NCCER Welding Unit 2
 Oxyfuel cutting is a process that uses
the flame and oxygen from a cutting
torch to cut ferrous metals.
 Flame is produced by mixing a fuel
gas with pure oxygen.
 The flame heats the metal and then a
flow of oxygen is used to cut the
metal which produces dross. (The cut
metal fragments)
 Fast and easy way to cut metal…Not
the most precise
 Always use safety cutting glasses
with the proper shade. (shade filter of
at least 3 to 6)
 Wear protective clothing…sleeves,
leathers, and gloves
 Always wear 8’’ or taller high top
safety boots.
 Ake sure any flammable material in
the work area is moved or shielded
from the source of an open flame. ‘
 Make sure fire extinguishers are in
working order and located in an well
seen area.
 Before cutting tanks or barrels, check
to see if they have contained any
flammable material. Always clean
and fill with water, or purge them
with a flow of inert gas to displace
any oxygen.
 Always perform cutting operations in
a well ventilated area.
 If the material contains any kind of
mercury, lead, or zinc coating always
wear an approved full face, supplied
air respirator. This will prevent you
from breathing toxic fumes.
 Oxygen is a colorless, odorless,
tasteless gas that supports
combustion. Combined with burning
material, pure oxygen causes a fire to
flare and burn out of control.
 Oxygen is stored at more than 2,000
psi in hollow steel cylinders.
 These cylinders must be tested every
10 years.
 Acetylene gas is a compound of carbon and hydrogen and is lighter than air. It is
formed by dissolving calcium carbide in water.
 It has a strong, garlic like odor which is added so the gas can be detected.
 It is very unstable and will explode easily under pressure, this is why it must never
exceed 15 psi when in a gaseous form.
 When combined with oxygen, acetylene creates a flame that burns hotter than
5,500 degrees.
 Because of its explosive nature, acetylene cannot be stored above 15 psi in a
hollow cylinder.
 To solve this problem, acetylene cylinders are filled with a porous material that
creates a solid, instead of a hollow cylinder.
 Acetylene cylinders must always be stored in the upright position and if one is
ever tipped over, stand the cylinder upright and wait at least one hour before
using.
 Acetylene cylinders have safety fuse plugs in the top and bottom of the cylinder
that melt at 220 degrees. These prevent the tank from exploding.
 Many fuel gasses other than
acetylene can be used in oxyfuel
cutting.
 They include natural gas,
methylacetylene propadiene(MAP
gas), propylene, and propane.
 Flames are not as hot, but may be
cheaper or safer to use.
 MAP gas is mixture of acetylene and
propane.
 Propylene mixtures are stable and
shock resistant and burn at around
5,193 degrees.
 Liquified fuel gases are shipped in hollow steel cylinders.
 Can hold up to 225 pounds of liquid fuel gas.
 If high volumes of gas are removed from a liquid fuel gas cylinder, the pressure will
drop, and the temperature of the cylinder will also drop.
 A ring of frost can sometimes form around the base of the cylinder.
 Regulators are attached to the
cylinder and reduce the pressure
from the tank before it gets to the
torch handle. Also helps maintain a
steady flow of gas from the cylinder.
 Oxygen regulators have green
markings and always have right
handed threads. Will read up to 3000
psi on its high pressure gauge.
 Acetylene regulators are red and
have left hand threads. A v-notch is
cut on the nut for a reminder. The
high pressure gauge will read up to
400 psi.
 2 types… One piece cutting torch
and a combination torch
 Combination torch is what we use.
 Consists of a cutting torch attachment
that connects to a welding torch
handle.
 The fuel gas and oxygen valves are
on the torch handle.
 These are used in light to medium
duty jobs.
 The cutting tip to be used depends on the base metal thickness and fuel gas being
used.
 Special tips are also made for gouging or grooving.
 Rivet cutting heads are used to cut of rivets, bolts, and nuts.
 A variety of fixed and portable
motorized cutting equipment is
available for straight and curved cuts.
 CNC machines like the Torchmate
are used to cut metal using a
computer driven system.
 Portable track cutting machines
(track burners) can be used in the
field for straight or curved cuts and
beveling.
 As a safety precaution, always check equipment periodically for leaks before
using.
 The torch should be checked before every use.
 We can use soapy water to check for leaks, if bubbles form… then a leak is present.
 There are 3 types of oxyfuel flames:
 Neutral flame- burns equal amount of
oxygen and acetylene. Used for all
cutting operations
 Carburizing flame- has a white feather
caused by excess fuel. Length of
feather depends on amount of excess
gas.
 Oxidizing flame- has an excess of
oxygen, inner cone is shorter and
much bluer in color, more pointed than
a neutral flame
 Once finished cutting, always
remember to shut down the torch for
safety reasons.
 First step in shutting down is to
always close the fuel gas and oxygen
valves.
 Once everything is shut down, always
wrap up the hose to eliminate any
tripping hazards.
 Once cylinders become to low to use,
we should prepare them to be
changed out.
 Remove the regulator and replace
the cylinder cap on top of the
cylinder.
 Mark MT(empty) and the date near
the top of the cylinder using
soapstone.
 Thin steel is 3/16” thick or less.
Distortion can be caused when
cutting due to the heat and thinness
of the steel.
 To minimize distortion, move as
quickly as you can without loosing
the cut.
 Hold the torch tip so that it is
traveling in a 15 to 20 degree angle.
 Washing is a term used to describe
the process of cutting out bolts or
rivets.
 Washing tips can also be used to
remove items such as blocks, angles,
or channels that are welded onto a
surface.
 Gouging is the process of cutting a
groove into a surface.
 Uses a special kind of cutting tip.
 Not as effective as washing tips but