This document discusses oxyacetylene welding (OAW). OAW uses oxygen and acetylene gases to produce a high temperature flame for welding. The equipment needed includes oxygen and acetylene gas cylinders, pressure regulators to reduce the gas pressures, hoses to carry the gases to the torch, and check valves and flashback arrestors for safety. There are three types of oxyacetylene flames - neutral, oxidizing, and carburizing - which are produced by adjusting the ratio of oxygen to acetylene. The document provides details on setting up and using the equipment safely and properly for OAW.

2. Oxyacetylene Welding (OAW)
•
by
WAQAS AHMED

3. Oxyacetylene Welding (OAW)
The oxyacetylene welding process
uses a combination of oxygen and
acetylene gas to provide a high
temperature flame.

4. Oxyacetylene Welding (OAW)
• OAW is a manual process in which the
welder must personally control the the torch
movement and filler rod application
• The term oxyfuel gas welding outfit refers
to all the equipment needed to weld.
• Cylinders contain oxygen and acetylene gas
at extremely high pressure.

5. Typical Oxyacetylene Welding
(OAW) Station

6. Oxygen Cylinders
• Oxygen is stored within cylinders of various
sizes and pressures ranging from 20002640 PSI. (Pounds Per square inch)
• Oxygen cylinders are forged from solid
armor plate steel. No part of the cylinder
may be less than 1/4” thick.
• Cylinders are then tested to over 3,300 PSI
using a (NDE) hydrostatic pressure test.

7. Oxygen Cylinders
• Cylinders are regularly
re-tested using
hydrostatic (NDE)
while in service
• Cylinders are regularly
chemically cleaned
and annealed to relieve
“jobsite” stresses
created by handling .

8. Oxygen Cylinders
• Oxygen cylinders
incorporate a thin metal
“pressure safety disk”
made from stainless steel
and are designed to
rupture prior to the
cylinder becoming
damaged by pressure.
• The cylinder valve should
always be handled
carefully

9. Pressure Regulators for
Cylinders
• Reduce high storage
cylinder pressure to
lower working
pressure.
• Most regulators have a
gauge for cylinder
pressure and working
pressure.

10. Pressure Regulators for
Cylinders
• Regulators are shut off
when the adjusting screw
is turn out completely.
• Regulators maintain a
constant torch pressure
although cylinder pressure
may vary
• Regulator diaphragms are
made of stainless steel

11. Pressure Regulators Gauges
Using a “Bourdon” movement
• Gas entering the gauge fills a
Bourdon tube
• As pressure in the semicircular
end increases it causes the free
end of the tube to move
outward.
• This movement is transmitted
through to a curved rack which
engages a pinion gear on the
pointer shaft ultimately
showing pressure.

12. Regulator Hoses
• Hoses are are fabricated from
rubber
• Oxygen hoses are green in
color and have right hand
thread.
• Acetylene hoses are red in
color with left hand thread.
• Left hand threads can be
identified by a grove in the
body of the nut and it may
have “ACET” stamped on it

13. Check Valves &
Flashback Arrestors
• Check valves allow gas
flow in one direction only
• Flashback arrestors are
designed to eliminate the
possibility of an explosion
at the cylinder.
• Combination Check/
Flashback Valves can be
placed at the torch or
regulator.

14. Acetylene Gas
• Virtually all the acetylene distributed for welding and cutting use
is created by allowing calcium carbide (a man made product) to
react with water.
• The nice thing about the calcium carbide method of producing
acetylene is that it can be done on almost any scale desired.
Placed in tightly-sealed cans, calcium carbide keeps indefinitely.
For years, miners’ lamps produced acetylene by adding water, a
drop at a time, to lumps of carbide.
• Before acetylene in cylinders became available in almost every
community of appreciable size produced their own gas from
calcium carbide.

15. Acetylene Cylinders
• Acetylene is stored in cylinders specially designed
for this purpose only.
• Acetylene is extremely unstable in its pure form at
pressure above 15 PSI (Pounds per Square Inch)
• Acetone is also present within the cylinder to
stabilize the acetylene.
• Acetylene cylinders should always be stored in the
upright position to prevent the acetone form
escaping thus causing the acetylene to become
unstable.

16. Acetylene Cylinders
• Cylinders are filled with a
very porous substance
“monolithic filler” to help
prevent large pockets of
pure acetylene form
forming
• Cylinders have safety
(Fuse) plugs in the top and
bottom designed to melt at
212° F (100 °C)

17. Acetylene Valves
• Acetylene cylinder shut
off valves should only be
opened 1/4 to 1/2 turn
• This will allow the
cylinder to be closed
quickly in case of fire.
• Cylinder valve wrenches
should be left in place on
cylinders that do not
have a hand wheel.

18. Oxygen and Acetylene Regulator
Pressure Settings
• Regulator pressure may vary with different
torch styles and tip sizes.
• PSI (pounds per square inch) is sometimes shown as
PSIG (pounds per square inch -gauge)
• Common gauge settings for cutting
– 1/4” material Oxy 30-35psi Acet 3-9 psi
– 1/2” material Oxy 55-85psi Acet 6-12 psi
– 1” material Oxy 110-160psi Acet 7-15 psi
• Check the torch manufactures data for
optimum pressure settings

19. Types of Flame
• There are three distinct types of oxy-acetylene
flames, usually termed:
– Neutral
– Carburizing (or “excess acetylene”)
– Oxidizing (or “excess oxygen” )
• The type of flame produced depends upon the
ratio of oxygen to acetylene in the gas mixture
which leaves the torch tip.

20. FLAME Settings
• Oxygen is turned on, flame immediately changes into a long white inner
area (Feather) surrounded by a transparent blue envelope is called
Carburizing flame (30000c)
• Addition of little more oxygen give a bright whitish cone surrounded by the
transparent blue envelope is called Neutral flame (It has a balance of fuel
gas and oxygen) (32000c)
• Used for welding steels, aluminium, copper and cast iron
• If more oxygen is added, the cone becomes darker and more pointed, while
the envelope becomes shorter and more fierce is called Oxidizing flame
• Has the highest temperature about 34000c
• Used for welding brass and brazing operation

21. Pure Acetylene and Carburizing
Flame profiles

22. Neutral and Oxidizing Flame
Profiles

23. Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting
operations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flame.

24. •Three basic types of oxyacetylene flames used in
oxyfuel-gas welding and cutting operations:
• (a) neutral flame; (b) oxidizing flame; (c)
carburizing, or reducing flame.