View
269
Download
0
Category
Preview:
Citation preview
8/2/2019 Oxyacetylene Cutting
1/24
Oxy-Acetylene SafetyAwareness
8/2/2019 Oxyacetylene Cutting
2/24
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
8/2/2019 Oxyacetylene Cutting
3/24
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.
http://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gifhttp://d/ClipArt/flash.gif8/2/2019 Oxyacetylene Cutting
4/24
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
8/2/2019 Oxyacetylene Cutting
5/24
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
8/2/2019 Oxyacetylene Cutting
6/24
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.
8/2/2019 Oxyacetylene Cutting
7/24
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
8/2/2019 Oxyacetylene Cutting
8/24
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
8/2/2019 Oxyacetylene Cutting
9/24
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
http://d/ClipArt/boom.gifhttp://d/ClipArt/boom.gifhttp://d/ClipArt/boom.gif8/2/2019 Oxyacetylene Cutting
10/24
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.
8/2/2019 Oxyacetylene Cutting
11/24
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
8/2/2019 Oxyacetylene Cutting
12/24
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
8/2/2019 Oxyacetylene Cutting
13/24
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
8/2/2019 Oxyacetylene Cutting
14/24
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.
8/2/2019 Oxyacetylene Cutting
15/24
Torch handle
Torch head
Control valve &bodyY
Barrel
8/2/2019 Oxyacetylene Cutting
16/24
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.
8/2/2019 Oxyacetylene Cutting
17/24
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
8/2/2019 Oxyacetylene Cutting
18/24
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 $$$$.
8/2/2019 Oxyacetylene Cutting
19/24
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
8/2/2019 Oxyacetylene Cutting
20/24
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
8/2/2019 Oxyacetylene Cutting
21/24
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
8/2/2019 Oxyacetylene Cutting
22/24
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
8/2/2019 Oxyacetylene Cutting
23/24
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
8/2/2019 Oxyacetylene Cutting
24/24
Thank you and Be Careful
Recommended