Industrial Safety and Health for Goods and Materials Services - Chapter 10 doc

Always stand away from the face and back of the gauge when opening the cylinder valve Figure 10.3.. When a special wrench is required to open a cylinder or manifold valve, the wrench sha

10 Compressed Gases

There are two types of hazards associated with the use, stor age, and handling ofcompressed gas cylinders: the chemi cal hazard associa ted with the c ylinder conten ts(corrosive , toxi c, flammable, etc.) and the p hysical hazards repres ented by thepresence of a high-press ure vessel in the wor kplace or laboratory Figure 10.1

outlines some of the physical attribut es of compr essed gas c ylinders and describessome of the dangers that may resul t from imp roper use

Wheth er we like it or not, there are a lways safet y rules to follow But when itcomes to safet y procedu res for co mpressed gas, these rules are doub ly imp ortant.They shoul d be practiced daily because the safe way is the only way W hen dealingwith compressed gases, there are several items that one needs to be aware of at alltimes so that handli ng, trans porting, stor age, and use of compressed g as cylinderscan be accom plished ef ficient ly and safely

Mishandl ed cylinders may cause a viol ent ruptu re, relea sing the hazardo us tents or the cyli nder itself, whi ch can become a dange rous proje ctile If the neck of apressurized cylinder breaks accidentally, the energy released would be sufficient topropel the cylinder to over three-quart ers of a mile in height (F igure 10.2)

con-A standard 250 cu ft cylinder pressurized to 2500 psig can become a rocketattaining a speed of over 30 miles=h in a fraction of a second after venting from thebroken cylinder connection

Compressed gases have a variety of uses and require special handling procedures

10.1 CORROSIVE AND TOXIC GASES

Many gases used throughout industry have additional hazards other than those offire, asphyxiation, or oxygen enrichment Exposure to some gases may presentserious health hazards to unprotected personnel Before using a corrosive, toxic, orhighly toxic gas, read the label and material safety data sheet (MSDS) for theparticular gas Personnel working in the immediate vicinity where exposure tothese gases is possible should be informed of their hazards Exposure to thesegases must be kept as low as possible, but in no case should concentrations exceedOccupational Safety and Health Administration (OSHA) permissible exposure limits(PELs) or the current ACGIH threshold limit values (TLVs) set by the American

I have a wall thickness of about ¼ in.

I wear a label to identify the gas I am holding.

My color is not the answer.

I transform miscellaneous stacks of material into glistening plants and many other things, when properly used.

I may transform glistening plants and many other things into miscellaneous stacks of material, when allowed to unleash my fury unchecked.

I can be ruthless and deadly in the hands

of the careless or uninformed.

I am proud of my capabilities, here are a few of them:

• I have on rare occasions been known to jetaway, faster than any dragster.

• I might smash my way through brick walls.

• I might even fly through the air.

You can be my master only under the following terms:

Treat me with respect—I am a sleeping giant.

• I may spin, ricochet, crash, and slash through anything in my path.

• Full or empty—see to it that my cap is on, straight, and snug.

• Never, repeat, never leave me standing alone Secure me so that I cannot fall.

I am frequently left standing alone on my small base without other visible means of support—my cap removed and lost by

an unthinking worker.

I am ready to be toppled over—where

my naked valve can be damaged or even snapped off—and all my power unleased through an opening no larger than a lead pencil.

Conference of Governmental Industrial Hygienists (ACGIH) Contact an industrialhygienist for information on these exposure limits.

10.1.1 POISONOUSGASES

Poisonous compressed gases represent a significant hazard Special precautionsnot otherwise necessary become prudent when using poisonous gases Commonpoisonous or highly toxic gases include the following:

. Emergency procedures should be made clear to all involved, including

personnel from adjacent work areas and managers who might be affected

. Poisonous gas used after normal working hours should require the approval

of the chemical hygiene officer for your operation

FIGURE 10.2 Compressed gas cylinder can become a missile, which can penetrate ablock wall

. Fume hoods and other ventilation need to be tested before use and checked

frequently during the project that involves poisonous gas

. Notify the environmental health, safety, and risk department before your

first use of the poisonous gas

. Police should also be informed about the locations and types of poisonous

gas in use

. Document the procedures in your work area according to the chemicalhygiene plan As with all chemicals, obtain and review the MSDS for thepoisonous gas Maintain an extra copy of the MSDS in your workplace’schemical hygiene plan

Disposal of poisonous gas cylinders can often cause problems If the cylindercannot be returned to the manufacturer, disposal cost may be as large as $1000per cylinder, or more Even cylinders that can be returned must be shipped on

a vehicle that does not simultaneously carry any other hazardous materials orfoodstuffs

The energy potential of compressed gas cylinders whether chemical or ical can be mitigated by following safe work procedures These safe proceduresinclude use, handling, storage, transportation, and movement of compressed gascylinders, and those using them should not fail to follow these procedures

mechan-10.2 PREVENTING COMPRESSED GAS CYLINDER ACCIDENTSAll systems in manned areas have unmodified, DOT-approved, compressed gascylinders and the appropriate regulators may not require engineering controls ifgeneral safety rules are followed Compressed gas cylinders are the most commonsource of gas for many operations As a precaution, these cylinders must beadequately secured when in use or storage The DOE, ASME, DOT, and OSHAagencies all refer to the Compressed Gas Association (CGA) pamphlet (CGA P-l,1991) for instructions on how to safely handle compressed gas cylinders Manyfactors must be addressed to assure safety in the handling and use of compressed gascylinders The great amount of energy stored in the cylinders makes preventingaccidents paramount in preventing injury, illnesses, and deaths

10.2.1 CYLINDERUSE

Follow these recommendations for safe use of cylinders:

. Make sure all connections are tight Use soap water to locate leaks.

. Keep cylinder valves, regulators, couplings, hose, and apparatus clean and

free of oil and grease

. Keep cylinders away from openflames and sources of heat

. Safety devices and valves should not be tampered with, nor repairs

attempted

. Useflashback arrestors and reverse-flow check valves to prevent flashbackwhen using oxy-fuel systems

. Regulators should be removed when moving cylinders, when work is

complete, and when cylinders are empty

. Cylinders are to be used and stored in the upright position.

. Cylinder valve should always be opened slowly Always stand away from the

face and back of the gauge when opening the cylinder valve (Figure 10.3)

. When a special wrench is required to open a cylinder or manifold valve, the

wrench shall be left in place on the valve stem when in use; this precaution

is taken so the gas supply can be shut off quickly in case of an emergency,and that nothing should be placed on top of a cylinder that may damage thesafety device or interfere with the quick closing of the valve

. Fire extinguishing equipment should be readily available when combustible

materials have a possibility of getting exposed to welding or cuttingoperations using compressed cylinder gases

10.2.2 HANDLING

Even though the cylinders are constructed of steel, they must be handled withextreme care to avoid damage Physical abuse, such as dropping, or violently strikingcylinders together, can cause damage to the cylinder, valve, or fuse plug, and in turnpresent a potential hazard There are several methods of unloading cylinders from atruck to ground level that help prevent damage These include the following:

. V-shaped trough—it allows cylinders to be lowered carefully down onto ashock-absorbing mat on the ground

. Angle-iron cradle—these are used to upend the cylinders and lower them tothe ground

Inproper crackingFIGURE 10.3 Care must be taken when opening cylinder valves (Courtesy of Department

of Energy.)

. Elevator tailgate—this is one of the easiest and safest means of unloadingcylinders, and is to be used whenever it is available on the transport truck.But remember, the important thing is to be sure the cylinders are notdropped.

. Use a four-wheel cylinder cart for moving Standard No 1 and larger gas

cylinders These cylinders are difficult to move manually because of theirshape, smooth surface, and weight (Figure 10.4)

. Make sure that the protective valve cover is in place when a cylinder is not

connected to a regulator or manifold (Figure 10.5)

. Measure the pressure of contents of half-empty cylinders and mark them.

. Always assume a cylinder is pressurized; handle it carefully and avoid

bumping or dropping

. Never drop cylinders from trucks or any raised surface to the ground.. Lifting a standard cylinder, or any cylinder weighing more than 50 lb,

requires two people Never lift a cylinder by the cylinder cap (Figure 10.6)

. Do not handle oxygen cylinders with greasy, oily hands or gloves The

reaction between oxygen and hydrocarbons can be violent, even whensmall quantities are involved

. Secure cylinders in suitable cradles or skid boxes before raising them with

cranes, fork trucks, or hoists Do not use ropes or chain slings alone for thispurpose

. Never use a gas cylinder as a roller for moving materials or for supporting

other items

10.2.3 STORAGE

Cylinders are sometimes shipped tied horizontally on wooden pallets, individuallycontained by saddle blocks, and double-banded to prevent rolling and sliding Theseare not recommended methods for cylinder storage Instead, the work practicesprescribed in this section should be followed (from pamphlet CGA P-l-1991):

. Store adequately secured cylinders upright on solid, dry, level footings,

preferably outside of occupied buildings and away from traffic lanes

. Shade cylinders stored in the sun during the summer, whenever possible.. Store cylinders away from sources of intense heat (furnaces, steam lines,

and radiators)

Improper hoisting

FIGURE 10.6 Unsafe hoisting practices for gas cylinders (Courtesy of Department ofEnergy.)

. Cylinders should be stored in compatible groups.

. Flammables from oxidizers

. Corrosives fromflammables

. Full cylinders from empties

. Empty cylinders should be clearly marked and stored as carefully as full

cylinders are because of the presence of residual gas

. All cylinders should be protected from corrosive vapors

. Store cylinders in an upright position.

. Keep oxygen cylinders a minimum of 20 ft fromflammable gas cylinders orcombustible materials If this cannot be done, separation by a noncombus-tible barrier at least 5 ft high having afire-rating of at least 1.5 h is required(Figure 10.7)

. Compressed gas cylinders should be securedfirmly at all times A clampand belt or chain, securing the cylinder between cylinder waist and shoulder

to a wall, are generally suitable for this purpose

. Cylinders should be individually secured; using a single restraint strap

around a number of cylinders is often not effective

20 ft minimum

Minimum: 5 ft high 1/2 h fire rating

Flammable Keep away from fire

the Occupational Health and Safety Administration.)

. Keep valve protective caps in place when the cylinder is not in use Always

store cylinders with the protective caps in place

. Mark empty cylinders EMPTY or MT.

. Keep valves closed on empty cylinders.

. Keep cylinders away from magnetized equipment.

. Cylinders must be kept away from electrical wiring as the cylinder could

become part of the circuit

. Store cylinders in well-ventilated areas designated and marked only for

cylinders

. Do not stockpile gas, especiallyflammables, poisons, or corrosives, beyondthe amount required for immediate use Consider direct delivery from thedistributor when gases are needed

. Limit the use and storage of poisons and corrosives to less than 1 year to

prevent stockpiling Documentation should be required for these materials.The environmental safety and health (ES&H) department’s industrialhygienist should establish and document the maximum quantities of suchmaterials in use and storage to ensure reasonable turnover The emergencypreparedness group should track the materials as an element of its emer-gency response planning program Extended use or storage of hazardousmaterials should occur after discussion by the user, the industrial hygienist,and the emergency preparedness group The agreed upon storage processshould be documented

. Ensure that containers stored or used in public areas are protected against

tampering and damage Furthermore, containers stored inside or outsideshall not obstruct exit routes or other areas that are normally used orintended for the safe exit of people

. Use a storage basket for smaller cylinders (<5 L) These baskets areavailable commercially

10.2.3.1 Outside Storage

Store cylinders outside whenever it is possible Care must be taken to protect themfrom bad weather and direct sunlight Remember, the heat from direct sunlight willcause gas to expand, which creates higher pressure within the cylinder

. Near loading platforms

. By entrances or exits where they might be accidentally hit

. Near sources of electricity

. Near sources of excessive heat, such as the sparks resulting from welding or

cutting

. Where they may become hotter than 1308F

. Closer than 20 ft from combustibles such as grease, gasoline, paint, oil, and

dirty rags

In addition, if a cylinder is frozen to the ground, use warm, not hot, water to free

it If the valve is frozen, again, use warm water, not hot, to thaw it or take the cylinderinside and let it thaw at room temperature

10.2.4 MOVINGCYLINDERS

Here are some pointers that should be remembered when moving compressed gascylinders:

. Use of a hand truck simplifies moving cylinders from one location to another

. Cylinders are to be chained or secured in some manner, in an upright position.. Avoid moving in a horizontal position whenever possible, especially cylin-

ders containing acetylene

. Protect valves from being damaged or accidentally broken off by the use of

properly placed cylinder caps

. Never drag a cylinder, tilt it sideways, and roll it along on its bottom rim or

edge This gets the job done in an easier and much safer way

. Use a cylinder cart and secure cylinders with a chain.

. Do not use the protective valve caps for moving or lifting cylinders.

. Do not drop a cylinder or permit them to strike each other violently or be

handled roughly

. Unless cylinders are secured on a cart, regulators are to be removed, valves

closed, and protective caps in place before cylinders are moved

10.2.5 TRANSPORTATION OFCYLINDERS

Cylinders containing compressed gases are primarily shipping containers and shouldnot be subjected to rough handling or abuse Such misuse can seriously weaken thecylinder and render it unfit for further use or transform it into a rocket havingsufficient thrust to drive it through masonry walls:

. To protect the valve during transportation, the cover cap should be screwed

on hand tight and remain on until the cylinder is in place and ready to use

. Cylinders should never be rolled or dragged.

. When moving large cylinders, they should be strapped to a properly

design-wheeled cart or cradle to insure stability

. Only one cylinder should be handled (moved) at a time.

10.2.6 EMPTYCYLINDERS

Leave some positive pressure (a minimum of 20 psig) in empty cylinders to preventsuck-back and contamination Close the valves on empty cylinders to prevent

internal contamination; remove the regulators and replace the protective cap Use acylinder status tag to indicate whether the cylinder is full, in service, or if residue isstill in the cylinder This tag is to be installed by the ES&H department and shallremain on the cylinder Empty cylinders should be stored separately from fullcylinders Properly label and dispose of cylinders Call the vendor to pick upcylinders that are no longer needed.

10.2.7 IDENTIFICATION ANDCOLORCODING

Stencils, DOT shoulder labels, cautionary sidewall labels, or tags are used to identifythe contents of all gas cylinders Do not remove these labels without specificauthorization from the ES&H department Color codes for gas cylinders are notreliable to identify contents since there is no standardization by manufacturers andsuppliers:

. Cylinders must be properly labeled, including the gas composition and

appropriate hazards (e.g., health,flammability, and reactivity)

. Cylinders have several stamped markings The top mark is either a DOT or

an ICC marking indicating pertinent regulations for that cylinder Thesecond mark is the serial number Under the serial number is the symbol

of the manufacturer, user, or purchaser Of the remaining marks the bers represent the date of manufacture, and retest date (month and year)

num-A (þ) sign indicates the cylinder may be 10% overcharged, and a starindicates a 10 year test interval (Figure 10.8)

The hazard classification or the name of the gas being stored shall be ently marked in container storage areas, and No Smoking signs shall be posted where

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No stamping below this line All stamping at least 1/4 in high

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appropriate Placards, container labels, and markings provide information on theproducts involved.

The MSDS for the products or other recognized emergency response guidesshould be consulted for specific hazards, safety precautions, and related emergencyresponse information

10.2.8 ADEQUATELY SECURINGCYLINDERS

All compressed gas cylinders in service or storage at the user’s location are to besecured to prevent them from falling Gas cylinders with a water volume of less than

5 L (305 cu in.) may be stored in a horizontal position, as long as they are preventedfrom rolling and they would be considered to be adequately secured Since 1980,cylinder and manifold racks have been fabricated, purchased, or equipped withtwo chains whenever possible If available, both chains are to be used to securethese cylinders

10.2.9 CYLINDERSTORAGESHEDS

Cylinder storage sheds and delivery sheds should be equipped with double chains.Thus, cylinders shall be adequately secured with individual restraining bars or chainrestraints (1=4 in welded chains and safety clips are preferred) The rails on whichthe restraining bars slide must be pinned and secured to the shed to prevent the barsfrom sliding off

10.3 HOSES AND REGULATORS

10.3.1 INSPECTION

Complete the following procedures:

. Inspect hoses and manifolds frequently, and replace worn hoses and

connections Contact the engineering staff for hose or connector ments

replace-. Report leaking cylinders that contain hazardous materials to the emergency

dispatcher (dial 911) Evacuate the area until the emergency response teamarrives

. Contact your area ES&H department before handling faulty or corroded

cylinders; these cylinders should be segregated Caution: Only the vendorshall alter or repair cylinders or cylinder valves

10.3.2 GENERALPRECAUTIONS

General precautions are as follows:

. Secure both ends of the hose with a hose restraint to prevent whipping in

the event the hose orfitting fails For systems in manned areas, support andsecure the hose and tubing at least every 7 ft

. Do not use an openflame to leak-check a gas cylinder; use soapsuds or aleak-detection solution

. Remove the talc and dust from a new hose before connecting it.

. Do not use white lead, oil, grease, or any other nonapproved joint

com-pound to seal thefittings on an oxygen system; a fire or an explosion couldoccur if oxygen contacts such materials Threaded connections in oxygenpiping should be sealed with solder, glycerin, or other sealants approved foroxygen service Gaskets should be made of noncombustible materials

. Never interchange regulators and hose lines (with one type of gas for

another) Explosions can occur if flammable gases or organic materialscome in contact with oxidizers (e.g., oxygen) under pressure

. Never use oxygen to purge lines, operate pneumatic tools, or dust clothing.

Remember, oxygen is not a substitute for compressed air Do not transfer ormix gases in commercial vendor- or laboratory-owned DOT cylinders, ortransfer gases from one DOT cylinder to another

. Do not use vendor-owned cylinders for purposes other than as a source of

gas These cylinders may only be pressurized by the owner

. Do not strike a welding arc on a cylinder.

10.3.3 OPERATION

The following operations should be completed before using compressed gascylinders:

. Before installing a regulator on a compressed gas cylinder, vacuum the

valve port clean or crack the valve gently to expel any foreign material Donot perform this task if the gas in the cylinder is toxic, reactive, orflammable

. After installing the regulator and before opening the cylinder valve, fully

release (turning counterclockwise) the regulator pressure-adjusting screw

. Open the cylinder valves slowly Never use a wrench on a cylinder valve

that will not rotate manually Stand clear of pressure regulator gauge faceswhen opening the cylinder valves If the valves are defective, return thecylinder to the vendor immediately

. Keep removable keys or handles from valve spindles or stems in place

while the cylinders are in service

. Never leave pressure on a hose or line that is not being used To shut

down a system, close the cylinder valve and vent the pressure from theentire system