor

Relief valve activates

Pressure increases beyond the PRV capacity

Container, thermally stressed, violently ruptures

If the gas is flammable, the fireball is

devastating


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BLEVE (Boiling Liquid Expanding Vapor Explosion)

PPT-043-01 46

BLEVEs can occur withliquefied nitrogen andhelium or refrigerantsand cryogens as well

as LP gas or LNG

The pressure, volume,temperature

relationship drives theBLEVE


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BLEVE

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Cylinder exploded inside a

building

Cylinder exploded outside

May occur with liquefied

petroleum gas (LPG)propane and butanebeing main componentsor

With liquefied natural gas(LNG) of which methaneis the largest component


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Railroad Tank Car BLEVE

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Crescent City, Illinois;June 21, 1970,

7:30 am

Train No. 20 derailed

involving three tankcars

BLEVE was 34,000gallons of Propane

Emergency planningpaid off


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Fixed Location BLEVE

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65,000 gallons ofpropane at bulkstorage location inCanada, 2008


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Hydrocarbon Gases

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Contain flammablehydrogen andcombustible carbon intheir make-up

Flammable

Non-corrosive

Non-toxic

Colorless

Examples include:

Propane and

Butane


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Hydrocarbon Gases

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Ignition

Gas Formula Temperature (F)

Methane CH4

999

Ethane C2H6 959

Propane C3H8 871

Butane C4H10 761


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Oxygen

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Not flammable

Sensitizes flammable andcombustible materialsrequiring less input heatfor ignition

In some cases, materialsimpregnated with oxygencan be ignited with static

electricity


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PELs/IDHL

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TWA:

Gas CAS # OSHA PEL IDLH

Methane 74-82-8

Ethane 74-84-0

Propane 74-98-6 1,000 ppm 2,100 ppm (10% LEL)Butane 106-97-8 None Not DeterminedNitrogen 7727-37-9

Oxygen 7782-44-7

Arsine 7784-42-1 0.05ppm Ca (3 ppm)

Chlorine 7782-50-5 1 ppm 10 ppm

(*Note: to convert ppm into percent by volume, divide the number given in ppmby 10,000; this will give you the percentage by volume)


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Effects of Exposure

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Explosive rupture ofcontents which candestroy vehicles

Cylinders may gothrough barriers orwalls


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Other Gas Accidents

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Flammability Chemical burns

Handling safety requiresan understanding of the

gas properties and use ofpersonal protectiveequipment (PPE):

Gloves

Eye protection

Respirator

Foot/body protection


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Safe Handling & Storage

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Determine safe handlingand storage needsbased on your industry

and the gases withwhich you work

Create or follow checklists to best ensure acontinuous safetyprogram


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Proper Handling

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Use proper hand trucks - donot roll the cylinder on itsside

Provide a forklift cylinder

change-out area whichmaximizes safety for theoperator and other staff

Provide:

Ventilation Fire extinguisher

PPE


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Handling

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Take time to planwhat you are going todo with a cylinderand how you aregoing to do it

Always decide onthe side of personalsafety


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Storage

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Proper ventilation

Out of the weather

Not subject totemperature extremes

Segregate gas types toeliminate fire orchemical reactionhazards

Use good house keepingpractices

Post signage


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Lab Ventilation

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Critical for safe and healthy operation

Occupied lab air exchange rates should be sixto 10 times an hour per applicable standards

Unoccupied lab air exchange rates includingstorerooms should be four times in one hour

(NFPA 45) Air supplies to labs, storerooms, prep rooms

should never be recycled to any other part ofthe building, offices

Only conduct experiments the ventilationsystem can handle without a fume hood

HVAC filters should be changed quarterly


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Fume Hood

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Provides local exhaust ventilation Essential in exhausting hazardous gases,

particulates, vapors, etc.

Use hood to remove airborne chemicals (e.g.

aerosols, dusts, fumes, vapors) Do not store items within fume hoods

Place apparatus far back to rear of hood forefficient air flow

Ensure only necessary materials are underhood during an operation


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Fume Hoods

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Always keep the sash between the face andexperiment sash should be lowered

Check air flow before and during operation(face velocity of 80-120 fpm)

Compressed Gas Cylinders


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Compressed Gas Cylinders Storage, Maintenance, Handling

PPT-043-01 63

Isolate threats:

Hourly fire rated walls

Distances

Methods of securing:

Adjustable bay rack

Individually supported

Eye bolts, chain and latch

Compressed Gas Cylinders Storage


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Compressed Gas Cylinders Storage,Maintenance, Handling

PPT-043-01 64

Compressed gases can be hazardous because

each cylinder contains large amounts of energyand may also have high flammability and toxicitypotential - think safety:

Ensure the contents of all compressed gas cylindersare clearly stenciled or stamped on the cylinder ordurable label

Do not identify a gas cylinder only by themanufacturers color code

Never use cylinders with missing

or unreadable labels

Compressed Gas Cylinders Storage,


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PPT-043-01 65

Check all cylinders for damage before use

Be familiar with the properties and hazards ofthe gas inside the cylinder before use

Wear appropriate PPE before handling/use

Check for leaks after attaching a cylinder byusing a soap solution, snoop liquid or gasdetector

Label empty cylinders as EMPTY or MT

Always attach safety caps when storing ormoving cylinders

Compressed Gas Cylinders Storage


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PPT-043-01 66

Larger cylinders should be secured to a wall or lab

bench by a clamp or chain Store cylinders by gas type; separate oxidizing

gases from flammable gases by either 20 feet or a30 minute 5 foot high firewall

Store cylinders in a cool, dry, well-ventilated areaaway from incompatible materials and ignitionsources

Store empty cylinders separately from full ones

Do not subject any part of a cylinder totemperatures higher than 125F or lower than50F

H ti


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Heating

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Use only approvedmethods to heatcylinders to guardagainst a rapid rise in

temperature andpressure in cylinder

Do NOT heat withsalamander heaters or

direct impingementheaters

Inspection


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Inspection

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Physical:

Rust, chemical reactions,fire or heat impact

Leaking Bulging, distortions

Paint changes due tochemical reaction or heat

Inspection


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Inspection

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Fatigue or stress

Dents, gouges, impactpoints

Internal problems Repair methods and

correctness

Protective valve caps

Inspect


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Inspect

PPT-043-01 70

For leaking fittingsand correctconnections

Know what to do

when finding suchsituations:

Handle alone?

Call a co-worker?

Call the supervisor? Evacuate?

Checking Connections


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Checking Connections

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Ensure proper valveshave been used

Snoop connections toeliminate leakage of gasto surrounding areas*

* Snooping uses a soap solution on

a compatible gas connection to

determine leakage; no bubbles = no

leakage

Welding Gases


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Welding Gases

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Exercise the needed care

when dealing with dualgases such as oxygen andacetylene

Practice storage and use

safety Secured and capped

Not taken into confinedspaces or work areas

Segregated fromcombustibles

Inspect Set Ups


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Inspect Set Ups

PPT-043-01 73

Check:

Valves

Hoses

Flashback arrestor

Confirm operatingpressures

Connections are secure

Personal protectiveequipment is in use

Area secured from otherhazards

Hydrostatic Testing (Hydro)


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Hydrostatic Testing (Hydro)

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Pressurizing a cylinder for aperiod of time thendetermining if the shellreturns to a percentage ofits normal shape within a

set time period Determines serviceability of

the cylinder

Determine hydro schedule

for your cylinders and keepa record on file

Hydro Test Intervals


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Hydro Test Intervals

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Hydro test intervalsare based on thecomposition of thecylinder

Retesting of cylinders

can be found in 49 CFR 173.34, and

CGA C-1 Methods forHydrostatic Testing ofCompressed GasCylinders

Emergency Response


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Emergency Response

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Gas emergency responsewould fall under HazardousMaterials response per 29CFR 1910.120(q)

Certain likely events mayresult from the gases youuse and the methods oftransport, storage or

handling

Possible Gas Accidents


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Possible Gas Accidents

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LP gas tank fire

Gas pipeline explosion

Release Events


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Release Events

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Detection Monitoring


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Detection Monitoring

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To determine leaks, use

various detectors: Combustible gas

indicators (CGI), or

Gas detector (gas

specific)

You will need to know:

Gas LEL/UEL and

IDLH limits before

monitoring for gas

Detection


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Detection

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Portable leak detector

Broom used to detectburning hydrogen,

which burns light blueto almost invisible

Detection


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Detection

PPT-043-01 81

Similar broom method may also be used:

If attempting to detect presence of chlorine

Wrap clean cloth around broom

Put ammonia on cloth and wave in suspected chlorine cloud

If cloth fumes, you have detected presence of chlorine

If looking for ammonia leaks Wrap cloth treated with chlorine bleach around broom

Wave in suspect area

If fuming occurs, ammonia is present

Both methods rely on chemical reactions youll needtraining and PPE: USE CAUTION

Emergency Response Methods


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Emergency Response Methods

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An extraction hood used fordaily operations may beused to vent escaping gasfrom a cylinder up through afilter

Hoods and vents may alsobe equipped with ascrubber to neutralizevarious gases

Some poison gases may bescrubbed this way

Response


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Response

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Do you have a trainedteam?

Or will you call specialtyresponders?

Will special responseequipment be needed?

Special precautions arerequired for spontaneously

combustible gases such assilane

Recovery Vessel


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Recovery Vessel

PPT-043-01 84

Recovery vessel is a DOTexempt containment vessel

It can handle large cylinders

as well as smaller Service pressures vary

It may be the mostexpedient means to control

a leaking cylinder

Containment


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Containment

PPT-043-01 85

Containment is a team effort

Remote openers also existfor containers which may be

suspect so responders arenot subjected to pressureinjuries

Chlorine A Kit


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Chlorine A Kit

PPT-043-01 86

Chlorine A kit to beused for leakingchlorine cylinders

The pressures of somegases may limit the kitsuse to chlorine

Teams should betrained in proper use

Chlorine B Kit


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Chlorine B Kit

PPT-043-01 87

B kit is used to controlleaks on one toncontainers of chlorine

Where contents can not be

pumped out of a container,the container might beable to be drilled

Drilling requires pressure

reduction (cooling) andhighly trained responders

Response


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p

PPT-043-01 88

Determine if you willhandle an event aloneor with off-site help

Pre-plan potential zonesof harm should yourfacility have a release

Practice safety and besafe in handling, use,storage and response to

gas incidents

Some Standards to Aid You


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PPT-043-01 89

The following 29 CFR 1910 Standards mayguide you in developing your own program:

1910.101 Compressed Gases (GeneralRequirements)

1910.102 Acetylene

1910.103 Hydrogen

1910.104 Oxygen

1910.111 Storage and Handling of LP Gas

Compressed Gas Assn., Inc., 14501 George

Carter Way, Suite 103, Chantilly, VA 20151

Questions


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Q

compressed gas safety (2)

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