Oxyacetylene Cutting

8/2/2019 Oxyacetylene Cutting

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Oxy-Acetylene SafetyAwareness


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W hat is Oxygen Remember, oxygen is not air

There is approximately 21% oxygen in normal air

Oxygen is found naturally in the atmosphere

It is produced industrially by distilling air below its freezing point

Pure oxygen does not burn or explode

Oxygen is an accelerant , it causes every thing it comes incontact with to burn hotter and faster

Air has a vapor density of 1.000, Oxygen is heavier than air (1.105)This means if a oxygen bottle is leaking, the gas will settle in lowareas before diffusing back into the atmosphere.

30% oxygen in the atmosphere will cause things to burn orexplode 8 times faster


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in pneumatic tools- the oil and the gas pressure friction can causea fire or explosion

in oil pre-heating burners- these burners are set to burn with 21%oxygen to air ratio

to start internal combustion engines- gasoline is flammableenough with 21% oxygen available

to blow out pipelines- Leftover flammable or combustible vaporsmay still be present to cause an explosion

to dust off clothing or work area- the oxygen will remain present inthe cloth fibers causing them to be more flammable

to create pressure

for ventilation

Remember, oxygen is not air

Never use oxygen.
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How are oxygen bottles constructed

Usually of steel construction 244 cu. ft is standard size (K size)

2000 to 2600 psi

Hollow in construction

An electric arc can cause an oxygen bottle to explode (thecarbon in the steel will atomize into a fuel)

The orifice at the top of the bottle is the diameter of thelead in a pencil ( if the bottle top is damaged, the bottlecan become projectile causing injury or property damage

Never allow a tank to go empty (this may allow acetyleneto travel into the oxygen lines or bottle

Keep free from oil and grease


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What is acetylene Acetylene is a compound of Hydrogen and Carbon(C

2H

2) a member of the hydrocarbon gases

Explosive range is 3.0 to 93% Needs only 10% of oxygen to ignite Produced when calcium carbide is mixed withwater It is an unstable gas, will violently decomposewhen in a pure state above 15 psi Has a burning temperature of 4,600o F, 5,700o Fwhen burned with oxygen Auto-ignition temperature is 763o - 824o F, thismeans if acetylene reaches 30 psi in a free state, it

can explode by itself without a spark or flame beingpresent Remember, acetylene is a very dangerous gas


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Why doesnt acetylene explode in the bottle Acetylene burns in air readily, and is most safely hand-

led/stored in cylinders filled with crushed firebrick wetwith acetone.

Acetylene happens to dissolve readily into acetone, andthe dissolved gas is no longer in contact with gaseous O2

(which does not tend to dissolve in acetone) and thereforeis not as prone to decomposition by O2.

The firebrick also helps by minimizing the free volume ofthe cylinder, cooling and controlling any thermaldecomposition before it gets out of control (each

decomposition of acetylene gives off heat).

Acetylene cylinders must, therefore, be refilled only byauthorized gas distributors. Acetylene cylinders mustnever be transfilled.


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How are acetylene bottles constructed

Usually are steel construction Filled with a porous material to allow the acetone

to dissolve the acetylene, which makes it stable

Porous filler(8-10%), Acetone(42%)

Acetylene gas(36%),

Reserve volume-70o F(10-12%) Never allow a tank to go empty

Oxygen may back pressure into the bottle

Comes in various sizes

Must always be stored upright

This prevents the acetone and acetylenefrom separating

Should not be stored below freezing

Acetone may come out instead of acetylene

and may clog the regulators


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Care & maintenance of the Gas RegulatorsThe internal working parts of the regulator are precision units. Only

qualified technicians should clean or repair a regulator

The Inlet Connections

Oxygen are right handthread/Acetylene areleft hand thread

Keep free of oil,

grease, & dirt

The Pressure adjusting screw

Turning clockwise allows the gas allows toflow

Turning counterclockwise reduces or stopsthe gas flow

The High pressure gauge

Indicates thepressure from tank

The Lowpressure gauge

Indicatesthe delivery

pressure tothe hoses &torch


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Some more info onregulators

Warning -Always keep the regulator free of oil, grease and other

flammable substances

Never use oil or grease on the regulator, cylinder or manifoldconnection

DO NOT change the inlet connection on a regulator in an

attempt to use the regulator for a different gas service

Never stand in front or behind a regulator when opening the

cylinder valve
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Backfires and flashbacks

Backfires occur when the torch flame burns back into the

torch tip and is extinguished with a loud pop.

They occur either because the torch tip touched the work or

because of insufficient gas pressure.

They are generally harmless. However, flashbacks are more

serious when the flame front does not extinguish, but burns

back sometimes beyond the mixing chamber, through the

hoses, and even into regulator and supply.

A common inside diameter of oxy-fuel gas hose is 1/4 inch. If

you calculate the volume of 100 feet of hose with an inside

diameter of 1/4 inch, this means, should oxygen enter thefuel gas hose or should fuel gas enter the oxygen hose, a

mixed gas explosion with the force potential of 20 sticks of

dynamite could occur.


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Check valves

Flow of gas keeps valve open

The purpose of an internal check valve is to reduce the

possibility of reverse flow gas.

It isnot intended to act as a fire stop!Ensure that the internal check valves are working properly

by testing at least every six months, more often if the

hoses are frequently removed from the torch.

Spring activated

Gas flow Once flowpressuredecreases, valve

will closespreventing backflow of gas


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Flashback arrestors

Flame path is extinguished by meshed

material inside

Flashback arrestors are designed to prevent aflashback from reaching upstream equipment.They offer added safety and often include reverse flowcheck valves in a single unit

Torch handle


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The Hoses The hoses are usually color coded, but not always

Oxygen(green) Acetylene(red) Be careful not to use other hoses, such as air lines, LPgas, etc.

They are neoprene over braided inner section Be careful around sharp objects, they can be cut veryeasily

They are constructed of flame retardant materials, butwill burn if there is a flashback or exposed to sustainedheat Hoses are graded

Make sure you are using the right hose for the rightgas


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More hose stuff

Keep welding hoses clear of any failing metal, slag orsparks.

Never allow hoses to become coated with oil, grease ordirt. Such coatings could conceal damaged areas.

Examine the hoses before attaching to welding torchhandle or regulators.

If cuts, burns, worn areas or damaged fittings are found,replace the hose.

Completely replace welding hose if it contains multiplesplices or when cracks or severe wear is noticed.


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Torch handle

Torch head

Control valve &bodyY

Barrel


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Torch cutting attachment

There must always be two

o-rings on the cone end.The absence or damage ofeither of these o-ringsallows premixing and leaksof oxygen and fuel gases.This can lead to flashbackwithin the torch handle.


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Always make sure your equipment is rated for the size tip you

have selected.

A tip with too much capacity for the equipment can starve or

choke the tip. This causes overheating of the head and aflashback may result.

A damaged seating surfaceon either the tip or the head can

create a dangerous condition, resulting in a fire or flashback.

This may damage the cutting attachment.

If the seating surface of a tip becomes damaged,DO NOT use

it. Discard the damaged tip.

If the head requires repair, take the torch to a qualified repair

technician.

What size cutting-tip do I need?

The type of torch you are using and the thickness of material

being cut determine the proper size cutting-tip for use in oxy-

acetylene flame cutting


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What tip sizes do I use for oxy-acetylene cutting and whatpressures do I set on my regulators?

Tip sizes and gas regulator settings are dependent on the

thickness of the material to be cut and the type torch beingused

Always refer to themanufactures supplied

cutting chart for the cuttingtips you are using.

Remember, if you do not use

the proper oxygen toacetylene ratio, you maycause an accident, at the veryleast you will waste gas,which costs $$$$.


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Never starve or choke a multi-flame heating nozzle. This

causes overheating of the head and a flashback may result. Should a flashback occur (flame disappears and/or a

hissing soundis heard, theflame is burning inside thenozzle), immediately turn off the oxygen valve on the torchhandle. Then, turn off the fuel valve.

Allow the nozzle to cool before using. If a flashback reoccurs, have the apparatus checked by a

qualified technician before using again.

Cuttingtips andnozzles


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Never allow oxygen to contact oil, grease or other

flammable substances

Never mix brands

Purge the lines before and after usage

Always wear protective clothing

Use proper eye protection

Lets Finish With Some Final General Safety Tips


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If flashback occurs, immediately turn off the O2, then theacetylene, and allow unit to cool

Always work in a well ventilated area

Always light the acetylene first

Oxygen cylinders must be opened the whole way

Use an approved striker, never use matches or cigarette lighter

Use the proper regulator for each specific gas

Only qualified technicians should repair a regulator

Keep regulators free of oil, grease and other flammable

substances


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General Safety TipsKeep regulators free of oil, grease and other flammablesubstances

Check valves stop reverse gas flow, they do not act as a firestop

Never starve a tip, this can cause a flashback

Always keep cylinders in an upright position

Never stand in front or behind a regulator when opening the

cylinder valve

Always make sure area is safe and flammable free


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Safety Checklist for Getting StartedWhat is the necessary safety equipment you need?Proper Eye protection

Appropriate gloves

Clothing free of grease & oil

Clean work area

Proper Task Training

Fire extinguisher


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Thank you and Be Careful

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Oxyacetylene Cutting