OAW/OAC/SAFETY Flashcards
Combustibles
Easily ignited materials that stay ignited easily.
-wood, paper, etc
Non-combustibles
Not easily ignited
- metal, asbestos
Materials that are not usually combustible can be with excess oxygen
Fire extinguishers- Class A
Class a fired are ordinary combustion- wood, paper- and there’s just water inside
Fire extinguishers- Class B
Caused by flammable liquids - filled with carbon dioxide to get rid of oxygen.
Fire extinguishers- Class C
Caused by electrical equipment - filled with foam
Fire extinguishers- Class D
By combustible metals like lithium - filled with fire retardant powders or dry chemicals
Welding in confined spaces - must haves
Ventilation and a fire watcher
Ventilation keep harmful vapours out of your lungs
Fire watcher keep watch for fires while you’re welding.
Deep burns
Third degree burns
Damage nerves, blood, muscles, etc, and cause permanent damage.
Skin is black and charred or a ring around the wound.
Superficial burns
First and second degree burns
Less damage and surface burns
First degree are sunburns, slight burns, etc
Second degree it starts to blister
Fire triangle
Fire needs the triangle to survive - oxygen, fuel, and heat
Respirator
Block out tiny little particles and vapours, the stuff you can’t see.
There are two kinds, negative pressure and positive pressure.
Dust mask
Same job as respirator but larger particles.
Metal fumes fever
Caused by inhaling metal vapours, zinc oxide, a condition characterized by flu symptoms
Types of light
Three types of light associated with welding:
Ultraviolet - can’t experience but get sunburnt
Infrared - experienced through heat
And viable light
Exposure can cause serious damage
Safety glasses: why?
Protect you from sparks flying or metal particles that hike grinding or cutting. Also protect you from uv rays - clear glass
Welding helmet/lenses
Protect you from bright light rays. Your helmet protects your periphery vision. There are three lenses in your helmet, two clear to protect you from uv and one dark that can change. That one protects from visible and infrared.
Acetylene
C2H2
Acetone is saturated into cement and then acetylene is pumped into the porous holes as carbonized material.
Draw limit - 1/7 of tanks volume per hour
Calcium carbide and water.
Working pressure - 10psi
Slightly unstable - 15psi
Explosive - 25psi
Stored - 250psi
Oxygen
O2
Added to fire and makes it burn harder
Stored at 2200psi
Pumped into tank that is made with one seamless forged metal tank - extrusion. Air is pumped in and out at freezing levels and oxygen bubbles out, then it’s collected.
OAC
Oxy-acetylene cutting
OAW
Oxy-acetylene welding
Gas leak
Spray soap and leak will bubble
Cylinder pressure
oxygen - 2200 psi (stored), 10 psi (working)
acetylene - 250 psi (stored), 10 psi (working)
pressure is always the same no matter the size of the tank, the volume would just be different.
Cylinder safety features
How it’s made - one seam
Acetylene & acetone - made this way so it won’t explode
Safety plug - melts at 100 degrees C when it heats up (pressure gets higher too) so it can slowly release the gas so it doesn’t explode
Which way do you turn oxygen valve?
righty tighty lefty loosey
Which way do you turn fuel gas valve?
lefty tighty righty loosey
Bursting disc fracture pressure
Safety valve prevents explosions. Disc bursts when temperature gets higher than 3000-3500 degrees C.
Backfire
not as dangerous as flashback.
a small explosion that produces a popping sound, making the flame recede back into the torch.
Caused by gas burning faster than it’s coming out.
Flashback
Occurs when the flame recedes into or further than the mixing chamber, hose, or regulator. This is very dangerous and may cause explosion. Happens when the flame is able to go back and cross the valves.
Caused by reverse flow of gas or loose connections.
Check valve
a valve that allows the flow of gas in only one direction. Gas pressure one way opens the valve but from the other direction it closes. Not as good as a flashback arrestor because sometimes it may not close fast enough and traps fire inside the hose.
Flashback arrestor
prevents reverse flow of fuel gas back into the hose, regulator, or cylinder. Similar to a check valve but this one has a special chamber inside that allows the fire to burn inside to allow a split second longer for the valve to close.
Neutral flame
correct balance of oxygen to acetylene (or other fuel gas). correct ratio is 2.5 (O2) : 1 (C2H2), but set oxygen to 1 because the rest will come from the air.
Flame has to flame areas, the envelope (even and smooth and round) and the cone (shaped like a bullet).
wont be dirty with excess carbon.
Carburizing/Carbonizing flame
produced when excess acetylene (carbon) is present or when too little oxygen is present.
Three flame areas are visible:
cone, rougher envelope, and feather inside.
Results in large carbon pockets in the weld and make the weld brittle.
Oxidizing flame
produced when too much oxygen is present.
Two flame areas are present:
very bright, tiny, pointed corner, and more turbulent and shorter envelope.
instead of melting and welding metal, it just burns away.
Oxygen : acetylene ratio
2.5 : 1
1.5 of oxygen comes from air so set it to one.
Arc/welding flash
a bright flash of uv light usually from the flame or torch that can severely damage eyes. similar to a sunburn but for your eyes.
Bourdon tubes
part of the pressure gauge. One side is connected to the pressure and the other is out to the atmosphere. Hollow inside and fills with gas to detect pressure.
There are two: one on the working hose and the other on the cylinder.
Regulator
regulators detect the pressure in a cylinder or hose and help it to lessen.
Gauges
pressure regulators usually have two gauges - one shows cylinder pressure and the other shows pressure through the tube. Shows when psi gets to unsafe levels.
Lighting welding torch
1) open acetylene and oxygen valves slightly
2) open valves completely
3) set to working pressure
4) open acetylene to torch slowly until turbulent and no more smoke
5)open oxygen to torch slowly until a neutral flame is achieved.
slowly open acetylene, then strike it with flint, the open torch valve
Shutting down
1) turn off acetylene to torch valve
2) turn off oxygen to torch valve
3) close acetylene valve
4) close oxygen valve
5) close acetylene pressure
6) close oxygen pressure
7) slightly open torch valves to clear hose
attaching regulator to hose
start by screwing hose into the regulator with your hand, and once you can’t move it anymore, take a proper sized wrench and slightly tighten it only a little bit.
attaching regulator to cylinder
line up the regulation in the correct position and start screwing it in by hand until you cant then tighten with wrench.
